[input.output] - C++14 → C++17

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@@ -12,22 +12,23 @@ formatting and manipulators, string streams, and file streams, as
 summarized in Table  [[tab:iostreams.lib.summary]].
 **Table: Input/output library summary** <a id="tab:iostreams.lib.summary">[tab:iostreams.lib.summary]</a>
 | Subclause                  |                             | Header         |
-| -------------------------- | --------------------------- | ------------- |
 | [[iostreams.requirements]] | Requirements                |                |
 | [[iostream.forward]]       | Forward declarations        | `<iosfwd>`     |
 | [[iostream.objects]]       | Standard iostream objects   | `<iostream>`   |
 | [[iostreams.base]]         | Iostreams base classes      | `<ios>`        |
 | [[stream.buffers]]         | Stream buffers              | `<streambuf>`  |
 | [[iostream.format]]        | Formatting and manipulators | `<istream>`    |
 |                            |                             | `<ostream>`    |
 |                            |                             | `<iomanip>`    |
 | [[string.streams]]         | String streams              | `<sstream>`    |
 | [[file.streams]]           | File streams                | `<fstream>`    |
-| | | `<cstdio>` |
 |                            |                             | `<cinttypes>`  |
 Figure  [[fig:streampos]] illustrates relationships among various types
 described in this clause. A line from **A** to **B** indicates that
@@ -57,30 +58,34 @@ and `traits` behave as described if `traits::pos_type` and
 as noted explicitly below, their behavior when `traits::pos_type` and
 `traits::off_type` are other types is *implementation-defined*.
 In the classes of Clause  [[input.output]], a template parameter with
 name `charT` represents a member of the set of types containing `char`,
-`wchar_t`, and any other implementation-defined character types that
 satisfy the requirements for a character on which any of the iostream
 components can be instantiated.
 ### Thread safety <a id="iostreams.threadsafety">[[iostreams.threadsafety]]</a>
 Concurrent access to a stream object ([[string.streams]],
 [[file.streams]]), stream buffer object ([[stream.buffers]]), or C
 Library stream ([[c.files]]) by multiple threads may result in a data
 race ([[intro.multithread]]) unless otherwise specified (
-[[iostream.objects]]). Data races result in undefined behavior (
-[[intro.multithread]]).
 If one thread makes a library call *a* that writes a value to a stream
 and, as a result, another thread reads this value from the stream
 through a library call *b* such that this does not result in a data
 race, then *a*’s write synchronizes with *b*’s read.
 ## Forward declarations <a id="iostream.forward">[[iostream.forward]]</a>
 ``` cpp
 namespace std {
   template<class charT> class char_traits;
   template<> class char_traits<char>;
   template<> class char_traits<char16_t>;
@@ -125,61 +130,63 @@ namespace std {
   template <class charT, class traits = char_traits<charT>>
     class istreambuf_iterator;
   template <class charT, class traits = char_traits<charT>>
     class ostreambuf_iterator;
- typedef basic_ios<char>       ios;
- typedef basic_ios<wchar_t>    wios;
- typedef basic_streambuf<char> streambuf;
- typedef basic_istream<char>   istream;
- typedef basic_ostream<char>   ostream;
- typedef basic_iostream<char>  iostream;
- typedef basic_stringbuf<char>     stringbuf;
- typedef basic_istringstream<char> istringstream;
- typedef basic_ostringstream<char> ostringstream;
- typedef basic_stringstream<char>  stringstream;
- typedef basic_filebuf<char>  filebuf;
- typedef basic_ifstream<char> ifstream;
- typedef basic_ofstream<char> ofstream;
- typedef basic_fstream<char>  fstream;
- typedef basic_streambuf<wchar_t> wstreambuf;
- typedef basic_istream<wchar_t>   wistream;
- typedef basic_ostream<wchar_t>   wostream;
- typedef basic_iostream<wchar_t>  wiostream;
- typedef basic_stringbuf<wchar_t>     wstringbuf;
- typedef basic_istringstream<wchar_t> wistringstream;
- typedef basic_ostringstream<wchar_t> wostringstream;
- typedef basic_stringstream<wchar_t>  wstringstream;
- typedef basic_filebuf<wchar_t>  wfilebuf;
- typedef basic_ifstream<wchar_t> wifstream;
- typedef basic_ofstream<wchar_t> wofstream;
- typedef basic_fstream<wchar_t>  wfstream;
   template <class state> class fpos;
- typedef fpos<char_traits<char>::state_type>    streampos;
- typedef fpos<char_traits<wchar_t>::state_type> wstreampos;
 }
 ```
 Default template arguments are described as appearing both in `<iosfwd>`
 and in the synopsis of other headers but it is well-formed to include
 both `<iosfwd>` and one or more of the other headers.[^1]
 The class template specialization `basic_ios<charT, traits>` serves as a
 virtual base class for the class templates `basic_istream`,
 `basic_ostream`, and class templates derived from them. `basic_iostream`
 is a class template derived from both `basic_istream<charT, traits>` and
 `basic_ostream<charT, traits>`.
-The class template specialization `basic_streambuf<charT,traits>` serves
-as a base class for class templates `basic_stringbuf` and
 `basic_filebuf`.
 The class template specialization `basic_istream<charT, traits>` serves
 as a base class for class templates `basic_istringstream` and
 `basic_ifstream`.
@@ -190,44 +197,47 @@ as a base class for class templates `basic_ostringstream` and
 The class template specialization `basic_iostream<charT, traits>` serves
 as a base class for class templates `basic_stringstream` and
 `basic_fstream`.
-Other typedefs define instances of class templates specialized for
-`char` or `wchar_t` types.
 Specializations of the class template `fpos` are used for specifying
 file position information.
 The types `streampos` and `wstreampos` are used for positioning streams
 specialized on `char` and `wchar_t` respectively.
 This synopsis suggests a circularity between `streampos` and
 `char_traits<char>`. An implementation can avoid this circularity by
 substituting equivalent types. One way to do this might be
 ``` cpp
 template<class stateT> class fpos { ... };      // depends on nothing
-typedef ... _STATE;             // implementation private declaration of stateT
-typedef fpos<_STATE> streampos;
 template<> struct char_traits<char> {
- typedef streampos
-  pos_type;
 }
 ```
 ## Standard iostream objects <a id="iostream.objects">[[iostream.objects]]</a>
-### Overview <a id="iostream.objects.overview">[[iostream.objects.overview]]</a>
 ``` cpp
-#include <ios>
-#include <streambuf>
-#include <istream>
-#include <ostream>
 namespace std {
   extern istream cin;
   extern ostream cout;
   extern ostream cerr;
@@ -238,129 +248,136 @@ namespace std {
   extern wostream wcerr;
   extern wostream wclog;
 }
 ```
 The header `<iostream>` declares objects that associate objects with the
 standard C streams provided for by the functions declared in
 `<cstdio>` ([[c.files]]), and includes all the headers necessary to use
 these objects.
 The objects are constructed and the associations are established at some
 time prior to or during the first time an object of class
 `ios_base::Init` is constructed, and in any case before the body of
-`main` begins execution.[^2] The objects are not destroyed during
-program execution.[^3] The results of including `<iostream>` in a
-translation unit shall be as if `<iostream>` defined an instance of
-`ios_base::Init` with static storage duration. Similarly, the entire
-program shall behave as if there were at least one instance of
-`ios_base::Init` with static storage duration.
 Mixing operations on corresponding wide- and narrow-character streams
 follows the same semantics as mixing such operations on `FILE`s, as
-specified in Amendment 1 of the ISO C standard.
 Concurrent access to a synchronized ([[ios.members.static]]) standard
 iostream object’s formatted and unformatted input ([[istream]]) and
 output ([[ostream]]) functions or a standard C stream by multiple
-threads shall not result in a data race ([[intro.multithread]]). Users
-must still synchronize concurrent use of these objects and streams by
-multiple threads if they wish to avoid interleaved characters.
 ### Narrow stream objects <a id="narrow.stream.objects">[[narrow.stream.objects]]</a>
 ``` cpp
 istream cin;
 ```
 The object `cin` controls input from a stream buffer associated with the
-object `stdin`, declared in `<cstdio>`.
 After the object `cin` is initialized, `cin.tie()` returns `&cout`. Its
 state is otherwise the same as required for
 `basic_ios<char>::init` ([[basic.ios.cons]]).
 ``` cpp
 ostream cout;
 ```
 The object `cout` controls output to a stream buffer associated with the
-object `stdout`, declared in `<cstdio>` ([[c.files]]).
 ``` cpp
 ostream cerr;
 ```
 The object `cerr` controls output to a stream buffer associated with the
-object `stderr`, declared in `<cstdio>` ([[c.files]]).
 After the object `cerr` is initialized, `cerr.flags() & unitbuf` is
 nonzero and `cerr.tie()` returns `&cout`. Its state is otherwise the
 same as required for `basic_ios<char>::init` ([[basic.ios.cons]]).
 ``` cpp
 ostream clog;
 ```
 The object `clog` controls output to a stream buffer associated with the
-object `stderr`, declared in `<cstdio>` ([[c.files]]).
 ### Wide stream objects <a id="wide.stream.objects">[[wide.stream.objects]]</a>
 ``` cpp
 wistream wcin;
 ```
 The object `wcin` controls input from a stream buffer associated with
-the object `stdin`, declared in `<cstdio>`.
 After the object `wcin` is initialized, `wcin.tie()` returns `&wcout`.
 Its state is otherwise the same as required for
 `basic_ios<wchar_t>::init` ([[basic.ios.cons]]).
 ``` cpp
 wostream wcout;
 ```
 The object `wcout` controls output to a stream buffer associated with
-the object `stdout`, declared in `<cstdio>` ([[c.files]]).
 ``` cpp
 wostream wcerr;
 ```
 The object `wcerr` controls output to a stream buffer associated with
-the object `stderr`, declared in `<cstdio>` ([[c.files]]).
 After the object `wcerr` is initialized, `wcerr.flags() & unitbuf` is
 nonzero and `wcerr.tie()` returns `&wcout`. Its state is otherwise the
 same as required for `basic_ios<wchar_t>::init` ([[basic.ios.cons]]).
 ``` cpp
 wostream wclog;
 ```
 The object `wclog` controls output to a stream buffer associated with
-the object `stderr`, declared in `<cstdio>` ([[c.files]]).
 ## Iostreams base classes <a id="iostreams.base">[[iostreams.base]]</a>
-### Overview <a id="iostreams.base.overview">[[iostreams.base.overview]]</a>
 ``` cpp
-#include <iosfwd>
 namespace std {
- typedef implementation-defined streamoff;
- typedef implementation-defined streamsize;
   template <class stateT> class fpos;
   class ios_base;
   template <class charT, class traits = char_traits<charT>>
     class basic_ios;
-  // [std.ios.manip], manipulators:
   ios_base& boolalpha  (ios_base& str);
   ios_base& noboolalpha(ios_base& str);
   ios_base& showbase   (ios_base& str);
   ios_base& noshowbase (ios_base& str);
@@ -378,27 +395,27 @@ namespace std {
   ios_base& nouppercase(ios_base& str);
   ios_base& unitbuf    (ios_base& str);
   ios_base& nounitbuf  (ios_base& str);
-  // [adjustfield.manip] adjustfield:
   ios_base& internal   (ios_base& str);
   ios_base& left       (ios_base& str);
   ios_base& right      (ios_base& str);
-  // [basefield.manip] basefield:
   ios_base& dec        (ios_base& str);
   ios_base& hex        (ios_base& str);
   ios_base& oct        (ios_base& str);
-  // [floatfield.manip] floatfield:
   ios_base& fixed      (ios_base& str);
   ios_base& scientific (ios_base& str);
   ios_base& hexfloat   (ios_base& str);
   ios_base& defaultfloat(ios_base& str);
-  // [error.reporting] error reporting:
   enum class io_errc {
     stream = 1
   };
   template <> struct is_error_code_enum<io_errc> : public true_type { };
@@ -409,19 +426,19 @@ namespace std {
 ```
 ### Types <a id="stream.types">[[stream.types]]</a>
 ``` cpp
-typedef implementation-defined streamoff;
 ```
 The type `streamoff` is a synonym for one of the signed basic integral
 types of sufficient size to represent the maximum possible file size for
 the operating system.[^4]
 ``` cpp
-typedef implementation-defined streamsize;
 ```
 The type `streamsize` is a synonym for one of the signed basic integral
 types. It is used to represent the number of characters transferred in
 an I/O operation, or the size of I/O buffers.[^5]
@@ -430,14 +447,14 @@ an I/O operation, or the size of I/O buffers.[^5]
 ``` cpp
 namespace std {
   class ios_base {
   public:
-    class failure;
-    // [ios::fmtflags] fmtflags
- typedef T1 fmtflags;
     static constexpr fmtflags boolalpha = unspecified;
     static constexpr fmtflags dec = unspecified;
     static constexpr fmtflags fixed = unspecified;
     static constexpr fmtflags hex = unspecified;
     static constexpr fmtflags internal = unspecified;
@@ -453,35 +470,35 @@ namespace std {
     static constexpr fmtflags uppercase = unspecified;
     static constexpr fmtflags adjustfield = see below;
     static constexpr fmtflags basefield = see below;
     static constexpr fmtflags floatfield = see below;
-    // [ios::iostate] iostate
- typedef T2 iostate;
     static constexpr iostate badbit = unspecified;
     static constexpr iostate eofbit = unspecified;
     static constexpr iostate failbit = unspecified;
     static constexpr iostate goodbit = see below;
-    // [ios::openmode] openmode
- typedef T3 openmode;
     static constexpr openmode app = unspecified;
     static constexpr openmode ate = unspecified;
     static constexpr openmode binary = unspecified;
     static constexpr openmode in = unspecified;
     static constexpr openmode out = unspecified;
     static constexpr openmode trunc = unspecified;
-    // [ios::seekdir] seekdir
- typedef T4 seekdir;
     static constexpr seekdir beg = unspecified;
     static constexpr seekdir cur = unspecified;
     static constexpr seekdir end = unspecified;
     class Init;
-    // [fmtflags.state] fmtflags state:
     fmtflags flags() const;
     fmtflags flags(fmtflags fmtfl);
     fmtflags setf(fmtflags fmtfl);
     fmtflags setf(fmtflags fmtfl, fmtflags mask);
     void unsetf(fmtflags mask);
@@ -489,25 +506,25 @@ namespace std {
     streamsize precision() const;
     streamsize precision(streamsize prec);
     streamsize width() const;
     streamsize width(streamsize wide);
-    // [ios.base.locales] locales:
     locale imbue(const locale& loc);
     locale getloc() const;
-    // [ios.base.storage] storage:
     static int xalloc();
     long&  iword(int index);
     void*& pword(int index);
-    // destructor
     virtual ~ios_base();
-    // [ios.base.callback] callbacks;
     enum event { erase_event, imbue_event, copyfmt_event };
- typedef void (*event_callback)(event, ios_base&, int index);
     void register_callback(event_callback fn, int index);
     ios_base(const ios_base&) = delete;
     ios_base& operator=(const ios_base&) = delete;
@@ -526,11 +543,12 @@ namespace std {
 `ios_base`
 defines several member types:
-- a class `failure` derived from `system_error`;
 - a class `Init`;
 - three bitmask types, `fmtflags`, `iostate`, and `openmode`;
 - an enumerated type, `seekdir`.
 It maintains several kinds of data:
@@ -539,20 +557,24 @@ It maintains several kinds of data:
 - control information that influences how to interpret (format) input
   sequences and how to generate (format) output sequences;
 - additional information that is stored by the program for its private
   use.
 For the sake of exposition, the maintained data is presented here as:
 - `static int index`, specifies the next available unique index for the
   integer or pointer arrays maintained for the private use of the
   program, initialized to an unspecified value;
 - `long* iarray`, points to the first element of an arbitrary-length
   `long` array maintained for the private use of the program;
 - `void** parray`, points to the first element of an arbitrary-length
   pointer array maintained for the private use of the program.
 #### Types <a id="ios.types">[[ios.types]]</a>
 ##### Class `ios_base::failure` <a id="ios::failure">[[ios::failure]]</a>
 ``` cpp
@@ -563,22 +585,32 @@ namespace std {
     explicit failure(const char* msg, const error_code& ec = io_errc::stream);
   };
 }
 ```
 The class `failure` defines the base class for the types of all objects
 thrown as exceptions, by functions in the iostreams library, to report
 errors detected during stream buffer operations.
 When throwing `ios_base::failure` exceptions, implementations should
 provide values of `ec` that identify the specific reason for the
-failure. Errors arising from the operating system would typically be
 reported as `system_category()` errors with an error value of the error
 number reported by the operating system. Errors arising from within the
 stream library would typically be reported as
 `error_code(io_errc::stream,
-iostream_category())`.
 ``` cpp
 explicit failure(const string& msg, const error_code& ec = io_errc::stream);
 ```
@@ -593,11 +625,11 @@ explicit failure(const char* msg, const error_code& ec = io_errc::stream);
 base class with `msg` and `ec`.
 ##### Type `ios_base::fmtflags` <a id="ios::fmtflags">[[ios::fmtflags]]</a>
 ``` cpp
-typedef T1 fmtflags;
 ```
 The type `fmtflags` is a bitmask type ([[bitmask.types]]). Setting its
 elements has the effects indicated in
 Table  [[tab:iostreams.fmtflags.effects]].
@@ -636,11 +668,11 @@ Table  [[tab:iostreams.fmtflags.constants]].
 ##### Type `ios_base::iostate` <a id="ios::iostate">[[ios::iostate]]</a>
 ``` cpp
-typedef T2 iostate;
 ```
 The type `iostate` is a bitmask type ([[bitmask.types]]) that contains
 the elements indicated in Table  [[tab:iostreams.iostate.effects]].
@@ -658,11 +690,11 @@ Type `iostate` also defines the constant:
 - `goodbit`, the value zero.
 ##### Type `ios_base::openmode` <a id="ios::openmode">[[ios::openmode]]</a>
 ``` cpp
-typedef T3 openmode;
 ```
 The type `openmode` is a bitmask type ([[bitmask.types]]). It contains
 the elements indicated in Table  [[tab:iostreams.openmode.effects]].
@@ -679,11 +711,11 @@ the elements indicated in Table  [[tab:iostreams.openmode.effects]].
 ##### Type `ios_base::seekdir` <a id="ios::seekdir">[[ios::seekdir]]</a>
 ``` cpp
-typedef T4 seekdir;
 ```
 The type `seekdir` is an enumerated type ([[enumerated.types]]) that
 contains the elements indicated in
 Table  [[tab:iostreams.seekdir.effects]].
@@ -713,11 +745,11 @@ namespace std {
 The class `Init` describes an object whose construction ensures the
 construction of the eight objects declared in `<iostream>` (
 [[iostream.objects]]) that associate file stream buffers with the
 standard C streams provided for by the functions declared in
-`<cstdio>` ([[c.files]]).
 For the sake of exposition, the maintained data is presented here as:
 - `static int init_cnt`, counts the number of constructor and destructor
   calls for class `Init`, initialized to zero.
@@ -750,11 +782,11 @@ fmtflags flags() const;
 ``` cpp
 fmtflags flags(fmtflags fmtfl);
 ```
-`fmtfl == flags()`.
 *Returns:* The previous value of `flags()`.
 ``` cpp
 fmtflags setf(fmtflags fmtfl);
@@ -786,11 +818,11 @@ streamsize precision() const;
 ``` cpp
 streamsize precision(streamsize prec);
 ```
-`prec == precision()`.
 *Returns:* The previous value of `precision()`.
 ``` cpp
 streamsize width() const;
@@ -801,11 +833,11 @@ certain output conversions.
 ``` cpp
 streamsize width(streamsize wide);
 ```
-`wide == width()`.
 *Returns:* The previous value of `width()`.
 #### `ios_base` functions <a id="ios.base.locales">[[ios.base.locales]]</a>
@@ -819,11 +851,11 @@ locale imbue(const locale& loc);
 `ios_base::getloc()` from within `fn` returns the new locale value
 `loc`.
 *Returns:* The previous value of `getloc()`.
-`loc == getloc()`.
 ``` cpp
 locale getloc() const;
 ```
@@ -842,11 +874,11 @@ bool sync_with_stdio(bool sync = true);
 objects ([[iostream.objects]]) was synchronized and otherwise returns
 `false`. The first time it is called, the function returns `true`.
 *Effects:* If any input or output operation has occurred using the
 standard streams prior to the call, the effect is
-*implementation-defined*. Otherwise, called with a false argument, it
 allows the standard streams to operate independently of the standard C
 streams.
 When a standard iostream object `str` is *synchronized* with a standard
 stdio stream `f`, the effect of inserting a character `c` by
@@ -910,11 +942,11 @@ of unspecified size and stores a pointer to its first element in
 necessary to include the element `iarray[idx]`. Each newly allocated
 element of the array is initialized to zero. The reference returned is
 invalid after any other operations on the object.[^7] However, the value
 of the storage referred to is retained, so that until the next call to
 `copyfmt`, calling `iword` with the same index yields another reference
-to the same value. If the function fails[^8] and `*this` is a base
 subobject of a `basic_ios<>` object or subobject, the effect is
 equivalent to calling `basic_ios<>::setstate(badbit)` on the derived
 object (which may throw `failure`).
 *Returns:* On success `iarray[idx]`. On failure, a valid `long&`
@@ -931,12 +963,12 @@ as necessary to include the element `parray[idx]`. Each newly allocated
 element of the array is initialized to a null pointer. The reference
 returned is invalid after any other operations on the object. However,
 the value of the storage referred to is retained, so that until the next
 call to `copyfmt`, calling `pword` with the same index yields another
 reference to the same value. If the function fails[^9] and `*this` is a
-base subobject of a `basic_ios<>` object or subobject, the effect is
-equivalent to calling `basic_ios<>::setstate(badbit)` on the derived
 object (which may throw `failure`).
 *Returns:* On success `parray[idx]`. On failure a valid `void*&`
 initialized to 0.
@@ -985,11 +1017,11 @@ member function called from within `fn` has well defined results.
 ``` cpp
 namespace std {
   template <class stateT> class fpos {
   public:
-    // [fpos.members] Members
     stateT state() const;
     void state(stateT);
   private;
     stateT st; // exposition only
   };
@@ -1000,11 +1032,11 @@ namespace std {
 ``` cpp
 void state(stateT s);
 ```
-*Effects:* Assign `s` to `st`.
 ``` cpp
 stateT state() const;
 ```
@@ -1020,14 +1052,15 @@ are permitted. In that table,
 - `O` refers to type `streamoff`,
 - `o` refers to a value of type `streamoff`,
 - `sz` refers to a value of type `streamsize` and
 - `i` refers to a value of type `int`.
-Every implementation is required to supply overloaded operators on
-`fpos` objects to satisfy the requirements of  [[fpos.operations]]. It
-is unspecified whether these operators are members of `fpos`, global
-operators, or provided in some other way.
 Stream operations that return a value of type `traits::pos_type` return
 `P(O(-1))` as an invalid value to signal an error. If this value is used
 as an argument to any `istream`, `ostream`, or `streambuf` member that
 accepts a value of type `traits::pos_type` then the behavior of that
@@ -1040,18 +1073,17 @@ function is undefined.
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ios : public ios_base {
   public:
-    // types:
-    typedef charT                     char_type;
-    typedef typename traits::int_type int_type;
-    typedef typename traits::pos_type pos_type;
-    typedef typename traits::off_type off_type;
-    typedef traits                    traits_type;
     explicit operator bool() const;
     bool operator!() const;
     iostate rdstate() const;
     void clear(iostate state = goodbit);
     void setstate(iostate state);
@@ -1061,15 +1093,15 @@ namespace std {
     bool bad()  const;
     iostate exceptions() const;
     void exceptions(iostate except);
-    // [basic.ios.cons] Constructor/destructor:
     explicit basic_ios(basic_streambuf<charT, traits>* sb);
     virtual ~basic_ios();
-    // [basic.ios.members] Members:
     basic_ostream<charT, traits>* tie() const;
     basic_ostream<charT, traits>* tie(basic_ostream<charT, traits>* tiestr);
     basic_streambuf<charT, traits>* rdbuf() const;
     basic_streambuf<charT, traits>* rdbuf(basic_streambuf<charT, traits>* sb);
@@ -1140,11 +1172,11 @@ Table  [[tab:iostreams.basicios.init.effects]].
 | `rdstate()`    | `goodbit` if `sb` is not a null pointer, otherwise `badbit`. |
 | `exceptions()` | `goodbit`                                                    |
 | `flags()`      | `skipws | dec`                                               |
 | `width()`      | `0`                                                          |
 | `precision()`  | `6`                                                          |
-| `fill()`       | `widen(' ');` |
 | `getloc()`     | a copy of the value returned by `locale()`                   |
 | `iarray`       | a null pointer                                               |
 | `parray`       | a null pointer                                               |
@@ -1163,11 +1195,11 @@ basic_ostream<charT,traits>* tie(basic_ostream<charT,traits>* tiestr);
 *Requires:* If `tiestr` is not null, `tiestr` must not be reachable by
 traversing the linked list of tied stream objects starting from
 `tiestr->tie()`.
-`tiestr == tie()`.
 *Returns:* The previous value of `tie()`.
 ``` cpp
 basic_streambuf<charT, traits>* rdbuf() const;
@@ -1177,11 +1209,11 @@ basic_streambuf<charT,traits>* rdbuf() const;
 ``` cpp
 basic_streambuf<charT, traits>* rdbuf(basic_streambuf<charT, traits>* sb);
 ```
-`sb == rdbuf()`.
 *Effects:* Calls `clear()`.
 *Returns:* The previous value of `rdbuf()`.
@@ -1215,11 +1247,11 @@ specified field width.
 ``` cpp
 char_type fill(char_type fillch);
 ```
-`traits::eq(fillch, fill())`
 *Returns:* The previous value of `fill()`.
 ``` cpp
 basic_ios& copyfmt(const basic_ios& rhs);
@@ -1240,15 +1272,15 @@ follows:
       stored outside the object `rhs` and those objects are destroyed
       when `rhs` is destroyed, the newly stored pointer values are
       altered to point at newly constructed copies of the objects;
 3.  calls each callback pair that was copied from `rhs` as
     `(*fn)(copyfmt_event, *this, index)`;
-4.  calls `exceptions(rhs.except())`.
-*Note:* The second pass through the callback pairs permits a copied
 `pword` value to be zeroed, or to have its referent deep copied or
-reference counted, or to have other special action taken.
 *Postconditions:* The postconditions of this function are indicated in
 Table  [[tab:iostreams.copyfmt.effects]].
 **Table: `basic_ios::copyfmt()` effects** <a id="tab:iostreams.copyfmt.effects">[tab:iostreams.copyfmt.effects]</a>
@@ -1323,16 +1355,16 @@ iostate rdstate() const;
 ``` cpp
 void clear(iostate state = goodbit);
 ```
-If `rdbuf()!=0` then `state == rdstate()`; otherwise
 `rdstate() == (state | ios_base::badbit)`.
 *Effects:* If
 `((state | (rdbuf() ? goodbit : badbit)) & exceptions()) == 0`, returns.
-Otherwise, the function throws an object `fail` of class
 `basic_ios::failure` ([[ios::failure]]), constructed with
 *implementation-defined* argument values.
 ``` cpp
 void setstate(iostate state);
@@ -1374,11 +1406,11 @@ exceptions to be thrown.
 ``` cpp
 void exceptions(iostate except);
 ```
-`except == exceptions()`.
 *Effects:* Calls `clear(rdstate())`.
 ### `ios_base` manipulators <a id="std.ios.manip">[[std.ios.manip]]</a>
@@ -1573,14 +1605,14 @@ ios_base& hexfloat(ios_base& str);
 *Effects:* Calls
 `str.setf(ios_base::fixed | ios_base::scientific, ios_base::floatfield)`.
 *Returns:* `str`.
-The more obvious use of `ios_base::hex` to specify hexadecimal
-floating-point format would change the meaning of existing well defined
-programs. C++2003 gives no meaning to the combination of `fixed` and
-`scientific`.
 ``` cpp
 ios_base& defaultfloat(ios_base& str);
 ```
@@ -1614,18 +1646,18 @@ functions shall behave as specified for the class `error_category`. The
 object’s `name` virtual function shall return a pointer to the string
 `"iostream"`.
 ## Stream buffers <a id="stream.buffers">[[stream.buffers]]</a>
-### Overview <a id="stream.buffers.overview">[[stream.buffers.overview]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
     class basic_streambuf;
- typedef basic_streambuf<char>     streambuf;
- typedef basic_streambuf<wchar_t> wstreambuf;
 }
 ```
 The header `<streambuf>` defines types that control input from and
 output to *character* sequences.
@@ -1679,123 +1711,121 @@ above:
 - If `xnext` is not a null pointer and `xnext < xend` for an input
   sequence, then a *read position* is available. In this case, `*xnext`
   shall have a defined value and is the next element to read (to get, or
   to obtain a character value, from the sequence).
-### Class template `basic_streambuf<charT,traits>` <a id="streambuf">[[streambuf]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_streambuf {
   public:
- // types:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
-    typedef typename traits::off_type off_type;
-    typedef traits                    traits_type;
     virtual ~basic_streambuf();
-    // [streambuf.locales] locales:
     locale   pubimbue(const locale& loc);
     locale   getloc() const;
-    // [streambuf.buffer] buffer and positioning:
-    basic_streambuf<char_type,traits>*
-       pubsetbuf(char_type* s, streamsize n);
     pos_type pubseekoff(off_type off, ios_base::seekdir way,
- ios_base::openmode which =
- ios_base::in | ios_base::out);
     pos_type pubseekpos(pos_type sp,
- ios_base::openmode which =
- ios_base::in | ios_base::out);
     int      pubsync();
-    // Get and put areas:
-    // [streambuf.pub.get] Get area:
     streamsize in_avail();
     int_type snextc();
     int_type sbumpc();
     int_type sgetc();
     streamsize sgetn(char_type* s, streamsize n);
-    // [streambuf.pub.pback] Putback:
     int_type sputbackc(char_type c);
     int_type sungetc();
-    // [streambuf.pub.put] Put area:
     int_type   sputc(char_type c);
     streamsize sputn(const char_type* s, streamsize n);
   protected:
     basic_streambuf();
     basic_streambuf(const basic_streambuf& rhs);
     basic_streambuf& operator=(const basic_streambuf& rhs);
     void swap(basic_streambuf& rhs);
-    // [streambuf.get.area] Get area:
     char_type* eback() const;
     char_type* gptr()  const;
     char_type* egptr() const;
     void       gbump(int n);
     void       setg(char_type* gbeg, char_type* gnext, char_type* gend);
-    // [streambuf.put.area] Put area:
     char_type* pbase() const;
     char_type* pptr() const;
     char_type* epptr() const;
     void       pbump(int n);
     void       setp(char_type* pbeg, char_type* pend);
-    // [streambuf.virtuals] virtual functions:
-    // [streambuf.virt.locales] Locales:
     virtual void imbue(const locale& loc);
-    // [streambuf.virt.buffer] Buffer management and positioning:
-    virtual basic_streambuf<char_type,traits>*
-         setbuf(char_type* s, streamsize n);
     virtual pos_type seekoff(off_type off, ios_base::seekdir way,
- ios_base::openmode which = ios_base::in | ios_base::out);
     virtual pos_type seekpos(pos_type sp,
- ios_base::openmode which = ios_base::in | ios_base::out);
     virtual int      sync();
-    // [streambuf.virt.get] Get area:
     virtual streamsize showmanyc();
     virtual streamsize xsgetn(char_type* s, streamsize n);
     virtual int_type   underflow();
     virtual int_type   uflow();
-    // [streambuf.virt.pback] Putback:
     virtual int_type   pbackfail(int_type c = traits::eof());
-    // [streambuf.virt.put] Put area:
     virtual streamsize xsputn(const char_type* s, streamsize n);
     virtual int_type   overflow(int_type c = traits::eof());
   };
 }
 ```
-The class template `basic_streambuf<charT,traits>` serves as an abstract
-base class for deriving various *stream buffers* whose objects each
-control two *character sequences*:
 - a character *input sequence*;
 - a character *output sequence*.
 #### `basic_streambuf` constructors <a id="streambuf.cons">[[streambuf.cons]]</a>
 ``` cpp
 basic_streambuf();
 ```
-*Effects:* Constructs an object of class `basic_streambuf<charT,traits>`
-and initializes:[^13]
 - all its pointer member objects to null pointers,
 - the `getloc()` member to a copy the global locale, `locale()`, at the
   time of construction.
@@ -1831,11 +1861,11 @@ basic_streambuf(const basic_streambuf& rhs);
 ``` cpp
 locale pubimbue(const locale& loc);
 ```
-`loc == getloc()`.
 *Effects:* Calls `imbue(loc)`.
 *Returns:* Previous value of `getloc()`.
@@ -1850,25 +1880,27 @@ been called but before `pubimbue` has returned (i.e., from within the
 call of `imbue()`) then it returns the previous value.
 ##### Buffer management and positioning <a id="streambuf.buffer">[[streambuf.buffer]]</a>
 ``` cpp
-basic_streambuf<char_type,traits>* pubsetbuf(char_type* s, streamsize n);
 ```
 *Returns:* `setbuf(s, n)`.
 ``` cpp
 pos_type pubseekoff(off_type off, ios_base::seekdir way,
- ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 *Returns:* `seekoff(off, way, which)`.
 ``` cpp
 pos_type pubseekpos(pos_type sp,
- ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 *Returns:* `seekpos(sp, which)`.
 ``` cpp
@@ -1921,11 +1953,11 @@ streamsize sgetn(char_type* s, streamsize n);
 ``` cpp
 int_type sputbackc(char_type c);
 ```
 *Returns:* If the input sequence putback position is not available, or
-if `traits::eq(c,gptr()[-1])` is false, returns
 `pbackfail(traits::to_int_type(c))`. Otherwise, decrements the next
 pointer for the input sequence and returns
 `traits::to_int_type(*gptr())`.
 ``` cpp
@@ -2109,12 +2141,12 @@ int sync();
 *Effects:* Synchronizes the controlled sequences with the arrays. That
 is, if `pbase()` is non-null the characters between `pbase()` and
 `pptr()` are written to the controlled sequence. The pointers may then
 be reset as appropriate.
-*Returns:* -1 on failure. What constitutes failure is determined by each
-derived class ([[filebuf.virtuals]]).
 *Default behavior:* Returns zero.
 ##### Get area <a id="streambuf.virt.get">[[streambuf.virt.get]]</a>
@@ -2158,22 +2190,38 @@ function only if `gptr()` is null or `gptr() >= egptr()`
 *Returns:* `traits::to_int_type(c)`, where `c` is the first *character*
 of the *pending sequence*, without moving the input sequence position
 past it. If the pending sequence is null then the function returns
 `traits::eof()` to indicate failure.
-The *pending sequence* of characters is defined as the concatenation of:
-The *result character* is
-The *backup sequence* is defined as the concatenation of:
-*Effects:* The function sets up the `gptr()` and `egptr()` satisfying
-one of:
 If `eback()` and `gptr()` are non-null then the function is not
 constrained as to their contents, but the “usual backup condition” is
-that either:
 *Default behavior:* Returns `traits::eof()`.
 ``` cpp
 int_type uflow();
@@ -2206,16 +2254,16 @@ The *pending sequence* is defined as for `underflow()`, with the
 modifications that
 - If `traits::eq_int_type(c, traits::eof())` returns `true`, then the
   input sequence is backed up one character before the pending sequence
   is determined.
-- If `traits::eq_int_type(c,traits::eof())` returns `false`, then `c` is
-  prepended. Whether the input sequence is backed up or modified in any
-  other way is unspecified.
-On return, the constraints of `gptr()`, `eback()`, and `pptr()` are the
-same as for `underflow()`.
 *Returns:* `traits::eof()` to indicate failure. Failure may occur
 because the input sequence could not be backed up, or if for some other
 reason the pointers could not be set consistent with the constraints.
 `pbackfail()` is called only when put back has really failed.
@@ -2232,13 +2280,13 @@ streamsize xsputn(const char_type* s, streamsize n);
 *Effects:* Writes up to `n` characters to the output sequence as if by
 repeated calls to `sputc(c)`. The characters written are obtained from
 successive elements of the array whose first element is designated by
 `s`. Writing stops when either `n` characters have been written or a
-call to `sputc(c)` would return `traits::eof()`. Is is unspecified
 whether the function calls `overflow()` when `pptr() == epptr()` becomes
-true or whether it achieves the same effects by other means.
 *Returns:* The number of characters written.
 ``` cpp
 int_type overflow(int_type c = traits::eof());
@@ -2246,71 +2294,92 @@ int_type overflow(int_type c = traits::eof());
 *Effects:* Consumes some initial subsequence of the characters of the
 *pending sequence*. The pending sequence is defined as the concatenation
 of
 *Remarks:* The member functions `sputc()` and `sputn()` call this
 function in case that no room can be found in the put buffer enough to
 accommodate the argument character sequence.
 *Requires:* Every overriding definition of this virtual function shall
 obey the following constraints:
 *Returns:* `traits::eof()` or throws an exception if the function fails.
 Otherwise, returns some value other than `traits::eof()` to indicate
-success.[^16]
 *Default behavior:* Returns `traits::eof()`.
 ## Formatting and manipulators <a id="iostream.format">[[iostream.format]]</a>
-### Overview <a id="iostream.format.overview">[[iostream.format.overview]]</a>
-\synopsis{Header \texttt{\<istream\>} synopsis}
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
     class basic_istream;
-  typedef basic_istream<char>     istream;
- typedef basic_istream<wchar_t> wistream;
   template <class charT, class traits = char_traits<charT>>
     class basic_iostream;
-  typedef basic_iostream<char>    iostream;
- typedef basic_iostream<wchar_t> wiostream;
   template <class charT, class traits>
     basic_istream<charT, traits>& ws(basic_istream<charT, traits>& is);
   template <class charT, class traits, class T>
-    basic_istream<charT, traits>&
-    operator>>(basic_istream<charT, traits>&& is, T& x);
 }
 ```
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
     class basic_ostream;
-  typedef basic_ostream<char>     ostream;
- typedef basic_ostream<wchar_t> wostream;
   template <class charT, class traits>
     basic_ostream<charT, traits>& endl(basic_ostream<charT, traits>& os);
   template <class charT, class traits>
     basic_ostream<charT, traits>& ends(basic_ostream<charT, traits>& os);
   template <class charT, class traits>
     basic_ostream<charT, traits>& flush(basic_ostream<charT, traits>& os);
   template <class charT, class traits, class T>
-    basic_ostream<charT, traits>&
-    operator<<(basic_ostream<charT, traits>&& os, const T& x);
 }
 ```
 ``` cpp
 namespace std {
   // types T1, T2, ... are unspecified implementation types
   T1 resetiosflags(ios_base::fmtflags mask);
   T2 setiosflags  (ios_base::fmtflags mask);
@@ -2326,15 +2395,19 @@ namespace std {
   template <class charT>
     T11 quoted(const charT* s, charT delim = charT('"'), charT escape = charT('\\'));
   template <class charT, class traits, class Allocator>
     T12 quoted(const basic_string<charT, traits, Allocator>& s,
- charT delim=charT('"'), charT escape=charT('\\'));
   template <class charT, class traits, class Allocator>
     T13 quoted(basic_string<charT, traits, Allocator>& s,
- charT delim=charT('"'), charT escape=charT('\\'));
 }
 ```
 ### Input streams <a id="input.streams">[[input.streams]]</a>
@@ -2348,30 +2421,30 @@ extracts from stream rvalues.
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_istream : virtual public basic_ios<charT, traits> {
   public:
     // types (inherited from basic_ios ([ios])):
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
-    // [istream.cons] Constructor/destructor:
     explicit basic_istream(basic_streambuf<charT, traits>* sb);
     virtual ~basic_istream();
-    // [istream::sentry] Prefix/suffix:
     class sentry;
-    // [istream.formatted] Formatted input:
-    basic_istream<charT,traits>& operator>>(
-      basic_istream<charT,traits>& (*pf)(basic_istream<charT,traits>&));
-    basic_istream<charT,traits>& operator>>(
- basic_ios<charT,traits>& (*pf)(basic_ios<charT,traits>&));
-    basic_istream<charT,traits>& operator>>(
-      ios_base& (*pf)(ios_base&));
     basic_istream<charT, traits>& operator>>(bool& n);
     basic_istream<charT, traits>& operator>>(short& n);
     basic_istream<charT, traits>& operator>>(unsigned short& n);
     basic_istream<charT, traits>& operator>>(int& n);
@@ -2383,30 +2456,25 @@ namespace std {
     basic_istream<charT, traits>& operator>>(float& f);
     basic_istream<charT, traits>& operator>>(double& f);
     basic_istream<charT, traits>& operator>>(long double& f);
     basic_istream<charT, traits>& operator>>(void*& p);
-    basic_istream<charT,traits>& operator>>(
-      basic_streambuf<char_type,traits>* sb);
-    // [istream.unformatted] Unformatted input:
     streamsize gcount() const;
     int_type get();
     basic_istream<charT, traits>& get(char_type& c);
     basic_istream<charT, traits>& get(char_type* s, streamsize n);
-    basic_istream<charT,traits>& get(char_type* s, streamsize n,
-                                     char_type delim);
     basic_istream<charT, traits>& get(basic_streambuf<char_type, traits>& sb);
-    basic_istream<charT,traits>& get(basic_streambuf<char_type,traits>& sb,
-                                    char_type delim);
     basic_istream<charT, traits>& getline(char_type* s, streamsize n);
-    basic_istream<charT,traits>& getline(char_type* s, streamsize n,
-                                         char_type delim);
-    basic_istream<charT,traits>& ignore(
-      streamsize n = 1, int_type delim = traits::eof());
     int_type                      peek();
     basic_istream<charT, traits>& read    (char_type* s, streamsize n);
     streamsize                    readsome(char_type* s, streamsize n);
     basic_istream<charT, traits>& putback(char_type c);
@@ -2416,45 +2484,40 @@ namespace std {
     pos_type tellg();
     basic_istream<charT, traits>& seekg(pos_type);
     basic_istream<charT, traits>& seekg(off_type, ios_base::seekdir);
   protected:
     basic_istream(const basic_istream& rhs) = delete;
     basic_istream(basic_istream&& rhs);
-    // [istream.assign] Assign/swap:
     basic_istream& operator=(const basic_istream& rhs) = delete;
     basic_istream& operator=(basic_istream&& rhs);
     void swap(basic_istream& rhs);
   };
-  // [istream::extractors] character extraction templates:
   template<class charT, class traits>
-    basic_istream<charT,traits>& operator>>(basic_istream<charT,traits>&,
-                                            charT&);
   template<class traits>
-    basic_istream<char,traits>& operator>>(basic_istream<char,traits>&,
-                                           unsigned char&);
   template<class traits>
-    basic_istream<char,traits>& operator>>(basic_istream<char,traits>&,
-                                           signed char&);
   template<class charT, class traits>
-    basic_istream<charT,traits>& operator>>(basic_istream<charT,traits>&,
-                                            charT*);
   template<class traits>
-    basic_istream<char,traits>& operator>>(basic_istream<char,traits>&,
-                                           unsigned char*);
   template<class traits>
-    basic_istream<char,traits>& operator>>(basic_istream<char,traits>&,
-                                           signed char*);
 }
 ```
-The class `basic_istream` defines a number of member function signatures
-that assist in reading and interpreting input from sequences controlled
-by a stream buffer.
 Two groups of member function signatures share common properties: the
 *formatted input functions* (or *extractors*) and the *unformatted input
 functions.* Both groups of input functions are described as if they
 obtain (or *extract*) input *characters* by calling `rdbuf()->sbumpc()`
@@ -2476,15 +2539,15 @@ failure indication.
 ``` cpp
 explicit basic_istream(basic_streambuf<charT, traits>* sb);
 ```
-*Effects:* Constructs an object of class `basic_istream`, assigning
-initial values to the base class by calling
 `basic_ios::init(sb)` ([[basic.ios.cons]]).
-`gcount() == 0`
 ``` cpp
 basic_istream(basic_istream&& rhs);
 ```
@@ -2505,11 +2568,11 @@ virtual ~basic_istream();
 ``` cpp
 basic_istream& operator=(basic_istream&& rhs);
 ```
-*Effects:* `swap(rhs);`.
 *Returns:* `*this`.
 ``` cpp
 void swap(basic_istream& rhs);
@@ -2522,11 +2585,11 @@ values returned by `gcount()` and `rhs.gcount()`.
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_istream<charT, traits>::sentry {
- typedef traits traits_type;
     bool ok_; // exposition only
   public:
     explicit sentry(basic_istream<charT, traits>& is, bool noskipws = false);
     ~sentry();
     explicit operator bool() const { return ok_; }
@@ -2549,19 +2612,23 @@ Otherwise, prepares for formatted or unformatted input. First, if
 to synchronize the output sequence with any associated external C
 stream. Except that this call can be suppressed if the put area of
 `is.tie()` is empty. Further an implementation is allowed to defer the
 call to `flush` until a call of `is.rdbuf()->underflow()` occurs. If no
 such call occurs before the `sentry` object is destroyed, the call to
-`flush` may be eliminated entirely.[^17] If `noskipws` is zero and
 `is.flags() & ios_base::skipws` is nonzero, the function extracts and
 discards each character as long as the next available input character
 `c` is a whitespace character. If `is.rdbuf()->sbumpc()` or
 `is.rdbuf()->sgetc()` returns `traits::eof()`, the function calls
 `setstate(failbit | eofbit)` (which may throw `ios_base::failure`).
 *Remarks:* The constructor
-`explicit sentry(basic_istream<charT,traits>& is, bool noskipws = false)`
 uses the currently imbued locale in `is`, to determine whether the next
 input character is whitespace or not.
 To decide if the character `c` is a whitespace character, the
 constructor performs as if it executes the following code fragment:
@@ -2573,11 +2640,11 @@ if (ctype.is(ctype.space,c)!=0)
 ```
 If, after any preparation is completed, `is.good()` is `true`,
 `ok_ != false` otherwise, `ok_ == false`. During preparation, the
 constructor may call `setstate(failbit)` (which may throw
-`ios_base::failure` ([[iostate.flags]]))[^18]
 ``` cpp
 ~sentry();
 ```
@@ -2595,11 +2662,11 @@ explicit operator bool() const;
 Each formatted input function begins execution by constructing an object
 of class `sentry` with the `noskipws` (second) argument `false`. If the
 `sentry` object returns `true`, when converted to a value of type
 `bool`, the function endeavors to obtain the requested input. If an
-exception is thrown during input then `ios::badbit` is turned on[^19] in
 `*this`’s error state. If `(exceptions()&badbit) != 0` then the
 exception is rethrown. In any case, the formatted input function
 destroys the `sentry` object. If no exception has been thrown, it
 returns `*this`.
@@ -2625,32 +2692,36 @@ stream data. These extractors behave as formatted input functions (as
 described in  [[istream.formatted.reqmts]]). After a sentry object is
 constructed, the conversion occurs as if performed by the following code
 fragment:
 ``` cpp
-typedef num_get< charT,istreambuf_iterator<charT,traits> > numget;
 iostate err = iostate::goodbit;
 use_facet<numget>(loc).get(*this, 0, *this, err, val);
 setstate(err);
 ```
 In the above fragment, `loc` stands for the private member of the
-`basic_ios` class. The first argument provides an object of the
 `istreambuf_iterator` class which is an iterator pointed to an input
-stream. It bypasses istreams and uses streambufs directly. Class
-`locale` relies on this type as its interface to `istream`, so that it
-does not need to depend directly on `istream`.
 ``` cpp
 operator>>(short& val);
 ```
 The conversion occurs as if performed by the following code fragment
 (using the same notation as for the preceding code fragment):
 ``` cpp
-typedef num_get<charT,istreambuf_iterator<charT,traits> > numget;
 iostate err = ios_base::goodbit;
 long lval;
 use_facet<numget>(loc).get(*this, 0, *this, err, lval);
 if (lval < numeric_limits<short>::min()) {
   err |= ios_base::failbit;
@@ -2669,11 +2740,11 @@ operator>>(int& val);
 The conversion occurs as if performed by the following code fragment
 (using the same notation as for the preceding code fragment):
 ``` cpp
-typedef num_get<charT,istreambuf_iterator<charT,traits> > numget;
 iostate err = ios_base::goodbit;
 long lval;
 use_facet<numget>(loc).get(*this, 0, *this, err, lval);
 if (lval < numeric_limits<int>::min()) {
   err |= ios_base::failbit;
@@ -2684,54 +2755,50 @@ if (lval < numeric_limits<int>::min()) {
 }  else
   val = static_cast<int>(lval);
 setstate(err);
 ```
-##### `basic_istream::operator>>` <a id="istream::extractors">[[istream::extractors]]</a>
 ``` cpp
-basic_istream<charT,traits>& operator>>
- (basic_istream<charT,traits>& (*pf)(basic_istream<charT,traits>&));
 ```
 *Effects:* None. This extractor does not behave as a formatted input
-function (as described in  [[istream.formatted.reqmts]].)
-*Returns:* `pf(*this)`.[^20]
 ``` cpp
-basic_istream<charT,traits>& operator>>
- (basic_ios<charT,traits>& (*pf)(basic_ios<charT,traits>&));
 ```
 *Effects:* Calls `pf(*this)`. This extractor does not behave as a
 formatted input function (as described
 in  [[istream.formatted.reqmts]]).
 *Returns:* `*this`.
 ``` cpp
-basic_istream<charT,traits>& operator>>
-    (ios_base& (*pf)(ios_base&));
 ```
-*Effects:* Calls `pf(*this)`.[^21] This extractor does not behave as a
 formatted input function (as described
 in  [[istream.formatted.reqmts]]).
 *Returns:* `*this`.
 ``` cpp
 template<class charT, class traits>
-  basic_istream<charT,traits>& operator>>(basic_istream<charT,traits>& in,
-                                          charT* s);
 template<class traits>
-  basic_istream<char,traits>& operator>>(basic_istream<char,traits>& in,
-                                         unsigned char* s);
 template<class traits>
-  basic_istream<char,traits>& operator>>(basic_istream<char,traits>& in,
-                                         signed char* s);
 ```
 *Effects:* Behaves like a formatted input member (as described
 in  [[istream.formatted.reqmts]]) of `in`. After a `sentry` object is
 constructed, `operator>>` extracts characters and stores them into
@@ -2743,12 +2810,12 @@ stored.
 Characters are extracted and stored until any of the following occurs:
 - `n-1` characters are stored;
 - end of file occurs on the input sequence;
-- `ct.is(ct.space,c)` is `true` for the next available input character
-  `c`, where `ct` is `use_facet<ctype<charT> >(in.getloc())`.
 `operator>>` then stores a null byte (`charT()`) in the next position,
 which may be the first position if no characters were extracted.
 `operator>>` then calls `width(0)`.
@@ -2757,38 +2824,33 @@ which may throw `ios_base::failure` ([[iostate.flags]]).
 *Returns:* `in`.
 ``` cpp
 template<class charT, class traits>
-  basic_istream<charT,traits>& operator>>(basic_istream<charT,traits>& in,
-                                          charT& c);
 template<class traits>
-  basic_istream<char,traits>& operator>>(basic_istream<char,traits>& in,
-                                         unsigned char& c);
 template<class traits>
-  basic_istream<char,traits>& operator>>(basic_istream<char,traits>& in,
-                                         signed char& c);
 ```
 *Effects:* Behaves like a formatted input member (as described
 in  [[istream.formatted.reqmts]]) of `in`. After a `sentry` object is
 constructed a character is extracted from `in`, if one is available, and
 stored in `c`. Otherwise, the function calls `in.setstate(failbit)`.
 *Returns:* `in`.
 ``` cpp
-basic_istream<charT,traits>& operator>>
-  (basic_streambuf<charT,traits>* sb);
 ```
-*Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). If `sb` is null, calls
-`setstate(failbit)`, which may throw
-`ios_base::failure` ([[iostate.flags]]). After a sentry object is
-constructed, extracts characters from `*this` and inserts them in the
-output sequence controlled by `sb`. Characters are extracted and
 inserted until any of the following occurs:
 - end-of-file occurs on the input sequence;
 - inserting in the output sequence fails (in which case the character to
   be inserted is not extracted);
@@ -2808,18 +2870,18 @@ rethrown.
 Each unformatted input function begins execution by constructing an
 object of class `sentry` with the default argument `noskipws` (second)
 argument `true`. If the `sentry` object returns `true`, when converted
 to a value of type `bool`, the function endeavors to obtain the
 requested input. Otherwise, if the sentry constructor exits by throwing
-an exception or if the sentry object returns false, when converted to a
-value of type `bool`, the function returns without attempting to obtain
-any input. In either case the number of extracted characters is set to
-0; unformatted input functions taking a character array of non-zero size
-as an argument shall also store a null character (using `charT()`) in
-the first location of the array. If an exception is thrown during input
-then `ios::badbit` is turned on[^22] in `*this`’s error state.
-(Exceptions thrown from `basic_ios<>::clear()` are not caught or
 rethrown.) If `(exceptions()&badbit) != 0` then the exception is
 rethrown. It also counts the number of characters extracted. If no
 exception has been thrown it ends by storing the count in a member
 object and returning the value specified. In any event the `sentry`
 object is destroyed before leaving the unformatted input function.
@@ -2827,49 +2889,47 @@ object is destroyed before leaving the unformatted input function.
 ``` cpp
 streamsize gcount() const;
 ```
 *Effects:* None. This member function does not behave as an unformatted
-input function (as described in  [[istream.unformatted]], paragraph 1).
 *Returns:* The number of characters extracted by the last unformatted
 input member function called for the object.
 ``` cpp
 int_type get();
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, extracts a character `c`, if one is available. Otherwise, the
-function calls `setstate(failbit)`, which may throw
-`ios_base::failure` ([[iostate.flags]]),
 *Returns:* `c` if available, otherwise `traits::eof()`.
 ``` cpp
 basic_istream<charT, traits>& get(char_type& c);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, extracts a character, if one is available, and assigns it to
-`c`.[^23] Otherwise, the function calls `setstate(failbit)` (which may
-throw `ios_base::failure` ([[iostate.flags]])).
 *Returns:* `*this`.
 ``` cpp
-basic_istream<charT,traits>& get(char_type* s, streamsize n,
-                  char_type delim );
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, extracts characters and stores them into successive locations of
-an array whose first element is designated by `s`.[^24] Characters are
-extracted and stored until any of the following occurs:
 - `n` is less than one or `n - 1` characters are stored;
 - end-of-file occurs on the input sequence (in which case the function
   calls `setstate(eofbit)`);
 - `traits::eq(c, delim)` for the next available input character `c` (in
@@ -2884,24 +2944,22 @@ next successive location of the array.
 ``` cpp
 basic_istream<charT, traits>& get(char_type* s, streamsize n);
 ```
-*Effects:* Calls `get(s,n,widen(’\n’))`
 *Returns:* Value returned by the call.
 ``` cpp
-basic_istream<charT,traits>& get(basic_streambuf<char_type,traits>& sb,
-                  char_type delim );
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, extracts characters and inserts them in the output sequence
-controlled by `sb`. Characters are extracted and inserted until any of
-the following occurs:
 - end-of-file occurs on the input sequence;
 - inserting in the output sequence fails (in which case the character to
   be inserted is not extracted);
 - `traits::eq(c, delim)` for the next available input character `c` (in
@@ -2916,44 +2974,45 @@ which may throw `ios_base::failure` ([[iostate.flags]]).
 ``` cpp
 basic_istream<charT, traits>& get(basic_streambuf<char_type, traits>& sb);
 ```
-*Effects:* Calls `get(sb, widen(’\n’))`
 *Returns:* Value returned by the call.
 ``` cpp
-basic_istream<charT,traits>& getline(char_type* s, streamsize n,
-                      char_type delim);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, extracts characters and stores them into successive locations of
-an array whose first element is designated by `s`.[^25] Characters are
-extracted and stored until one of the following occurs:
 1.  end-of-file occurs on the input sequence (in which case the function
     calls `setstate(eofbit)`);
 2.  `traits::eq(c, delim)` for the next available input character `c`
     (in which case the input character is extracted but not
-    stored);[^26]
 3.  `n` is less than one or `n - 1` characters are stored (in which case
     the function calls `setstate(failbit)`).
-These conditions are tested in the order shown.[^27]
 If the function extracts no characters, it calls `setstate(failbit)`
-(which may throw `ios_base::failure` ([[iostate.flags]])).[^28]
 In any case, if `n` is greater than zero, it then stores a null
 character (using `charT()`) into the next successive location of the
 array.
 *Returns:* `*this`.
 ``` cpp
 #include <iostream>
 int main() {
   using namespace std;
@@ -2975,27 +3034,28 @@ int main() {
     cout << " (" << count << " chars): " << buffer << endl;
   }
 }
 ```
 ``` cpp
 basic_istream<charT, traits>& getline(char_type* s, streamsize n);
 ```
 *Returns:* `getline(s, n, widen(’\n’))`
 ``` cpp
-basic_istream<charT,traits>&
-    ignore(streamsize n = 1, int_type delim = traits::eof());
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, extracts characters and discards them. Characters are extracted
-until any of the following occurs:
-- `n != numeric_limits<streamsize>::max()` ([[limits]]) and `n`
   characters have been extracted so far
 - end-of-file occurs on the input sequence (in which case the function
   calls `setstate(eofbit)`, which may throw
   `ios_base::failure` ([[iostate.flags]]));
 - `traits::eq_int_type(traits::to_int_type(c), delim)` for the next
@@ -3009,27 +3069,26 @@ until any of the following occurs:
 ``` cpp
 int_type peek();
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, reads but does not extract the current input character.
 *Returns:* `traits::eof()` if `good()` is `false`. Otherwise, returns
 `rdbuf()->sgetc()`.
 ``` cpp
 basic_istream<charT, traits>& read(char_type* s, streamsize n);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, if `!good()` calls `setstate(failbit)` which may throw an
-exception, and return. Otherwise extracts characters and stores them
-into successive locations of an array whose first element is designated
-by `s`.[^29] Characters are extracted and stored until either of the
-following occurs:
 - `n` characters are stored;
 - end-of-file occurs on the input sequence (in which case the function
   calls `setstate(failbit | eofbit)`, which may throw
   `ios_base::failure` ([[iostate.flags]])).
@@ -3039,17 +3098,16 @@ following occurs:
 ``` cpp
 streamsize readsome(char_type* s, streamsize n);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1). After constructing a sentry
-object, if `!good()` calls `setstate(failbit)` which may throw an
-exception, and return. Otherwise extracts characters and stores them
-into successive locations of an array whose first element is designated
-by `s`. If `rdbuf()->in_avail() == -1`, calls `setstate(eofbit)` (which
-may throw `ios_base::failure` ([[iostate.flags]])), and extracts no
-characters;
 - If `rdbuf()->in_avail() == 0`, extracts no characters
 - If `rdbuf()->in_avail() > 0`, extracts `min(rdbuf()->in_avail(), n))`.
 *Returns:* The number of characters extracted.
@@ -3057,86 +3115,87 @@ characters;
 ``` cpp
 basic_istream<charT, traits>& putback(char_type c);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that the function
-first clears `eofbit`. After constructing a sentry object, if `!good()`
-calls `setstate(failbit)` which may throw an exception, and return. If
-`rdbuf()` is not null, calls `rdbuf->sputbackc()`. If `rdbuf()` is null,
-or if `sputbackc()` returns `traits::eof()`, calls `setstate(badbit)`
-(which may throw `ios_base::failure` ([[iostate.flags]])). This
-function extracts no characters, so the value returned by the next call
-to `gcount()` is 0.
 *Returns:* `*this`.
 ``` cpp
 basic_istream<charT, traits>& unget();
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that the function
-first clears `eofbit`. After constructing a sentry object, if `!good()`
-calls `setstate(failbit)` which may throw an exception, and return. If
-`rdbuf()` is not null, calls `rdbuf()->sungetc()`. If `rdbuf()` is null,
-or if `sungetc()` returns `traits::eof()`, calls `setstate(badbit)`
-(which may throw `ios_base::failure` ([[iostate.flags]])). This
-function extracts no characters, so the value returned by the next call
-to `gcount()` is 0.
 *Returns:* `*this`.
 ``` cpp
 int sync();
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that it does not count
-the number of characters extracted and does not affect the value
-returned by subsequent calls to `gcount()`. After constructing a sentry
-object, if `rdbuf()` is a null pointer, returns -1 . Otherwise, calls
-`rdbuf()->pubsync()` and, if that function returns -1 calls
-`setstate(badbit)` (which may throw
 `ios_base::failure` ([[iostate.flags]]), and returns `-1`. Otherwise,
 returns zero.
 ``` cpp
 pos_type tellg();
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that it does not count
-the number of characters extracted and does not affect the value
-returned by subsequent calls to `gcount()`.
 *Returns:* After constructing a sentry object, if `fail() != false`,
 returns `pos_type(-1)` to indicate failure. Otherwise, returns
 `rdbuf()->pubseekoff(0, cur, in)`.
 ``` cpp
 basic_istream<charT, traits>& seekg(pos_type pos);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that the function
-first clears `eofbit`, it does not count the number of characters
-extracted, and it does not affect the value returned by subsequent calls
-to `gcount()`. After constructing a sentry object, if `fail() != true`,
-executes `rdbuf()->pubseekpos(pos, ios_base::in)`. In case of failure,
-the function calls `setstate(failbit)` (which may throw
 `ios_base::failure`).
 *Returns:* `*this`.
 ``` cpp
 basic_istream<charT, traits>& seekg(off_type off, ios_base::seekdir dir);
 ```
 *Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that it does not count
-the number of characters extracted and does not affect the value
 returned by subsequent calls to `gcount()`. After constructing a sentry
 object, if `fail() != true`, executes
 `rdbuf()->pubseekoff(off, dir, ios_base::in)`. In case of failure, the
 function calls `setstate(failbit)` (which may throw
 `ios_base::failure`).
@@ -3144,77 +3203,94 @@ function calls `setstate(failbit)` (which may throw
 *Returns:* `*this`.
 #### Standard `basic_istream` manipulators <a id="istream.manip">[[istream.manip]]</a>
 ``` cpp
-namespace std {
 template <class charT, class traits>
   basic_istream<charT, traits>& ws(basic_istream<charT, traits>& is);
-}
 ```
-*Effects:* Behaves as an unformatted input function (as described
-in  [[istream.unformatted]], paragraph 1), except that it does not count
-the number of characters extracted and does not affect the value
-returned by subsequent calls to is.gcount(). After constructing a sentry
-object extracts characters as long as the next available character `c`
-is whitespace or until there are no more characters in the sequence.
 Whitespace characters are distinguished with the same criterion as used
 by `sentry::sentry` ([[istream::sentry]]). If `ws` stops extracting
 characters because there are no more available it sets `eofbit`, but not
 `failbit`.
 *Returns:* `is`.
 #### Class template `basic_iostream` <a id="iostreamclass">[[iostreamclass]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
-  class basic_iostream :
-    public basic_istream<charT,traits>,
       public basic_ostream<charT, traits> {
   public:
- // types:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
-    typedef traits                    traits_type;
-    // constructor/destructor
     explicit basic_iostream(basic_streambuf<charT, traits>* sb);
     virtual ~basic_iostream();
   protected:
     basic_iostream(const basic_iostream& rhs) = delete;
     basic_iostream(basic_iostream&& rhs);
-    // assign/swap
     basic_iostream& operator=(const basic_iostream& rhs) = delete;
     basic_iostream& operator=(basic_iostream&& rhs);
     void swap(basic_iostream& rhs);
   };
 }
 ```
-The class `basic_iostream` inherits a number of functions that allow
-reading input and writing output to sequences controlled by a stream
-buffer.
 ##### `basic_iostream` constructors <a id="iostream.cons">[[iostream.cons]]</a>
 ``` cpp
 explicit basic_iostream(basic_streambuf<charT, traits>* sb);
 ```
-*Effects:* Constructs an object of class `basic_iostream`, assigning
-initial values to the base classes by calling
 `basic_istream<charT, traits>(sb)` ([[istream]]) and
-`basic_ostream<charT,traits>(sb)` ([[ostream]])
-`rdbuf()==sb` and `gcount()==0`.
 ``` cpp
 basic_iostream(basic_iostream&& rhs);
 ```
@@ -3235,30 +3311,18 @@ virtual ~basic_iostream();
 ``` cpp
 basic_iostream& operator=(basic_iostream&& rhs);
 ```
-*Effects:* `swap(rhs)`.
 ``` cpp
 void swap(basic_iostream& rhs);
 ```
 *Effects:* Calls `basic_istream<charT, traits>::swap(rhs)`.
-#### Rvalue stream extraction <a id="istream.rvalue">[[istream.rvalue]]</a>
-``` cpp
-template <class charT, class traits, class T>
-  basic_istream<charT, traits>&
-  operator>>(basic_istream<charT, traits>&& is, T& x);
-```
-*Effects:* `is >>x`
-*Returns:* `is`
 ### Output streams <a id="output.streams">[[output.streams]]</a>
 The header `<ostream>` defines a type and several function signatures
 that control output to a stream buffer along with a function template
 that inserts into stream rvalues.
@@ -3269,30 +3333,30 @@ that inserts into stream rvalues.
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ostream : virtual public basic_ios<charT, traits> {
   public:
     // types (inherited from basic_ios ([ios])):
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
-    // [ostream.cons] Constructor/destructor:
     explicit basic_ostream(basic_streambuf<char_type, traits>* sb);
     virtual ~basic_ostream();
-    // [ostream::sentry] Prefix/suffix:
     class sentry;
-    // [ostream.formatted] Formatted output:
-    basic_ostream<charT,traits>& operator<<(
-      basic_ostream<charT,traits>& (*pf)(basic_ostream<charT,traits>&));
-    basic_ostream<charT,traits>& operator<<(
-      basic_ios<charT,traits>& (*pf)(basic_ios<charT,traits>&));
-    basic_ostream<charT,traits>& operator<<(
-      ios_base& (*pf)(ios_base&));
     basic_ostream<charT, traits>& operator<<(bool n);
     basic_ostream<charT, traits>& operator<<(short n);
     basic_ostream<charT, traits>& operator<<(unsigned short n);
     basic_ostream<charT, traits>& operator<<(int n);
@@ -3304,75 +3368,65 @@ namespace std {
     basic_ostream<charT, traits>& operator<<(float f);
     basic_ostream<charT, traits>& operator<<(double f);
     basic_ostream<charT, traits>& operator<<(long double f);
     basic_ostream<charT, traits>& operator<<(const void* p);
-    basic_ostream<charT,traits>& operator<<(
- basic_streambuf<char_type,traits>* sb);
-    // [ostream.unformatted] Unformatted output:
     basic_ostream<charT, traits>& put(char_type c);
     basic_ostream<charT, traits>& write(const char_type* s, streamsize n);
     basic_ostream<charT, traits>& flush();
-    // [ostream.seeks] seeks:
     pos_type tellp();
     basic_ostream<charT, traits>& seekp(pos_type);
     basic_ostream<charT, traits>& seekp(off_type, ios_base::seekdir);
   protected:
     basic_ostream(const basic_ostream& rhs) = delete;
     basic_ostream(basic_ostream&& rhs);
-    // [ostream.assign] Assign/swap
     basic_ostream& operator=(const basic_ostream& rhs) = delete;
     basic_ostream& operator=(basic_ostream&& rhs);
     void swap(basic_ostream& rhs);
   };
-  // [ostream.inserters.character] character inserters
   template<class charT, class traits>
-    basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>&,
-                                            charT);
   template<class charT, class traits>
-    basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>&,
-                                            char);
   template<class traits>
-    basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>&,
-                                           char);
-  // signed and unsigned
   template<class traits>
-    basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>&,
-                                           signed char);
   template<class traits>
-    basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>&,
-                                           unsigned char);
   template<class charT, class traits>
-    basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>&,
-                                            const charT*);
   template<class charT, class traits>
-    basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>&,
-                                            const char*);
   template<class traits>
-    basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>&,
-                                           const char*);
-  // signed and unsigned
   template<class traits>
-    basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>&,
-                                           const signed char*);
   template<class traits>
-    basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>&,
-                                           const unsigned char*);
 }
 ```
-The class `basic_ostream` defines a number of member function signatures
-that assist in formatting and writing output to output sequences
-controlled by a stream buffer.
 Two groups of member function signatures share common properties: the
 *formatted output functions* (or *inserters*) and the *unformatted
 output functions.* Both groups of output functions generate (or
 *insert*) output *characters* by actions equivalent to calling
@@ -3384,45 +3438,55 @@ If one of these called functions throws an exception, then unless
 explicitly noted otherwise the output function sets `badbit` in error
 state. If `badbit` is on in `exceptions()`, the output function rethrows
 the exception without completing its actions, otherwise it does not
 throw anything and treat as an error.
-#### `basic_ostream` constructors <a id="ostream.cons">[[ostream.cons]]</a>
 ``` cpp
 explicit basic_ostream(basic_streambuf<charT, traits>* sb);
 ```
-``` cpp
-virtual ~basic_ostream();
-```
 ``` cpp
 basic_ostream(basic_ostream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by default constructing the base class and calling
 `basic_ios<charT, traits>::move(rhs)` to initialize the base class.
-#### Class `basic_ostream` assign and swap <a id="ostream.assign">[[ostream.assign]]</a>
 ``` cpp
 basic_ostream& operator=(basic_ostream&& rhs);
 ```
-*Effects:* `swap(rhs)`.
 *Returns:* `*this`.
 ``` cpp
 void swap(basic_ostream& rhs);
 ```
 *Effects:* Calls `basic_ios<charT, traits>::swap(rhs)`.
-#### Class `basic_ostream::sentry` <a id="ostream::sentry">[[ostream::sentry]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ostream<charT, traits>::sentry {
@@ -3444,45 +3508,55 @@ exception safe prefix and suffix operations.
 ``` cpp
 explicit sentry(basic_ostream<charT, traits>& os);
 ```
 If `os.good()` is nonzero, prepares for formatted or unformatted output.
-If `os.tie()` is not a null pointer, calls `os.tie()->flush()`.[^30]
 If, after any preparation is completed, `os.good()` is `true`,
 `ok_ == true` otherwise, `ok_ == false`. During preparation, the
 constructor may call `setstate(failbit)` (which may throw
-`ios_base::failure` ([[iostate.flags]]))[^31]
 ``` cpp
 ~sentry();
 ```
 If
-`((os.flags() & ios_base::unitbuf) && !uncaught_exception() && os.good())`
 is `true`, calls `os.rdbuf()->pubsync()`. If that function returns -1,
 sets `badbit` in `os.rdstate()` without propagating an exception.
 ``` cpp
 explicit operator bool() const;
 ```
 *Effects:* Returns `ok_`.
-#### `basic_ostream` seek members <a id="ostream.seeks">[[ostream.seeks]]</a>
 Each seek member function begins execution by constructing an object of
 class `sentry`. It returns by destroying the `sentry` object.
 ``` cpp
 pos_type tellp();
 ```
 ``` cpp
 basic_ostream<charT, traits>& seekp(pos_type pos);
 ```
 ``` cpp
 basic_ostream<charT, traits>& seekp(off_type off, ios_base::seekdir dir);
 ```
 *Effects:* If `fail() != true`, executes
@@ -3500,11 +3574,11 @@ Each formatted output function begins execution by constructing an
 object of class `sentry`. If this object returns `true` when converted
 to a value of type `bool`, the function endeavors to generate the
 requested output. If the generation fails, then the formatted output
 function does `setstate(ios_base::failbit)`, which might throw an
 exception. If an exception is thrown during output, then `ios::badbit`
-is turned on[^32] in `*this`’s error state. If
 `(exceptions()&badbit) != 0` then the exception is rethrown. Whether or
 not an exception is thrown, the `sentry` object is destroyed before
 leaving the formatted output function. If no exception is thrown, the
 result of the formatted output function is `*this`.
@@ -3601,59 +3675,57 @@ bool failed = use_facet<
 The first argument provides an object of the `ostreambuf_iterator<>`
 class which is an iterator for class `basic_ostream<>`. It bypasses
 `ostream`s and uses `streambuf`s directly. Class `locale` relies on
 these types as its interface to iostreams, since for flexibility it has
 been abstracted away from direct dependence on `ostream`. The second
-parameter is a reference to the base subobject of type `ios_base`. It
-provides formatting specifications such as field width, and a locale
 from which to obtain other facets. If `failed` is `true` then does
 `setstate(badbit)`, which may throw an exception, and returns.
 *Returns:* `*this`.
 ##### `basic_ostream::operator<<` <a id="ostream.inserters">[[ostream.inserters]]</a>
 ``` cpp
-basic_ostream<charT,traits>& operator<<
- (basic_ostream<charT,traits>& (*pf)(basic_ostream<charT,traits>&));
 ```
 *Effects:* None. Does not behave as a formatted output function (as
 described in  [[ostream.formatted.reqmts]]).
-*Returns:* `pf(*this)`.[^33]
 ``` cpp
-basic_ostream<charT,traits>& operator<<
- (basic_ios<charT,traits>& (*pf)(basic_ios<charT,traits>&));
 ```
 *Effects:* Calls `pf(*this)`. This inserter does not behave as a
 formatted output function (as described
 in  [[ostream.formatted.reqmts]]).
-*Returns:* `*this`.[^34]
 ``` cpp
-basic_ostream<charT,traits>& operator<<
-    (ios_base& (*pf)(ios_base&));
 ```
 *Effects:* Calls `pf(*this)`. This inserter does not behave as a
 formatted output function (as described
 in  [[ostream.formatted.reqmts]]).
 *Returns:* `*this`.
 ``` cpp
-basic_ostream<charT,traits>& operator<<
-    (basic_streambuf<charT,traits>* sb);
 ```
-*Effects:* Behaves as an unformatted output function (as described
-in  [[ostream.unformatted]], paragraph 1). After the sentry object is
-constructed, if `sb` is null calls `setstate(badbit)` (which may throw
 `ios_base::failure`).
 Gets characters from `sb` and inserts them in `*this`. Characters are
 read from `sb` and inserted until any of the following occurs:
@@ -3668,55 +3740,58 @@ exception was thrown while extracting a character, the function sets
 `failbit` in error state, and if `failbit` is on in `exceptions()` the
 caught exception is rethrown.
 *Returns:* `*this`.
 ##### Character inserter function templates <a id="ostream.inserters.character">[[ostream.inserters.character]]</a>
 ``` cpp
 template<class charT, class traits>
-  basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>& out,
-                                          charT c);
 template<class charT, class traits>
-  basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>& out,
-                                          char c);
 // specialization
 template<class traits>
-  basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>& out,
-                                         char c);
 // signed and unsigned
 template<class traits>
-  basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>& out,
-                                         signed char c);
 template<class traits>
-  basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>& out,
-                                         unsigned char c);
 ```
-*Effects:* Behaves as a formatted output function
-(  [[ostream.formatted.reqmts]]) of `out`. Constructs a character
-sequence `seq`. If `c` has type `char` and the character type of the
-stream is not `char`, then `seq` consists of `out.widen(c)`; otherwise
-`seq` consists of `c`. Determines padding for `seq` as described
-in  [[ostream.formatted.reqmts]]. Inserts `seq` into `out`. Calls
-`os.width(0)`.
 *Returns:* `out`.
 ``` cpp
 template<class charT, class traits>
-  basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>& out,
-                                          const charT* s);
 template<class charT, class traits>
-  basic_ostream<charT,traits>& operator<<(basic_ostream<charT,traits>& out,
-                                          const char* s);
 template<class traits>
-  basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>& out,
-                                         const char* s);
 template<class traits>
-  basic_ostream<char,traits>& operator<<(basic_ostream<char,traits>& out,
-                                         const signed char* s);
 template<class traits>
   basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out,
                                           const unsigned char* s);
 ```
@@ -3731,11 +3806,11 @@ would be computed as if by:
 - `traits::length(s)` for the overload where the first argument is of
   type `basic_ostream<charT, traits>&` and the second is of type
   `const charT*`, and also for the overload where the first argument is
   of type `basic_ostream<char, traits>&` and the second is of type
   `const char*`,
-- `std::char_traits<char>::length(s)` for the overload where the first
   argument is of type `basic_ostream<charT, traits>&` and the second is
   of type `const char*`,
 - `traits::length(reinterpret_cast<const char*>(s))` for the other two
   overloads.
@@ -3749,23 +3824,23 @@ in  [[ostream.formatted.reqmts]]. Inserts `seq` into `out`. Calls
 Each unformatted output function begins execution by constructing an
 object of class `sentry`. If this object returns `true`, while
 converting to a value of type `bool`, the function endeavors to generate
 the requested output. If an exception is thrown during output, then
-`ios::badbit` is turned on[^35] in `*this`’s error state. If
 `(exceptions() & badbit) != 0` then the exception is rethrown. In any
 case, the unformatted output function ends by destroying the sentry
 object, then, if no exception was thrown, returning the value specified
 for the unformatted output function.
 ``` cpp
 basic_ostream<charT, traits>& put(char_type c);
 ```
 *Effects:* Behaves as an unformatted output function (as described
-in  [[ostream.unformatted]], paragraph 1). After constructing a sentry
-object, inserts the character `c`, if possible.[^36]
 Otherwise, calls `setstate(badbit)` (which may throw
 `ios_base::failure` ([[iostate.flags]])).
 *Returns:* `*this`.
@@ -3773,14 +3848,14 @@ Otherwise, calls `setstate(badbit)` (which may throw
 ``` cpp
 basic_ostream& write(const char_type* s, streamsize n);
 ```
 *Effects:* Behaves as an unformatted output function (as described
-in  [[ostream.unformatted]], paragraph 1). After constructing a sentry
-object, obtains characters to insert from successive locations of an
-array whose first element is designated by `s`.[^37] Characters are
-inserted until either of the following occurs:
 - `n` characters are inserted;
 - inserting in the output sequence fails (in which case the function
   calls `setstate(badbit)`, which may throw
   `ios_base::failure` ([[iostate.flags]])).
@@ -3790,67 +3865,62 @@ inserted until either of the following occurs:
 ``` cpp
 basic_ostream& flush();
 ```
 *Effects:* Behaves as an unformatted output function (as described
-in  [[ostream.formatted.reqmts]], paragraph 1). If `rdbuf()` is not a
-null pointer, constructs a sentry object. If this object returns `true`
-when converted to a value of type `bool` the function calls
-`rdbuf()->pubsync()`. If that function returns -1 calls
-`setstate(badbit)` (which may throw
 `ios_base::failure` ([[iostate.flags]])). Otherwise, if the sentry
 object returns `false`, does nothing.
 *Returns:* `*this`.
 #### Standard `basic_ostream` manipulators <a id="ostream.manip">[[ostream.manip]]</a>
 ``` cpp
-namespace std {
 template <class charT, class traits>
   basic_ostream<charT, traits>& endl(basic_ostream<charT, traits>& os);
-}
 ```
 *Effects:* Calls `os.put(os.widen(’\n’))`, then `os.flush()`.
 *Returns:* `os`.
 ``` cpp
-namespace std {
 template <class charT, class traits>
   basic_ostream<charT, traits>& ends(basic_ostream<charT, traits>& os);
-}
 ```
 *Effects:* Inserts a null character into the output sequence: calls
 `os.put(charT())`.
 *Returns:* `os`.
 ``` cpp
-namespace std {
 template <class charT, class traits>
   basic_ostream<charT, traits>& flush(basic_ostream<charT, traits>& os);
-}
 ```
 *Effects:* Calls `os.flush()`.
 *Returns:* `os`.
 #### Rvalue stream insertion <a id="ostream.rvalue">[[ostream.rvalue]]</a>
 ``` cpp
 template <class charT, class traits, class T>
-  basic_ostream<charT, traits>&
-  operator<<(basic_ostream<charT, traits>&& os, const T& x);
 ```
-*Effects:* `os << x`
-*Returns:* `os`
 ### Standard manipulators <a id="std.manip">[[std.manip]]</a>
 The header `<iomanip>` defines several functions that support extractors
 and inserters that alter information maintained by class `ios_base` and
@@ -3860,59 +3930,59 @@ its derived classes.
 unspecified resetiosflags(ios_base::fmtflags mask);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
-`out << resetiosflags(mask)` behaves as if it called `f(out, mask)`, or
 if `in` is an object of type `basic_istream<charT, traits>` then the
-expression `in >> resetiosflags(mask)` behaves as if it called
-`f(in, mask)`, where the function `f` is defined as:[^38]
 ``` cpp
 void f(ios_base& str, ios_base::fmtflags mask) {
   // reset specified flags
   str.setf(ios_base::fmtflags(0), mask);
 }
 ```
-The expression `out << resetiosflags(mask)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
-`in >> resetiosflags(mask)` shall have type
 `basic_istream<charT, traits>&` and value `in`.
 ``` cpp
 unspecified setiosflags(ios_base::fmtflags mask);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
-`out << setiosflags(mask)` behaves as if it called `f(out, mask)`, or if
 `in` is an object of type `basic_istream<charT, traits>` then the
-expression `in >> setiosflags(mask)` behaves as if it called
 `f(in, mask)`, where the function `f` is defined as:
 ``` cpp
 void f(ios_base& str, ios_base::fmtflags mask) {
   // set specified flags
   str.setf(mask);
 }
 ```
-The expression `out << setiosflags(mask)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
-`in >> setiosflags(mask)` shall have type `basic_istream<charT,`
 `traits>&` and value `in`.
 ``` cpp
 unspecified setbase(int base);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
-`out << setbase(base)` behaves as if it called `f(out, base)`, or if
 `in` is an object of type `basic_istream<charT, traits>` then the
-expression `in >> setbase(base)` behaves as if it called `f(in, base)`,
 where the function `f` is defined as:
 ``` cpp
 void f(ios_base& str, int base) {
   // set basefield
@@ -3921,79 +3991,79 @@ void f(ios_base& str, int base) {
       base == 16 ? ios_base::hex :
       ios_base::fmtflags(0), ios_base::basefield);
 }
 ```
-The expression `out << setbase(base)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
-`in >> setbase(base)` shall have type `basic_istream<charT, traits>&`
 and value `in`.
 ``` cpp
 unspecified setfill(char_type c);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` and `c` has type `charT` then the
-expression `out << setfill(c)` behaves as if it called `f(out, c)`,
 where the function `f` is defined as:
 ``` cpp
 template<class charT, class traits>
 void f(basic_ios<charT, traits>& str, charT c) {
   // set fill character
   str.fill(c);
 }
 ```
-The expression `out << setfill(c)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ``` cpp
 unspecified setprecision(int n);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
-`out << setprecision(n)` behaves as if it called `f(out, n)`, or if `in`
 is an object of type `basic_istream<charT, traits>` then the expression
-`in >> setprecision(n)` behaves as if it called `f(in, n)`, where the
 function `f` is defined as:
 ``` cpp
 void f(ios_base& str, int n) {
   // set precision
   str.precision(n);
 }
 ```
-The expression `out << setprecision(n)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
-`in >> setprecision(n)` shall have type `basic_istream<charT, traits>&`
 and value `in`.
 ``` cpp
 unspecified setw(int n);
 ```
 *Returns:* An object of unspecified type such that if `out` is an
 instance of `basic_ostream<charT, traits>` then the expression
-`out << setw(n)` behaves as if it called `f(out, n)`, or if `in` is an
 object of type `basic_istream<charT, traits>` then the expression
-`in >> setw(n)` behaves as if it called `f(in, n)`, where the function
 `f` is defined as:
 ``` cpp
 void f(ios_base& str, int n) {
   // set width
   str.width(n);
 }
 ```
-The expression `out << setw(n)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
-`in >> setw(n)` shall have type `basic_istream<charT, traits>&` and
 value `in`.
 ### Extended manipulators <a id="ext.manip">[[ext.manip]]</a>
 The header `<iomanip>` defines several functions that support extractors
@@ -4010,18 +4080,18 @@ specialization of the `basic_string` template (Clause  [[strings]]).
 *Effects:* The expression `in >> get_money(mon, intl)` described below
 behaves as a formatted input function ([[istream.formatted.reqmts]]).
 *Returns:* An object of unspecified type such that if `in` is an object
 of type `basic_istream<charT, traits>` then the expression
-`in >> get_money(mon, intl)` behaves as if it called `f(in, mon, intl)`,
 where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits, class moneyT>
 void f(basic_ios<charT, traits>& str, moneyT& mon, bool intl) {
- typedef istreambuf_iterator<charT, traits> Iter;
- typedef money_get<charT, Iter> MoneyGet;
   ios_base::iostate err = ios_base::goodbit;
   const MoneyGet& mg = use_facet<MoneyGet>(str.getloc());
   mg.get(Iter(str.rdbuf()), Iter(), intl, str, err, mon);
@@ -4029,11 +4099,11 @@ void f(basic_ios<charT, traits>& str, moneyT& mon, bool intl) {
   if (ios_base::goodbit != err)
     str.setstate(err);
 }
 ```
-The expression `in >> get_money(mon, intl)` shall have type
 `basic_istream<charT, traits>&` and value `in`.
 ``` cpp
 template <class moneyT> unspecified put_money(const moneyT& mon, bool intl = false);
 ```
@@ -4041,62 +4111,63 @@ template <class moneyT> unspecified put_money(const moneyT& mon, bool intl = fal
 *Requires:* The type `moneyT` shall be either `long double` or a
 specialization of the `basic_string` template (Clause  [[strings]]).
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
-`out << put_money(mon, intl)` behaves as a formatted input function that
-calls `f(out, mon, intl)`, where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits, class moneyT>
 void f(basic_ios<charT, traits>& str, const moneyT& mon, bool intl) {
- typedef ostreambuf_iterator<charT, traits> Iter;
- typedef money_put<charT, Iter> MoneyPut;
   const MoneyPut& mp = use_facet<MoneyPut>(str.getloc());
   const Iter end = mp.put(Iter(str.rdbuf()), intl, str, str.fill(), mon);
   if (end.failed())
     str.setstate(ios::badbit);
 }
 ```
-The expression `out << put_money(mon, intl)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ``` cpp
 template <class charT> unspecified get_time(struct tm* tmb, const charT* fmt);
 ```
 *Requires:* The argument `tmb` shall be a valid pointer to an object of
-type `struct tm`, and the argument `fmt` shall be a valid pointer to an
 array of objects of type `charT` with `char_traits<charT>::length(fmt)`
 elements.
 *Returns:* An object of unspecified type such that if `in` is an object
 of type `basic_istream<charT, traits>` then the expression
-`in >> get_time(tmb, fmt)` behaves as if it called `f(in, tmb, fmt)`,
 where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits>
 void f(basic_ios<charT, traits>& str, struct tm* tmb, const charT* fmt) {
- typedef istreambuf_iterator<charT, traits> Iter;
- typedef time_get<charT, Iter> TimeGet;
   ios_base::iostate err = ios_base::goodbit;
   const TimeGet& tg = use_facet<TimeGet>(str.getloc());
   tg.get(Iter(str.rdbuf()), Iter(), str, err, tmb,
     fmt, fmt + traits::length(fmt));
   if (err != ios_base::goodbit)
-    str.setstate(err):
 }
 ```
-The expression `in >> get_time(tmb, fmt)` shall have type
 `basic_istream<charT, traits>&` and value `in`.
 ``` cpp
 template <class charT> unspecified put_time(const struct tm* tmb, const charT* fmt);
 ```
@@ -4106,51 +4177,55 @@ type `struct tm`, and the argument `fmt` shall be a valid pointer to an
 array of objects of type `charT` with `char_traits<charT>::length(fmt)`
 elements.
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
-`out << put_time(tmb, fmt)` behaves as if it called `f(out, tmb, fmt)`,
 where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits>
 void f(basic_ios<charT, traits>& str, const struct tm* tmb, const charT* fmt) {
- typedef ostreambuf_iterator<charT, traits> Iter;
- typedef time_put<charT, Iter> TimePut;
   const TimePut& tp = use_facet<TimePut>(str.getloc());
   const Iter end = tp.put(Iter(str.rdbuf()), str, str.fill(), tmb,
     fmt, fmt + traits::length(fmt));
   if (end.failed())
     str.setstate(ios_base::badbit);
 }
 ```
-The expression `out << put_time(tmb, fmt)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ### Quoted manipulators <a id="quoted.manip">[[quoted.manip]]</a>
-Quoted manipulators provide string insertion and extraction of quoted
-strings (for example, XML and CSV formats). Quoted manipulators are
-useful in ensuring that the content of a string with embedded spaces
-remains unchanged if inserted and then extracted via stream I/O.
 ``` cpp
 template <class charT>
   unspecified quoted(const charT* s, charT delim = charT('"'), charT escape = charT('\\'));
 template <class charT, class traits, class Allocator>
   unspecified quoted(const basic_string<charT, traits, Allocator>& s,
- charT delim=charT('"'), charT escape=charT('\\'));
 ```
 *Returns:* An object of unspecified type such that if `out` is an
 instance of `basic_ostream` with member type `char_type` the same as
-`charT` and with member type `traits_type`, which in the second form is
-the same as `traits`, then the expression
-`out << quoted(s, delim, escape)` behaves as a formatted output
 function ([[ostream.formatted.reqmts]]) of `out`. This forms a
 character sequence `seq`, initially consisting of the following
 elements:
 - `delim`.
@@ -4161,135 +4236,134 @@ elements:
 Let `x` be the number of elements initially in `seq`. Then padding is
 determined for `seq` as described in  [[ostream.formatted.reqmts]],
 `seq` is inserted as if by calling `out.rdbuf()->sputn(seq, n)`, where
 `n` is the larger of `out.width()` and `x`, and `out.width(0)` is
-called. The expression `out << quoted(s, delim, escape)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ``` cpp
 template <class charT, class traits, class Allocator>
   unspecified quoted(basic_string<charT, traits, Allocator>& s,
- charT delim=charT('"'), charT escape=charT('\\'));
 ```
 *Returns:* An object of unspecified type such that:
 - If `in` is an instance of `basic_istream` with member types
   `char_type` and `traits_type` the same as `charT` and `traits`,
-  respectively, then the expression `in >> quoted(s, delim, escape)`
   behaves as if it extracts the following characters from `in` using
-  `basic_istream::operator>>` ([[istream::extractors]]) which may throw
-  `ios_base::failure` ([[ios::failure]]):
   - If the first character extracted is equal to `delim`, as determined
     by `traits_type::eq`, then:
     - Turn off the `skipws` flag.
     - `s.clear()`
     - Until an unescaped `delim` character is reached or `!in`, extract
       characters from `in` and append them to `s`, except that if an
       `escape` is reached, ignore it and append the next character to
       `s`.
     - Discard the final `delim` character.
     - Restore the `skipws` flag to its original value.
-  - Otherwise, `in >> s`.
 - If `out` is an instance of `basic_ostream` with member types
   `char_type` and `traits_type` the same as `charT` and `traits`,
-  respectively, then the expression `out << quoted(s, delim, escape)`
   behaves as specified for the
   `const basic_string<charT, traits, Allocator>&` overload of the
   `quoted` function.
-The expression `in >> quoted(s, delim, escape)` shall have type
 `basic_istream<charT, traits>&` and value `in`. The expression
-`out << quoted(s, delim, escape)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ## String-based streams <a id="string.streams">[[string.streams]]</a>
-### Overview <a id="string.streams.overview">[[string.streams.overview]]</a>
 The header `<sstream>` defines four class templates and eight types that
 associate stream buffers with objects of class `basic_string`, as
 described in  [[string.classes]].
-``` cpp
-namespace std {
-  template <class charT, class traits = char_traits<charT>,
-        class Allocator = allocator<charT> >
-    class basic_stringbuf;
-  typedef basic_stringbuf<char>     stringbuf;
-  typedef basic_stringbuf<wchar_t> wstringbuf;
-  template <class charT, class traits = char_traits<charT>,
-        class Allocator = allocator<charT> >
-    class basic_istringstream;
-  typedef basic_istringstream<char>     istringstream;
-  typedef basic_istringstream<wchar_t> wistringstream;
-  template <class charT, class traits = char_traits<charT>,
-        class Allocator = allocator<charT> >
-    class basic_ostringstream;
-  typedef basic_ostringstream<char>     ostringstream;
-  typedef basic_ostringstream<wchar_t> wostringstream;
-  template <class charT, class traits = char_traits<charT>,
-        class Allocator = allocator<charT> >
-    class basic_stringstream;
-  typedef basic_stringstream<char>     stringstream;
-  typedef basic_stringstream<wchar_t> wstringstream;
-}
-```
 ### Class template `basic_stringbuf` <a id="stringbuf">[[stringbuf]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
   class basic_stringbuf : public basic_streambuf<charT, traits> {
   public:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
- typedef Allocator                 allocator_type;
-    // [stringbuf.cons] Constructors:
-    explicit basic_stringbuf(ios_base::openmode which
- = ios_base::in | ios_base::out);
-    explicit basic_stringbuf
-    (const basic_string<charT,traits,Allocator>& str,
       ios_base::openmode which = ios_base::in | ios_base::out);
     basic_stringbuf(const basic_stringbuf& rhs) = delete;
     basic_stringbuf(basic_stringbuf&& rhs);
-    // [stringbuf.assign] Assign and swap:
     basic_stringbuf& operator=(const basic_stringbuf& rhs) = delete;
     basic_stringbuf& operator=(basic_stringbuf&& rhs);
     void swap(basic_stringbuf& rhs);
-    // [stringbuf.members] Get and set:
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& s);
   protected:
-    // [stringbuf.virtuals] Overridden virtual functions:
- virtual int_type underflow();
- virtual int_type pbackfail(int_type c = traits::eof());
- virtual int_type overflow (int_type c = traits::eof());
- virtual  basic_streambuf<charT,traits>* setbuf(charT*, streamsize);
-    virtual pos_type seekoff(off_type off, ios_base::seekdir way,
                      ios_base::openmode which
- = ios_base::in | ios_base::out);
- virtual pos_type seekpos(pos_type sp,
                      ios_base::openmode which
- = ios_base::in | ios_base::out);
   private:
     ios_base::openmode mode;  // exposition only
   };
@@ -4311,22 +4385,23 @@ For the sake of exposition, the maintained data is presented here as:
   read, and `out` set if the output sequence can be written.
 #### `basic_stringbuf` constructors <a id="stringbuf.cons">[[stringbuf.cons]]</a>
 ``` cpp
-explicit basic_stringbuf(ios_base::openmode which =
- ios_base::in | ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_stringbuf`, initializing
 the base class with `basic_streambuf()` ([[streambuf.cons]]), and
 initializing `mode` with `which`.
-`str() == ""`.
 ``` cpp
-explicit basic_stringbuf(const basic_string<charT,traits,Allocator>& s,
   ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_stringbuf`, initializing
 the base class with `basic_streambuf()` ([[streambuf.cons]]), and
@@ -4381,11 +4456,11 @@ void swap(basic_stringbuf& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_stringbuf<charT, traits, Allocator>& x,
             basic_stringbuf<charT, traits, Allocator>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="stringbuf.members">[[stringbuf.members]]</a>
 ``` cpp
 basic_string<charT, traits, Allocator> str() const;
@@ -4394,11 +4469,11 @@ basic_string<charT,traits,Allocator> str() const;
 *Returns:* A `basic_string` object whose content is equal to the
 `basic_stringbuf` underlying character sequence. If the
 `basic_stringbuf` was created only in input mode, the resultant
 `basic_string` contains the character sequence in the range \[`eback()`,
 `egptr()`). If the `basic_stringbuf` was created with
-`which & ios_base::out` being true then the resultant `basic_string`
 contains the character sequence in the range \[`pbase()`, `high_mark`),
 where `high_mark` represents the position one past the highest
 initialized character in the buffer. Characters can be initialized by
 writing to the stream, by constructing the `basic_stringbuf` with a
 `basic_string`, or by calling the `str(basic_string)` member function.
@@ -4415,31 +4490,31 @@ void str(const basic_string<charT,traits,Allocator>& s);
 *Effects:* Copies the content of `s` into the `basic_stringbuf`
 underlying character sequence and initializes the input and output
 sequences according to `mode`.
-*Postconditions:* If `mode & ios_base::out` is true, `pbase()` points to
-the first underlying character and `epptr()` `>= pbase() + s.size()`
-holds; in addition, if `mode & ios_base::ate` is true,
 `pptr() == pbase() + s.size()` holds, otherwise `pptr() == pbase()` is
-true. If `mode & ios_base::in` is true, `eback()` points to the first
-underlying character, and both `gptr() == eback()` and
 `egptr() == eback() + s.size()` hold.
 #### Overridden virtual functions <a id="stringbuf.virtuals">[[stringbuf.virtuals]]</a>
 ``` cpp
-int_type underflow();
 ```
 *Returns:* If the input sequence has a read position available, returns
 `traits::to_int_type(*gptr())`. Otherwise, returns `traits::eof()`. Any
 character in the underlying buffer which has been initialized is
 considered to be part of the input sequence.
 ``` cpp
-int_type pbackfail(int_type c = traits::eof());
 ```
 *Effects:* Puts back the character designated by `c` to the input
 sequence, if possible, in one of three ways:
@@ -4458,11 +4533,11 @@ sequence, if possible, in one of three ways:
 *Remarks:* If the function can succeed in more than one of these ways,
 it is unspecified which way is chosen.
 ``` cpp
-int_type overflow(int_type c = traits::eof());
 ```
 *Effects:* Appends the character designated by `c` to the output
 sequence, if possible, in one of two ways:
@@ -4488,11 +4563,11 @@ plus at least one additional write position. If
 `egptr()` to point just past the new write position.
 ``` cpp
 pos_type seekoff(off_type off, ios_base::seekdir way,
                  ios_base::openmode which
-                   = ios_base::in | ios_base::out);
 ```
 *Effects:* Alters the stream position within one of the controlled
 sequences, if possible, as indicated in
 Table  [[tab:iostreams.seekoff.positioning]].
@@ -4520,23 +4595,24 @@ as indicated in Table  [[tab:iostreams.newoff.values]].
 | `way == ios_base::cur` | the next pointer minus the beginning pointer (`xnext - xbeg`).          |
 | `way == ios_base::end` | the high mark pointer minus the beginning pointer (`high_mark - xbeg`). |
 If `(newoff + off) < 0`, or if `newoff + off` refers to an uninitialized
-character (as defined in  [[stringbuf.members]] paragraph 1), the
-positioning operation fails. Otherwise, the function assigns
-`xbeg + newoff + off` to the next pointer `xnext`.
 *Returns:* `pos_type(newoff)`, constructed from the resultant offset
 `newoff` (of type `off_type`), that stores the resultant stream
 position, if possible. If the positioning operation fails, or if the
 constructed object cannot represent the resultant stream position, the
 return value is `pos_type(off_type(-1))`.
 ``` cpp
-pos_type seekpos(pos_type sp, ios_base::openmode which
-                   = ios_base::in | ios_base::out);
 ```
 *Effects:* Equivalent to `seekoff(off_type(sp), ios_base::beg, which)`.
 *Returns:* `sp` to indicate success, or `pos_type(off_type(-1))` to
@@ -4557,31 +4633,32 @@ effect.
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
   class basic_istringstream : public basic_istream<charT, traits> {
   public:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
- typedef Allocator                 allocator_type;
-    // [istringstream.cons] Constructors:
-    explicit basic_istringstream(ios_base::openmode which = ios_base::in);
     explicit basic_istringstream(
       const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::in);
     basic_istringstream(const basic_istringstream& rhs) = delete;
     basic_istringstream(basic_istringstream&& rhs);
-    // [istringstream.assign] Assign and swap:
     basic_istringstream& operator=(const basic_istringstream& rhs) = delete;
     basic_istringstream& operator=(basic_istringstream&& rhs);
     void swap(basic_istringstream& rhs);
-    // [istringstream.members] Members:
     basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& s);
   private:
@@ -4628,12 +4705,12 @@ explicit basic_istringstream(
 basic_istringstream(basic_istringstream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by move constructing the base class, and the contained
-`basic_stringbuf`. Next `basic_istream<charT,traits>::set_rdbuf(&sb)` is
-called to install the contained `basic_stringbuf`.
 #### Assign and swap <a id="istringstream.assign">[[istringstream.assign]]</a>
 ``` cpp
 basic_istringstream& operator=(basic_istringstream&& rhs);
@@ -4655,19 +4732,20 @@ void swap(basic_istringstream& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_istringstream<charT, traits, Allocator>& x,
             basic_istringstream<charT, traits, Allocator>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="istringstream.members">[[istringstream.members]]</a>
 ``` cpp
 basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
 ```
-*Returns:* `const_cast<basic_stringbuf<charT,traits,Allocator>*>(&sb)`.
 ``` cpp
 basic_string<charT, traits, Allocator> str() const;
 ```
@@ -4685,33 +4763,32 @@ void str(const basic_string<charT,traits,Allocator>& s);
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
   class basic_ostringstream : public basic_ostream<charT, traits> {
   public:
-    // types:
- typedef charT                     char_type;
-    typedef typename traits::int_type int_type;
-    typedef typename traits::pos_type pos_type;
-    typedef typename traits::off_type off_type;
-    typedef traits                    traits_type;
-    typedef Allocator                 allocator_type;
-    // [ostringstream.cons] Constructors/destructor:
-    explicit basic_ostringstream(ios_base::openmode which = ios_base::out);
     explicit basic_ostringstream(
       const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::out);
     basic_ostringstream(const basic_ostringstream& rhs) = delete;
     basic_ostringstream(basic_ostringstream&& rhs);
-    // [ostringstream.assign] Assign/swap:
     basic_ostringstream& operator=(const basic_ostringstream& rhs) = delete;
     basic_ostringstream& operator=(basic_ostringstream&& rhs);
     void swap(basic_ostringstream& rhs);
-    // [ostringstream.members] Members:
     basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& s);
    private:
@@ -4732,11 +4809,12 @@ the sake of exposition, the maintained data is presented here as:
 - `sb`, the `stringbuf` object.
 #### `basic_ostringstream` constructors <a id="ostringstream.cons">[[ostringstream.cons]]</a>
 ``` cpp
-explicit basic_ostringstream(ios_base::openmode which = ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_ostringstream`,
 initializing the base class with `basic_ostream(&sb)` and initializing
 `sb` with
@@ -4757,12 +4835,12 @@ explicit basic_ostringstream(
 basic_ostringstream(basic_ostringstream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by move constructing the base class, and the contained
-`basic_stringbuf`. Next `basic_ostream<charT,traits>::set_rdbuf(&sb)` is
-called to install the contained `basic_stringbuf`.
 #### Assign and swap <a id="ostringstream.assign">[[ostringstream.assign]]</a>
 ``` cpp
 basic_ostringstream& operator=(basic_ostringstream&& rhs);
@@ -4784,19 +4862,20 @@ void swap(basic_ostringstream& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_ostringstream<charT, traits, Allocator>& x,
             basic_ostringstream<charT, traits, Allocator>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="ostringstream.members">[[ostringstream.members]]</a>
 ``` cpp
 basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
 ```
-*Returns:* `const_cast<basic_stringbuf<charT,traits,Allocator>*>(&sb)`.
 ``` cpp
 basic_string<charT, traits, Allocator> str() const;
 ```
@@ -4812,37 +4891,34 @@ void str(const basic_string<charT,traits,Allocator>& s);
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
-  class basic_stringstream
-    : public basic_iostream<charT,traits> {
   public:
-    // types:
-    typedef charT                     char_type;
-    typedef typename traits::int_type int_type;
-    typedef typename traits::pos_type pos_type;
-    typedef typename traits::off_type off_type;
-    typedef traits                    traits_type;
-    typedef Allocator                 allocator_type;
-    // constructors/destructor
     explicit basic_stringstream(
       ios_base::openmode which = ios_base::out | ios_base::in);
     explicit basic_stringstream(
       const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::out | ios_base::in);
     basic_stringstream(const basic_stringstream& rhs) = delete;
     basic_stringstream(basic_stringstream&& rhs);
-    // [stringstream.assign] Assign/swap:
     basic_stringstream& operator=(const basic_stringstream& rhs) = delete;
     basic_stringstream& operator=(basic_stringstream&& rhs);
     void swap(basic_stringstream& rhs);
-    // Members:
     basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& str);
   private:
@@ -4862,11 +4938,11 @@ and writing from objects of class
 associated sequence. For the sake of exposition, the maintained data is
 presented here as
 - `sb`, the `stringbuf` object.
-#### basic_stringstream constructors <a id="stringstream.cons">[[stringstream.cons]]</a>
 ``` cpp
 explicit basic_stringstream(
   ios_base::openmode which = ios_base::out | ios_base::in);
 ```
@@ -4891,12 +4967,12 @@ explicit basic_stringstream(
 basic_stringstream(basic_stringstream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by move constructing the base class, and the contained
-`basic_stringbuf`. Next `basic_istream<charT,traits>::set_rdbuf(&sb)` is
-called to install the contained `basic_stringbuf`.
 #### Assign and swap <a id="stringstream.assign">[[stringstream.assign]]</a>
 ``` cpp
 basic_stringstream& operator=(basic_stringstream&& rhs);
@@ -4918,11 +4994,11 @@ void swap(basic_stringstream& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_stringstream<charT, traits, Allocator>& x,
             basic_stringstream<charT, traits, Allocator>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="stringstream.members">[[stringstream.members]]</a>
 ``` cpp
 basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
@@ -4942,96 +5018,106 @@ void str(const basic_string<charT,traits,Allocator>& str);
 *Effects:* Calls `rdbuf()->str(str)`.
 ## File-based streams <a id="file.streams">[[file.streams]]</a>
-### File streams <a id="fstreams">[[fstreams]]</a>
 The header `<fstream>` defines four class templates and eight types that
 associate stream buffers with files and assist reading and writing
 files.
-``` cpp
-namespace std {
-  template <class charT, class traits = char_traits<charT> >
-    class basic_filebuf;
-  typedef basic_filebuf<char>    filebuf;
-  typedef basic_filebuf<wchar_t> wfilebuf;
-  template <class charT, class traits = char_traits<charT> >
-    class basic_ifstream;
-  typedef basic_ifstream<char>    ifstream;
-  typedef basic_ifstream<wchar_t> wifstream;
-  template <class charT, class traits = char_traits<charT> >
-    class basic_ofstream;
-  typedef basic_ofstream<char>    ofstream;
-  typedef basic_ofstream<wchar_t> wofstream;
-  template <class charT, class traits = char_traits<charT> >
-    class basic_fstream;
-  typedef basic_fstream<char>     fstream;
-  typedef basic_fstream<wchar_t> wfstream;
-}
-```
-In this subclause, the type name `FILE` refers to the type `FILE`
-declared in `<cstdio>` ([[c.files]]).
-The class template `basic_filebuf` treats a file as a source or sink of
-bytes. In an environment that uses a large character set, the file
-typically holds multibyte character sequences and the `basic_filebuf`
-object converts those multibyte sequences into wide character sequences.
-#### Class template `basic_filebuf` <a id="filebuf">[[filebuf]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_filebuf : public basic_streambuf<charT, traits> {
   public:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
-    // [filebuf.cons] Constructors/destructor:
     basic_filebuf();
     basic_filebuf(const basic_filebuf& rhs) = delete;
     basic_filebuf(basic_filebuf&& rhs);
     virtual ~basic_filebuf();
-    // [filebuf.assign] Assign/swap:
     basic_filebuf& operator=(const basic_filebuf& rhs) = delete;
     basic_filebuf& operator=(basic_filebuf&& rhs);
     void swap(basic_filebuf& rhs);
- // [filebuf.members] Members:
     bool is_open() const;
-    basic_filebuf<charT,traits>* open(const char* s,
                         ios_base::openmode mode);
-    basic_filebuf<charT,traits>* open(const string& s,
                         ios_base::openmode mode);
-    basic_filebuf<charT,traits>* close();
   protected:
-    // [filebuf.virtuals] Overridden virtual functions:
- virtual streamsize showmanyc();
- virtual int_type underflow();
- virtual int_type uflow();
- virtual int_type pbackfail(int_type c = traits::eof());
- virtual int_type overflow (int_type c = traits::eof());
- virtual basic_streambuf<charT,traits>*
-        setbuf(char_type* s, streamsize n);
- virtual pos_type seekoff(off_type off, ios_base::seekdir way,
- ios_base::openmode which = ios_base::in | ios_base::out);
-    virtual pos_type seekpos(pos_type sp,
-        ios_base::openmode which = ios_base::in | ios_base::out);
-    virtual int      sync();
-    virtual void     imbue(const locale& loc);
   };
   template <class charT, class traits>
     void swap(basic_filebuf<charT, traits>& x,
               basic_filebuf<charT, traits>& y);
@@ -5041,23 +5127,23 @@ namespace std {
 The class `basic_filebuf<charT, traits>` associates both the input
 sequence and the output sequence with a file.
 The restrictions on reading and writing a sequence controlled by an
 object of class `basic_filebuf<charT, traits>` are the same as for
-reading and writing with the Standard C library `FILE`s.
 In particular:
 - If the file is not open for reading the input sequence cannot be read.
 - If the file is not open for writing the output sequence cannot be
   written.
 - A joint file position is maintained for both the input sequence and
   the output sequence.
 An instance of `basic_filebuf` behaves as described in  [[filebuf]]
-provided `traits::pos_type` is `fpos<traits::state_type>`. Otherwise the
-behavior is undefined.
 In order to support file I/O and multibyte/wide character conversion,
 conversions are performed using members of a facet, referred to as
 `a_codecvt` in following sections, obtained as if by
@@ -5074,11 +5160,11 @@ basic_filebuf();
 *Effects:* Constructs an object of class `basic_filebuf<charT, traits>`,
 initializing the base class with
 `basic_streambuf<charT, traits>()` ([[streambuf.cons]]).
-`is_open() == false`.
 ``` cpp
 basic_filebuf(basic_filebuf&& rhs);
 ```
@@ -5121,13 +5207,13 @@ rethrown (see  [[res.on.exception.handling]]).
 ``` cpp
 basic_filebuf& operator=(basic_filebuf&& rhs);
 ```
-*Effects:* Calls `this->close()` then move assigns from `rhs`. After the
-move assignment `*this` has the observable state it would have had if it
-had been move constructed from `rhs` (see  [[filebuf.cons]]).
 *Returns:* `*this`.
 ``` cpp
 void swap(basic_filebuf& rhs);
@@ -5139,11 +5225,11 @@ void swap(basic_filebuf& rhs);
 template <class charT, class traits>
   void swap(basic_filebuf<charT, traits>& x,
             basic_filebuf<charT, traits>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="filebuf.members">[[filebuf.members]]</a>
 ``` cpp
 bool is_open() const;
@@ -5151,18 +5237,19 @@ bool is_open() const;
 *Returns:* `true` if a previous call to `open` succeeded (returned a
 non-null value) and there has been no intervening call to close.
 ``` cpp
-basic_filebuf<charT,traits>* open(const char* s,
-    ios_base::openmode mode);
 ```
 *Effects:* If `is_open() != false`, returns a null pointer. Otherwise,
 initializes the `filebuf` as required. It then opens a file, if
 possible, whose name is the NTBS`s` (as if by calling
-`std::fopen(s,modstr)`). The NTBS`modstr` is determined from
 `mode & ~ios_base::ate` as indicated in
 Table  [[tab:iostreams.file.open.modes]]. If `mode` is not some
 combination of flags shown in the table then the open fails.
 **Table: File open modes** <a id="tab:iostreams.file.open.modes">[tab:iostreams.file.open.modes]</a>
@@ -5188,67 +5275,67 @@ combination of flags shown in the table then the open fails.
 | +        | +    |       |         | +     | `"a+b"` |
 If the open operation succeeds and `(mode & ios_base::ate) != 0`,
 positions the file to the end (as if by calling
-`std::fseek(file,0,SEEK_END)`).[^39]
 If the repositioning operation fails, calls `close()` and returns a null
 pointer to indicate failure.
 *Returns:* `this` if successful, a null pointer otherwise.
 ``` cpp
-basic_filebuf<charT,traits>* open(const string& s,
- ios_base::openmode mode);
 ```
 *Returns:* `open(s.c_str(), mode);`
 ``` cpp
-basic_filebuf<charT,traits>* close();
 ```
 *Effects:* If `is_open() == false`, returns a null pointer. If a put
 area exists, calls `overflow(traits::eof())` to flush characters. If the
 last virtual member function called on `*this` (between `underflow`,
 `overflow`, `seekoff`, and `seekpos`) was `overflow` then calls
 `a_codecvt.unshift` (possibly several times) to determine a termination
 sequence, inserts those characters and calls `overflow(traits::eof())`
 again. Finally, regardless of whether any of the preceding calls fails
 or throws an exception, the function closes the file (as if by calling
-`std::fclose(file)`).[^40] If any of the calls made by the function,
-including `std::fclose`, fails, `close` fails by returning a null
-pointer. If one of these calls throws an exception, the exception is
-caught and rethrown after closing the file.
 *Returns:* `this` on success, a null pointer otherwise.
-`is_open() == false`.
 #### Overridden virtual functions <a id="filebuf.virtuals">[[filebuf.virtuals]]</a>
 ``` cpp
-streamsize showmanyc();
 ```
 *Effects:* Behaves the same as
 `basic_streambuf::showmanyc()` ([[streambuf.virtuals]]).
 *Remarks:* An implementation might well provide an overriding definition
 for this function signature if it can determine that more characters can
 be read from the input sequence.
 ``` cpp
-int_type underflow();
 ```
 *Effects:* Behaves according to the description of
 `basic_streambuf<charT, traits>::underflow()`, with the specialization
 that a sequence of characters is read from the input sequence as if by
 reading from the associated file into an internal buffer (`extern_buf`)
-and then as if by doing
 ``` cpp
 char   extern_buf[XSIZE];
 char*  extern_end;
 charT  intern_buf[ISIZE];
@@ -5262,20 +5349,20 @@ This shall be done in such a way that the class can recover the position
 (`fpos_t`) corresponding to each character between `intern_buf` and
 `intern_end`. If the value of `r` indicates that `a_codecvt.in()` ran
 out of space in `intern_buf`, retry with a larger `intern_buf`.
 ``` cpp
-int_type uflow();
 ```
 *Effects:* Behaves according to the description of
-`basic_streambuf<charT,traits>::uflow()`, with the specialization that a
-sequence of characters is read from the input with the same method as
 used by `underflow`.
 ``` cpp
-int_type pbackfail(int_type c = traits::eof());
 ```
 *Effects:* Puts back the character designated by `c` to the input
 sequence, if possible, in one of three ways:
@@ -5303,11 +5390,11 @@ sequence.
 If the function can succeed in more than one of these ways, it is
 unspecified which way is chosen. The function can alter the number of
 putback positions available as a result of any call.
 ``` cpp
-int_type overflow(int_type c = traits::eof());
 ```
 *Effects:* Behaves according to the description of
 `basic_streambuf<charT, traits>::overflow(c)`, except that the behavior
 of “consuming characters” is performed by first converting as if by:
@@ -5336,31 +5423,32 @@ and then
 *Returns:* `traits::not_eof(c)` to indicate success, and `traits::eof()`
 to indicate failure. If `is_open() == false`, the function always fails.
 ``` cpp
-basic_streambuf* setbuf(char_type* s, streamsize n);
 ```
 *Effects:* If `setbuf(0, 0)` is called on a stream before any I/O has
 occurred on that stream, the stream becomes unbuffered. Otherwise the
 results are *implementation-defined*. “Unbuffered” means that `pbase()`
 and `pptr()` always return null and output to the file should appear as
 soon as possible.
 ``` cpp
 pos_type seekoff(off_type off, ios_base::seekdir way,
- ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 *Effects:* Let `width` denote `a_codecvt.encoding()`. If
 `is_open() == false`, or `off != 0 && width <= 0`, then the positioning
 operation fails. Otherwise, if `way != basic_ios::cur` or `off != 0`,
 and if the last operation was output, then update the output sequence
 and write any unshift sequence. Next, seek to the new position: if
-`width > 0`, call `std::fseek(file, width * off, whence)`, otherwise
-call `std::fseek(file, 0, whence)`.
 *Remarks:* “The last operation was output” means either the last virtual
 operation was overflow or the put buffer is non-empty. “Write any
 unshift sequence” means, if `width` if less than zero then call
 `a_codecvt.unshift(state, xbuf, xbuf+XSIZE, xbuf_end)` and output the
@@ -5382,90 +5470,99 @@ resultant stream position, if possible. If the positioning operation
 fails, or if the object cannot represent the resultant stream position,
 returns `pos_type(off_type(-1))`.
 ``` cpp
 pos_type seekpos(pos_type sp,
- ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 Alters the file position, if possible, to correspond to the position
 stored in `sp` (as described below). Altering the file position performs
 as follows:
 1.  if `(om & ios_base::out) != 0`, then update the output sequence and
     write any unshift sequence;
-2.  set the file position to `sp`;
 3.  if `(om & ios_base::in) != 0`, then update the input sequence;
 where `om` is the open mode passed to the last call to `open()`. The
-operation fails if `is_open()` returns false.
 If `sp` is an invalid stream position, or if the function positions
 neither sequence, the positioning operation fails. If `sp` has not been
 obtained by a previous successful call to one of the positioning
 functions (`seekoff` or `seekpos`) on the same file the effects are
 undefined.
 *Returns:* `sp` on success. Otherwise returns `pos_type(off_type(-1))`.
 ``` cpp
-int sync();
 ```
 *Effects:* If a put area exists, calls `filebuf::overflow` to write the
-characters to the file. If a get area exists, the effect is
 *implementation-defined*.
 ``` cpp
-void imbue(const locale& loc);
 ```
-If the file is not positioned at its beginning and the encoding of the
-current locale as determined by `a_codecvt.encoding()` is
-state-dependent ([[locale.codecvt.virtuals]]) then that facet is the
 same as the corresponding facet of `loc`.
 *Effects:* Causes characters inserted or extracted after this call to be
 converted according to `loc` until another call of `imbue`.
-This may require reconversion of previously converted characters. This
-in turn may require the implementation to be able to reconstruct the
-original contents of the file.
-#### Class template `basic_ifstream` <a id="ifstream">[[ifstream]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ifstream : public basic_istream<charT, traits> {
   public:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
-    // [ifstream.cons] Constructors:
     basic_ifstream();
     explicit basic_ifstream(const char* s,
                             ios_base::openmode mode = ios_base::in);
     explicit basic_ifstream(const string& s,
                             ios_base::openmode mode = ios_base::in);
     basic_ifstream(const basic_ifstream& rhs) = delete;
     basic_ifstream(basic_ifstream&& rhs);
-    // [ifstream.assign] Assign/swap:
     basic_ifstream& operator=(const basic_ifstream& rhs) = delete;
     basic_ifstream& operator=(basic_ifstream&& rhs);
     void swap(basic_ifstream& rhs);
-    // [ifstream.members] Members:
     basic_filebuf<charT, traits>* rdbuf() const;
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::in);
     void open(const string& s, ios_base::openmode mode = ios_base::in);
     void close();
   private:
     basic_filebuf<charT, traits> sb; // exposition only
   };
@@ -5486,18 +5583,20 @@ presented here as:
 ``` cpp
 basic_ifstream();
 ```
-*Effects:* Constructs an object of class `basic_ifstream<charT,traits>`,
-initializing the base class with `basic_istream(&sb)` and initializing
-`sb` with `basic_filebuf<charT,traits>())` ([[istream.cons]],
-[[filebuf.cons]]).
 ``` cpp
 explicit basic_ifstream(const char* s,
                         ios_base::openmode mode = ios_base::in);
 ```
 *Effects:* Constructs an object of class `basic_ifstream`, initializing
 the base class with `basic_istream(&sb)` and initializing `sb` with
 `basic_filebuf<charT, traits>())` ([[istream.cons]], [[filebuf.cons]]),
@@ -5505,13 +5604,15 @@ then calls `rdbuf()->open(s, mode | ios_base::in)`. If that function
 returns a null pointer, calls `setstate(failbit)`.
 ``` cpp
 explicit basic_ifstream(const string& s,
                         ios_base::openmode mode = ios_base::in);
 ```
-*Effects:* the same as `basic_ifstream(s.c_str(), mode)`.
 ``` cpp
 basic_ifstream(basic_ifstream&& rhs);
 ```
@@ -5542,11 +5643,11 @@ void swap(basic_ifstream& rhs);
 template <class charT, class traits>
   void swap(basic_ifstream<charT, traits>& x,
             basic_ifstream<charT, traits>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="ifstream.members">[[ifstream.members]]</a>
 ``` cpp
 basic_filebuf<charT, traits>* rdbuf() const;
@@ -5560,64 +5661,74 @@ bool is_open() const;
 *Returns:* `rdbuf()->is_open()`.
 ``` cpp
 void open(const char* s, ios_base::openmode mode = ios_base::in);
 ```
 *Effects:* Calls `rdbuf()->open(s, mode | ios_base::in)`. If that
 function does not return a null pointer calls `clear()`, otherwise calls
-`setstate(failbit)` (which may throw `ios_base::failure`
-([[iostate.flags]])).
 ``` cpp
 void open(const string& s, ios_base::openmode mode = ios_base::in);
 ```
-*Effects:* calls `open(s.c_str(), mode)`.
 ``` cpp
 void close();
 ```
 *Effects:* Calls `rdbuf()->close()` and, if that function returns a null
 pointer, calls `setstate(failbit)` (which may throw
-`ios_base::failure` ([[iostate.flags]])).
-#### Class template `basic_ofstream` <a id="ofstream">[[ofstream]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ofstream : public basic_ostream<charT, traits> {
   public:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
-    // [ofstream.cons] Constructors:
     basic_ofstream();
     explicit basic_ofstream(const char* s,
                             ios_base::openmode mode = ios_base::out);
     explicit basic_ofstream(const string& s,
                             ios_base::openmode mode = ios_base::out);
     basic_ofstream(const basic_ofstream& rhs) = delete;
     basic_ofstream(basic_ofstream&& rhs);
-    // [ofstream.assign] Assign/swap:
     basic_ofstream& operator=(const basic_ofstream& rhs) = delete;
     basic_ofstream& operator=(basic_ofstream&& rhs);
     void swap(basic_ofstream& rhs);
-    // [ofstream.members] Members:
     basic_filebuf<charT, traits>* rdbuf() const;
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::out);
     void open(const string& s, ios_base::openmode mode = ios_base::out);
     void close();
   private:
     basic_filebuf<charT, traits> sb; // exposition only
   };
@@ -5638,32 +5749,37 @@ presented here as:
 ``` cpp
 basic_ofstream();
 ```
-*Effects:* Constructs an object of class `basic_ofstream<charT,traits>`,
-initializing the base class with `basic_ostream(&sb)` and initializing
-`sb` with `basic_filebuf<charT,traits>())` ([[ostream.cons]],
-[[filebuf.cons]]).
 ``` cpp
 explicit basic_ofstream(const char* s,
                         ios_base::openmode mode = ios_base::out);
 ```
-*Effects:* Constructs an object of class `basic_ofstream<charT,traits>`,
-initializing the base class with `basic_ostream(&sb)` and initializing
-`sb` with `basic_filebuf<charT,traits>())` ([[ostream.cons]],
-[[filebuf.cons]]), then calls `rdbuf()->open(s, mode|ios_base::out)`. If
-that function returns a null pointer, calls `setstate(failbit)`.
 ``` cpp
 explicit basic_ofstream(const string& s,
                         ios_base::openmode mode = ios_base::out);
 ```
-*Effects:* the same as `basic_ofstream(s.c_str(), mode);`
 ``` cpp
 basic_ofstream(basic_ofstream&& rhs);
 ```
@@ -5694,11 +5810,11 @@ void swap(basic_ofstream& rhs);
 template <class charT, class traits>
   void swap(basic_ofstream<charT, traits>& x,
             basic_ofstream<charT, traits>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="ofstream.members">[[ofstream.members]]</a>
 ``` cpp
 basic_filebuf<charT, traits>* rdbuf() const;
@@ -5712,66 +5828,83 @@ bool is_open() const;
 *Returns:* `rdbuf()->is_open()`.
 ``` cpp
 void open(const char* s, ios_base::openmode mode = ios_base::out);
 ```
 *Effects:* Calls `rdbuf()->open(s, mode | ios_base::out)`. If that
 function does not return a null pointer calls `clear()`, otherwise calls
-`setstate(failbit)` (which may throw `ios_base::failure`
-([[iostate.flags]])).
 ``` cpp
 void close();
 ```
 *Effects:* Calls `rdbuf()->close()` and, if that function fails (returns
 a null pointer), calls `setstate(failbit)` (which may throw
-`ios_base::failure` ([[iostate.flags]])).
 ``` cpp
 void open(const string& s, ios_base::openmode mode = ios_base::out);
 ```
-*Effects:* calls `open(s.c_str(), mode);`
-#### Class template `basic_fstream` <a id="fstream">[[fstream]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
-  class basic_fstream
-    : public basic_iostream<charT,traits> {
   public:
- typedef charT                     char_type;
- typedef typename traits::int_type int_type;
- typedef typename traits::pos_type pos_type;
- typedef typename traits::off_type off_type;
- typedef traits                    traits_type;
-    // constructors/destructor
     basic_fstream();
-    explicit basic_fstream(const char* s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
-    explicit basic_fstream(const string& s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
     basic_fstream(const basic_fstream& rhs) = delete;
     basic_fstream(basic_fstream&& rhs);
-    // [fstream.assign] Assign/swap:
     basic_fstream& operator=(const basic_fstream& rhs) = delete;
     basic_fstream& operator=(basic_fstream&& rhs);
     void swap(basic_fstream& rhs);
-    // Members:
     basic_filebuf<charT, traits>* rdbuf() const;
     bool is_open() const;
-    void open(const char* s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
-    void open(const string& s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
     void close();
   private:
     basic_filebuf<charT, traits> sb; // exposition only
@@ -5782,13 +5915,13 @@ namespace std {
               basic_fstream<charT, traits>& y);
 }
 ```
 The class template `basic_fstream<charT, traits>` supports reading and
-writing from named files. It uses a `basic_filebuf<charT,traits>` object
-to control the associated sequences. For the sake of exposition, the
-maintained data is presented here as:
 - `sb`, the `basic_filebuf` object.
 #### `basic_fstream` constructors <a id="fstream.cons">[[fstream.cons]]</a>
@@ -5799,26 +5932,34 @@ basic_fstream();
 *Effects:* Constructs an object of class `basic_fstream<charT, traits>`,
 initializing the base class with `basic_iostream(&sb)` and initializing
 `sb` with `basic_filebuf<charT, traits>()`.
 ``` cpp
-explicit basic_fstream(const char* s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_fstream<charT, traits>`,
 initializing the base class with `basic_iostream(&sb)` and initializing
 `sb` with `basic_filebuf<charT, traits>()`. Then calls
 `rdbuf()->open(s, mode)`. If that function returns a null pointer, calls
 `setstate(failbit)`.
 ``` cpp
-explicit basic_fstream(const string& s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
 ```
-*Effects:* the same as `basic_fstream(s.c_str(), mode);`
 ``` cpp
 basic_fstream(basic_fstream&& rhs);
 ```
@@ -5849,11 +5990,11 @@ void swap(basic_fstream& rhs);
 template <class charT, class traits>
   void swap(basic_fstream<charT, traits>& x,
             basic_fstream<charT, traits>& y);
 ```
-*Effects:* `x.swap(y)`.
 #### Member functions <a id="fstream.members">[[fstream.members]]</a>
 ``` cpp
 basic_filebuf<charT, traits>* rdbuf() const;
@@ -5866,54 +6007,4248 @@ bool is_open() const;
 ```
 *Returns:* `rdbuf()->is_open()`.
 ``` cpp
-void open(const char* s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
 ```
 *Effects:* Calls `rdbuf()->open(s, mode)`. If that function does not
 return a null pointer calls `clear()`, otherwise calls
-`setstate(failbit)`, (which may throw
 `ios_base::failure`) ([[iostate.flags]]).
 ``` cpp
-void open(const string& s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
 ```
-*Effects:* calls `open(s.c_str(), mode);`
 ``` cpp
 void close();
 ```
-*Effects:* Calls `rdbuf()->close()` and, if that function returns
-returns a null pointer, calls `setstate(failbit)` ([[iostate.flags]])
-(which may throw `ios_base::failure`).
-### C library files <a id="c.files">[[c.files]]</a>
-Table  [[tab:iostreams.hdr.cstdio]] describes header `<cstdio>`. C++does
-not define the function `gets`.
-Calls to the function `tmpnam` with an argument of `NULL` may introduce
-a data race ([[res.on.data.races]]) with other calls to `tmpnam` with
-an argument of `NULL`.
-ISO C 7.9, Amendment 1 4.6.2.
-Table  [[tab:iostreams.hdr.cinttypes]] describes header `<cinttypes>`.
-The macros defined by `<cinttypes>` are provided unconditionally. In
-particular, the symbol `__STDC_FORMAT_MACROS`, mentioned in footnote 182
-of the C standard, plays no role in C++.
-The contents of header `<cinttypes>` are the same as the Standard C
-Library header `<inttypes.h>`, with the following changes:
-- the header `<cinttypes>` includes the header `<cstdint>` instead of
   `<stdint.h>`, and
 - if and only if the type `intmax_t` designates an extended integer
   type ([[basic.fundamental]]), the following function signatures are
   added:
   ``` cpp
@@ -5923,97 +10258,220 @@ Library header `<inttypes.h>`, with the following changes:
   which shall have the same semantics as the function signatures
   `intmax_t imaxabs(intmax_t)` and
   `imaxdiv_t imaxdiv(intmax_t, intmax_t)`, respectively.
 <!-- Link reference definitions -->
 [adjustfield.manip]: #adjustfield.manip
 [basefield.manip]: #basefield.manip
 [basic.fundamental]: basic.md#basic.fundamental
 [basic.ios.cons]: #basic.ios.cons
 [basic.ios.members]: #basic.ios.members
 [bitmask.types]: library.md#bitmask.types
 [c.files]: #c.files
 [enumerated.types]: library.md#enumerated.types
 [error.reporting]: #error.reporting
 [ext.manip]: #ext.manip
 [fig:streampos]: #fig:streampos
 [file.streams]: #file.streams
 [filebuf]: #filebuf
 [filebuf.assign]: #filebuf.assign
 [filebuf.cons]: #filebuf.cons
 [filebuf.members]: #filebuf.members
 [filebuf.virtuals]: #filebuf.virtuals
 [floatfield.manip]: #floatfield.manip
 [fmtflags.manip]: #fmtflags.manip
 [fmtflags.state]: #fmtflags.state
 [fpos]: #fpos
 [fpos.members]: #fpos.members
 [fpos.operations]: #fpos.operations
 [fstream]: #fstream
 [fstream.assign]: #fstream.assign
 [fstream.cons]: #fstream.cons
 [fstream.members]: #fstream.members
-[fstreams]: #fstreams
 [ifstream]: #ifstream
 [ifstream.assign]: #ifstream.assign
 [ifstream.cons]: #ifstream.cons
 [ifstream.members]: #ifstream.members
 [input.output]: #input.output
 [input.output.general]: #input.output.general
 [input.streams]: #input.streams
 [intro.multithread]: intro.md#intro.multithread
 [ios]: #ios
 [ios.base]: #ios.base
 [ios.base.callback]: #ios.base.callback
 [ios.base.cons]: #ios.base.cons
 [ios.base.locales]: #ios.base.locales
 [ios.base.storage]: #ios.base.storage
 [ios.members.static]: #ios.members.static
 [ios.overview]: #ios.overview
 [ios.types]: #ios.types
 [ios::Init]: #ios::Init
 [ios::failure]: #ios::failure
 [ios::fmtflags]: #ios::fmtflags
 [ios::iostate]: #ios::iostate
 [ios::openmode]: #ios::openmode
 [ios::seekdir]: #ios::seekdir
 [iostate.flags]: #iostate.flags
 [iostream.assign]: #iostream.assign
 [iostream.cons]: #iostream.cons
 [iostream.dest]: #iostream.dest
 [iostream.format]: #iostream.format
-[iostream.format.overview]: #iostream.format.overview
 [iostream.forward]: #iostream.forward
 [iostream.limits.imbue]: #iostream.limits.imbue
 [iostream.objects]: #iostream.objects
 [iostream.objects.overview]: #iostream.objects.overview
 [iostreamclass]: #iostreamclass
 [iostreams.base]: #iostreams.base
-[iostreams.base.overview]: #iostreams.base.overview
 [iostreams.limits.pos]: #iostreams.limits.pos
 [iostreams.requirements]: #iostreams.requirements
 [iostreams.threadsafety]: #iostreams.threadsafety
 [istream]: #istream
 [istream.assign]: #istream.assign
 [istream.cons]: #istream.cons
 [istream.formatted]: #istream.formatted
 [istream.formatted.arithmetic]: #istream.formatted.arithmetic
 [istream.formatted.reqmts]: #istream.formatted.reqmts
 [istream.manip]: #istream.manip
 [istream.rvalue]: #istream.rvalue
 [istream.unformatted]: #istream.unformatted
-[istream::extractors]: #istream::extractors
 [istream::sentry]: #istream::sentry
 [istringstream]: #istringstream
 [istringstream.assign]: #istringstream.assign
 [istringstream.cons]: #istringstream.cons
 [istringstream.members]: #istringstream.members
-[limits]: language.md#limits
 [locale.codecvt.virtuals]: localization.md#locale.codecvt.virtuals
 [locale.num.get]: localization.md#locale.num.get
 [narrow.stream.objects]: #narrow.stream.objects
 [ofstream]: #ofstream
 [ofstream.assign]: #ofstream.assign
 [ofstream.cons]: #ofstream.cons
 [ofstream.members]: #ofstream.members
 [ostream]: #ostream
@@ -6025,24 +10483,25 @@ Library header `<inttypes.h>`, with the following changes:
 [ostream.inserters.arithmetic]: #ostream.inserters.arithmetic
 [ostream.inserters.character]: #ostream.inserters.character
 [ostream.manip]: #ostream.manip
 [ostream.rvalue]: #ostream.rvalue
 [ostream.seeks]: #ostream.seeks
 [ostream.unformatted]: #ostream.unformatted
 [ostream::sentry]: #ostream::sentry
 [ostringstream]: #ostringstream
 [ostringstream.assign]: #ostringstream.assign
 [ostringstream.cons]: #ostringstream.cons
 [ostringstream.members]: #ostringstream.members
 [output.streams]: #output.streams
 [quoted.manip]: #quoted.manip
 [res.on.data.races]: library.md#res.on.data.races
 [res.on.exception.handling]: library.md#res.on.exception.handling
 [std.ios.manip]: #std.ios.manip
 [std.manip]: #std.manip
 [stream.buffers]: #stream.buffers
-[stream.buffers.overview]: #stream.buffers.overview
 [stream.types]: #stream.types
 [streambuf]: #streambuf
 [streambuf.assign]: #streambuf.assign
 [streambuf.buffer]: #streambuf.buffer
 [streambuf.cons]: #streambuf.cons
@@ -6053,44 +10512,53 @@ Library header `<inttypes.h>`, with the following changes:
 [streambuf.pub.get]: #streambuf.pub.get
 [streambuf.pub.pback]: #streambuf.pub.pback
 [streambuf.pub.put]: #streambuf.pub.put
 [streambuf.put.area]: #streambuf.put.area
 [streambuf.reqts]: #streambuf.reqts
 [streambuf.virt.buffer]: #streambuf.virt.buffer
 [streambuf.virt.get]: #streambuf.virt.get
 [streambuf.virt.locales]: #streambuf.virt.locales
 [streambuf.virt.pback]: #streambuf.virt.pback
 [streambuf.virt.put]: #streambuf.virt.put
 [streambuf.virtuals]: #streambuf.virtuals
 [string.classes]: strings.md#string.classes
 [string.streams]: #string.streams
-[string.streams.overview]: #string.streams.overview
 [stringbuf]: #stringbuf
 [stringbuf.assign]: #stringbuf.assign
 [stringbuf.cons]: #stringbuf.cons
 [stringbuf.members]: #stringbuf.members
 [stringbuf.virtuals]: #stringbuf.virtuals
 [strings]: strings.md#strings
 [stringstream]: #stringstream
 [stringstream.assign]: #stringstream.assign
 [stringstream.cons]: #stringstream.cons
 [stringstream.members]: #stringstream.members
 [tab:iostreams.basicios.init.effects]: #tab:iostreams.basicios.init.effects
 [tab:iostreams.copyfmt.effects]: #tab:iostreams.copyfmt.effects
 [tab:iostreams.file.open.modes]: #tab:iostreams.file.open.modes
 [tab:iostreams.fmtflags.constants]: #tab:iostreams.fmtflags.constants
 [tab:iostreams.fmtflags.effects]: #tab:iostreams.fmtflags.effects
-[tab:iostreams.hdr.cinttypes]: #tab:iostreams.hdr.cinttypes
-[tab:iostreams.hdr.cstdio]: #tab:iostreams.hdr.cstdio
 [tab:iostreams.iostate.effects]: #tab:iostreams.iostate.effects
 [tab:iostreams.lib.summary]: #tab:iostreams.lib.summary
 [tab:iostreams.newoff.values]: #tab:iostreams.newoff.values
 [tab:iostreams.openmode.effects]: #tab:iostreams.openmode.effects
 [tab:iostreams.position.requirements]: #tab:iostreams.position.requirements
 [tab:iostreams.seekdir.effects]: #tab:iostreams.seekdir.effects
 [tab:iostreams.seekoff.effects]: #tab:iostreams.seekoff.effects
 [tab:iostreams.seekoff.positioning]: #tab:iostreams.seekoff.positioning
 [wide.stream.objects]: #wide.stream.objects
 [^1]: It is the implementation’s responsibility to implement headers so
     that including `<iosfwd>` and other headers does not violate the
     rules about multiple occurrences of default arguments.
@@ -6124,11 +10592,11 @@ Library header `<inttypes.h>`, with the following changes:
 [^9]: for example, because it cannot allocate space.
 [^10]: This suggests an infinite amount of copying, but the
     implementation can keep track of the maximum element of the arrays
-    that is non-zero.
 [^11]: Checking `badbit` also for `fail()` is historical practice.
 [^12]: The function signature `dec(ios_base&)` can be called by the
     function signature
@@ -6140,91 +10608,99 @@ Library header `<inttypes.h>`, with the following changes:
     to assure that only objects for classes derived from this class may
     be constructed.
 [^14]: `underflow` or `uflow` might fail by throwing an exception
     prematurely. The intention is not only that the calls will not
-    return `eof()` but that they will return “immediately.”
 [^15]: Classes derived from `basic_streambuf` can provide more efficient
     ways to implement `xsgetn()` and `xsputn()` by overriding these
     definitions from the base class.
-[^16]: Typically, `overflow` returns `c` to indicate success, except
- when `traits::eq_int_type(c,traits::eof())` returns `true`, in which
- case it returns `traits::not_eof(c)`.
-[^17]: This will be possible only in functions that are part of the
     library. The semantics of the constructor used in user code is as
     specified.
-[^18]: The sentry constructor and destructor can also perform additional
     implementation-dependent operations.
-[^19]: This is done without causing an `ios::failure` to be thrown.
-[^20]: See, for example, the function signature
-    `ws(basic_istream&)` ([[istream.manip]]).
 [^21]: See, for example, the function signature
     `dec(ios_base&)` ([[basefield.manip]]).
-[^22]: This is done without causing an `ios::failure` to be thrown.
-[^23]: Note that this function is not overloaded on types `signed char`
-    and `unsigned char`.
 [^24]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
 [^25]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
-[^26]: Since the final input character is “extracted,” it is counted in
     the `gcount()`, even though it is not stored.
-[^27]: This allows an input line which exactly fills the buffer, without
     setting `failbit`. This is different behavior than the historical
     AT&T implementation.
-[^28]: This implies an empty input line will not cause `failbit` to be
     set.
-[^29]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
-[^30]: The call `os.tie()->flush()` does not necessarily occur if the
     function can determine that no synchronization is necessary.
-[^31]: The `sentry` constructor and destructor can also perform
     additional implementation-dependent operations.
-[^32]: without causing an `ios::failure` to be thrown.
-[^33]: See, for example, the function signature
-    `endl(basic_ostream&)` ([[ostream.manip]]).
 [^34]: See, for example, the function signature
     `dec(ios_base&)` ([[basefield.manip]]).
-[^35]: without causing an `ios::failure` to be thrown.
-[^36]: Note that this function is not overloaded on types `signed char`
-    and `unsigned char`.
 [^37]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
-[^38]: The expression `cin >>resetiosflags(ios_base::skipws)` clears
     `ios_base::skipws` in the format flags stored in the
     `basic_istream<charT, traits>` object `cin` (the same as
     `cin >> noskipws`), and the expression
     `cout << resetiosflags(ios_base::showbase)` clears
     `ios_base::showbase` in the format flags stored in the
     `basic_ostream<charT, traits>` object `cout` (the same as
     `cout << noshowbase`).
-[^39]: The macro `SEEK_END` is defined, and the function signatures
     `fopen(const char*, const char*)` and `fseek(FILE*, long, int)` are
-    declared, in `<cstdio>` ([[c.files]]).
-[^40]: The function signature `fclose(FILE*)` is declared in `<cstdio>`
- ([[c.files]]).

 summarized in Table  [[tab:iostreams.lib.summary]].
 **Table: Input/output library summary** <a id="tab:iostreams.lib.summary">[tab:iostreams.lib.summary]</a>
 | Subclause                  |                             | Header         |
+| -------------------------- | --------------------------- | -------------- |
 | [[iostreams.requirements]] | Requirements                |                |
 | [[iostream.forward]]       | Forward declarations        | `<iosfwd>`     |
 | [[iostream.objects]]       | Standard iostream objects   | `<iostream>`   |
 | [[iostreams.base]]         | Iostreams base classes      | `<ios>`        |
 | [[stream.buffers]]         | Stream buffers              | `<streambuf>`  |
 | [[iostream.format]]        | Formatting and manipulators | `<istream>`    |
 |                            |                             | `<ostream>`    |
 |                            |                             | `<iomanip>`    |
 | [[string.streams]]         | String streams              | `<sstream>`    |
 | [[file.streams]]           | File streams                | `<fstream>`    |
+| [[filesystems]]            | File systems                | `<filesystem>` |
+| [[c.files]]                | C library files             | `<cstdio>`     |
 |                            |                             | `<cinttypes>`  |
 Figure  [[fig:streampos]] illustrates relationships among various types
 described in this clause. A line from **A** to **B** indicates that
 as noted explicitly below, their behavior when `traits::pos_type` and
 `traits::off_type` are other types is *implementation-defined*.
 In the classes of Clause  [[input.output]], a template parameter with
 name `charT` represents a member of the set of types containing `char`,
+`wchar_t`, and any other *implementation-defined* character types that
 satisfy the requirements for a character on which any of the iostream
 components can be instantiated.
 ### Thread safety <a id="iostreams.threadsafety">[[iostreams.threadsafety]]</a>
 Concurrent access to a stream object ([[string.streams]],
 [[file.streams]]), stream buffer object ([[stream.buffers]]), or C
 Library stream ([[c.files]]) by multiple threads may result in a data
 race ([[intro.multithread]]) unless otherwise specified (
+[[iostream.objects]]).
+[*Note 1*: Data races result in undefined behavior (
+[[intro.multithread]]). — *end note*]
 If one thread makes a library call *a* that writes a value to a stream
 and, as a result, another thread reads this value from the stream
 through a library call *b* such that this does not result in a data
 race, then *a*’s write synchronizes with *b*’s read.
 ## Forward declarations <a id="iostream.forward">[[iostream.forward]]</a>
+### Header `<iosfwd>` synopsis <a id="iosfwd.syn">[[iosfwd.syn]]</a>
 ``` cpp
 namespace std {
   template<class charT> class char_traits;
   template<> class char_traits<char>;
   template<> class char_traits<char16_t>;
   template <class charT, class traits = char_traits<charT>>
     class istreambuf_iterator;
   template <class charT, class traits = char_traits<charT>>
     class ostreambuf_iterator;
+ using ios  = basic_ios<char>;
+ using wios = basic_ios<wchar_t>;
+ using streambuf = basic_streambuf<char>;
+ using istream   = basic_istream<char>;
+ using ostream   = basic_ostream<char>;
+ using iostream  = basic_iostream<char>;
+ using stringbuf     = basic_stringbuf<char>;
+ using istringstream = basic_istringstream<char>;
+ using ostringstream = basic_ostringstream<char>;
+ using stringstream  = basic_stringstream<char>;
+ using filebuf  = basic_filebuf<char>;
+ using ifstream = basic_ifstream<char>;
+ using ofstream = basic_ofstream<char>;
+ using fstream  = basic_fstream<char>;
+ using wstreambuf = basic_streambuf<wchar_t>;
+ using wistream   = basic_istream<wchar_t>;
+ using wostream   = basic_ostream<wchar_t>;
+ using wiostream  = basic_iostream<wchar_t>;
+ using wstringbuf     = basic_stringbuf<wchar_t>;
+ using wistringstream = basic_istringstream<wchar_t>;
+ using wostringstream = basic_ostringstream<wchar_t>;
+ using wstringstream  = basic_stringstream<wchar_t>;
+ using wfilebuf  = basic_filebuf<wchar_t>;
+ using wifstream = basic_ifstream<wchar_t>;
+ using wofstream = basic_ofstream<wchar_t>;
+ using wfstream  = basic_fstream<wchar_t>;
   template <class state> class fpos;
+ using streampos  = fpos<char_traits<char>::state_type>;
+ using wstreampos = fpos<char_traits<wchar_t>::state_type>;
 }
 ```
 Default template arguments are described as appearing both in `<iosfwd>`
 and in the synopsis of other headers but it is well-formed to include
 both `<iosfwd>` and one or more of the other headers.[^1]
+### Overview <a id="iostream.forward.overview">[[iostream.forward.overview]]</a>
 The class template specialization `basic_ios<charT, traits>` serves as a
 virtual base class for the class templates `basic_istream`,
 `basic_ostream`, and class templates derived from them. `basic_iostream`
 is a class template derived from both `basic_istream<charT, traits>` and
 `basic_ostream<charT, traits>`.
+The class template specialization `basic_streambuf<charT, traits>`
+serves as a base class for class templates `basic_stringbuf` and
 `basic_filebuf`.
 The class template specialization `basic_istream<charT, traits>` serves
 as a base class for class templates `basic_istringstream` and
 `basic_ifstream`.
 The class template specialization `basic_iostream<charT, traits>` serves
 as a base class for class templates `basic_stringstream` and
 `basic_fstream`.
+Other *typedef-name*s define instances of class templates specialized
+for `char` or `wchar_t` types.
 Specializations of the class template `fpos` are used for specifying
 file position information.
 The types `streampos` and `wstreampos` are used for positioning streams
 specialized on `char` and `wchar_t` respectively.
+[*Note 1*:
 This synopsis suggests a circularity between `streampos` and
 `char_traits<char>`. An implementation can avoid this circularity by
 substituting equivalent types. One way to do this might be
 ``` cpp
 template<class stateT> class fpos { ... };      // depends on nothing
+using _STATE = ... ;             // implementation private declaration of stateT
+using streampos = fpos<_STATE>;
 template<> struct char_traits<char> {
+ using pos_type = streampos;
 }
 ```
+— *end note*]
 ## Standard iostream objects <a id="iostream.objects">[[iostream.objects]]</a>
+### Header `<iostream>` synopsis <a id="iostream.syn">[[iostream.syn]]</a>
 ``` cpp
+#include <ios>          // see [ios.syn]
+#include <streambuf>    // see [streambuf.syn]
+#include <istream>      // see [istream.syn]
+#include <ostream>      // see [ostream.syn]
 namespace std {
   extern istream cin;
   extern ostream cout;
   extern ostream cerr;
   extern wostream wcerr;
   extern wostream wclog;
 }
 ```
+### Overview <a id="iostream.objects.overview">[[iostream.objects.overview]]</a>
+In this Clause, the type name `FILE` refers to the type `FILE` declared
+in `<cstdio>` ([[cstdio.syn]]).
 The header `<iostream>` declares objects that associate objects with the
 standard C streams provided for by the functions declared in
 `<cstdio>` ([[c.files]]), and includes all the headers necessary to use
 these objects.
 The objects are constructed and the associations are established at some
 time prior to or during the first time an object of class
 `ios_base::Init` is constructed, and in any case before the body of
+`main` ([[basic.start.main]]) begins execution.[^2] The objects are not
+destroyed during program execution.[^3] The results of including
+`<iostream>` in a translation unit shall be as if `<iostream>` defined
+an instance of `ios_base::Init` with static storage duration.
 Mixing operations on corresponding wide- and narrow-character streams
 follows the same semantics as mixing such operations on `FILE`s, as
+specified in the C standard library.
 Concurrent access to a synchronized ([[ios.members.static]]) standard
 iostream object’s formatted and unformatted input ([[istream]]) and
 output ([[ostream]]) functions or a standard C stream by multiple
+threads shall not result in a data race ([[intro.multithread]]).
+[*Note 1*: Users must still synchronize concurrent use of these objects
+and streams by multiple threads if they wish to avoid interleaved
+characters. — *end note*]
+ ISO C 7.21.2.
 ### Narrow stream objects <a id="narrow.stream.objects">[[narrow.stream.objects]]</a>
 ``` cpp
 istream cin;
 ```
 The object `cin` controls input from a stream buffer associated with the
+object `stdin`, declared in `<cstdio>` ([[cstdio.syn]]).
 After the object `cin` is initialized, `cin.tie()` returns `&cout`. Its
 state is otherwise the same as required for
 `basic_ios<char>::init` ([[basic.ios.cons]]).
 ``` cpp
 ostream cout;
 ```
 The object `cout` controls output to a stream buffer associated with the
+object `stdout`, declared in `<cstdio>` ([[cstdio.syn]]).
 ``` cpp
 ostream cerr;
 ```
 The object `cerr` controls output to a stream buffer associated with the
+object `stderr`, declared in `<cstdio>` ([[cstdio.syn]]).
 After the object `cerr` is initialized, `cerr.flags() & unitbuf` is
 nonzero and `cerr.tie()` returns `&cout`. Its state is otherwise the
 same as required for `basic_ios<char>::init` ([[basic.ios.cons]]).
 ``` cpp
 ostream clog;
 ```
 The object `clog` controls output to a stream buffer associated with the
+object `stderr`, declared in `<cstdio>` ([[cstdio.syn]]).
 ### Wide stream objects <a id="wide.stream.objects">[[wide.stream.objects]]</a>
 ``` cpp
 wistream wcin;
 ```
 The object `wcin` controls input from a stream buffer associated with
+the object `stdin`, declared in `<cstdio>` ([[cstdio.syn]]).
 After the object `wcin` is initialized, `wcin.tie()` returns `&wcout`.
 Its state is otherwise the same as required for
 `basic_ios<wchar_t>::init` ([[basic.ios.cons]]).
 ``` cpp
 wostream wcout;
 ```
 The object `wcout` controls output to a stream buffer associated with
+the object `stdout`, declared in `<cstdio>` ([[cstdio.syn]]).
 ``` cpp
 wostream wcerr;
 ```
 The object `wcerr` controls output to a stream buffer associated with
+the object `stderr`, declared in `<cstdio>` ([[cstdio.syn]]).
 After the object `wcerr` is initialized, `wcerr.flags() & unitbuf` is
 nonzero and `wcerr.tie()` returns `&wcout`. Its state is otherwise the
 same as required for `basic_ios<wchar_t>::init` ([[basic.ios.cons]]).
 ``` cpp
 wostream wclog;
 ```
 The object `wclog` controls output to a stream buffer associated with
+the object `stderr`, declared in `<cstdio>` ([[cstdio.syn]]).
 ## Iostreams base classes <a id="iostreams.base">[[iostreams.base]]</a>
+### Header `<ios>` synopsis <a id="ios.syn">[[ios.syn]]</a>
 ``` cpp
+#include <iosfwd>   // see [iosfwd.syn]
 namespace std {
+ using streamoff  = implementation-defined;
+ using streamsize = implementation-defined;
   template <class stateT> class fpos;
   class ios_base;
   template <class charT, class traits = char_traits<charT>>
     class basic_ios;
+  // [std.ios.manip], manipulators
   ios_base& boolalpha  (ios_base& str);
   ios_base& noboolalpha(ios_base& str);
   ios_base& showbase   (ios_base& str);
   ios_base& noshowbase (ios_base& str);
   ios_base& nouppercase(ios_base& str);
   ios_base& unitbuf    (ios_base& str);
   ios_base& nounitbuf  (ios_base& str);
+  // [adjustfield.manip], adjustfield
   ios_base& internal   (ios_base& str);
   ios_base& left       (ios_base& str);
   ios_base& right      (ios_base& str);
+  // [basefield.manip], basefield
   ios_base& dec        (ios_base& str);
   ios_base& hex        (ios_base& str);
   ios_base& oct        (ios_base& str);
+  // [floatfield.manip], floatfield
   ios_base& fixed      (ios_base& str);
   ios_base& scientific (ios_base& str);
   ios_base& hexfloat   (ios_base& str);
   ios_base& defaultfloat(ios_base& str);
+  // [error.reporting], error reporting
   enum class io_errc {
     stream = 1
   };
   template <> struct is_error_code_enum<io_errc> : public true_type { };
 ```
 ### Types <a id="stream.types">[[stream.types]]</a>
 ``` cpp
+using streamoff = implementation-defined;
 ```
 The type `streamoff` is a synonym for one of the signed basic integral
 types of sufficient size to represent the maximum possible file size for
 the operating system.[^4]
 ``` cpp
+using streamsize = implementation-defined;
 ```
 The type `streamsize` is a synonym for one of the signed basic integral
 types. It is used to represent the number of characters transferred in
 an I/O operation, or the size of I/O buffers.[^5]
 ``` cpp
 namespace std {
   class ios_base {
   public:
+    class failure; // see below
+    // [ios::fmtflags], fmtflags
+ using fmtflags = T1;
     static constexpr fmtflags boolalpha = unspecified;
     static constexpr fmtflags dec = unspecified;
     static constexpr fmtflags fixed = unspecified;
     static constexpr fmtflags hex = unspecified;
     static constexpr fmtflags internal = unspecified;
     static constexpr fmtflags uppercase = unspecified;
     static constexpr fmtflags adjustfield = see below;
     static constexpr fmtflags basefield = see below;
     static constexpr fmtflags floatfield = see below;
+    // [ios::iostate], iostate
+ using iostate = T2;
     static constexpr iostate badbit = unspecified;
     static constexpr iostate eofbit = unspecified;
     static constexpr iostate failbit = unspecified;
     static constexpr iostate goodbit = see below;
+    // [ios::openmode], openmode
+ using openmode = T3;
     static constexpr openmode app = unspecified;
     static constexpr openmode ate = unspecified;
     static constexpr openmode binary = unspecified;
     static constexpr openmode in = unspecified;
     static constexpr openmode out = unspecified;
     static constexpr openmode trunc = unspecified;
+    // [ios::seekdir], seekdir
+ using seekdir = T4;
     static constexpr seekdir beg = unspecified;
     static constexpr seekdir cur = unspecified;
     static constexpr seekdir end = unspecified;
     class Init;
+    // [fmtflags.state], fmtflags state
     fmtflags flags() const;
     fmtflags flags(fmtflags fmtfl);
     fmtflags setf(fmtflags fmtfl);
     fmtflags setf(fmtflags fmtfl, fmtflags mask);
     void unsetf(fmtflags mask);
     streamsize precision() const;
     streamsize precision(streamsize prec);
     streamsize width() const;
     streamsize width(streamsize wide);
+    // [ios.base.locales], locales
     locale imbue(const locale& loc);
     locale getloc() const;
+    // [ios.base.storage], storage
     static int xalloc();
     long&  iword(int index);
     void*& pword(int index);
+    // destructor:
     virtual ~ios_base();
+    // [ios.base.callback], callbacks;
     enum event { erase_event, imbue_event, copyfmt_event };
+ using event_callback = void (*)(event, ios_base&, int index);
     void register_callback(event_callback fn, int index);
     ios_base(const ios_base&) = delete;
     ios_base& operator=(const ios_base&) = delete;
 `ios_base`
 defines several member types:
+- a type `failure`, defined as either a class derived from
+  `system_error` or a synonym for a class derived from `system_error`;
 - a class `Init`;
 - three bitmask types, `fmtflags`, `iostate`, and `openmode`;
 - an enumerated type, `seekdir`.
 It maintains several kinds of data:
 - control information that influences how to interpret (format) input
   sequences and how to generate (format) output sequences;
 - additional information that is stored by the program for its private
   use.
+[*Note 1*:
 For the sake of exposition, the maintained data is presented here as:
 - `static int index`, specifies the next available unique index for the
   integer or pointer arrays maintained for the private use of the
   program, initialized to an unspecified value;
 - `long* iarray`, points to the first element of an arbitrary-length
   `long` array maintained for the private use of the program;
 - `void** parray`, points to the first element of an arbitrary-length
   pointer array maintained for the private use of the program.
+— *end note*]
 #### Types <a id="ios.types">[[ios.types]]</a>
 ##### Class `ios_base::failure` <a id="ios::failure">[[ios::failure]]</a>
 ``` cpp
     explicit failure(const char* msg, const error_code& ec = io_errc::stream);
   };
 }
 ```
+An implementation is permitted to define `ios_base::failure` as a
+synonym for a class with equivalent functionality to class
+`ios_base::failure` shown in this subclause.
+[*Note 1*: When `ios_base::failure` is a synonym for another type it
+shall provide a nested type `failure`, to emulate the injected class
+name. — *end note*]
 The class `failure` defines the base class for the types of all objects
 thrown as exceptions, by functions in the iostreams library, to report
 errors detected during stream buffer operations.
 When throwing `ios_base::failure` exceptions, implementations should
 provide values of `ec` that identify the specific reason for the
+failure.
+[*Note 2*: Errors arising from the operating system would typically be
 reported as `system_category()` errors with an error value of the error
 number reported by the operating system. Errors arising from within the
 stream library would typically be reported as
 `error_code(io_errc::stream,
+iostream_category())`. — *end note*]
 ``` cpp
 explicit failure(const string& msg, const error_code& ec = io_errc::stream);
 ```
 base class with `msg` and `ec`.
 ##### Type `ios_base::fmtflags` <a id="ios::fmtflags">[[ios::fmtflags]]</a>
 ``` cpp
+using fmtflags = T1;
 ```
 The type `fmtflags` is a bitmask type ([[bitmask.types]]). Setting its
 elements has the effects indicated in
 Table  [[tab:iostreams.fmtflags.effects]].
 ##### Type `ios_base::iostate` <a id="ios::iostate">[[ios::iostate]]</a>
 ``` cpp
+using iostate = T2;
 ```
 The type `iostate` is a bitmask type ([[bitmask.types]]) that contains
 the elements indicated in Table  [[tab:iostreams.iostate.effects]].
 - `goodbit`, the value zero.
 ##### Type `ios_base::openmode` <a id="ios::openmode">[[ios::openmode]]</a>
 ``` cpp
+using openmode = T3;
 ```
 The type `openmode` is a bitmask type ([[bitmask.types]]). It contains
 the elements indicated in Table  [[tab:iostreams.openmode.effects]].
 ##### Type `ios_base::seekdir` <a id="ios::seekdir">[[ios::seekdir]]</a>
 ``` cpp
+using seekdir = T4;
 ```
 The type `seekdir` is an enumerated type ([[enumerated.types]]) that
 contains the elements indicated in
 Table  [[tab:iostreams.seekdir.effects]].
 The class `Init` describes an object whose construction ensures the
 construction of the eight objects declared in `<iostream>` (
 [[iostream.objects]]) that associate file stream buffers with the
 standard C streams provided for by the functions declared in
+`<cstdio>` ([[cstdio.syn]]).
 For the sake of exposition, the maintained data is presented here as:
 - `static int init_cnt`, counts the number of constructor and destructor
   calls for class `Init`, initialized to zero.
 ``` cpp
 fmtflags flags(fmtflags fmtfl);
 ```
+*Postconditions:* `fmtfl == flags()`.
 *Returns:* The previous value of `flags()`.
 ``` cpp
 fmtflags setf(fmtflags fmtfl);
 ``` cpp
 streamsize precision(streamsize prec);
 ```
+*Postconditions:* `prec == precision()`.
 *Returns:* The previous value of `precision()`.
 ``` cpp
 streamsize width() const;
 ``` cpp
 streamsize width(streamsize wide);
 ```
+*Postconditions:* `wide == width()`.
 *Returns:* The previous value of `width()`.
 #### `ios_base` functions <a id="ios.base.locales">[[ios.base.locales]]</a>
 `ios_base::getloc()` from within `fn` returns the new locale value
 `loc`.
 *Returns:* The previous value of `getloc()`.
+*Postconditions:* `loc == getloc()`.
 ``` cpp
 locale getloc() const;
 ```
 objects ([[iostream.objects]]) was synchronized and otherwise returns
 `false`. The first time it is called, the function returns `true`.
 *Effects:* If any input or output operation has occurred using the
 standard streams prior to the call, the effect is
+*implementation-defined*. Otherwise, called with a `false` argument, it
 allows the standard streams to operate independently of the standard C
 streams.
 When a standard iostream object `str` is *synchronized* with a standard
 stdio stream `f`, the effect of inserting a character `c` by
 necessary to include the element `iarray[idx]`. Each newly allocated
 element of the array is initialized to zero. The reference returned is
 invalid after any other operations on the object.[^7] However, the value
 of the storage referred to is retained, so that until the next call to
 `copyfmt`, calling `iword` with the same index yields another reference
+to the same value. If the function fails[^8] and `*this` is a base class
 subobject of a `basic_ios<>` object or subobject, the effect is
 equivalent to calling `basic_ios<>::setstate(badbit)` on the derived
 object (which may throw `failure`).
 *Returns:* On success `iarray[idx]`. On failure, a valid `long&`
 element of the array is initialized to a null pointer. The reference
 returned is invalid after any other operations on the object. However,
 the value of the storage referred to is retained, so that until the next
 call to `copyfmt`, calling `pword` with the same index yields another
 reference to the same value. If the function fails[^9] and `*this` is a
+base class subobject of a `basic_ios<>` object or subobject, the effect
+is equivalent to calling `basic_ios<>::setstate(badbit)` on the derived
 object (which may throw `failure`).
 *Returns:* On success `parray[idx]`. On failure a valid `void*&`
 initialized to 0.
 ``` cpp
 namespace std {
   template <class stateT> class fpos {
   public:
+    // [fpos.members], members
     stateT state() const;
     void state(stateT);
   private;
     stateT st; // exposition only
   };
 ``` cpp
 void state(stateT s);
 ```
+*Effects:* Assigns `s` to `st`.
 ``` cpp
 stateT state() const;
 ```
 - `O` refers to type `streamoff`,
 - `o` refers to a value of type `streamoff`,
 - `sz` refers to a value of type `streamsize` and
 - `i` refers to a value of type `int`.
+[*Note 1*: Every implementation is required to supply overloaded
+operators on `fpos` objects to satisfy the requirements of
+[[fpos.operations]]. It is unspecified whether these operators are
+members of `fpos`, global operators, or provided in some other
+way. — *end note*]
 Stream operations that return a value of type `traits::pos_type` return
 `P(O(-1))` as an invalid value to signal an error. If this value is used
 as an argument to any `istream`, `ostream`, or `streambuf` member that
 accepts a value of type `traits::pos_type` then the behavior of that
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ios : public ios_base {
   public:
+    using char_type   = charT;
+    using int_type    = typename traits::int_type;
+    using pos_type    = typename traits::pos_type;
+    using off_type    = typename traits::off_type;
+    using traits_type = traits;
+    // [iostate.flags], flags functions
     explicit operator bool() const;
     bool operator!() const;
     iostate rdstate() const;
     void clear(iostate state = goodbit);
     void setstate(iostate state);
     bool bad()  const;
     iostate exceptions() const;
     void exceptions(iostate except);
+    // [basic.ios.cons], constructor/destructor
     explicit basic_ios(basic_streambuf<charT, traits>* sb);
     virtual ~basic_ios();
+    // [basic.ios.members], members
     basic_ostream<charT, traits>* tie() const;
     basic_ostream<charT, traits>* tie(basic_ostream<charT, traits>* tiestr);
     basic_streambuf<charT, traits>* rdbuf() const;
     basic_streambuf<charT, traits>* rdbuf(basic_streambuf<charT, traits>* sb);
 | `rdstate()`    | `goodbit` if `sb` is not a null pointer, otherwise `badbit`. |
 | `exceptions()` | `goodbit`                                                    |
 | `flags()`      | `skipws | dec`                                               |
 | `width()`      | `0`                                                          |
 | `precision()`  | `6`                                                          |
+| `fill()`       | `widen(' ')` |
 | `getloc()`     | a copy of the value returned by `locale()`                   |
 | `iarray`       | a null pointer                                               |
 | `parray`       | a null pointer                                               |
 *Requires:* If `tiestr` is not null, `tiestr` must not be reachable by
 traversing the linked list of tied stream objects starting from
 `tiestr->tie()`.
+*Postconditions:* `tiestr == tie()`.
 *Returns:* The previous value of `tie()`.
 ``` cpp
 basic_streambuf<charT, traits>* rdbuf() const;
 ``` cpp
 basic_streambuf<charT, traits>* rdbuf(basic_streambuf<charT, traits>* sb);
 ```
+*Postconditions:* `sb == rdbuf()`.
 *Effects:* Calls `clear()`.
 *Returns:* The previous value of `rdbuf()`.
 ``` cpp
 char_type fill(char_type fillch);
 ```
+*Postconditions:* `traits::eq(fillch, fill())`.
 *Returns:* The previous value of `fill()`.
 ``` cpp
 basic_ios& copyfmt(const basic_ios& rhs);
       stored outside the object `rhs` and those objects are destroyed
       when `rhs` is destroyed, the newly stored pointer values are
       altered to point at newly constructed copies of the objects;
 3.  calls each callback pair that was copied from `rhs` as
     `(*fn)(copyfmt_event, *this, index)`;
+4.  calls `exceptions(rhs.exceptions())`.
+[*Note 1*: The second pass through the callback pairs permits a copied
 `pword` value to be zeroed, or to have its referent deep copied or
+reference counted, or to have other special action taken. — *end note*]
 *Postconditions:* The postconditions of this function are indicated in
 Table  [[tab:iostreams.copyfmt.effects]].
 **Table: `basic_ios::copyfmt()` effects** <a id="tab:iostreams.copyfmt.effects">[tab:iostreams.copyfmt.effects]</a>
 ``` cpp
 void clear(iostate state = goodbit);
 ```
+*Postconditions:* If `rdbuf() != 0` then `state == rdstate()`; otherwise
 `rdstate() == (state | ios_base::badbit)`.
 *Effects:* If
 `((state | (rdbuf() ? goodbit : badbit)) & exceptions()) == 0`, returns.
+Otherwise, the function throws an object of class
 `basic_ios::failure` ([[ios::failure]]), constructed with
 *implementation-defined* argument values.
 ``` cpp
 void setstate(iostate state);
 ``` cpp
 void exceptions(iostate except);
 ```
+*Postconditions:* `except == exceptions()`.
 *Effects:* Calls `clear(rdstate())`.
 ### `ios_base` manipulators <a id="std.ios.manip">[[std.ios.manip]]</a>
 *Effects:* Calls
 `str.setf(ios_base::fixed | ios_base::scientific, ios_base::floatfield)`.
 *Returns:* `str`.
+[*Note 1*: The more obvious use of `ios_base::hex` to specify
+hexadecimal floating-point format would change the meaning of existing
+well defined programs. C++03 gives no meaning to the combination of
+`fixed` and `scientific`. — *end note*]
 ``` cpp
 ios_base& defaultfloat(ios_base& str);
 ```
 object’s `name` virtual function shall return a pointer to the string
 `"iostream"`.
 ## Stream buffers <a id="stream.buffers">[[stream.buffers]]</a>
+### Header `<streambuf>` synopsis <a id="streambuf.syn">[[streambuf.syn]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
     class basic_streambuf;
+ using streambuf  = basic_streambuf<char>;
+ using wstreambuf = basic_streambuf<wchar_t>;
 }
 ```
 The header `<streambuf>` defines types that control input from and
 output to *character* sequences.
 - If `xnext` is not a null pointer and `xnext < xend` for an input
   sequence, then a *read position* is available. In this case, `*xnext`
   shall have a defined value and is the next element to read (to get, or
   to obtain a character value, from the sequence).
+### Class template `basic_streambuf` <a id="streambuf">[[streambuf]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_streambuf {
   public:
+    using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
     virtual ~basic_streambuf();
+    // [streambuf.locales], locales
     locale   pubimbue(const locale& loc);
     locale   getloc() const;
+    // [streambuf.buffer], buffer and positioning
+    basic_streambuf* pubsetbuf(char_type* s, streamsize n);
     pos_type pubseekoff(off_type off, ios_base::seekdir way,
+ ios_base::openmode which
+                          = ios_base::in | ios_base::out);
     pos_type pubseekpos(pos_type sp,
+ ios_base::openmode which
+                          = ios_base::in | ios_base::out);
     int      pubsync();
+    // Get and put areas
+    // [streambuf.pub.get], get area
     streamsize in_avail();
     int_type snextc();
     int_type sbumpc();
     int_type sgetc();
     streamsize sgetn(char_type* s, streamsize n);
+    // [streambuf.pub.pback], putback
     int_type sputbackc(char_type c);
     int_type sungetc();
+    // [streambuf.pub.put], put area
     int_type   sputc(char_type c);
     streamsize sputn(const char_type* s, streamsize n);
   protected:
     basic_streambuf();
     basic_streambuf(const basic_streambuf& rhs);
     basic_streambuf& operator=(const basic_streambuf& rhs);
     void swap(basic_streambuf& rhs);
+    // [streambuf.get.area], get area access
     char_type* eback() const;
     char_type* gptr()  const;
     char_type* egptr() const;
     void       gbump(int n);
     void       setg(char_type* gbeg, char_type* gnext, char_type* gend);
+    // [streambuf.put.area], put area access
     char_type* pbase() const;
     char_type* pptr() const;
     char_type* epptr() const;
     void       pbump(int n);
     void       setp(char_type* pbeg, char_type* pend);
+    // [streambuf.virtuals], virtual functions
+    // [streambuf.virt.locales], locales
     virtual void imbue(const locale& loc);
+    // [streambuf.virt.buffer], buffer management and positioning
+    virtual basic_streambuf* setbuf(char_type* s, streamsize n);
     virtual pos_type seekoff(off_type off, ios_base::seekdir way,
+ ios_base::openmode which
+                               = ios_base::in | ios_base::out);
     virtual pos_type seekpos(pos_type sp,
+ ios_base::openmode which
+                               = ios_base::in | ios_base::out);
     virtual int      sync();
+    // [streambuf.virt.get], get area
     virtual streamsize showmanyc();
     virtual streamsize xsgetn(char_type* s, streamsize n);
     virtual int_type   underflow();
     virtual int_type   uflow();
+    // [streambuf.virt.pback], putback
     virtual int_type   pbackfail(int_type c = traits::eof());
+    // [streambuf.virt.put], put area
     virtual streamsize xsputn(const char_type* s, streamsize n);
     virtual int_type   overflow(int_type c = traits::eof());
   };
 }
 ```
+The class template `basic_streambuf` serves as an abstract base class
+for deriving various *stream buffers* whose objects each control two
+*character sequences*:
 - a character *input sequence*;
 - a character *output sequence*.
 #### `basic_streambuf` constructors <a id="streambuf.cons">[[streambuf.cons]]</a>
 ``` cpp
 basic_streambuf();
 ```
+*Effects:* Constructs an object of class
+`basic_streambuf<charT, traits>` and initializes:[^13]
 - all its pointer member objects to null pointers,
 - the `getloc()` member to a copy the global locale, `locale()`, at the
   time of construction.
 ``` cpp
 locale pubimbue(const locale& loc);
 ```
+*Postconditions:* `loc == getloc()`.
 *Effects:* Calls `imbue(loc)`.
 *Returns:* Previous value of `getloc()`.
 call of `imbue()`) then it returns the previous value.
 ##### Buffer management and positioning <a id="streambuf.buffer">[[streambuf.buffer]]</a>
 ``` cpp
+basic_streambuf* pubsetbuf(char_type* s, streamsize n);
 ```
 *Returns:* `setbuf(s, n)`.
 ``` cpp
 pos_type pubseekoff(off_type off, ios_base::seekdir way,
+ ios_base::openmode which
+                      = ios_base::in | ios_base::out);
 ```
 *Returns:* `seekoff(off, way, which)`.
 ``` cpp
 pos_type pubseekpos(pos_type sp,
+ ios_base::openmode which
+                      = ios_base::in | ios_base::out);
 ```
 *Returns:* `seekpos(sp, which)`.
 ``` cpp
 ``` cpp
 int_type sputbackc(char_type c);
 ```
 *Returns:* If the input sequence putback position is not available, or
+if `traits::eq(c, gptr()[-1])` is `false`, returns
 `pbackfail(traits::to_int_type(c))`. Otherwise, decrements the next
 pointer for the input sequence and returns
 `traits::to_int_type(*gptr())`.
 ``` cpp
 *Effects:* Synchronizes the controlled sequences with the arrays. That
 is, if `pbase()` is non-null the characters between `pbase()` and
 `pptr()` are written to the controlled sequence. The pointers may then
 be reset as appropriate.
+*Returns:* `-1` on failure. What constitutes failure is determined by
+each derived class ([[filebuf.virtuals]]).
 *Default behavior:* Returns zero.
 ##### Get area <a id="streambuf.virt.get">[[streambuf.virt.get]]</a>
 *Returns:* `traits::to_int_type(c)`, where `c` is the first *character*
 of the *pending sequence*, without moving the input sequence position
 past it. If the pending sequence is null then the function returns
 `traits::eof()` to indicate failure.
+The *pending sequence* of characters is defined as the concatenation of
+- the empty sequence if `gptr()` is null, otherwise the characters in
+  \[`gptr()`, `egptr()`), followed by
+- some (possibly empty) sequence of characters read from the input
+  sequence.
+The *result character* is the first character of the pending sequence if
+it is non-empty, otherwise the next character that would be read from
+the input sequence.
+The *backup sequence* is the empty sequence if `eback()` is null,
+otherwise the characters in \[`eback()`, `gptr()`).
+*Effects:* The function sets up the `gptr()` and `egptr()` such that if
+the pending sequence is non-empty, then `egptr()` is non-null and the
+characters in \[`gptr()`, `egptr()`) are the characters in the pending
+sequence, otherwise either `gptr()` is null or `gptr() == egptr()`.
 If `eback()` and `gptr()` are non-null then the function is not
 constrained as to their contents, but the “usual backup condition” is
+that either
+- the backup sequence contains at least `gptr() - eback()` characters,
+  in which case the characters in \[`eback()`, `gptr()`) agree with the
+  last `gptr() - eback()` characters of the backup sequence, or
+- the characters in \[`gptr() - n`, `gptr()`) agree with the backup
+  sequence (where `n` is the length of the backup sequence).
 *Default behavior:* Returns `traits::eof()`.
 ``` cpp
 int_type uflow();
 modifications that
 - If `traits::eq_int_type(c, traits::eof())` returns `true`, then the
   input sequence is backed up one character before the pending sequence
   is determined.
+- If `traits::eq_int_type(c, traits::eof())` returns `false`, then `c`
+ is prepended. Whether the input sequence is backed up or modified in
+ any other way is unspecified.
+*Postconditions:* On return, the constraints of `gptr()`, `eback()`, and
+`pptr()` are the same as for `underflow()`.
 *Returns:* `traits::eof()` to indicate failure. Failure may occur
 because the input sequence could not be backed up, or if for some other
 reason the pointers could not be set consistent with the constraints.
 `pbackfail()` is called only when put back has really failed.
 *Effects:* Writes up to `n` characters to the output sequence as if by
 repeated calls to `sputc(c)`. The characters written are obtained from
 successive elements of the array whose first element is designated by
 `s`. Writing stops when either `n` characters have been written or a
+call to `sputc(c)` would return `traits::eof()`. It is unspecified
 whether the function calls `overflow()` when `pptr() == epptr()` becomes
+`true` or whether it achieves the same effects by other means.
 *Returns:* The number of characters written.
 ``` cpp
 int_type overflow(int_type c = traits::eof());
 *Effects:* Consumes some initial subsequence of the characters of the
 *pending sequence*. The pending sequence is defined as the concatenation
 of
+- the empty sequence if `pbase()` is not null, otherwise the
+  `pptr() - pbase()` characters beginning at `pbase()`, followed by
+- the empty sequence if `traits::eq_int_type(c, traits::eof())` returns
+  `true`, otherwise the sequence consisting of `c`.
 *Remarks:* The member functions `sputc()` and `sputn()` call this
 function in case that no room can be found in the put buffer enough to
 accommodate the argument character sequence.
 *Requires:* Every overriding definition of this virtual function shall
 obey the following constraints:
+1.  The effect of consuming a character on the associated output
+    sequence is specified[^16]
+2.  Let `r` be the number of characters in the pending sequence not
+    consumed. If `r` is nonzero then `pbase()` and `pptr()` shall be set
+    so that: `pptr() - pbase() == r` and the `r` characters starting at
+    `pbase()` are the associated output stream. In case `r` is zero (all
+    characters of the pending sequence have been consumed) then either
+    `pbase()` is set to `nullptr`, or `pbase()` and `pptr()` are both
+    set to the same non-null value.
+3.  The function may fail if either appending some character to the
+    associated output stream fails or if it is unable to establish
+    `pbase()` and `pptr()` according to the above rules.
 *Returns:* `traits::eof()` or throws an exception if the function fails.
 Otherwise, returns some value other than `traits::eof()` to indicate
+success.[^17]
 *Default behavior:* Returns `traits::eof()`.
 ## Formatting and manipulators <a id="iostream.format">[[iostream.format]]</a>
+### Header `<istream>` synopsis <a id="istream.syn">[[istream.syn]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
     class basic_istream;
+ using istream  = basic_istream<char>;
+  using wistream = basic_istream<wchar_t>;
   template <class charT, class traits = char_traits<charT>>
     class basic_iostream;
+ using iostream  = basic_iostream<char>;
+  using wiostream = basic_iostream<wchar_t>;
   template <class charT, class traits>
     basic_istream<charT, traits>& ws(basic_istream<charT, traits>& is);
   template <class charT, class traits, class T>
+    basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&& is, T&& x);
 }
 ```
+### Header `<ostream>` synopsis <a id="ostream.syn">[[ostream.syn]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
     class basic_ostream;
+ using ostream  = basic_ostream<char>;
+  using wostream = basic_ostream<wchar_t>;
   template <class charT, class traits>
     basic_ostream<charT, traits>& endl(basic_ostream<charT, traits>& os);
   template <class charT, class traits>
     basic_ostream<charT, traits>& ends(basic_ostream<charT, traits>& os);
   template <class charT, class traits>
     basic_ostream<charT, traits>& flush(basic_ostream<charT, traits>& os);
   template <class charT, class traits, class T>
+    basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&& os, const T& x);
 }
 ```
+### Header `<iomanip>` synopsis <a id="iomanip.syn">[[iomanip.syn]]</a>
 ``` cpp
 namespace std {
   // types T1, T2, ... are unspecified implementation types
   T1 resetiosflags(ios_base::fmtflags mask);
   T2 setiosflags  (ios_base::fmtflags mask);
   template <class charT>
     T11 quoted(const charT* s, charT delim = charT('"'), charT escape = charT('\\'));
   template <class charT, class traits, class Allocator>
     T12 quoted(const basic_string<charT, traits, Allocator>& s,
+    \itcorr           charT delim = charT('"'), charT escape = charT('\\'));
   template <class charT, class traits, class Allocator>
     T13 quoted(basic_string<charT, traits, Allocator>& s,
+    \itcorr           charT delim = charT('"'), charT escape = charT('\\'));
+  template <class charT, class traits>
+    T14 quoted(basic_string_view<charT, traits> s,
+    \itcorr           charT delim = charT('"'), charT escape = charT('\\'));
 }
 ```
 ### Input streams <a id="input.streams">[[input.streams]]</a>
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_istream : virtual public basic_ios<charT, traits> {
   public:
     // types (inherited from basic_ios ([ios])):
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [istream.cons], constructor/destructor
     explicit basic_istream(basic_streambuf<charT, traits>* sb);
     virtual ~basic_istream();
+    // [istream::sentry], prefix/suffix
     class sentry;
+    // [istream.formatted], formatted input
+    basic_istream<charT, traits>&
+ operator>>(basic_istream<charT, traits>& (*pf)(basic_istream<charT, traits>&));
+    basic_istream<charT, traits>&
+      operator>>(basic_ios<charT, traits>& (*pf)(basic_ios<charT, traits>&));
+    basic_istream<charT, traits>&
+ operator>>(ios_base& (*pf)(ios_base&));
     basic_istream<charT, traits>& operator>>(bool& n);
     basic_istream<charT, traits>& operator>>(short& n);
     basic_istream<charT, traits>& operator>>(unsigned short& n);
     basic_istream<charT, traits>& operator>>(int& n);
     basic_istream<charT, traits>& operator>>(float& f);
     basic_istream<charT, traits>& operator>>(double& f);
     basic_istream<charT, traits>& operator>>(long double& f);
     basic_istream<charT, traits>& operator>>(void*& p);
+    basic_istream<charT, traits>& operator>>(basic_streambuf<char_type, traits>* sb);
+    // [istream.unformatted], unformatted input
     streamsize gcount() const;
     int_type get();
     basic_istream<charT, traits>& get(char_type& c);
     basic_istream<charT, traits>& get(char_type* s, streamsize n);
+    basic_istream<charT, traits>& get(char_type* s, streamsize n, char_type delim);
     basic_istream<charT, traits>& get(basic_streambuf<char_type, traits>& sb);
+    basic_istream<charT, traits>& get(basic_streambuf<char_type, traits>& sb, char_type delim);
     basic_istream<charT, traits>& getline(char_type* s, streamsize n);
+    basic_istream<charT, traits>& getline(char_type* s, streamsize n, char_type delim);
+    basic_istream<charT, traits>& ignore(streamsize n = 1, int_type delim = traits::eof());
     int_type                      peek();
     basic_istream<charT, traits>& read    (char_type* s, streamsize n);
     streamsize                    readsome(char_type* s, streamsize n);
     basic_istream<charT, traits>& putback(char_type c);
     pos_type tellg();
     basic_istream<charT, traits>& seekg(pos_type);
     basic_istream<charT, traits>& seekg(off_type, ios_base::seekdir);
   protected:
+    // [istream.cons], copy/move constructor
     basic_istream(const basic_istream& rhs) = delete;
     basic_istream(basic_istream&& rhs);
+    // [istream.assign], assign and swap
     basic_istream& operator=(const basic_istream& rhs) = delete;
     basic_istream& operator=(basic_istream&& rhs);
     void swap(basic_istream& rhs);
   };
+  // [istream.extractors], character extraction templates
   template<class charT, class traits>
+    basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&, charT&);
   template<class traits>
+    basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, unsigned char&);
   template<class traits>
+    basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, signed char&);
   template<class charT, class traits>
+    basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&, charT*);
   template<class traits>
+    basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, unsigned char*);
   template<class traits>
+    basic_istream<char, traits>& operator>>(basic_istream<char, traits>&, signed char*);
 }
 ```
+The class template `basic_istream` defines a number of member function
+signatures that assist in reading and interpreting input from sequences
+controlled by a stream buffer.
 Two groups of member function signatures share common properties: the
 *formatted input functions* (or *extractors*) and the *unformatted input
 functions.* Both groups of input functions are described as if they
 obtain (or *extract*) input *characters* by calling `rdbuf()->sbumpc()`
 ``` cpp
 explicit basic_istream(basic_streambuf<charT, traits>* sb);
 ```
+*Effects:* Constructs an object of class `basic_istream`, initializing
+the base class subobject with
 `basic_ios::init(sb)` ([[basic.ios.cons]]).
+*Postconditions:* `gcount() == 0`.
 ``` cpp
 basic_istream(basic_istream&& rhs);
 ```
 ``` cpp
 basic_istream& operator=(basic_istream&& rhs);
 ```
+*Effects:* As if by `swap(rhs)`.
 *Returns:* `*this`.
 ``` cpp
 void swap(basic_istream& rhs);
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_istream<charT, traits>::sentry {
+ using traits_type = traits;
     bool ok_; // exposition only
   public:
     explicit sentry(basic_istream<charT, traits>& is, bool noskipws = false);
     ~sentry();
     explicit operator bool() const { return ok_; }
 to synchronize the output sequence with any associated external C
 stream. Except that this call can be suppressed if the put area of
 `is.tie()` is empty. Further an implementation is allowed to defer the
 call to `flush` until a call of `is.rdbuf()->underflow()` occurs. If no
 such call occurs before the `sentry` object is destroyed, the call to
+`flush` may be eliminated entirely.[^18] If `noskipws` is zero and
 `is.flags() & ios_base::skipws` is nonzero, the function extracts and
 discards each character as long as the next available input character
 `c` is a whitespace character. If `is.rdbuf()->sbumpc()` or
 `is.rdbuf()->sgetc()` returns `traits::eof()`, the function calls
 `setstate(failbit | eofbit)` (which may throw `ios_base::failure`).
 *Remarks:* The constructor
+``` cpp
+explicit sentry(basic_istream<charT, traits>& is, bool noskipws = false)
+```
 uses the currently imbued locale in `is`, to determine whether the next
 input character is whitespace or not.
 To decide if the character `c` is a whitespace character, the
 constructor performs as if it executes the following code fragment:
 ```
 If, after any preparation is completed, `is.good()` is `true`,
 `ok_ != false` otherwise, `ok_ == false`. During preparation, the
 constructor may call `setstate(failbit)` (which may throw
+`ios_base::failure` ([[iostate.flags]]))[^19]
 ``` cpp
 ~sentry();
 ```
 Each formatted input function begins execution by constructing an object
 of class `sentry` with the `noskipws` (second) argument `false`. If the
 `sentry` object returns `true`, when converted to a value of type
 `bool`, the function endeavors to obtain the requested input. If an
+exception is thrown during input then `ios::badbit` is turned on[^20] in
 `*this`’s error state. If `(exceptions()&badbit) != 0` then the
 exception is rethrown. In any case, the formatted input function
 destroys the `sentry` object. If no exception has been thrown, it
 returns `*this`.
 described in  [[istream.formatted.reqmts]]). After a sentry object is
 constructed, the conversion occurs as if performed by the following code
 fragment:
 ``` cpp
+using numget = num_get<charT, istreambuf_iterator<charT, traits>>;
 iostate err = iostate::goodbit;
 use_facet<numget>(loc).get(*this, 0, *this, err, val);
 setstate(err);
 ```
 In the above fragment, `loc` stands for the private member of the
+`basic_ios` class.
+[*Note 1*: The first argument provides an object of the
 `istreambuf_iterator` class which is an iterator pointed to an input
+stream. It bypasses istreams and uses streambufs
+directly. — *end note*]
+Class `locale` relies on this type as its interface to `istream`, so
+that it does not need to depend directly on `istream`.
 ``` cpp
 operator>>(short& val);
 ```
 The conversion occurs as if performed by the following code fragment
 (using the same notation as for the preceding code fragment):
 ``` cpp
+using numget = num_get<charT, istreambuf_iterator<charT, traits>>;
 iostate err = ios_base::goodbit;
 long lval;
 use_facet<numget>(loc).get(*this, 0, *this, err, lval);
 if (lval < numeric_limits<short>::min()) {
   err |= ios_base::failbit;
 The conversion occurs as if performed by the following code fragment
 (using the same notation as for the preceding code fragment):
 ``` cpp
+using numget = num_get<charT, istreambuf_iterator<charT, traits>>;
 iostate err = ios_base::goodbit;
 long lval;
 use_facet<numget>(loc).get(*this, 0, *this, err, lval);
 if (lval < numeric_limits<int>::min()) {
   err |= ios_base::failbit;
 }  else
   val = static_cast<int>(lval);
 setstate(err);
 ```
+##### `basic_istream::operator>>` <a id="istream.extractors">[[istream.extractors]]</a>
 ``` cpp
+basic_istream<charT, traits>&
+  operator>>(basic_istream<charT, traits>& (*pf)(basic_istream<charT, traits>&));
 ```
 *Effects:* None. This extractor does not behave as a formatted input
+function (as described in  [[istream.formatted.reqmts]]).
+*Returns:* `pf(*this)`.[^21]
 ``` cpp
+basic_istream<charT, traits>&
+  operator>>(basic_ios<charT, traits>& (*pf)(basic_ios<charT, traits>&));
 ```
 *Effects:* Calls `pf(*this)`. This extractor does not behave as a
 formatted input function (as described
 in  [[istream.formatted.reqmts]]).
 *Returns:* `*this`.
 ``` cpp
+basic_istream<charT, traits>& operator>>(ios_base& (*pf)(ios_base&));
 ```
+*Effects:* Calls `pf(*this)`.[^22] This extractor does not behave as a
 formatted input function (as described
 in  [[istream.formatted.reqmts]]).
 *Returns:* `*this`.
 ``` cpp
 template<class charT, class traits>
+  basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& in, charT* s);
 template<class traits>
+  basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char* s);
 template<class traits>
+  basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char* s);
 ```
 *Effects:* Behaves like a formatted input member (as described
 in  [[istream.formatted.reqmts]]) of `in`. After a `sentry` object is
 constructed, `operator>>` extracts characters and stores them into
 Characters are extracted and stored until any of the following occurs:
 - `n-1` characters are stored;
 - end of file occurs on the input sequence;
+- letting `ct` be `use_facet<ctype<charT>>(in.getloc())`,
+  `ct.is(ct.space, c)` is `true`.
 `operator>>` then stores a null byte (`charT()`) in the next position,
 which may be the first position if no characters were extracted.
 `operator>>` then calls `width(0)`.
 *Returns:* `in`.
 ``` cpp
 template<class charT, class traits>
+  basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& in, charT& c);
 template<class traits>
+  basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, unsigned char& c);
 template<class traits>
+  basic_istream<char, traits>& operator>>(basic_istream<char, traits>& in, signed char& c);
 ```
 *Effects:* Behaves like a formatted input member (as described
 in  [[istream.formatted.reqmts]]) of `in`. After a `sentry` object is
 constructed a character is extracted from `in`, if one is available, and
 stored in `c`. Otherwise, the function calls `in.setstate(failbit)`.
 *Returns:* `in`.
 ``` cpp
+basic_istream<charT, traits>& operator>>(basic_streambuf<charT, traits>* sb);
 ```
+*Effects:* Behaves as an unformatted input function
+([[istream.unformatted]]). If `sb` is null, calls `setstate(failbit)`,
+which may throw `ios_base::failure` ([[iostate.flags]]). After a sentry
+object is constructed, extracts characters from `*this` and inserts them
+in the output sequence controlled by `sb`. Characters are extracted and
 inserted until any of the following occurs:
 - end-of-file occurs on the input sequence;
 - inserting in the output sequence fails (in which case the character to
   be inserted is not extracted);
 Each unformatted input function begins execution by constructing an
 object of class `sentry` with the default argument `noskipws` (second)
 argument `true`. If the `sentry` object returns `true`, when converted
 to a value of type `bool`, the function endeavors to obtain the
 requested input. Otherwise, if the sentry constructor exits by throwing
+an exception or if the sentry object returns `false`, when converted to
+a value of type `bool`, the function returns without attempting to
+obtain any input. In either case the number of extracted characters is
+set to 0; unformatted input functions taking a character array of
+nonzero size as an argument shall also store a null character (using
+`charT()`) in the first location of the array. If an exception is thrown
+during input then `ios::badbit` is turned on[^23] in `*this`’s error
+state. (Exceptions thrown from `basic_ios<>::clear()` are not caught or
 rethrown.) If `(exceptions()&badbit) != 0` then the exception is
 rethrown. It also counts the number of characters extracted. If no
 exception has been thrown it ends by storing the count in a member
 object and returning the value specified. In any event the `sentry`
 object is destroyed before leaving the unformatted input function.
 ``` cpp
 streamsize gcount() const;
 ```
 *Effects:* None. This member function does not behave as an unformatted
+input function (as described above).
 *Returns:* The number of characters extracted by the last unformatted
 input member function called for the object.
 ``` cpp
 int_type get();
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, extracts a character `c`, if
+one is available. Otherwise, the function calls `setstate(failbit)`,
+which may throw `ios_base::failure` ([[iostate.flags]]),
 *Returns:* `c` if available, otherwise `traits::eof()`.
 ``` cpp
 basic_istream<charT, traits>& get(char_type& c);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, extracts a character, if one
+is available, and assigns it to `c`.[^24] Otherwise, the function calls
+`setstate(failbit)` (which may throw
+`ios_base::failure` ([[iostate.flags]])).
 *Returns:* `*this`.
 ``` cpp
+basic_istream<charT, traits>& get(char_type* s, streamsize n, char_type delim);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, extracts characters and
+stores them into successive locations of an array whose first element is
+designated by `s`.[^25] Characters are extracted and stored until any of
+the following occurs:
 - `n` is less than one or `n - 1` characters are stored;
 - end-of-file occurs on the input sequence (in which case the function
   calls `setstate(eofbit)`);
 - `traits::eq(c, delim)` for the next available input character `c` (in
 ``` cpp
 basic_istream<charT, traits>& get(char_type* s, streamsize n);
 ```
+*Effects:* Calls `get(s, n, widen(’\n’))`.
 *Returns:* Value returned by the call.
 ``` cpp
+basic_istream<charT, traits>& get(basic_streambuf<char_type, traits>& sb, char_type delim);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, extracts characters and
+inserts them in the output sequence controlled by `sb`. Characters are
+extracted and inserted until any of the following occurs:
 - end-of-file occurs on the input sequence;
 - inserting in the output sequence fails (in which case the character to
   be inserted is not extracted);
 - `traits::eq(c, delim)` for the next available input character `c` (in
 ``` cpp
 basic_istream<charT, traits>& get(basic_streambuf<char_type, traits>& sb);
 ```
+*Effects:* Calls `get(sb, widen(’\n’))`.
 *Returns:* Value returned by the call.
 ``` cpp
+basic_istream<charT, traits>& getline(char_type* s, streamsize n, char_type delim);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, extracts characters and
+stores them into successive locations of an array whose first element is
+designated by `s`.[^26] Characters are extracted and stored until one of
+the following occurs:
 1.  end-of-file occurs on the input sequence (in which case the function
     calls `setstate(eofbit)`);
 2.  `traits::eq(c, delim)` for the next available input character `c`
     (in which case the input character is extracted but not
+    stored);[^27]
 3.  `n` is less than one or `n - 1` characters are stored (in which case
     the function calls `setstate(failbit)`).
+These conditions are tested in the order shown.[^28]
 If the function extracts no characters, it calls `setstate(failbit)`
+(which may throw `ios_base::failure` ([[iostate.flags]])).[^29]
 In any case, if `n` is greater than zero, it then stores a null
 character (using `charT()`) into the next successive location of the
 array.
 *Returns:* `*this`.
+[*Example 1*:
 ``` cpp
 #include <iostream>
 int main() {
   using namespace std;
     cout << " (" << count << " chars): " << buffer << endl;
   }
 }
 ```
+— *end example*]
 ``` cpp
 basic_istream<charT, traits>& getline(char_type* s, streamsize n);
 ```
 *Returns:* `getline(s, n, widen(’\n’))`
 ``` cpp
+basic_istream<charT, traits>& ignore(streamsize n = 1, int_type delim = traits::eof());
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, extracts characters and
+discards them. Characters are extracted until any of the following
+occurs:
+- `n != numeric_limits<streamsize>::max()` ([[numeric.limits]]) and `n`
   characters have been extracted so far
 - end-of-file occurs on the input sequence (in which case the function
   calls `setstate(eofbit)`, which may throw
   `ios_base::failure` ([[iostate.flags]]));
 - `traits::eq_int_type(traits::to_int_type(c), delim)` for the next
 ``` cpp
 int_type peek();
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, reads but does not extract
+the current input character.
 *Returns:* `traits::eof()` if `good()` is `false`. Otherwise, returns
 `rdbuf()->sgetc()`.
 ``` cpp
 basic_istream<charT, traits>& read(char_type* s, streamsize n);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, if `!good()` calls
+`setstate(failbit)` which may throw an exception, and return. Otherwise
+extracts characters and stores them into successive locations of an
+array whose first element is designated by `s`.[^30] Characters are
+extracted and stored until either of the following occurs:
 - `n` characters are stored;
 - end-of-file occurs on the input sequence (in which case the function
   calls `setstate(failbit | eofbit)`, which may throw
   `ios_base::failure` ([[iostate.flags]])).
 ``` cpp
 streamsize readsome(char_type* s, streamsize n);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above). After constructing a sentry object, if `!good()` calls
+`setstate(failbit)` which may throw an exception, and return. Otherwise
+extracts characters and stores them into successive locations of an
+array whose first element is designated by `s`. If
+`rdbuf()->in_avail() == -1`, calls `setstate(eofbit)` (which may throw
+`ios_base::failure` ([[iostate.flags]])), and extracts no characters;
 - If `rdbuf()->in_avail() == 0`, extracts no characters
 - If `rdbuf()->in_avail() > 0`, extracts `min(rdbuf()->in_avail(), n))`.
 *Returns:* The number of characters extracted.
 ``` cpp
 basic_istream<charT, traits>& putback(char_type c);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above), except that the function first clears `eofbit`. After
+constructing a sentry object, if `!good()` calls `setstate(failbit)`
+which may throw an exception, and return. If `rdbuf()` is not null,
+calls `rdbuf->sputbackc()`. If `rdbuf()` is null, or if `sputbackc()`
+returns `traits::eof()`, calls `setstate(badbit)` (which may throw
+`ios_base::failure` ([[iostate.flags]])).
+[*Note 1*: This function extracts no characters, so the value returned
+by the next call to `gcount()` is 0. — *end note*]
 *Returns:* `*this`.
 ``` cpp
 basic_istream<charT, traits>& unget();
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above), except that the function first clears `eofbit`. After
+constructing a sentry object, if `!good()` calls `setstate(failbit)`
+which may throw an exception, and return. If `rdbuf()` is not null,
+calls `rdbuf()->sungetc()`. If `rdbuf()` is null, or if `sungetc()`
+returns `traits::eof()`, calls `setstate(badbit)` (which may throw
+`ios_base::failure` ([[iostate.flags]])).
+[*Note 2*: This function extracts no characters, so the value returned
+by the next call to `gcount()` is 0. — *end note*]
 *Returns:* `*this`.
 ``` cpp
 int sync();
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above), except that it does not count the number of characters extracted
+and does not affect the value returned by subsequent calls to
+`gcount()`. After constructing a sentry object, if `rdbuf()` is a null
+pointer, returns `-1`. Otherwise, calls `rdbuf()->pubsync()` and, if
+that function returns `-1` calls `setstate(badbit)` (which may throw
 `ios_base::failure` ([[iostate.flags]]), and returns `-1`. Otherwise,
 returns zero.
 ``` cpp
 pos_type tellg();
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above), except that it does not count the number of characters extracted
+and does not affect the value returned by subsequent calls to
+`gcount()`.
 *Returns:* After constructing a sentry object, if `fail() != false`,
 returns `pos_type(-1)` to indicate failure. Otherwise, returns
 `rdbuf()->pubseekoff(0, cur, in)`.
 ``` cpp
 basic_istream<charT, traits>& seekg(pos_type pos);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above), except that the function first clears `eofbit`, it does not
+count the number of characters extracted, and it does not affect the
+value returned by subsequent calls to `gcount()`. After constructing a
+sentry object, if `fail() != true`, executes
+`rdbuf()->pubseekpos(pos, ios_base::in)`. In case of failure, the
+function calls `setstate(failbit)` (which may throw
 `ios_base::failure`).
 *Returns:* `*this`.
 ``` cpp
 basic_istream<charT, traits>& seekg(off_type off, ios_base::seekdir dir);
 ```
 *Effects:* Behaves as an unformatted input function (as described
+above), except that the function first clears `eofbit`, does not count
+the number of characters extracted, and does not affect the value
 returned by subsequent calls to `gcount()`. After constructing a sentry
 object, if `fail() != true`, executes
 `rdbuf()->pubseekoff(off, dir, ios_base::in)`. In case of failure, the
 function calls `setstate(failbit)` (which may throw
 `ios_base::failure`).
 *Returns:* `*this`.
 #### Standard `basic_istream` manipulators <a id="istream.manip">[[istream.manip]]</a>
 ``` cpp
 template <class charT, class traits>
   basic_istream<charT, traits>& ws(basic_istream<charT, traits>& is);
 ```
+*Effects:* Behaves as an unformatted input function
+([[istream.unformatted]]), except that it does not count the number of
+characters extracted and does not affect the value returned by
+subsequent calls to is.gcount(). After constructing a sentry object
+extracts characters as long as the next available character `c` is
+whitespace or until there are no more characters in the sequence.
 Whitespace characters are distinguished with the same criterion as used
 by `sentry::sentry` ([[istream::sentry]]). If `ws` stops extracting
 characters because there are no more available it sets `eofbit`, but not
 `failbit`.
 *Returns:* `is`.
+#### Rvalue stream extraction <a id="istream.rvalue">[[istream.rvalue]]</a>
+``` cpp
+template <class charT, class traits, class T>
+  basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&& is, T&& x);
+```
+*Effects:* Equivalent to:
+``` cpp
+is >> std::forward<T>(x);
+return is;
+```
+*Remarks:* This function shall not participate in overload resolution
+unless the expression `is >> std::forward<T>(x)` is well-formed.
 #### Class template `basic_iostream` <a id="iostreamclass">[[iostreamclass]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
+  class basic_iostream
+ : public basic_istream<charT, traits>,
       public basic_ostream<charT, traits> {
   public:
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [iostream.cons], constructor
     explicit basic_iostream(basic_streambuf<charT, traits>* sb);
+    // [iostream.dest], destructor
     virtual ~basic_iostream();
   protected:
+    // [iostream.cons], constructor
     basic_iostream(const basic_iostream& rhs) = delete;
     basic_iostream(basic_iostream&& rhs);
+    // [iostream.assign], assign and swap
     basic_iostream& operator=(const basic_iostream& rhs) = delete;
     basic_iostream& operator=(basic_iostream&& rhs);
     void swap(basic_iostream& rhs);
   };
 }
 ```
+The class template `basic_iostream` inherits a number of functions that
+allow reading input and writing output to sequences controlled by a
+stream buffer.
 ##### `basic_iostream` constructors <a id="iostream.cons">[[iostream.cons]]</a>
 ``` cpp
 explicit basic_iostream(basic_streambuf<charT, traits>* sb);
 ```
+*Effects:* Constructs an object of class `basic_iostream`, initializing
+the base class subobjects with
 `basic_istream<charT, traits>(sb)` ([[istream]]) and
+`basic_ostream<charT, traits>(sb)` ([[ostream]]).
+*Postconditions:* `rdbuf() == sb` and `gcount() == 0`.
 ``` cpp
 basic_iostream(basic_iostream&& rhs);
 ```
 ``` cpp
 basic_iostream& operator=(basic_iostream&& rhs);
 ```
+*Effects:* As if by `swap(rhs)`.
 ``` cpp
 void swap(basic_iostream& rhs);
 ```
 *Effects:* Calls `basic_istream<charT, traits>::swap(rhs)`.
 ### Output streams <a id="output.streams">[[output.streams]]</a>
 The header `<ostream>` defines a type and several function signatures
 that control output to a stream buffer along with a function template
 that inserts into stream rvalues.
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ostream : virtual public basic_ios<charT, traits> {
   public:
     // types (inherited from basic_ios ([ios])):
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [ostream.cons], constructor/destructor
     explicit basic_ostream(basic_streambuf<char_type, traits>* sb);
     virtual ~basic_ostream();
+    // [ostream::sentry], prefix/suffix
     class sentry;
+    // [ostream.formatted], formatted output
+    basic_ostream<charT, traits>&
+ operator<<(basic_ostream<charT, traits>& (*pf)(basic_ostream<charT, traits>&));
+    basic_ostream<charT, traits>&
+ operator<<(basic_ios<charT, traits>& (*pf)(basic_ios<charT, traits>&));
+    basic_ostream<charT, traits>&
+ operator<<(ios_base& (*pf)(ios_base&));
     basic_ostream<charT, traits>& operator<<(bool n);
     basic_ostream<charT, traits>& operator<<(short n);
     basic_ostream<charT, traits>& operator<<(unsigned short n);
     basic_ostream<charT, traits>& operator<<(int n);
     basic_ostream<charT, traits>& operator<<(float f);
     basic_ostream<charT, traits>& operator<<(double f);
     basic_ostream<charT, traits>& operator<<(long double f);
     basic_ostream<charT, traits>& operator<<(const void* p);
+    basic_ostream<charT, traits>& operator<<(nullptr_t);
+    basic_ostream<charT, traits>& operator<<(basic_streambuf<char_type, traits>* sb);
+    // [ostream.unformatted], unformatted output
     basic_ostream<charT, traits>& put(char_type c);
     basic_ostream<charT, traits>& write(const char_type* s, streamsize n);
     basic_ostream<charT, traits>& flush();
+    // [ostream.seeks], seeks
     pos_type tellp();
     basic_ostream<charT, traits>& seekp(pos_type);
     basic_ostream<charT, traits>& seekp(off_type, ios_base::seekdir);
   protected:
+    // [ostream.cons], copy/move constructor
     basic_ostream(const basic_ostream& rhs) = delete;
     basic_ostream(basic_ostream&& rhs);
+    // [ostream.assign], assign and swap
     basic_ostream& operator=(const basic_ostream& rhs) = delete;
     basic_ostream& operator=(basic_ostream&& rhs);
     void swap(basic_ostream& rhs);
   };
+  // [ostream.inserters.character], character inserters
   template<class charT, class traits>
+    basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&, charT);
   template<class charT, class traits>
+    basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&, char);
   template<class traits>
+    basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, char);
   template<class traits>
+    basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, signed char);
   template<class traits>
+    basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, unsigned char);
   template<class charT, class traits>
+    basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&, const charT*);
   template<class charT, class traits>
+    basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&, const char*);
   template<class traits>
+    basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, const char*);
   template<class traits>
+    basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, const signed char*);
   template<class traits>
+    basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>&, const unsigned char*);
 }
 ```
+The class template `basic_ostream` defines a number of member function
+signatures that assist in formatting and writing output to output
+sequences controlled by a stream buffer.
 Two groups of member function signatures share common properties: the
 *formatted output functions* (or *inserters*) and the *unformatted
 output functions.* Both groups of output functions generate (or
 *insert*) output *characters* by actions equivalent to calling
 explicitly noted otherwise the output function sets `badbit` in error
 state. If `badbit` is on in `exceptions()`, the output function rethrows
 the exception without completing its actions, otherwise it does not
 throw anything and treat as an error.
+##### `basic_ostream` constructors <a id="ostream.cons">[[ostream.cons]]</a>
 ``` cpp
 explicit basic_ostream(basic_streambuf<charT, traits>* sb);
 ```
+*Effects:* Constructs an object of class `basic_ostream`, initializing
+the base class subobject with
+`basic_ios<charT, traits>::init(sb)` ([[basic.ios.cons]]).
+*Postconditions:* `rdbuf() == sb`.
 ``` cpp
 basic_ostream(basic_ostream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by default constructing the base class and calling
 `basic_ios<charT, traits>::move(rhs)` to initialize the base class.
+``` cpp
+virtual ~basic_ostream();
+```
+*Effects:* Destroys an object of class `basic_ostream`.
+*Remarks:* Does not perform any operations on `rdbuf()`.
+##### Class `basic_ostream` assign and swap <a id="ostream.assign">[[ostream.assign]]</a>
 ``` cpp
 basic_ostream& operator=(basic_ostream&& rhs);
 ```
+*Effects:* As if by `swap(rhs)`.
 *Returns:* `*this`.
 ``` cpp
 void swap(basic_ostream& rhs);
 ```
 *Effects:* Calls `basic_ios<charT, traits>::swap(rhs)`.
+##### Class `basic_ostream::sentry` <a id="ostream::sentry">[[ostream::sentry]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ostream<charT, traits>::sentry {
 ``` cpp
 explicit sentry(basic_ostream<charT, traits>& os);
 ```
 If `os.good()` is nonzero, prepares for formatted or unformatted output.
+If `os.tie()` is not a null pointer, calls `os.tie()->flush()`.[^31]
 If, after any preparation is completed, `os.good()` is `true`,
 `ok_ == true` otherwise, `ok_ == false`. During preparation, the
 constructor may call `setstate(failbit)` (which may throw
+`ios_base::failure` ([[iostate.flags]]))[^32]
 ``` cpp
 ~sentry();
 ```
 If
+`(os.flags() & ios_base::unitbuf) && !uncaught_exceptions() && os.good()`
 is `true`, calls `os.rdbuf()->pubsync()`. If that function returns -1,
 sets `badbit` in `os.rdstate()` without propagating an exception.
 ``` cpp
 explicit operator bool() const;
 ```
 *Effects:* Returns `ok_`.
+##### `basic_ostream` seek members <a id="ostream.seeks">[[ostream.seeks]]</a>
 Each seek member function begins execution by constructing an object of
 class `sentry`. It returns by destroying the `sentry` object.
 ``` cpp
 pos_type tellp();
 ```
+*Returns:* If `fail() != false`, returns `pos_type(-1)` to indicate
+failure. Otherwise, returns `rdbuf()->pubseekoff(0, cur, out)`.
 ``` cpp
 basic_ostream<charT, traits>& seekp(pos_type pos);
 ```
+*Effects:* If `fail() != true`, executes
+`rdbuf()->pubseekpos(pos, ios_base::out)`. In case of failure, the
+function calls `setstate(failbit)` (which may throw
+`ios_base::failure`).
+*Returns:* `*this`.
 ``` cpp
 basic_ostream<charT, traits>& seekp(off_type off, ios_base::seekdir dir);
 ```
 *Effects:* If `fail() != true`, executes
 object of class `sentry`. If this object returns `true` when converted
 to a value of type `bool`, the function endeavors to generate the
 requested output. If the generation fails, then the formatted output
 function does `setstate(ios_base::failbit)`, which might throw an
 exception. If an exception is thrown during output, then `ios::badbit`
+is turned on[^33] in `*this`’s error state. If
 `(exceptions()&badbit) != 0` then the exception is rethrown. Whether or
 not an exception is thrown, the `sentry` object is destroyed before
 leaving the formatted output function. If no exception is thrown, the
 result of the formatted output function is `*this`.
 The first argument provides an object of the `ostreambuf_iterator<>`
 class which is an iterator for class `basic_ostream<>`. It bypasses
 `ostream`s and uses `streambuf`s directly. Class `locale` relies on
 these types as its interface to iostreams, since for flexibility it has
 been abstracted away from direct dependence on `ostream`. The second
+parameter is a reference to the base class subobject of type `ios_base`.
+It provides formatting specifications such as field width, and a locale
 from which to obtain other facets. If `failed` is `true` then does
 `setstate(badbit)`, which may throw an exception, and returns.
 *Returns:* `*this`.
 ##### `basic_ostream::operator<<` <a id="ostream.inserters">[[ostream.inserters]]</a>
 ``` cpp
+basic_ostream<charT, traits>&
+  operator<<(basic_ostream<charT, traits>& (*pf)(basic_ostream<charT, traits>&));
 ```
 *Effects:* None. Does not behave as a formatted output function (as
 described in  [[ostream.formatted.reqmts]]).
+*Returns:* `pf(*this)`.[^34]
 ``` cpp
+basic_ostream<charT, traits>&
+  operator<<(basic_ios<charT, traits>& (*pf)(basic_ios<charT, traits>&));
 ```
 *Effects:* Calls `pf(*this)`. This inserter does not behave as a
 formatted output function (as described
 in  [[ostream.formatted.reqmts]]).
+*Returns:* `*this`.[^35]
 ``` cpp
+basic_ostream<charT, traits>& operator<<(ios_base& (*pf)(ios_base&));
 ```
 *Effects:* Calls `pf(*this)`. This inserter does not behave as a
 formatted output function (as described
 in  [[ostream.formatted.reqmts]]).
 *Returns:* `*this`.
 ``` cpp
+basic_ostream<charT, traits>& operator<<(basic_streambuf<charT, traits>* sb);
 ```
+*Effects:* Behaves as an unformatted output function
+([[ostream.unformatted]]). After the sentry object is constructed, if
+`sb` is null calls `setstate(badbit)` (which may throw
 `ios_base::failure`).
 Gets characters from `sb` and inserts them in `*this`. Characters are
 read from `sb` and inserted until any of the following occurs:
 `failbit` in error state, and if `failbit` is on in `exceptions()` the
 caught exception is rethrown.
 *Returns:* `*this`.
+``` cpp
+basic_ostream<charT, traits>& operator<<(nullptr_t);
+```
+*Effects:* Equivalent to:
+``` cpp
+return *this << s;
+```
+where `s` is an *implementation-defined* NTCTS ([[defns.ntcts]]).
 ##### Character inserter function templates <a id="ostream.inserters.character">[[ostream.inserters.character]]</a>
 ``` cpp
 template<class charT, class traits>
+  basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& out, charT c);
 template<class charT, class traits>
+  basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& out, char c);
 // specialization
 template<class traits>
+  basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, char c);
 // signed and unsigned
 template<class traits>
+  basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, signed char c);
 template<class traits>
+  basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, unsigned char c);
 ```
+*Effects:* Behaves as a formatted output
+function ([[ostream.formatted.reqmts]]) of `out`. Constructs a
+character sequence `seq`. If `c` has type `char` and the character type
+of the stream is not `char`, then `seq` consists of `out.widen(c)`;
+otherwise `seq` consists of `c`. Determines padding for `seq` as
+described in  [[ostream.formatted.reqmts]]. Inserts `seq` into `out`.
+Calls `os.width(0)`.
 *Returns:* `out`.
 ``` cpp
 template<class charT, class traits>
+  basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& out, const charT* s);
 template<class charT, class traits>
+  basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& out, const char* s);
 template<class traits>
+  basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, const char* s);
 template<class traits>
+  basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out, const signed char* s);
 template<class traits>
   basic_ostream<char, traits>& operator<<(basic_ostream<char, traits>& out,
                                           const unsigned char* s);
 ```
 - `traits::length(s)` for the overload where the first argument is of
   type `basic_ostream<charT, traits>&` and the second is of type
   `const charT*`, and also for the overload where the first argument is
   of type `basic_ostream<char, traits>&` and the second is of type
   `const char*`,
+- `char_traits<char>::length(s)` for the overload where the first
   argument is of type `basic_ostream<charT, traits>&` and the second is
   of type `const char*`,
 - `traits::length(reinterpret_cast<const char*>(s))` for the other two
   overloads.
 Each unformatted output function begins execution by constructing an
 object of class `sentry`. If this object returns `true`, while
 converting to a value of type `bool`, the function endeavors to generate
 the requested output. If an exception is thrown during output, then
+`ios::badbit` is turned on[^36] in `*this`’s error state. If
 `(exceptions() & badbit) != 0` then the exception is rethrown. In any
 case, the unformatted output function ends by destroying the sentry
 object, then, if no exception was thrown, returning the value specified
 for the unformatted output function.
 ``` cpp
 basic_ostream<charT, traits>& put(char_type c);
 ```
 *Effects:* Behaves as an unformatted output function (as described
+above). After constructing a sentry object, inserts the character `c`,
+if possible.[^37]
 Otherwise, calls `setstate(badbit)` (which may throw
 `ios_base::failure` ([[iostate.flags]])).
 *Returns:* `*this`.
 ``` cpp
 basic_ostream& write(const char_type* s, streamsize n);
 ```
 *Effects:* Behaves as an unformatted output function (as described
+above). After constructing a sentry object, obtains characters to insert
+from successive locations of an array whose first element is designated
+by `s`.[^38] Characters are inserted until either of the following
+occurs:
 - `n` characters are inserted;
 - inserting in the output sequence fails (in which case the function
   calls `setstate(badbit)`, which may throw
   `ios_base::failure` ([[iostate.flags]])).
 ``` cpp
 basic_ostream& flush();
 ```
 *Effects:* Behaves as an unformatted output function (as described
+above). If `rdbuf()` is not a null pointer, constructs a sentry object.
+If this object returns `true` when converted to a value of type `bool`
+the function calls `rdbuf()->pubsync()`. If that function returns -1
+calls `setstate(badbit)` (which may throw
 `ios_base::failure` ([[iostate.flags]])). Otherwise, if the sentry
 object returns `false`, does nothing.
 *Returns:* `*this`.
 #### Standard `basic_ostream` manipulators <a id="ostream.manip">[[ostream.manip]]</a>
 ``` cpp
 template <class charT, class traits>
   basic_ostream<charT, traits>& endl(basic_ostream<charT, traits>& os);
 ```
 *Effects:* Calls `os.put(os.widen(’\n’))`, then `os.flush()`.
 *Returns:* `os`.
 ``` cpp
 template <class charT, class traits>
   basic_ostream<charT, traits>& ends(basic_ostream<charT, traits>& os);
 ```
 *Effects:* Inserts a null character into the output sequence: calls
 `os.put(charT())`.
 *Returns:* `os`.
 ``` cpp
 template <class charT, class traits>
   basic_ostream<charT, traits>& flush(basic_ostream<charT, traits>& os);
 ```
 *Effects:* Calls `os.flush()`.
 *Returns:* `os`.
 #### Rvalue stream insertion <a id="ostream.rvalue">[[ostream.rvalue]]</a>
 ``` cpp
 template <class charT, class traits, class T>
+  basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&& os, const T& x);
 ```
+*Effects:* As if by: `os << x;`
+*Returns:* `os`.
+*Remarks:* This function shall not participate in overload resolution
+unless the expression `os << x` is well-formed.
 ### Standard manipulators <a id="std.manip">[[std.manip]]</a>
 The header `<iomanip>` defines several functions that support extractors
 and inserters that alter information maintained by class `ios_base` and
 unspecified resetiosflags(ios_base::fmtflags mask);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
+`out << resetiosflags(mask)` behaves as if it called `f(out, mask)`, or
 if `in` is an object of type `basic_istream<charT, traits>` then the
+expression `in >> resetiosflags(mask)` behaves as if it called
+`f(in, mask)`, where the function `f` is defined as:[^39]
 ``` cpp
 void f(ios_base& str, ios_base::fmtflags mask) {
   // reset specified flags
   str.setf(ios_base::fmtflags(0), mask);
 }
 ```
+The expression `out << resetiosflags(mask)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
+`in >> resetiosflags(mask)` shall have type
 `basic_istream<charT, traits>&` and value `in`.
 ``` cpp
 unspecified setiosflags(ios_base::fmtflags mask);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
+`out << setiosflags(mask)` behaves as if it called `f(out, mask)`, or if
 `in` is an object of type `basic_istream<charT, traits>` then the
+expression `in >> setiosflags(mask)` behaves as if it called
 `f(in, mask)`, where the function `f` is defined as:
 ``` cpp
 void f(ios_base& str, ios_base::fmtflags mask) {
   // set specified flags
   str.setf(mask);
 }
 ```
+The expression `out << setiosflags(mask)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
+`in >> setiosflags(mask)` shall have type `basic_istream<charT,`
 `traits>&` and value `in`.
 ``` cpp
 unspecified setbase(int base);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
+`out << setbase(base)` behaves as if it called `f(out, base)`, or if
 `in` is an object of type `basic_istream<charT, traits>` then the
+expression `in >> setbase(base)` behaves as if it called `f(in, base)`,
 where the function `f` is defined as:
 ``` cpp
 void f(ios_base& str, int base) {
   // set basefield
       base == 16 ? ios_base::hex :
       ios_base::fmtflags(0), ios_base::basefield);
 }
 ```
+The expression `out << setbase(base)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
+`in >> setbase(base)` shall have type `basic_istream<charT, traits>&`
 and value `in`.
 ``` cpp
 unspecified setfill(char_type c);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` and `c` has type `charT` then the
+expression `out << setfill(c)` behaves as if it called `f(out, c)`,
 where the function `f` is defined as:
 ``` cpp
 template<class charT, class traits>
 void f(basic_ios<charT, traits>& str, charT c) {
   // set fill character
   str.fill(c);
 }
 ```
+The expression `out << setfill(c)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ``` cpp
 unspecified setprecision(int n);
 ```
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
+`out << setprecision(n)` behaves as if it called `f(out, n)`, or if `in`
 is an object of type `basic_istream<charT, traits>` then the expression
+`in >> setprecision(n)` behaves as if it called `f(in, n)`, where the
 function `f` is defined as:
 ``` cpp
 void f(ios_base& str, int n) {
   // set precision
   str.precision(n);
 }
 ```
+The expression `out << setprecision(n)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
+`in >> setprecision(n)` shall have type `basic_istream<charT, traits>&`
 and value `in`.
 ``` cpp
 unspecified setw(int n);
 ```
 *Returns:* An object of unspecified type such that if `out` is an
 instance of `basic_ostream<charT, traits>` then the expression
+`out << setw(n)` behaves as if it called `f(out, n)`, or if `in` is an
 object of type `basic_istream<charT, traits>` then the expression
+`in >> setw(n)` behaves as if it called `f(in, n)`, where the function
 `f` is defined as:
 ``` cpp
 void f(ios_base& str, int n) {
   // set width
   str.width(n);
 }
 ```
+The expression `out << setw(n)` shall have type
 `basic_ostream<charT, traits>&` and value `out`. The expression
+`in >> setw(n)` shall have type `basic_istream<charT, traits>&` and
 value `in`.
 ### Extended manipulators <a id="ext.manip">[[ext.manip]]</a>
 The header `<iomanip>` defines several functions that support extractors
 *Effects:* The expression `in >> get_money(mon, intl)` described below
 behaves as a formatted input function ([[istream.formatted.reqmts]]).
 *Returns:* An object of unspecified type such that if `in` is an object
 of type `basic_istream<charT, traits>` then the expression
+`in >> get_money(mon, intl)` behaves as if it called `f(in, mon, intl)`,
 where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits, class moneyT>
 void f(basic_ios<charT, traits>& str, moneyT& mon, bool intl) {
+ using Iter     = istreambuf_iterator<charT, traits>;
+ using MoneyGet = money_get<charT, Iter>;
   ios_base::iostate err = ios_base::goodbit;
   const MoneyGet& mg = use_facet<MoneyGet>(str.getloc());
   mg.get(Iter(str.rdbuf()), Iter(), intl, str, err, mon);
   if (ios_base::goodbit != err)
     str.setstate(err);
 }
 ```
+The expression `in >> get_money(mon, intl)` shall have type
 `basic_istream<charT, traits>&` and value `in`.
 ``` cpp
 template <class moneyT> unspecified put_money(const moneyT& mon, bool intl = false);
 ```
 *Requires:* The type `moneyT` shall be either `long double` or a
 specialization of the `basic_string` template (Clause  [[strings]]).
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
+`out << put_money(mon, intl)` behaves as a formatted output
+function ([[ostream.formatted.reqmts]]) that calls `f(out, mon, intl)`,
+where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits, class moneyT>
 void f(basic_ios<charT, traits>& str, const moneyT& mon, bool intl) {
+ using Iter     = ostreambuf_iterator<charT, traits>;
+ using MoneyPut = money_put<charT, Iter>;
   const MoneyPut& mp = use_facet<MoneyPut>(str.getloc());
   const Iter end = mp.put(Iter(str.rdbuf()), intl, str, str.fill(), mon);
   if (end.failed())
     str.setstate(ios::badbit);
 }
 ```
+The expression `out << put_money(mon, intl)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ``` cpp
 template <class charT> unspecified get_time(struct tm* tmb, const charT* fmt);
 ```
 *Requires:* The argument `tmb` shall be a valid pointer to an object of
+type `struct tm`. The argument `fmt` shall be a valid pointer to an
 array of objects of type `charT` with `char_traits<charT>::length(fmt)`
 elements.
 *Returns:* An object of unspecified type such that if `in` is an object
 of type `basic_istream<charT, traits>` then the expression
+`in >> get_time(tmb, fmt)` behaves as if it called `f(in, tmb, fmt)`,
 where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits>
 void f(basic_ios<charT, traits>& str, struct tm* tmb, const charT* fmt) {
+ using Iter    = istreambuf_iterator<charT, traits>;
+ using TimeGet = time_get<charT, Iter>;
   ios_base::iostate err = ios_base::goodbit;
   const TimeGet& tg = use_facet<TimeGet>(str.getloc());
   tg.get(Iter(str.rdbuf()), Iter(), str, err, tmb,
     fmt, fmt + traits::length(fmt));
   if (err != ios_base::goodbit)
+    str.setstate(err);
 }
 ```
+The expression `in >> get_time(tmb, fmt)` shall have type
 `basic_istream<charT, traits>&` and value `in`.
 ``` cpp
 template <class charT> unspecified put_time(const struct tm* tmb, const charT* fmt);
 ```
 array of objects of type `charT` with `char_traits<charT>::length(fmt)`
 elements.
 *Returns:* An object of unspecified type such that if `out` is an object
 of type `basic_ostream<charT, traits>` then the expression
+`out << put_time(tmb, fmt)` behaves as if it called `f(out, tmb, fmt)`,
 where the function `f` is defined as:
 ``` cpp
 template <class charT, class traits>
 void f(basic_ios<charT, traits>& str, const struct tm* tmb, const charT* fmt) {
+ using Iter    = ostreambuf_iterator<charT, traits>;
+ using TimePut = time_put<charT, Iter>;
   const TimePut& tp = use_facet<TimePut>(str.getloc());
   const Iter end = tp.put(Iter(str.rdbuf()), str, str.fill(), tmb,
     fmt, fmt + traits::length(fmt));
   if (end.failed())
     str.setstate(ios_base::badbit);
 }
 ```
+The expression `out << put_time(tmb, fmt)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ### Quoted manipulators <a id="quoted.manip">[[quoted.manip]]</a>
+[*Note 1*: Quoted manipulators provide string insertion and extraction
+of quoted strings (for example, XML and CSV formats). Quoted
+manipulators are useful in ensuring that the content of a string with
+embedded spaces remains unchanged if inserted and then extracted via
+stream I/O. — *end note*]
 ``` cpp
 template <class charT>
   unspecified quoted(const charT* s, charT delim = charT('"'), charT escape = charT('\\'));
 template <class charT, class traits, class Allocator>
   unspecified quoted(const basic_string<charT, traits, Allocator>& s,
+  \itcorr                   charT delim = charT('"'), charT escape = charT('\\'));
+template <class charT, class traits>
+  unspecified quoted(basic_string_view<charT, traits> s,
+  \itcorr                   charT delim = charT('"'), charT escape = charT('\\'));
 ```
 *Returns:* An object of unspecified type such that if `out` is an
 instance of `basic_ostream` with member type `char_type` the same as
+`charT` and with member type `traits_type`, which in the second and
+third forms is the same as `traits`, then the expression
+`out << quoted(s, delim, escape)` behaves as a formatted output
 function ([[ostream.formatted.reqmts]]) of `out`. This forms a
 character sequence `seq`, initially consisting of the following
 elements:
 - `delim`.
 Let `x` be the number of elements initially in `seq`. Then padding is
 determined for `seq` as described in  [[ostream.formatted.reqmts]],
 `seq` is inserted as if by calling `out.rdbuf()->sputn(seq, n)`, where
 `n` is the larger of `out.width()` and `x`, and `out.width(0)` is
+called. The expression `out << quoted(s, delim, escape)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ``` cpp
 template <class charT, class traits, class Allocator>
   unspecified quoted(basic_string<charT, traits, Allocator>& s,
+  \itcorr                   charT delim = charT('"'), charT escape = charT('\\'));
 ```
 *Returns:* An object of unspecified type such that:
 - If `in` is an instance of `basic_istream` with member types
   `char_type` and `traits_type` the same as `charT` and `traits`,
+  respectively, then the expression `in >> quoted(s, delim, escape)`
   behaves as if it extracts the following characters from `in` using
+  `operator>>(basic_istream<charT, traits>&, charT&)` ([[istream.extractors]])
+ which may throw `ios_base::failure` ([[ios::failure]]):
   - If the first character extracted is equal to `delim`, as determined
     by `traits_type::eq`, then:
     - Turn off the `skipws` flag.
     - `s.clear()`
     - Until an unescaped `delim` character is reached or `!in`, extract
       characters from `in` and append them to `s`, except that if an
       `escape` is reached, ignore it and append the next character to
       `s`.
     - Discard the final `delim` character.
     - Restore the `skipws` flag to its original value.
+  - Otherwise, `in >> s`.
 - If `out` is an instance of `basic_ostream` with member types
   `char_type` and `traits_type` the same as `charT` and `traits`,
+  respectively, then the expression `out << quoted(s, delim, escape)`
   behaves as specified for the
   `const basic_string<charT, traits, Allocator>&` overload of the
   `quoted` function.
+The expression `in >> quoted(s, delim, escape)` shall have type
 `basic_istream<charT, traits>&` and value `in`. The expression
+`out << quoted(s, delim, escape)` shall have type
 `basic_ostream<charT, traits>&` and value `out`.
 ## String-based streams <a id="string.streams">[[string.streams]]</a>
+### Header `<sstream>` synopsis <a id="sstream.syn">[[sstream.syn]]</a>
+``` cpp
+namespace std {
+  template <class charT, class traits = char_traits<charT>,
+            class Allocator = allocator<charT>>
+    class basic_stringbuf;
+  using stringbuf  = basic_stringbuf<char>;
+  using wstringbuf = basic_stringbuf<wchar_t>;
+  template <class charT, class traits = char_traits<charT>,
+            class Allocator = allocator<charT>>
+    class basic_istringstream;
+  using istringstream  = basic_istringstream<char>;
+  using wistringstream = basic_istringstream<wchar_t>;
+  template <class charT, class traits = char_traits<charT>,
+            class Allocator = allocator<charT>>
+    class basic_ostringstream;
+  using ostringstream  = basic_ostringstream<char>;
+  using wostringstream = basic_ostringstream<wchar_t>;
+  template <class charT, class traits = char_traits<charT>,
+            class Allocator = allocator<charT>>
+    class basic_stringstream;
+  using stringstream  = basic_stringstream<char>;
+  using wstringstream = basic_stringstream<wchar_t>;
+}
+```
 The header `<sstream>` defines four class templates and eight types that
 associate stream buffers with objects of class `basic_string`, as
 described in  [[string.classes]].
 ### Class template `basic_stringbuf` <a id="stringbuf">[[stringbuf]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
   class basic_stringbuf : public basic_streambuf<charT, traits> {
   public:
+ using char_type      = charT;
+ using int_type       = typename traits::int_type;
+ using pos_type       = typename traits::pos_type;
+ using off_type       = typename traits::off_type;
+ using traits_type    = traits;
+ using allocator_type = Allocator;
+    // [stringbuf.cons], constructors
+    explicit basic_stringbuf(
+      ios_base::openmode which = ios_base::in | ios_base::out);
+    explicit basic_stringbuf(
+ const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::in | ios_base::out);
     basic_stringbuf(const basic_stringbuf& rhs) = delete;
     basic_stringbuf(basic_stringbuf&& rhs);
+    // [stringbuf.assign], assign and swap
     basic_stringbuf& operator=(const basic_stringbuf& rhs) = delete;
     basic_stringbuf& operator=(basic_stringbuf&& rhs);
     void swap(basic_stringbuf& rhs);
+    // [stringbuf.members], get and set
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& s);
   protected:
+    // [stringbuf.virtuals], overridden virtual functions
+    int_type underflow() override;
+    int_type pbackfail(int_type c = traits::eof()) override;
+    int_type overflow (int_type c = traits::eof()) override;
+    basic_streambuf<charT, traits>* setbuf(charT*, streamsize) override;
+    pos_type seekoff(off_type off, ios_base::seekdir way,
                      ios_base::openmode which
+ = ios_base::in | ios_base::out) override;
+    pos_type seekpos(pos_type sp,
                      ios_base::openmode which
+ = ios_base::in | ios_base::out) override;
   private:
     ios_base::openmode mode;  // exposition only
   };
   read, and `out` set if the output sequence can be written.
 #### `basic_stringbuf` constructors <a id="stringbuf.cons">[[stringbuf.cons]]</a>
 ``` cpp
+explicit basic_stringbuf(
+ ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_stringbuf`, initializing
 the base class with `basic_streambuf()` ([[streambuf.cons]]), and
 initializing `mode` with `which`.
+*Postconditions:* `str() == ""`.
 ``` cpp
+explicit basic_stringbuf(
+  const basic_string<charT, traits, Allocator>& s,
   ios_base::openmode which = ios_base::in | ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_stringbuf`, initializing
 the base class with `basic_streambuf()` ([[streambuf.cons]]), and
 template <class charT, class traits, class Allocator>
   void swap(basic_stringbuf<charT, traits, Allocator>& x,
             basic_stringbuf<charT, traits, Allocator>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="stringbuf.members">[[stringbuf.members]]</a>
 ``` cpp
 basic_string<charT, traits, Allocator> str() const;
 *Returns:* A `basic_string` object whose content is equal to the
 `basic_stringbuf` underlying character sequence. If the
 `basic_stringbuf` was created only in input mode, the resultant
 `basic_string` contains the character sequence in the range \[`eback()`,
 `egptr()`). If the `basic_stringbuf` was created with
+`which & ios_base::out` being nonzero then the resultant `basic_string`
 contains the character sequence in the range \[`pbase()`, `high_mark`),
 where `high_mark` represents the position one past the highest
 initialized character in the buffer. Characters can be initialized by
 writing to the stream, by constructing the `basic_stringbuf` with a
 `basic_string`, or by calling the `str(basic_string)` member function.
 *Effects:* Copies the content of `s` into the `basic_stringbuf`
 underlying character sequence and initializes the input and output
 sequences according to `mode`.
+*Postconditions:* If `mode & ios_base::out` is nonzero, `pbase()` points
+to the first underlying character and `epptr()` `>= pbase() + s.size()`
+holds; in addition, if `mode & ios_base::ate` is nonzero,
 `pptr() == pbase() + s.size()` holds, otherwise `pptr() == pbase()` is
+`true`. If `mode & ios_base::in` is nonzero, `eback()` points to the
+first underlying character, and both `gptr() == eback()` and
 `egptr() == eback() + s.size()` hold.
 #### Overridden virtual functions <a id="stringbuf.virtuals">[[stringbuf.virtuals]]</a>
 ``` cpp
+int_type underflow() override;
 ```
 *Returns:* If the input sequence has a read position available, returns
 `traits::to_int_type(*gptr())`. Otherwise, returns `traits::eof()`. Any
 character in the underlying buffer which has been initialized is
 considered to be part of the input sequence.
 ``` cpp
+int_type pbackfail(int_type c = traits::eof()) override;
 ```
 *Effects:* Puts back the character designated by `c` to the input
 sequence, if possible, in one of three ways:
 *Remarks:* If the function can succeed in more than one of these ways,
 it is unspecified which way is chosen.
 ``` cpp
+int_type overflow(int_type c = traits::eof()) override;
 ```
 *Effects:* Appends the character designated by `c` to the output
 sequence, if possible, in one of two ways:
 `egptr()` to point just past the new write position.
 ``` cpp
 pos_type seekoff(off_type off, ios_base::seekdir way,
                  ios_base::openmode which
+                   = ios_base::in | ios_base::out) override;
 ```
 *Effects:* Alters the stream position within one of the controlled
 sequences, if possible, as indicated in
 Table  [[tab:iostreams.seekoff.positioning]].
 | `way == ios_base::cur` | the next pointer minus the beginning pointer (`xnext - xbeg`).          |
 | `way == ios_base::end` | the high mark pointer minus the beginning pointer (`high_mark - xbeg`). |
 If `(newoff + off) < 0`, or if `newoff + off` refers to an uninitialized
+character ([[stringbuf.members]]), the positioning operation fails.
+Otherwise, the function assigns `xbeg + newoff + off` to the next
+pointer `xnext`.
 *Returns:* `pos_type(newoff)`, constructed from the resultant offset
 `newoff` (of type `off_type`), that stores the resultant stream
 position, if possible. If the positioning operation fails, or if the
 constructed object cannot represent the resultant stream position, the
 return value is `pos_type(off_type(-1))`.
 ``` cpp
+pos_type seekpos(pos_type sp,
+ ios_base::openmode which
+                   = ios_base::in | ios_base::out) override;
 ```
 *Effects:* Equivalent to `seekoff(off_type(sp), ios_base::beg, which)`.
 *Returns:* `sp` to indicate success, or `pos_type(off_type(-1))` to
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
   class basic_istringstream : public basic_istream<charT, traits> {
   public:
+ using char_type      = charT;
+ using int_type       = typename traits::int_type;
+ using pos_type       = typename traits::pos_type;
+ using off_type       = typename traits::off_type;
+ using traits_type    = traits;
+ using allocator_type = Allocator;
+    // [istringstream.cons], constructors
+    explicit basic_istringstream(
+      ios_base::openmode which = ios_base::in);
     explicit basic_istringstream(
       const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::in);
     basic_istringstream(const basic_istringstream& rhs) = delete;
     basic_istringstream(basic_istringstream&& rhs);
+    // [istringstream.assign], assign and swap
     basic_istringstream& operator=(const basic_istringstream& rhs) = delete;
     basic_istringstream& operator=(basic_istringstream&& rhs);
     void swap(basic_istringstream& rhs);
+    // [istringstream.members], members
     basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& s);
   private:
 basic_istringstream(basic_istringstream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by move constructing the base class, and the contained
+`basic_stringbuf`. Next `basic_istream<charT, traits>::set_rdbuf(&sb)`
+is called to install the contained `basic_stringbuf`.
 #### Assign and swap <a id="istringstream.assign">[[istringstream.assign]]</a>
 ``` cpp
 basic_istringstream& operator=(basic_istringstream&& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_istringstream<charT, traits, Allocator>& x,
             basic_istringstream<charT, traits, Allocator>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="istringstream.members">[[istringstream.members]]</a>
 ``` cpp
 basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
 ```
+*Returns:*
+`const_cast<basic_stringbuf<charT, traits, Allocator>*>(&sb)`.
 ``` cpp
 basic_string<charT, traits, Allocator> str() const;
 ```
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
   class basic_ostringstream : public basic_ostream<charT, traits> {
   public:
+    using char_type      = charT;
+    using int_type       = typename traits::int_type;
+    using pos_type       = typename traits::pos_type;
+    using off_type       = typename traits::off_type;
+    using traits_type    = traits;
+    using allocator_type = Allocator;
+    // [ostringstream.cons], constructors
+ explicit basic_ostringstream(
+      ios_base::openmode which = ios_base::out);
     explicit basic_ostringstream(
       const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::out);
     basic_ostringstream(const basic_ostringstream& rhs) = delete;
     basic_ostringstream(basic_ostringstream&& rhs);
+    // [ostringstream.assign], assign and swap
     basic_ostringstream& operator=(const basic_ostringstream& rhs) = delete;
     basic_ostringstream& operator=(basic_ostringstream&& rhs);
     void swap(basic_ostringstream& rhs);
+    // [ostringstream.members], members
     basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& s);
    private:
 - `sb`, the `stringbuf` object.
 #### `basic_ostringstream` constructors <a id="ostringstream.cons">[[ostringstream.cons]]</a>
 ``` cpp
+explicit basic_ostringstream(
+  ios_base::openmode which = ios_base::out);
 ```
 *Effects:* Constructs an object of class `basic_ostringstream`,
 initializing the base class with `basic_ostream(&sb)` and initializing
 `sb` with
 basic_ostringstream(basic_ostringstream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by move constructing the base class, and the contained
+`basic_stringbuf`. Next `basic_ostream<charT, traits>::set_rdbuf(&sb)`
+is called to install the contained `basic_stringbuf`.
 #### Assign and swap <a id="ostringstream.assign">[[ostringstream.assign]]</a>
 ``` cpp
 basic_ostringstream& operator=(basic_ostringstream&& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_ostringstream<charT, traits, Allocator>& x,
             basic_ostringstream<charT, traits, Allocator>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="ostringstream.members">[[ostringstream.members]]</a>
 ``` cpp
 basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
 ```
+*Returns:*
+`const_cast<basic_stringbuf<charT, traits, Allocator>*>(&sb)`.
 ``` cpp
 basic_string<charT, traits, Allocator> str() const;
 ```
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>,
             class Allocator = allocator<charT>>
+  class basic_stringstream : public basic_iostream<charT, traits> {
   public:
+    using char_type      = charT;
+    using int_type       = typename traits::int_type;
+    using pos_type       = typename traits::pos_type;
+    using off_type       = typename traits::off_type;
+    using traits_type    = traits;
+    using allocator_type = Allocator;
+    // [stringstream.cons], constructors
     explicit basic_stringstream(
       ios_base::openmode which = ios_base::out | ios_base::in);
     explicit basic_stringstream(
       const basic_string<charT, traits, Allocator>& str,
       ios_base::openmode which = ios_base::out | ios_base::in);
     basic_stringstream(const basic_stringstream& rhs) = delete;
     basic_stringstream(basic_stringstream&& rhs);
+    // [stringstream.assign], assign and swap
     basic_stringstream& operator=(const basic_stringstream& rhs) = delete;
     basic_stringstream& operator=(basic_stringstream&& rhs);
     void swap(basic_stringstream& rhs);
+    // [stringstream.members], members
     basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
     basic_string<charT, traits, Allocator> str() const;
     void str(const basic_string<charT, traits, Allocator>& str);
   private:
 associated sequence. For the sake of exposition, the maintained data is
 presented here as
 - `sb`, the `stringbuf` object.
+#### `basic_stringstream` constructors <a id="stringstream.cons">[[stringstream.cons]]</a>
 ``` cpp
 explicit basic_stringstream(
   ios_base::openmode which = ios_base::out | ios_base::in);
 ```
 basic_stringstream(basic_stringstream&& rhs);
 ```
 *Effects:* Move constructs from the rvalue `rhs`. This is accomplished
 by move constructing the base class, and the contained
+`basic_stringbuf`. Next `basic_istream<charT, traits>::set_rdbuf(&sb)`
+is called to install the contained `basic_stringbuf`.
 #### Assign and swap <a id="stringstream.assign">[[stringstream.assign]]</a>
 ``` cpp
 basic_stringstream& operator=(basic_stringstream&& rhs);
 template <class charT, class traits, class Allocator>
   void swap(basic_stringstream<charT, traits, Allocator>& x,
             basic_stringstream<charT, traits, Allocator>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="stringstream.members">[[stringstream.members]]</a>
 ``` cpp
 basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
 *Effects:* Calls `rdbuf()->str(str)`.
 ## File-based streams <a id="file.streams">[[file.streams]]</a>
+### Header `<fstream>` synopsis <a id="fstream.syn">[[fstream.syn]]</a>
+``` cpp
+namespace std {
+  template <class charT, class traits = char_traits<charT>>
+    class basic_filebuf;
+  using filebuf  = basic_filebuf<char>;
+  using wfilebuf = basic_filebuf<wchar_t>;
+  template <class charT, class traits = char_traits<charT>>
+    class basic_ifstream;
+  using ifstream  = basic_ifstream<char>;
+  using wifstream = basic_ifstream<wchar_t>;
+  template <class charT, class traits = char_traits<charT>>
+    class basic_ofstream;
+  using ofstream  = basic_ofstream<char>;
+  using wofstream = basic_ofstream<wchar_t>;
+  template <class charT, class traits = char_traits<charT>>
+    class basic_fstream;
+  using fstream  = basic_fstream<char>;
+  using wfstream = basic_fstream<wchar_t>;
+}
+```
 The header `<fstream>` defines four class templates and eight types that
 associate stream buffers with files and assist reading and writing
 files.
+[*Note 1*: The class template `basic_filebuf` treats a file as a source
+or sink of bytes. In an environment that uses a large character set, the
+file typically holds multibyte character sequences and the
+`basic_filebuf` object converts those multibyte sequences into wide
+character sequences. — *end note*]
+In this subclause, member functions taking arguments of
+`const filesystem::path::value_type*` are only be provided on systems
+where `filesystem::path::value_type` ([[fs.class.path]]) is not `char`.
+[*Note 2*: These functions enable class `path` support for systems with
+a wide native path character type, such as `wchar_t`. — *end note*]
+### Class template `basic_filebuf` <a id="filebuf">[[filebuf]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_filebuf : public basic_streambuf<charT, traits> {
   public:
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [filebuf.cons], constructors/destructor
     basic_filebuf();
     basic_filebuf(const basic_filebuf& rhs) = delete;
     basic_filebuf(basic_filebuf&& rhs);
     virtual ~basic_filebuf();
+    // [filebuf.assign], assign and swap
     basic_filebuf& operator=(const basic_filebuf& rhs) = delete;
     basic_filebuf& operator=(basic_filebuf&& rhs);
     void swap(basic_filebuf& rhs);
+ // [filebuf.members], members
     bool is_open() const;
+    basic_filebuf* open(const char* s, ios_base::openmode mode);
+    basic_filebuf* open(const filesystem::path::value_type* s,
+                        ios_base::openmode mode);  // wide systems only; see [fstream.syn]
+    basic_filebuf* open(const string& s,
                         ios_base::openmode mode);
+    basic_filebuf* open(const filesystem::path& s,
                         ios_base::openmode mode);
+    basic_filebuf* close();
   protected:
+    // [filebuf.virtuals], overridden virtual functions
+    streamsize showmanyc() override;
+    int_type underflow() override;
+    int_type uflow() override;
+    int_type pbackfail(int_type c = traits::eof()) override;
+    int_type overflow (int_type c = traits::eof()) override;
+    basic_streambuf<charT, traits>* setbuf(char_type* s,
+ streamsize n) override;
+    pos_type seekoff(off_type off, ios_base::seekdir way,
+ ios_base::openmode which
+                      = ios_base::in | ios_base::out) override;
+    pos_type seekpos(pos_type sp,
+                     ios_base::openmode which
+                      = ios_base::in | ios_base::out) override;
+    int      sync() override;
+    void     imbue(const locale& loc) override;
   };
   template <class charT, class traits>
     void swap(basic_filebuf<charT, traits>& x,
               basic_filebuf<charT, traits>& y);
 The class `basic_filebuf<charT, traits>` associates both the input
 sequence and the output sequence with a file.
 The restrictions on reading and writing a sequence controlled by an
 object of class `basic_filebuf<charT, traits>` are the same as for
+reading and writing with the C standard library `FILE`s.
 In particular:
 - If the file is not open for reading the input sequence cannot be read.
 - If the file is not open for writing the output sequence cannot be
   written.
 - A joint file position is maintained for both the input sequence and
   the output sequence.
 An instance of `basic_filebuf` behaves as described in  [[filebuf]]
+provided `traits::pos_type` is `fpos<traits::{}state_type>`. Otherwise
+the behavior is undefined.
 In order to support file I/O and multibyte/wide character conversion,
 conversions are performed using members of a facet, referred to as
 `a_codecvt` in following sections, obtained as if by
 *Effects:* Constructs an object of class `basic_filebuf<charT, traits>`,
 initializing the base class with
 `basic_streambuf<charT, traits>()` ([[streambuf.cons]]).
+*Postconditions:* `is_open() == false`.
 ``` cpp
 basic_filebuf(basic_filebuf&& rhs);
 ```
 ``` cpp
 basic_filebuf& operator=(basic_filebuf&& rhs);
 ```
+*Effects:* Calls `close()` then move assigns from `rhs`. After the move
+assignment `*this` has the observable state it would have had if it had
+been move constructed from `rhs` (see  [[filebuf.cons]]).
 *Returns:* `*this`.
 ``` cpp
 void swap(basic_filebuf& rhs);
 template <class charT, class traits>
   void swap(basic_filebuf<charT, traits>& x,
             basic_filebuf<charT, traits>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="filebuf.members">[[filebuf.members]]</a>
 ``` cpp
 bool is_open() const;
 *Returns:* `true` if a previous call to `open` succeeded (returned a
 non-null value) and there has been no intervening call to close.
 ``` cpp
+basic_filebuf* open(const char* s, ios_base::openmode mode);
+basic_filebuf* open(const filesystem::path::value_type* s,
+                    ios_base::openmode mode);  // wide systems only; see [fstream.syn]
 ```
 *Effects:* If `is_open() != false`, returns a null pointer. Otherwise,
 initializes the `filebuf` as required. It then opens a file, if
 possible, whose name is the NTBS`s` (as if by calling
+`fopen(s, modstr)`). The NTBS`modstr` is determined from
 `mode & ~ios_base::ate` as indicated in
 Table  [[tab:iostreams.file.open.modes]]. If `mode` is not some
 combination of flags shown in the table then the open fails.
 **Table: File open modes** <a id="tab:iostreams.file.open.modes">[tab:iostreams.file.open.modes]</a>
 | +        | +    |       |         | +     | `"a+b"` |
 If the open operation succeeds and `(mode & ios_base::ate) != 0`,
 positions the file to the end (as if by calling
+`fseek(file, 0, SEEK_END)`).[^40]
 If the repositioning operation fails, calls `close()` and returns a null
 pointer to indicate failure.
 *Returns:* `this` if successful, a null pointer otherwise.
 ``` cpp
+basic_filebuf* open(const string& s, ios_base::openmode mode);
+basic_filebuf* open(const filesystem::path& s, ios_base::openmode mode);
 ```
 *Returns:* `open(s.c_str(), mode);`
 ``` cpp
+basic_filebuf* close();
 ```
 *Effects:* If `is_open() == false`, returns a null pointer. If a put
 area exists, calls `overflow(traits::eof())` to flush characters. If the
 last virtual member function called on `*this` (between `underflow`,
 `overflow`, `seekoff`, and `seekpos`) was `overflow` then calls
 `a_codecvt.unshift` (possibly several times) to determine a termination
 sequence, inserts those characters and calls `overflow(traits::eof())`
 again. Finally, regardless of whether any of the preceding calls fails
 or throws an exception, the function closes the file (as if by calling
+`fclose(file)`). If any of the calls made by the function, including
+`fclose`, fails, `close` fails by returning a null pointer. If one of
+these calls throws an exception, the exception is caught and rethrown
+after closing the file.
 *Returns:* `this` on success, a null pointer otherwise.
+*Postconditions:* `is_open() == false`.
 #### Overridden virtual functions <a id="filebuf.virtuals">[[filebuf.virtuals]]</a>
 ``` cpp
+streamsize showmanyc() override;
 ```
 *Effects:* Behaves the same as
 `basic_streambuf::showmanyc()` ([[streambuf.virtuals]]).
 *Remarks:* An implementation might well provide an overriding definition
 for this function signature if it can determine that more characters can
 be read from the input sequence.
 ``` cpp
+int_type underflow() override;
 ```
 *Effects:* Behaves according to the description of
 `basic_streambuf<charT, traits>::underflow()`, with the specialization
 that a sequence of characters is read from the input sequence as if by
 reading from the associated file into an internal buffer (`extern_buf`)
+and then as if by doing:
 ``` cpp
 char   extern_buf[XSIZE];
 char*  extern_end;
 charT  intern_buf[ISIZE];
 (`fpos_t`) corresponding to each character between `intern_buf` and
 `intern_end`. If the value of `r` indicates that `a_codecvt.in()` ran
 out of space in `intern_buf`, retry with a larger `intern_buf`.
 ``` cpp
+int_type uflow() override;
 ```
 *Effects:* Behaves according to the description of
+`basic_streambuf<charT, traits>::uflow()`, with the specialization that
+a sequence of characters is read from the input with the same method as
 used by `underflow`.
 ``` cpp
+int_type pbackfail(int_type c = traits::eof()) override;
 ```
 *Effects:* Puts back the character designated by `c` to the input
 sequence, if possible, in one of three ways:
 If the function can succeed in more than one of these ways, it is
 unspecified which way is chosen. The function can alter the number of
 putback positions available as a result of any call.
 ``` cpp
+int_type overflow(int_type c = traits::eof()) override;
 ```
 *Effects:* Behaves according to the description of
 `basic_streambuf<charT, traits>::overflow(c)`, except that the behavior
 of “consuming characters” is performed by first converting as if by:
 *Returns:* `traits::not_eof(c)` to indicate success, and `traits::eof()`
 to indicate failure. If `is_open() == false`, the function always fails.
 ``` cpp
+basic_streambuf* setbuf(char_type* s, streamsize n) override;
 ```
 *Effects:* If `setbuf(0, 0)` is called on a stream before any I/O has
 occurred on that stream, the stream becomes unbuffered. Otherwise the
 results are *implementation-defined*. “Unbuffered” means that `pbase()`
 and `pptr()` always return null and output to the file should appear as
 soon as possible.
 ``` cpp
 pos_type seekoff(off_type off, ios_base::seekdir way,
+ ios_base::openmode which
+                   = ios_base::in | ios_base::out) override;
 ```
 *Effects:* Let `width` denote `a_codecvt.encoding()`. If
 `is_open() == false`, or `off != 0 && width <= 0`, then the positioning
 operation fails. Otherwise, if `way != basic_ios::cur` or `off != 0`,
 and if the last operation was output, then update the output sequence
 and write any unshift sequence. Next, seek to the new position: if
+`width > 0`, call `fseek(file, width * off, whence)`, otherwise call
+`fseek(file, 0, whence)`.
 *Remarks:* “The last operation was output” means either the last virtual
 operation was overflow or the put buffer is non-empty. “Write any
 unshift sequence” means, if `width` if less than zero then call
 `a_codecvt.unshift(state, xbuf, xbuf+XSIZE, xbuf_end)` and output the
 fails, or if the object cannot represent the resultant stream position,
 returns `pos_type(off_type(-1))`.
 ``` cpp
 pos_type seekpos(pos_type sp,
+ ios_base::openmode which
+                   = ios_base::in | ios_base::out) override;
 ```
 Alters the file position, if possible, to correspond to the position
 stored in `sp` (as described below). Altering the file position performs
 as follows:
 1.  if `(om & ios_base::out) != 0`, then update the output sequence and
     write any unshift sequence;
+2.  set the file position to `sp` as if by a call to `fsetpos`;
 3.  if `(om & ios_base::in) != 0`, then update the input sequence;
 where `om` is the open mode passed to the last call to `open()`. The
+operation fails if `is_open()` returns `false`.
 If `sp` is an invalid stream position, or if the function positions
 neither sequence, the positioning operation fails. If `sp` has not been
 obtained by a previous successful call to one of the positioning
 functions (`seekoff` or `seekpos`) on the same file the effects are
 undefined.
 *Returns:* `sp` on success. Otherwise returns `pos_type(off_type(-1))`.
 ``` cpp
+int sync() override;
 ```
 *Effects:* If a put area exists, calls `filebuf::overflow` to write the
+characters to the file, then flushes the file as if by calling
+`fflush(file)`. If a get area exists, the effect is
 *implementation-defined*.
 ``` cpp
+void imbue(const locale& loc) override;
 ```
+*Requires:* If the file is not positioned at its beginning and the
+encoding of the current locale as determined by `a_codecvt.encoding()`
+is state-dependent ([[locale.codecvt.virtuals]]) then that facet is the
 same as the corresponding facet of `loc`.
 *Effects:* Causes characters inserted or extracted after this call to be
 converted according to `loc` until another call of `imbue`.
+*Remarks:* This may require reconversion of previously converted
+characters. This in turn may require the implementation to be able to
+reconstruct the original contents of the file.
+### Class template `basic_ifstream` <a id="ifstream">[[ifstream]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ifstream : public basic_istream<charT, traits> {
   public:
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [ifstream.cons], constructors
     basic_ifstream();
     explicit basic_ifstream(const char* s,
                             ios_base::openmode mode = ios_base::in);
+    explicit basic_ifstream(const filesystem::path::value_type* s,
+                            ios_base::openmode mode = ios_base::in);  // wide systems only; see [fstream.syn]
     explicit basic_ifstream(const string& s,
                             ios_base::openmode mode = ios_base::in);
+    explicit basic_ifstream(const filesystem::path& s,
+                            ios_base::openmode mode = ios_base::in);
     basic_ifstream(const basic_ifstream& rhs) = delete;
     basic_ifstream(basic_ifstream&& rhs);
+    // [ifstream.assign], assign and swap
     basic_ifstream& operator=(const basic_ifstream& rhs) = delete;
     basic_ifstream& operator=(basic_ifstream&& rhs);
     void swap(basic_ifstream& rhs);
+    // [ifstream.members], members
     basic_filebuf<charT, traits>* rdbuf() const;
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::in);
+    void open(const filesystem::path::value_type* s,
+              ios_base::openmode mode = ios_base::in);  // wide systems only; see [fstream.syn]
     void open(const string& s, ios_base::openmode mode = ios_base::in);
+    void open(const filesystem::path& s, ios_base::openmode mode = ios_base::in);
     void close();
   private:
     basic_filebuf<charT, traits> sb; // exposition only
   };
 ``` cpp
 basic_ifstream();
 ```
+*Effects:* Constructs an object of class
+`basic_ifstream<charT, traits>`, initializing the base class with
+`basic_istream(&sb)` and initializing `sb` with
+`basic_filebuf<charT, traits>())` ([[istream.cons]], [[filebuf.cons]]).
 ``` cpp
 explicit basic_ifstream(const char* s,
                         ios_base::openmode mode = ios_base::in);
+explicit basic_ifstream(const filesystem::path::value_type* s,
+                        ios_base::openmode mode = ios_base::in);  // wide systems only; see [fstream.syn]
 ```
 *Effects:* Constructs an object of class `basic_ifstream`, initializing
 the base class with `basic_istream(&sb)` and initializing `sb` with
 `basic_filebuf<charT, traits>())` ([[istream.cons]], [[filebuf.cons]]),
 returns a null pointer, calls `setstate(failbit)`.
 ``` cpp
 explicit basic_ifstream(const string& s,
                         ios_base::openmode mode = ios_base::in);
+explicit basic_ifstream(const filesystem::path& s,
+                        ios_base::openmode mode = ios_base::in);
 ```
+*Effects:* The same as `basic_ifstream(s.c_str(), mode)`.
 ``` cpp
 basic_ifstream(basic_ifstream&& rhs);
 ```
 template <class charT, class traits>
   void swap(basic_ifstream<charT, traits>& x,
             basic_ifstream<charT, traits>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="ifstream.members">[[ifstream.members]]</a>
 ``` cpp
 basic_filebuf<charT, traits>* rdbuf() const;
 *Returns:* `rdbuf()->is_open()`.
 ``` cpp
 void open(const char* s, ios_base::openmode mode = ios_base::in);
+void open(const filesystem::path::value_type* s,
+          ios_base::openmode mode = ios_base::in);  // wide systems only; see [fstream.syn]
 ```
 *Effects:* Calls `rdbuf()->open(s, mode | ios_base::in)`. If that
 function does not return a null pointer calls `clear()`, otherwise calls
+`setstate(failbit)` (which may throw `ios_base::failure`)
+([[iostate.flags]]).
 ``` cpp
 void open(const string& s, ios_base::openmode mode = ios_base::in);
+void open(const filesystem::path& s, ios_base::openmode mode = ios_base::in);
 ```
+*Effects:* Calls `open(s.c_str(), mode)`.
 ``` cpp
 void close();
 ```
 *Effects:* Calls `rdbuf()->close()` and, if that function returns a null
 pointer, calls `setstate(failbit)` (which may throw
+`ios_base::failure`) ([[iostate.flags]]).
+### Class template `basic_ofstream` <a id="ofstream">[[ofstream]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
   class basic_ofstream : public basic_ostream<charT, traits> {
   public:
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [ofstream.cons], constructors
     basic_ofstream();
     explicit basic_ofstream(const char* s,
                             ios_base::openmode mode = ios_base::out);
+    explicit basic_ofstream(const filesystem::path::value_type* s,
+                            ios_base::openmode mode = ios_base::out);  // wide systems only; see [fstream.syn]
     explicit basic_ofstream(const string& s,
                             ios_base::openmode mode = ios_base::out);
+    explicit basic_ofstream(const filesystem::path& s,
+                            ios_base::openmode mode = ios_base::out);
     basic_ofstream(const basic_ofstream& rhs) = delete;
     basic_ofstream(basic_ofstream&& rhs);
+    // [ofstream.assign], assign and swap
     basic_ofstream& operator=(const basic_ofstream& rhs) = delete;
     basic_ofstream& operator=(basic_ofstream&& rhs);
     void swap(basic_ofstream& rhs);
+    // [ofstream.members], members
     basic_filebuf<charT, traits>* rdbuf() const;
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::out);
+    void open(const filesystem::path::value_type* s,
+              ios_base::openmode mode = ios_base::out);  // wide systems only; see [fstream.syn]
     void open(const string& s, ios_base::openmode mode = ios_base::out);
+    void open(const filesystem::path& s, ios_base::openmode mode = ios_base::out);
     void close();
   private:
     basic_filebuf<charT, traits> sb; // exposition only
   };
 ``` cpp
 basic_ofstream();
 ```
+*Effects:* Constructs an object of class
+`basic_ofstream<charT, traits>`, initializing the base class with
+`basic_ostream(&sb)` and initializing `sb` with
+`basic_filebuf<charT, traits>())` ([[ostream.cons]], [[filebuf.cons]]).
 ``` cpp
 explicit basic_ofstream(const char* s,
                         ios_base::openmode mode = ios_base::out);
+explicit basic_ofstream(const filesystem::path::value_type* s,
+                        ios_base::openmode mode = ios_base::out); // wide systems only; see [fstream.syn]
 ```
+*Effects:* Constructs an object of class
+`basic_ofstream<charT, traits>`, initializing the base class with
+`basic_ostream(&sb)` and initializing `sb` with
+`basic_filebuf<charT, traits>())` ([[ostream.cons]], [[filebuf.cons]]),
+then calls `rdbuf()->open(s, mode | ios_base::out)`. If that function
+returns a null pointer, calls `setstate(failbit)`.
 ``` cpp
 explicit basic_ofstream(const string& s,
                         ios_base::openmode mode = ios_base::out);
+explicit basic_ofstream(const filesystem::path& s,
+                        ios_base::openmode mode = ios_base::out);
 ```
+*Effects:* The same as `basic_ofstream(s.c_str(), mode)`.
 ``` cpp
 basic_ofstream(basic_ofstream&& rhs);
 ```
 template <class charT, class traits>
   void swap(basic_ofstream<charT, traits>& x,
             basic_ofstream<charT, traits>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="ofstream.members">[[ofstream.members]]</a>
 ``` cpp
 basic_filebuf<charT, traits>* rdbuf() const;
 *Returns:* `rdbuf()->is_open()`.
 ``` cpp
 void open(const char* s, ios_base::openmode mode = ios_base::out);
+void open(const filesystem::path::value_type* s,
+          ios_base::openmode mode = ios_base::out);  // wide systems only; see [fstream.syn]
 ```
 *Effects:* Calls `rdbuf()->open(s, mode | ios_base::out)`. If that
 function does not return a null pointer calls `clear()`, otherwise calls
+`setstate(failbit)` (which may throw `ios_base::failure`)
+([[iostate.flags]]).
 ``` cpp
 void close();
 ```
 *Effects:* Calls `rdbuf()->close()` and, if that function fails (returns
 a null pointer), calls `setstate(failbit)` (which may throw
+`ios_base::failure`) ([[iostate.flags]]).
 ``` cpp
 void open(const string& s, ios_base::openmode mode = ios_base::out);
+void open(const filesystem::path& s, ios_base::openmode mode = ios_base::out);
 ```
+*Effects:* Calls `open(s.c_str(), mode)`.
+### Class template `basic_fstream` <a id="fstream">[[fstream]]</a>
 ``` cpp
 namespace std {
   template <class charT, class traits = char_traits<charT>>
+  class basic_fstream : public basic_iostream<charT, traits> {
   public:
+ using char_type   = charT;
+ using int_type    = typename traits::int_type;
+ using pos_type    = typename traits::pos_type;
+ using off_type    = typename traits::off_type;
+ using traits_type = traits;
+    // [fstream.cons], constructors
     basic_fstream();
+    explicit basic_fstream(
+      const char* s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
+    explicit basic_fstream(
+      const std::filesystem::path::value_type* s,
+      ios_base::openmode mode = ios_base::in|ios_base::out);  // wide systems only; see [fstream.syn]
+    explicit basic_fstream(
+      const string& s,
+      ios_base::openmode mode = ios_base::in | ios_base::out);
+    explicit basic_fstream(
+      const filesystem::path& s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
     basic_fstream(const basic_fstream& rhs) = delete;
     basic_fstream(basic_fstream&& rhs);
+    // [fstream.assign], assign and swap
     basic_fstream& operator=(const basic_fstream& rhs) = delete;
     basic_fstream& operator=(basic_fstream&& rhs);
     void swap(basic_fstream& rhs);
+    // [fstream.members], members
     basic_filebuf<charT, traits>* rdbuf() const;
     bool is_open() const;
+    void open(
+      const char* s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
+    void open(
+      const std::filesystem::path::value_type* s,
+      ios_base::openmode mode = ios_base::in|ios_base::out);  // wide systems only; see [fstream.syn]
+    void open(
+      const string& s,
+      ios_base::openmode mode = ios_base::in | ios_base::out);
+    void open(
+      const filesystem::path& s,
       ios_base::openmode mode = ios_base::in | ios_base::out);
     void close();
   private:
     basic_filebuf<charT, traits> sb; // exposition only
               basic_fstream<charT, traits>& y);
 }
 ```
 The class template `basic_fstream<charT, traits>` supports reading and
+writing from named files. It uses a `basic_filebuf<charT, traits>`
+object to control the associated sequences. For the sake of exposition,
+the maintained data is presented here as:
 - `sb`, the `basic_filebuf` object.
 #### `basic_fstream` constructors <a id="fstream.cons">[[fstream.cons]]</a>
 *Effects:* Constructs an object of class `basic_fstream<charT, traits>`,
 initializing the base class with `basic_iostream(&sb)` and initializing
 `sb` with `basic_filebuf<charT, traits>()`.
 ``` cpp
+explicit basic_fstream(
+  const char* s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
+explicit basic_fstream(
+  const filesystem::path::value_type* s,
+  ios_base::openmode mode = ios_base::in | ios_base::out);  // wide systems only; see [fstream.syn]
 ```
 *Effects:* Constructs an object of class `basic_fstream<charT, traits>`,
 initializing the base class with `basic_iostream(&sb)` and initializing
 `sb` with `basic_filebuf<charT, traits>()`. Then calls
 `rdbuf()->open(s, mode)`. If that function returns a null pointer, calls
 `setstate(failbit)`.
 ``` cpp
+explicit basic_fstream(
+  const string& s,
+  ios_base::openmode mode = ios_base::in | ios_base::out);
+explicit basic_fstream(
+  const filesystem::path& s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
 ```
+*Effects:* The same as `basic_fstream(s.c_str(), mode)`.
 ``` cpp
 basic_fstream(basic_fstream&& rhs);
 ```
 template <class charT, class traits>
   void swap(basic_fstream<charT, traits>& x,
             basic_fstream<charT, traits>& y);
 ```
+*Effects:* As if by `x.swap(y)`.
 #### Member functions <a id="fstream.members">[[fstream.members]]</a>
 ``` cpp
 basic_filebuf<charT, traits>* rdbuf() const;
 ```
 *Returns:* `rdbuf()->is_open()`.
 ``` cpp
+void open(
+  const char* s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
+void open(
+  const filesystem::path::value_type* s,
+  ios_base::openmode mode = ios_base::in | ios_base::out);  // wide systems only; see [fstream.syn]
 ```
 *Effects:* Calls `rdbuf()->open(s, mode)`. If that function does not
 return a null pointer calls `clear()`, otherwise calls
+`setstate(failbit)` (which may throw
 `ios_base::failure`) ([[iostate.flags]]).
 ``` cpp
+void open(
+  const string& s,
+  ios_base::openmode mode = ios_base::in | ios_base::out);
+void open(
+  const filesystem::path& s,
   ios_base::openmode mode = ios_base::in | ios_base::out);
 ```
+*Effects:* Calls `open(s.c_str(), mode)`.
 ``` cpp
 void close();
 ```
+*Effects:* Calls `rdbuf()->close()` and, if that function returns a null
+pointer, calls `setstate(failbit)` (which may throw
+`ios_base::failure`) ([[iostate.flags]]).
+## File systems <a id="filesystems">[[filesystems]]</a>
+### General <a id="fs.general">[[fs.general]]</a>
+This subclause describes operations on file systems and their
+components, such as paths, regular files, and directories.
+### Conformance <a id="fs.conformance">[[fs.conformance]]</a>
+Conformance is specified in terms of behavior. Ideal behavior is not
+always implementable, so the conformance subclauses take that into
+account.
+#### POSIX conformance <a id="fs.conform.9945">[[fs.conform.9945]]</a>
+Some behavior is specified by reference to POSIX ([[fs.norm.ref]]). How
+such behavior is actually implemented is unspecified.
+[*Note 1*: This constitutes an “as if” rule allowing implementations to
+call native operating system or other APIs. — *end note*]
+Implementations are encouraged to provide such behavior as it is defined
+by POSIX. Implementations shall document any behavior that differs from
+the behavior defined by POSIX. Implementations that do not support exact
+POSIX behavior are encouraged to provide behavior as close to POSIX
+behavior as is reasonable given the limitations of actual operating
+systems and file systems. If an implementation cannot provide any
+reasonable behavior, the implementation shall report an error as
+specified in  [[fs.err.report]].
+[*Note 2*: This allows users to rely on an exception being thrown or an
+error code being set when an implementation cannot provide any
+reasonable behavior. — *end note*]
+Implementations are not required to provide behavior that is not
+supported by a particular file system.
+[*Example 1*: The FAT file system used by some memory cards, camera
+memory, and floppy disks does not support hard links, symlinks, and many
+other features of more capable file systems, so implementations are not
+required to support those features on the FAT file system but instead
+are required to report an error as described above. — *end example*]
+#### Operating system dependent behavior conformance <a id="fs.conform.os">[[fs.conform.os]]</a>
+Some behavior is specified as being operating system dependent (
+[[fs.def.osdep]]). The operating system an implementation is dependent
+upon is *implementation-defined*.
+It is permissible for an implementation to be dependent upon an
+operating system emulator rather than the actual underlying operating
+system.
+#### File system race behavior <a id="fs.race.behavior">[[fs.race.behavior]]</a>
+Behavior is undefined if calls to functions provided by this subclause
+introduce a file system race ([[fs.def.race]]).
+If the possibility of a file system race would make it unreliable for a
+program to test for a precondition before calling a function described
+herein, *Requires:* is not specified for the function.
+[*Note 1*: As a design practice, preconditions are not specified when
+it is unreasonable for a program to detect them prior to calling the
+function. — *end note*]
+### Normative references <a id="fs.norm.ref">[[fs.norm.ref]]</a>
+This subclause mentions commercially available operating systems for
+purposes of exposition.[^41]
+### Terms and definitions <a id="fs.definitions">[[fs.definitions]]</a>
+A path that unambiguously identifies the location of a file without
+reference to an additional starting location. The elements of a path
+that determine if it is absolute are operating system dependent.
+A file within a file system that acts as a container of directory
+entries that contain information about other files, possibly including
+other directory files.
+An object within a file system that holds user or system data. Files can
+be written to, or read from, or both. A file has certain attributes,
+including type. File types include regular files and directories. Other
+types of files, such as symbolic links ([[fs.def.symlink]]), may be
+supported by the implementation.
+A collection of files and their attributes.
+The condition that occurs when multiple threads, processes, or computers
+interleave access and modification of the same object within a file
+system.
+The name of a file. Filenames *dot* and *dot-dot*, consisting solely of
+one and two period characters respectively, have special meaning. The
+following characteristics of filenames are operating system dependent:
+- The permitted characters. \[*Example 1*: Some operating systems
+  prohibit the ASCII control characters (0x00 – 0x1F) in
+  filenames. — *end example*]
+- The maximum permitted length.
+- Filenames that are not permitted.
+- Filenames that have special meaning.
+- Case awareness and sensitivity during path resolution.
+- Special rules that may apply to file types other than regular files,
+  such as directories.
+A link ([[fs.def.link]]) to an existing file. Some file systems support
+multiple hard links to a file. If the last hard link to a file is
+removed, the file itself is removed.
+[*Note 1*: A hard link can be thought of as a shared-ownership smart
+pointer to a file. — *end note*]
+An object that associates a filename with a file. Several links can
+associate names with the same file.
+For narrow character strings, the operating system dependent current
+encoding for pathnames ([[fs.def.pathname]]). For wide character
+strings, the implementation-defined execution wide-character set
+encoding ([[lex.charset]]).
+The operating system dependent pathname format accepted by the host
+operating system.
+A path in normal form is said to be *normalized*. The process of
+obtaining a normalized path from a path that is not in normal form is
+called *normalization*.
+Normalization of a generic format pathname means:
+1.  If the path is empty, stop.
+2.  Replace each slash character in the *root-name* with a
+    *preferred-separator*.
+3.  Replace each *directory-separator* with a *preferred-separator*.
+    \[*Note 2*: The generic pathname grammar ([[fs.path.generic]])
+    defines *directory-separator* as one or more slashes and
+    *preferred-separator*s. — *end note*]
+4.  Remove each *dot* filename and any immediately following
+    *directory-separator*.
+5.  As long as any appear, remove a non-*dot-dot* filename immediately
+    followed by a *directory-separator* and a *dot-dot* filename, along
+    with any immediately following *directory-separator*.
+6.  If there is a *root-directory*, remove all *dot-dot* filenames and
+    any *directory-separator*s immediately following them.
+    \[*Note 3*: These *dot-dot* filenames attempt to refer to
+    nonexistent parent directories. — *end note*]
+7.  If the last filename is *dot-dot*, remove any trailing
+    *directory-separator*.
+8.  If the path is empty, add a *dot*.
+Behavior that is dependent upon the behavior and characteristics of an
+operating system. See  [[fs.conform.os]].
+the directory that both contains a directory entry for the given
+directory and is represented by the filename *dot-dot* in the given
+directory.
+a directory containing a directory entry for the file under discussion.
+A sequence of elements that identify the location of a file within a
+filesystem. The elements are the *root-name*ₒₚₜ , *root-directory*ₒₚₜ ,
+and an optional sequence of filenames. The maximum number of elements in
+the sequence is operating system dependent.
+A character string that represents the name of a path. Pathnames are
+formatted according to the generic pathname format grammar (
+[[fs.path.generic]]) or an operating system dependent native pathname
+format.
+Pathname resolution is the operating system dependent mechanism for
+resolving a pathname to a particular file in a file hierarchy. There may
+be multiple pathnames that resolve to the same file.
+[*Example 2*: POSIX specifies the mechanism in section 4.11, Pathname
+resolution. — *end example*]
+A path that is not absolute, and as such, only unambiguously identifies
+the location of a file when resolved ([[fs.def.pathres]]) relative to
+an implied starting location. The elements of a path that determine if
+it is relative are operating system dependent.
+[*Note 4*: Pathnames “.” and “..” are relative paths. — *end note*]
+A type of file with the property that when the file is encountered
+during pathname resolution, a string stored by the file is used to
+modify the pathname resolution.
+[*Note 5*: Symbolic links are often called symlinks. A symbolic link
+can be thought of as a raw pointer to a file. If the file pointed to
+does not exist, the symbolic link is said to be a “dangling” symbolic
+link. — *end note*]
+### Requirements <a id="fs.req">[[fs.req]]</a>
+Throughout this subclause, `char`, `wchar_t`, `char16_t`, and `char32_t`
+are collectively called *encoded character types*.
+Functions with template parameters named `EcharT` shall not participate
+in overload resolution unless `EcharT` is one of the encoded character
+types.
+Template parameters named `InputIterator` shall meet the input iterator
+requirements ([[input.iterators]]) and shall have a value type that is
+one of the encoded character types.
+[*Note 1*: Use of an encoded character type implies an associated
+character set and encoding. Since `signed char` and `unsigned char` have
+no implied character set and encoding, they are not included as
+permitted types. — *end note*]
+Template parameters named `Allocator` shall meet the Allocator
+requirements ([[allocator.requirements]]).
+#### Namespaces and headers <a id="fs.req.namespace">[[fs.req.namespace]]</a>
+Unless otherwise specified, references to entities described in this
+subclause are assumed to be qualified with `::std::filesystem::`.
+### Header `<filesystem>` synopsis <a id="fs.filesystem.syn">[[fs.filesystem.syn]]</a>
+``` cpp
+namespace std::filesystem {
+  // [fs.class.path], paths
+  class path;
+  // [fs.path.nonmember], path non-member functions
+  void swap(path& lhs, path& rhs) noexcept;
+  size_t hash_value(const path& p) noexcept;
+  bool operator==(const path& lhs, const path& rhs) noexcept;
+  bool operator!=(const path& lhs, const path& rhs) noexcept;
+  bool operator< (const path& lhs, const path& rhs) noexcept;
+  bool operator<=(const path& lhs, const path& rhs) noexcept;
+  bool operator> (const path& lhs, const path& rhs) noexcept;
+  bool operator>=(const path& lhs, const path& rhs) noexcept;
+  path operator/ (const path& lhs, const path& rhs);
+  // [fs.path.io], path inserter and extractor
+  template <class charT, class traits>
+    basic_ostream<charT, traits>&
+      operator<<(basic_ostream<charT, traits>& os, const path& p);
+  template <class charT, class traits>
+    basic_istream<charT, traits>&
+      operator>>(basic_istream<charT, traits>& is, path& p);
+  // [fs.path.factory], path factory functions
+  template <class Source>
+    path u8path(const Source& source);
+  template <class InputIterator>
+    path u8path(InputIterator first, InputIterator last);
+  // [fs.class.filesystem_error], filesystem errors
+  class filesystem_error;
+  // [fs.class.directory_entry], directory entries
+  class directory_entry;
+  // [fs.class.directory_iterator], directory iterators
+  class directory_iterator;
+  // [fs.dir.itr.nonmembers], range access for directory iterators
+  directory_iterator begin(directory_iterator iter) noexcept;
+  directory_iterator end(const directory_iterator&) noexcept;
+  // [fs.class.rec.dir.itr], recursive directory iterators
+  class recursive_directory_iterator;
+  // [fs.rec.dir.itr.nonmembers], range access for recursive directory iterators
+  recursive_directory_iterator begin(recursive_directory_iterator iter) noexcept;
+  recursive_directory_iterator end(const recursive_directory_iterator&) noexcept;
+  // [fs.class.file_status], file status
+  class file_status;
+  struct space_info {
+    uintmax_t capacity;
+    uintmax_t free;
+    uintmax_t available;
+  };
+  // [fs.enum], enumerations
+  enum class file_type;
+  enum class perms;
+  enum class perm_options;
+  enum class copy_options;
+  enum class directory_options;
+  using file_time_type = chrono::time_point<trivial-clock>;
+  // [fs.op.funcs], filesystem operations
+  path absolute(const path& p, const path& base = current_path());
+  path canonical(const path& p, const path& base = current_path());
+  path canonical(const path& p, error_code& ec);
+  path canonical(const path& p, const path& base, error_code& ec);
+  void copy(const path& from, const path& to);
+  void copy(const path& from, const path& to, error_code& ec) noexcept;
+  void copy(const path& from, const path& to, copy_options options);
+  void copy(const path& from, const path& to, copy_options options,
+            error_code& ec) noexcept;
+  bool copy_file(const path& from, const path& to);
+  bool copy_file(const path& from, const path& to, error_code& ec) noexcept;
+  bool copy_file(const path& from, const path& to, copy_options option);
+  bool copy_file(const path& from, const path& to, copy_options option,
+                 error_code& ec) noexcept;
+  void copy_symlink(const path& existing_symlink, const path& new_symlink);
+  void copy_symlink(const path& existing_symlink, const path& new_symlink,
+                    error_code& ec) noexcept;
+  bool create_directories(const path& p);
+  bool create_directories(const path& p, error_code& ec) noexcept;
+  bool create_directory(const path& p);
+  bool create_directory(const path& p, error_code& ec) noexcept;
+  bool create_directory(const path& p, const path& attributes);
+  bool create_directory(const path& p, const path& attributes,
+                        error_code& ec) noexcept;
+  void create_directory_symlink(const path& to, const path& new_symlink);
+  void create_directory_symlink(const path& to, const path& new_symlink,
+                                error_code& ec) noexcept;
+  void create_hard_link(const path& to, const path& new_hard_link);
+  void create_hard_link(const path& to, const path& new_hard_link,
+                        error_code& ec) noexcept;
+  void create_symlink(const path& to, const path& new_symlink);
+  void create_symlink(const path& to, const path& new_symlink,
+                      error_code& ec) noexcept;
+  path current_path();
+  path current_path(error_code& ec);
+  void current_path(const path& p);
+  void current_path(const path& p, error_code& ec) noexcept;
+  bool exists(file_status s) noexcept;
+  bool exists(const path& p);
+  bool exists(const path& p, error_code& ec) noexcept;
+  bool equivalent(const path& p1, const path& p2);
+  bool equivalent(const path& p1, const path& p2, error_code& ec) noexcept;
+  uintmax_t file_size(const path& p);
+  uintmax_t file_size(const path& p, error_code& ec) noexcept;
+  uintmax_t hard_link_count(const path& p);
+  uintmax_t hard_link_count(const path& p, error_code& ec) noexcept;
+  bool is_block_file(file_status s) noexcept;
+  bool is_block_file(const path& p);
+  bool is_block_file(const path& p, error_code& ec) noexcept;
+  bool is_character_file(file_status s) noexcept;
+  bool is_character_file(const path& p);
+  bool is_character_file(const path& p, error_code& ec) noexcept;
+  bool is_directory(file_status s) noexcept;
+  bool is_directory(const path& p);
+  bool is_directory(const path& p, error_code& ec) noexcept;
+  bool is_empty(const path& p);
+  bool is_empty(const path& p, error_code& ec) noexcept;
+  bool is_fifo(file_status s) noexcept;
+  bool is_fifo(const path& p);
+  bool is_fifo(const path& p, error_code& ec) noexcept;
+  bool is_other(file_status s) noexcept;
+  bool is_other(const path& p);
+  bool is_other(const path& p, error_code& ec) noexcept;
+  bool is_regular_file(file_status s) noexcept;
+  bool is_regular_file(const path& p);
+  bool is_regular_file(const path& p, error_code& ec) noexcept;
+  bool is_socket(file_status s) noexcept;
+  bool is_socket(const path& p);
+  bool is_socket(const path& p, error_code& ec) noexcept;
+  bool is_symlink(file_status s) noexcept;
+  bool is_symlink(const path& p);
+  bool is_symlink(const path& p, error_code& ec) noexcept;
+  file_time_type last_write_time(const path& p);
+  file_time_type last_write_time(const path& p, error_code& ec) noexcept;
+  void last_write_time(const path& p, file_time_type new_time);
+  void last_write_time(const path& p, file_time_type new_time,
+                       error_code& ec) noexcept;
+  void permissions(const path& p, perms prms, perm_options opts=perm_options::replace);
+  void permissions(const path& p, perms prms, error_code& ec) noexcept;
+  void permissions(const path& p, perms prms, perm_options opts, error_code& ec);
+  path proximate(const path& p, error_code& ec);
+  path proximate(const path& p, const path& base = current_path());
+  path proximate(const path& p, const path& base, error_code& ec);
+  path read_symlink(const path& p);
+  path read_symlink(const path& p, error_code& ec);
+  path relative(const path& p, error_code& ec);
+  path relative(const path& p, const path& base = current_path());
+  path relative(const path& p, const path& base, error_code& ec);
+  bool remove(const path& p);
+  bool remove(const path& p, error_code& ec) noexcept;
+  uintmax_t remove_all(const path& p);
+  uintmax_t remove_all(const path& p, error_code& ec) noexcept;
+  void rename(const path& from, const path& to);
+  void rename(const path& from, const path& to, error_code& ec) noexcept;
+  void resize_file(const path& p, uintmax_t size);
+  void resize_file(const path& p, uintmax_t size, error_code& ec) noexcept;
+  space_info space(const path& p);
+  space_info space(const path& p, error_code& ec) noexcept;
+  file_status status(const path& p);
+  file_status status(const path& p, error_code& ec) noexcept;
+  bool status_known(file_status s) noexcept;
+  file_status symlink_status(const path& p);
+  file_status symlink_status(const path& p, error_code& ec) noexcept;
+  path temp_directory_path();
+  path temp_directory_path(error_code& ec);
+  path weakly_canonical(const path& p);
+  path weakly_canonical(const path& p, error_code& ec);
+}
+```
+`trivial-clock` is an *implementation-defined* type that satisfies the
+`TrivialClock` requirements ([[time.clock.req]]) and that is capable of
+representing and measuring file time values. Implementations should
+ensure that the resolution and range of `file_time_type` reflect the
+operating system dependent resolution and range of file time values.
+### Error reporting <a id="fs.err.report">[[fs.err.report]]</a>
+Filesystem library functions often provide two overloads, one that
+throws an exception to report file system errors, and another that sets
+an `error_code`.
+[*Note 1*:
+This supports two common use cases:
+- Uses where file system errors are truly exceptional and indicate a
+  serious failure. Throwing an exception is an appropriate response.
+- Uses where file system errors are routine and do not necessarily
+  represent failure. Returning an error code is the most appropriate
+  response. This allows application specific error handling, including
+  simply ignoring the error.
+— *end note*]
+Functions not having an argument of type `error_code&` handle errors as
+follows, unless otherwise specified:
+- When a call by the implementation to an operating system or other
+  underlying API results in an error that prevents the function from
+  meeting its specifications, an exception of type `filesystem_error`
+  shall be thrown. For functions with a single path argument, that
+  argument shall be passed to the `filesystem_error` constructor with a
+  single path argument. For functions with two path arguments, the first
+  of these arguments shall be passed to the `filesystem_error`
+  constructor as the `path1` argument, and the second shall be passed as
+  the `path2` argument. The `filesystem_error` constructor’s
+  `error_code` argument is set as appropriate for the specific operating
+  system dependent error.
+- Failure to allocate storage is reported by throwing an exception as
+  described in  [[res.on.exception.handling]].
+- Destructors throw nothing.
+Functions having an argument of type `error_code&` handle errors as
+follows, unless otherwise specified:
+- If a call by the implementation to an operating system or other
+  underlying API results in an error that prevents the function from
+  meeting its specifications, the `error_code&` argument is set as
+  appropriate for the specific operating system dependent error.
+  Otherwise, `clear()` is called on the `error_code&` argument.
+### Class `path` <a id="fs.class.path">[[fs.class.path]]</a>
+An object of class `path` represents a path ([[fs.def.path]]) and
+contains a pathname ([[fs.def.pathname]]). Such an object is concerned
+only with the lexical and syntactic aspects of a path. The path does not
+necessarily exist in external storage, and the pathname is not
+necessarily valid for the current operating system or for a particular
+file system.
+[*Note 1*: Class `path` is used to support the differences between the
+string types used by different operating systems to represent pathnames,
+and to perform conversions between encodings when
+necessary. — *end note*]
+``` cpp
+namespace std::filesystem {
+  class path {
+  public:
+    using value_type  = see below;
+    using string_type = basic_string<value_type>;
+    static constexpr value_type preferred_separator = see below;
+    // [fs.enum.path.format], enumeration format
+    enum format;
+    // [fs.path.construct], constructors and destructor
+    path() noexcept;
+    path(const path& p);
+    path(path&& p) noexcept;
+    path(string_type&& source, format fmt = auto_format);
+    template <class Source>
+      path(const Source& source, format fmt = auto_format);
+    template <class InputIterator>
+      path(InputIterator first, InputIterator last, format fmt = auto_format);
+    template <class Source>
+      path(const Source& source, const locale& loc, format fmt = auto_format);
+    template <class InputIterator>
+      path(InputIterator first, InputIterator last, const locale& loc, format fmt = auto_format);
+    ~path();
+    // [fs.path.assign], assignments
+    path& operator=(const path& p);
+    path& operator=(path&& p) noexcept;
+    path& operator=(string_type&& source);
+    path& assign(string_type&& source);
+    template <class Source>
+      path& operator=(const Source& source);
+    template <class Source>
+      path& assign(const Source& source)
+    template <class InputIterator>
+      path& assign(InputIterator first, InputIterator last);
+    // [fs.path.append], appends
+    path& operator/=(const path& p);
+    template <class Source>
+      path& operator/=(const Source& source);
+    template <class Source>
+      path& append(const Source& source);
+    template <class InputIterator>
+      path& append(InputIterator first, InputIterator last);
+    // [fs.path.concat], concatenation
+    path& operator+=(const path& x);
+    path& operator+=(const string_type& x);
+    path& operator+=(basic_string_view<value_type> x);
+    path& operator+=(const value_type* x);
+    path& operator+=(value_type x);
+    template <class Source>
+      path& operator+=(const Source& x);
+    template <class EcharT>
+      path& operator+=(EcharT x);
+    template <class Source>
+      path& concat(const Source& x);
+    template <class InputIterator>
+      path& concat(InputIterator first, InputIterator last);
+    // [fs.path.modifiers], modifiers
+    void  clear() noexcept;
+    path& make_preferred();
+    path& remove_filename();
+    path& replace_filename(const path& replacement);
+    path& replace_extension(const path& replacement = path());
+    void  swap(path& rhs) noexcept;
+    // [fs.path.native.obs], native format observers
+    const string_type& native() const noexcept;
+    const value_type*  c_str() const noexcept;
+    operator string_type() const;
+    template <class EcharT, class traits = char_traits<EcharT>,
+              class Allocator = allocator<EcharT>>
+      basic_string<EcharT, traits, Allocator>
+        string(const Allocator& a = Allocator()) const;
+    std::string    string() const;
+    std::wstring   wstring() const;
+    std::string    u8string() const;
+    std::u16string u16string() const;
+    std::u32string u32string() const;
+    // [fs.path.generic.obs], generic format observers
+    template <class EcharT, class traits = char_traits<EcharT>,
+              class Allocator = allocator<EcharT>>
+      basic_string<EcharT, traits, Allocator>
+        generic_string(const Allocator& a = Allocator()) const;
+    std::string    generic_string() const;
+    std::wstring   generic_wstring() const;
+    std::string    generic_u8string() const;
+    std::u16string generic_u16string() const;
+    std::u32string generic_u32string() const;
+    // [fs.path.compare], compare
+    int  compare(const path& p) const noexcept;
+    int  compare(const string_type& s) const;
+    int  compare(basic_string_view<value_type> s) const;
+    int  compare(const value_type* s) const;
+    // [fs.path.decompose], decomposition
+    path root_name() const;
+    path root_directory() const;
+    path root_path() const;
+    path relative_path() const;
+    path parent_path() const;
+    path filename() const;
+    path stem() const;
+    path extension() const;
+    // [fs.path.query], query
+    bool empty() const noexcept;
+    bool has_root_name() const;
+    bool has_root_directory() const;
+    bool has_root_path() const;
+    bool has_relative_path() const;
+    bool has_parent_path() const;
+    bool has_filename() const;
+    bool has_stem() const;
+    bool has_extension() const;
+    bool is_absolute() const;
+    bool is_relative() const;
+    // [fs.path.gen], generation
+    path lexically_normal() const;
+    path lexically_relative(const path& base) const;
+    path lexically_proximate(const path& base) const;
+    // [fs.path.itr], iterators
+    class iterator;
+    using const_iterator = iterator;
+    iterator begin() const;
+    iterator end() const;
+  };
+}
+```
+`value_type` is a `typedef` for the operating system dependent encoded
+character type used to represent pathnames.
+The value of the `preferred_separator` member is the operating system
+dependent *preferred-separator* character ([[fs.path.generic]]).
+[*Example 1*: For POSIX-based operating systems, `value_type` is `char`
+and `preferred_separator` is the slash character (`'/'`). For
+Windows-based operating systems, `value_type` is `wchar_t` and
+`preferred_separator` is the backslash character
+(`L'\\'`). — *end example*]
+#### Generic pathname format <a id="fs.path.generic">[[fs.path.generic]]</a>
+``` bnf
+pathname:
+    root-nameₒₚₜ root-directoryₒₚₜ relative-path
+```
+``` bnf
+root-name:
+    operating system dependent sequences of characters
+    implementation-defined sequences of characters
+```
+``` bnf
+root-directory:
+    directory-separator
+```
+``` bnf
+relative-path:
+    filename
+    filename directory-separator relative-path
+    an empty path
+```
+``` bnf
+filename:
+    non-empty sequence of characters other than *directory-separator* characters
+```
+``` bnf
+directory-separator:
+    preferred-separator directory-separatorₒₚₜ
+    fallback-separator directory-separatorₒₚₜ
+```
+``` bnf
+preferred-separator:
+    operating system dependent directory separator character
+```
+``` bnf
+fallback-separator:
+    /, if *preferred-separator* is not /
+```
+[*Note 1*: Operating systems often place restrictions on the characters
+that may be used in a *filename*. For wide portability, users may wish
+to limit *filename* characters to the POSIX Portable Filename Character
+Set:
+`A B C D E F G H I J K L M N O P Q R S T U V W X Y Z`
+`a b c d e f g h i j k l m n o p q r s t u v w x y z`
+`0 1 2 3 4 5 6 7 8 9 . _ -` — *end note*]
+Except in a *root-name*, multiple successive *directory-separator*
+characters are considered to be the same as one *directory-separator*
+character.
+The filename *dot* ([[fs.def.filename]]) is treated as a reference to
+the current directory. The filename *dot-dot* ([[fs.def.filename]]) is
+treated as a reference to the parent directory. What the filename
+*dot-dot* refers to relative to *root-directory* is
+*implementation-defined*. Specific filenames may have special meanings
+for a particular operating system.
+A *root-name* identifies the starting location for pathname resolution (
+[[fs.def.pathres]]). If there are no operating system dependent
+*root-name*s, at least one *implementation-defined* *root-name* is
+required.
+[*Note 2*: Many operating systems define a name beginning with two
+*directory-separator* characters as a *root-name* that identifies
+network or other resource locations. Some operating systems define a
+single letter followed by a colon as a drive specifier – a *root-name*
+identifying a specific device such as a disk drive. — *end note*]
+If a *root-name* is otherwise ambiguous, the possibility with the
+longest sequence of characters is chosen.
+[*Note 3*: On a POSIX-like operating system, it is impossible to have a
+*root-name* and a *relative-path* without an intervening
+*root-directory* element. — *end note*]
+#### `path` conversions <a id="fs.path.cvt">[[fs.path.cvt]]</a>
+##### `path` argument format conversions <a id="fs.path.fmt.cvt">[[fs.path.fmt.cvt]]</a>
+[*Note 1*:
+The format conversions described in this section are not applied on
+POSIX-based operating systems because on these systems:
+- The generic format is acceptable as a native path.
+- There is no need to distinguish between native format and generic
+  format in function arguments.
+- Paths for regular files and paths for directories share the same
+  syntax.
+— *end note*]
+Several functions are defined to accept *detected-format* arguments,
+which are character sequences. A detected-format argument represents a
+path using either a pathname in the generic format (
+[[fs.path.generic]]) or a pathname in the native format (
+[[fs.def.native]]). Such an argument is taken to be in the generic
+format if and only if it matches the generic format and is not
+acceptable to the operating system as a native path.
+[*Note 2*: Some operating systems may have no unambiguous way to
+distinguish between native format and generic format arguments. This is
+by design as it simplifies use for operating systems that do not require
+disambiguation. An implementation for an operating system where
+disambiguation is required is permitted to distinguish between the
+formats. — *end note*]
+Pathnames are converted as needed between the generic and native formats
+in an operating-system-dependent manner. Let *G(n)* and *N(g)* in a
+mathematical sense be the implementation’s functions that convert
+native-to-generic and generic-to-native formats respectively. If
+*g=G(n)* for some *n*, then *G(N(g))=g*; if *n=N(g)* for some *g*, then
+*N(G(n))=n*.
+[*Note 3*: Neither *G* nor *N* need be invertible. — *end note*]
+If the native format requires paths for regular files to be formatted
+differently from paths for directories, the path shall be treated as a
+directory path if its last element is a *directory-separator*, otherwise
+it shall be treated as a path to a regular file.
+[*Note 4*: A path stores a native format pathname (
+[[fs.path.native.obs]]) and acts as if it also stores a generic format
+pathname, related as given below. The implementation may generate the
+generic format pathname based on the native format pathname (and
+possibly other information) when requested. — *end note*]
+When a path is constructed from or is assigned a single representation
+separate from any path, the other representation is selected by the
+appropriate conversion function (*G* or *N*).
+When the (new) value *p* of one representation of a path is derived from
+the representation of that or another path, a value *q* is chosen for
+the other representation. The value *q* converts to *p* (by *G* or *N*
+as appropriate) if any such value does so; *q* is otherwise unspecified.
+[*Note 5*: If *q* is the result of converting any path at all, it is
+the result of converting *p*. — *end note*]
+##### `path` type and encoding conversions <a id="fs.path.type.cvt">[[fs.path.type.cvt]]</a>
+For member function arguments that take character sequences representing
+paths and for member functions returning strings, value type and
+encoding conversion is performed if the value type of the argument or
+return value differs from `path::value_type`. For the argument or return
+value, the method of conversion and the encoding to be converted to is
+determined by its value type:
+- `char`: The encoding is the native narrow encoding (
+  [[fs.def.native.encode]]). The method of conversion, if any, is
+  operating system dependent. \[*Note 6*: For POSIX-based operating
+  systems `path::value_type` is `char` so no conversion from `char`
+  value type arguments or to `char` value type return values is
+  performed. For Windows-based operating systems, the native narrow
+  encoding is determined by calling a Windows API
+  function. — *end note*] \[*Note 7*: This results in behavior
+  identical to other C and C++ standard library functions that perform
+  file operations using narrow character strings to identify paths.
+  Changing this behavior would be surprising and error
+  prone. — *end note*]
+- `wchar_t`: The encoding is the native wide encoding (
+  [[fs.def.native.encode]]). The method of conversion is unspecified.
+  \[*Note 8*: For Windows-based operating systems `path::value_type` is
+  `wchar_t` so no conversion from `wchar_t` value type arguments or to
+  `wchar_t` value type return values is performed. — *end note*]
+- `char16_t`: The encoding is UTF-16. The method of conversion is
+  unspecified.
+- `char32_t`: The encoding is UTF-32. The method of conversion is
+  unspecified.
+If the encoding being converted to has no representation for source
+characters, the resulting converted characters, if any, are unspecified.
+Implementations should not modify member function arguments if already
+of type `path::value_type`.
+#### `path` requirements <a id="fs.path.req">[[fs.path.req]]</a>
+In addition to the requirements ([[fs.req]]), function template
+parameters named `Source` shall be one of:
+- `basic_string<EcharT, traits, Allocator>`. A function argument
+  `const Source&` `source` shall have an effective range
+  \[`source.begin()`, `source.end()`).
+- `basic_string_view<EcharT, traits>`. A function argument
+  `const Source&` `source` shall have an effective range
+  \[`source.begin()`, `source.end()`).
+- A type meeting the input iterator requirements that iterates over a
+  NTCTS. The value type shall be an encoded character type. A function
+  argument `const Source&` `source` shall have an effective range
+  \[`source`, `end`) where `end` is the first iterator value with an
+  element value equal to `iterator_traits<Source>::value_type()`.
+- A character array that after array-to-pointer decay results in a
+  pointer to the start of a NTCTS. The value type shall be an encoded
+  character type. A function argument `const Source&` `source` shall
+  have an effective range \[`source`, `end`) where `end` is the first
+  iterator value with an element value equal to
+  `iterator_traits<decay_t<Source>>::value_type()`.
+Functions taking template parameters named `Source` shall not
+participate in overload resolution unless either
+- `Source` is a specialization of `basic_string` or `basic_string_view`,
+  or
+- the *qualified-id* `iterator_traits<decay_t<Source>>::value_type` is
+  valid and denotes a possibly `const` encoded character type (
+  [[temp.deduct]]).
+[*Note 1*: See path conversions ([[fs.path.cvt]]) for how the value
+types above and their encodings convert to `path::value_type` and its
+encoding. — *end note*]
+Arguments of type `Source` shall not be null pointers.
+#### `path` members <a id="fs.path.member">[[fs.path.member]]</a>
+##### `path` constructors <a id="fs.path.construct">[[fs.path.construct]]</a>
+``` cpp
+path() noexcept;
+```
+*Effects:* Constructs an object of class `path`.
+*Postconditions:* `empty() == true`.
+``` cpp
+path(const path& p);
+path(path&& p) noexcept;
+```
+*Effects:* Constructs an object of class `path` having the same pathname
+in the native and generic formats, respectively, as the original value
+of `p`. In the second form, `p` is left in a valid but unspecified
+state.
+``` cpp
+path(string_type&& source, format fmt = auto_format);
+```
+*Effects:* Constructs an object of class `path` for which the pathname
+in the detected-format of `source` has the original value of
+`source` ([[fs.path.fmt.cvt]]), converting format if
+required ([[fs.path.fmt.cvt]]). `source` is left in a valid but
+unspecified state.
+``` cpp
+template <class Source>
+  path(const Source& source, format fmt = auto_format);
+template <class InputIterator>
+  path(InputIterator first, InputIterator last, format fmt = auto_format);
+```
+*Effects:* Let `s` be the effective range of `source` ([[fs.path.req]])
+or the range \[`first`, `last`), with the encoding converted if
+required ([[fs.path.cvt]]). Finds the detected-format of
+`s` ([[fs.path.fmt.cvt]]) and constructs an object of class `path` for
+which the pathname in that format is `s`.
+``` cpp
+template <class Source>
+  path(const Source& source, const locale& loc, format fmt = auto_format);
+template <class InputIterator>
+  path(InputIterator first, InputIterator last, const locale& loc, format fmt = auto_format);
+```
+*Requires:* The value type of `Source` and `InputIterator` is `char`.
+*Effects:* Let `s` be the effective range of `source` or the range
+\[`first`, `last`), after converting the encoding as follows:
+- If `value_type` is `wchar_t`, converts to the native wide
+  encoding ([[fs.def.native.encode]]) using the
+  `codecvt<wchar_t, char, mbstate_t>` facet of `loc`.
+- Otherwise a conversion is performed using the
+  `codecvt<wchar_t, char, mbstate_t>` facet of `loc`, and then a second
+  conversion to the current narrow encoding.
+Finds the detected-format of `s` ([[fs.path.fmt.cvt]]) and constructs
+an object of class `path` for which the pathname in that format is `s`.
+[*Example 1*:
+A string is to be read from a database that is encoded in ISO/IEC
+8859-1, and used to create a directory:
+``` cpp
+namespace fs = std::filesystem;
+std::string latin1_string = read_latin1_data();
+codecvt_8859_1<wchar_t> latin1_facet;
+std::locale latin1_locale(std::locale(), latin1_facet);
+fs::create_directory(fs::path(latin1_string, latin1_locale));
+```
+For POSIX-based operating systems, the path is constructed by first
+using `latin1_facet` to convert ISO/IEC 8859-1 encoded `latin1_string`
+to a wide character string in the native wide
+encoding ([[fs.def.native.encode]]). The resulting wide string is then
+converted to a narrow character pathname string in the current native
+narrow encoding. If the native wide encoding is UTF-16 or UTF-32, and
+the current native narrow encoding is UTF-8, all of the characters in
+the ISO/IEC 8859-1 character set will be converted to their Unicode
+representation, but for other native narrow encodings some characters
+may have no representation.
+For Windows-based operating systems, the path is constructed by using
+`latin1_facet` to convert ISO/IEC 8859-1 encoded `latin1_string` to a
+UTF-16 encoded wide character pathname string. All of the characters in
+the ISO/IEC 8859-1 character set will be converted to their Unicode
+representation.
+— *end example*]
+##### `path` assignments <a id="fs.path.assign">[[fs.path.assign]]</a>
+``` cpp
+path& operator=(const path& p);
+```
+*Effects:* If `*this` and `p` are the same object, has no effect.
+Otherwise, sets both respective pathnames of `*this` to the respective
+pathnames of `p`.
+*Returns:* `*this`.
+``` cpp
+path& operator=(path&& p) noexcept;
+```
+*Effects:* If `*this` and `p` are the same object, has no effect.
+Otherwise, sets both respective pathnames of `*this` to the respective
+pathnames of `p`. `p` is left in a valid but unspecified state.
+[*Note 1*: A valid implementation is `swap(p)`. — *end note*]
+*Returns:* `*this`.
+``` cpp
+path& operator=(string_type&& source);
+path& assign(string_type&& source);
+```
+*Effects:* Sets the pathname in the detected-format of `source` to the
+original value of `source`. `source` is left in a valid but unspecified
+state.
+*Returns:* `*this`.
+``` cpp
+template <class Source>
+  path& operator=(const Source& source);
+template <class Source>
+  path& assign(const Source& source);
+template <class InputIterator>
+  path& assign(InputIterator first, InputIterator last);
+```
+*Effects:* Let `s` be the effective range of `source` ([[fs.path.req]])
+or the range \[`first`, `last`), with the encoding converted if
+required ([[fs.path.cvt]]). Finds the detected-format of
+`s` ([[fs.path.fmt.cvt]]) and sets the pathname in that format to `s`.
+*Returns:* `*this`.
+##### `path` appends <a id="fs.path.append">[[fs.path.append]]</a>
+The append operations use `operator/=` to denote their semantic effect
+of appending *preferred-separator* when needed.
+``` cpp
+path& operator/=(const path& p);
+```
+*Effects:* If
+`p.is_absolute() || (p.has_root_name() && p.root_name() != root_name())`,
+then `operator=(p)`.
+Otherwise, modifies `*this` as if by these steps:
+- If `p.has_root_directory()`, then removes any root directory and
+  relative path from the generic format pathname. Otherwise, if
+  `!has_root_directory() && is_absolute()` is `true` or if
+  `has_filename()` is `true`, then appends `path::preferred_separator`
+  to the generic format pathname.
+- Then appends the native format pathname of `p`, omitting any
+  *root-name* from its generic format pathname, to the native format
+  pathname.
+[*Example 2*:
+Even if `//host` is interpreted as a *root-name*, both of the paths
+`path("//host")/"foo"` and `path("//host/")/"foo"` equal `"//host/foo"`.
+Expression examples:
+``` cpp
+// On POSIX,
+path("foo") / "";     // yields "foo/"
+path("foo") / "/bar"; // yields "/bar"
+// On Windows, backslashes replace slashes in the above yields
+// On Windows,
+path("foo") / "c:/bar";  // yields "c:/bar"
+path("foo") / "c:";      // yields "c:"
+path("c:") / "";         // yields "c:"
+path("c:foo") / "/bar";  // yields "c:/bar"
+path("c:foo") / "c:bar"; // yields "c:foo/bar"
+```
+— *end example*]
+*Returns:* `*this`.
+``` cpp
+template <class Source>
+  path& operator/=(const Source& source);
+template <class Source>
+  path& append(const Source& source);
+```
+*Effects:* Equivalent to: `return operator/=(path(source));`
+``` cpp
+template <class InputIterator>
+  path& append(InputIterator first, InputIterator last);
+```
+*Effects:* Equivalent to: `return operator/=(path(first, last));`
+##### `path` concatenation <a id="fs.path.concat">[[fs.path.concat]]</a>
+``` cpp
+path& operator+=(const path& x);
+path& operator+=(const string_type& x);
+path& operator+=(basic_string_view<value_type> x);
+path& operator+=(const value_type* x);
+path& operator+=(value_type x);
+template <class Source>
+  path& operator+=(const Source& x);
+template <class EcharT>
+  path& operator+=(EcharT x);
+template <class Source>
+  path& concat(const Source& x);
+```
+*Effects:* Appends `path(x).native()` to the pathname in the native
+format.
+[*Note 2*: This directly manipulates the value of `native()` and may
+not be portable between operating systems. — *end note*]
+*Returns:* `*this`.
+``` cpp
+template <class InputIterator>
+  path& concat(InputIterator first, InputIterator last);
+```
+*Effects:* Equivalent to `return *this += path(first, last)`.
+##### `path` modifiers <a id="fs.path.modifiers">[[fs.path.modifiers]]</a>
+``` cpp
+void clear() noexcept;
+```
+*Postconditions:* `empty() == true`.
+``` cpp
+path& make_preferred();
+```
+*Effects:* Each *directory-separator* of the pathname in the generic
+format is converted to *preferred-separator*.
+*Returns:* `*this`.
+[*Example 3*:
+``` cpp
+path p("foo/bar");
+std::cout << p << '\n';
+p.make_preferred();
+std::cout << p << '\n';
+```
+On an operating system where *preferred-separator* is a slash, the
+output is:
+``` cpp
+"foo/bar"
+"foo/bar"
+```
+On an operating system where *preferred-separator* is a backslash, the
+output is:
+``` cpp
+"foo/bar"
+"foo\bar"
+```
+— *end example*]
+``` cpp
+path& remove_filename();
+```
+*Postconditions:* `!has_filename()`.
+*Effects:* Remove the generic format pathname of `filename()` from the
+generic format pathname.
+*Returns:* `*this`.
+[*Example 4*:
+``` cpp
+path("foo/bar").remove_filename(); // yields "foo/"
+path("foo/").remove_filename();    // yields "foo/"
+path("/foo").remove_filename();    // yields "/"
+path("/").remove_filename();       // yields "/"
+```
+— *end example*]
+``` cpp
+path& replace_filename(const path& replacement);
+```
+*Effects:* Equivalent to:
+``` cpp
+remove_filename();
+operator/=(replacement);
+```
+*Returns:* `*this`.
+[*Example 5*:
+``` cpp
+path("/foo").replace_filename("bar");  // yields "/bar" on POSIX
+path("/").replace_filename("bar");     // yields "/bar" on POSIX
+```
+— *end example*]
+``` cpp
+path& replace_extension(const path& replacement = path());
+```
+*Effects:*
+- Any existing `extension()(` [[fs.path.decompose]]`)` is removed from
+  the pathname in the generic format, then
+- If `replacement` is not empty and does not begin with a dot character,
+  a dot character is appended to the pathname in the generic format,
+  then
+- `operator+=(replacement);`.
+*Returns:* `*this`.
+``` cpp
+void swap(path& rhs) noexcept;
+```
+*Effects:* Swaps the contents (in all formats) of the two paths.
+*Complexity:* Constant time.
+##### `path` native format observers <a id="fs.path.native.obs">[[fs.path.native.obs]]</a>
+The string returned by all native format observers is in the native
+pathname format ([[fs.def.native]]).
+``` cpp
+const string_type& native() const noexcept;
+```
+*Returns:* The pathname in the native format.
+``` cpp
+const value_type* c_str() const noexcept;
+```
+*Returns:* Equivalent to `native().c_str()`.
+``` cpp
+operator string_type() const;
+```
+*Returns:* `native()`.
+[*Note 3*: Conversion to `string_type` is provided so that an object of
+class `path` can be given as an argument to existing standard library
+file stream constructors and open functions. — *end note*]
+``` cpp
+template <class EcharT, class traits = char_traits<EcharT>,
+          class Allocator = allocator<EcharT>>
+  basic_string<EcharT, traits, Allocator>
+    string(const Allocator& a = Allocator()) const;
+```
+*Returns:* `native()`.
+*Remarks:* All memory allocation, including for the return value, shall
+be performed by `a`. Conversion, if any, is specified by
+[[fs.path.cvt]].
+``` cpp
+std::string string() const;
+std::wstring wstring() const;
+std::string u8string() const;
+std::u16string u16string() const;
+std::u32string u32string() const;
+```
+*Returns:* `pathstring`.
+*Remarks:* Conversion, if any, is performed as specified by
+[[fs.path.cvt]]. The encoding of the string returned by `u8string()` is
+always UTF-8.
+##### `path` generic format observers <a id="fs.path.generic.obs">[[fs.path.generic.obs]]</a>
+Generic format observer functions return strings formatted according to
+the generic pathname format ([[fs.path.generic]]). A single slash
+(`'/'`) character is used as the *directory-separator*.
+[*Example 1*:
+On an operating system that uses backslash as its *preferred-separator*,
+``` cpp
+path("foo\\bar").generic_string()
+```
+returns `"foo/bar"`.
+— *end example*]
+``` cpp
+template <class EcharT, class traits = char_traits<EcharT>,
+          class Allocator = allocator<EcharT>>
+  basic_string<EcharT, traits, Allocator>
+    generic_string(const Allocator& a = Allocator()) const;
+```
+*Returns:* The pathname in the generic format.
+*Remarks:* All memory allocation, including for the return value, shall
+be performed by `a`. Conversion, if any, is specified by
+[[fs.path.cvt]].
+``` cpp
+std::string generic_string() const;
+std::wstring generic_wstring() const;
+std::string generic_u8string() const;
+std::u16string generic_u16string() const;
+std::u32string generic_u32string() const;
+```
+*Returns:* The pathname in the generic format.
+*Remarks:* Conversion, if any, is specified by  [[fs.path.cvt]]. The
+encoding of the string returned by `generic_u8string()` is always UTF-8.
+##### `path` compare <a id="fs.path.compare">[[fs.path.compare]]</a>
+``` cpp
+int compare(const path& p) const noexcept;
+```
+*Returns:*
+- A value less than `0`, if `native()` for the elements of `*this` are
+  lexicographically less than `native()` for the elements of `p`;
+  otherwise,
+- a value greater than `0`, if `native()` for the elements of `*this`
+  are lexicographically greater than `native()` for the elements of `p`;
+  otherwise,
+- `0`.
+*Remarks:* The elements are determined as if by iteration over the
+half-open range \[`begin()`, `end()`) for `*this` and `p`.
+``` cpp
+int compare(const string_type& s) const
+int compare(basic_string_view<value_type> s) const;
+```
+*Returns:* `compare(path(s))`.
+``` cpp
+int compare(const value_type* s) const
+```
+*Returns:* `compare(path(s))`.
+##### `path` decomposition <a id="fs.path.decompose">[[fs.path.decompose]]</a>
+``` cpp
+path root_name() const;
+```
+*Returns:* *root-name*, if the pathname in the generic format includes
+*root-name*, otherwise `path()`.
+``` cpp
+path root_directory() const;
+```
+*Returns:* *root-directory*, if the pathname in the generic format
+includes *root-directory*, otherwise `path()`.
+``` cpp
+path root_path() const;
+```
+*Returns:* `root_name() / root_directory()`.
+``` cpp
+path relative_path() const;
+```
+*Returns:* A `path` composed from the pathname in the generic format, if
+`!empty()`, beginning with the first *filename* after *root-path*.
+Otherwise, `path()`.
+``` cpp
+path parent_path() const;
+```
+*Returns:* `*this` if `!has_relative_path()`, otherwise a path whose
+generic format pathname is the longest prefix of the generic format
+pathname of `*this` that produces one fewer element in its iteration.
+``` cpp
+path filename() const;
+```
+*Returns:* `relative_path().empty() ? path() : *–end()`.
+[*Example 6*:
+``` cpp
+path("/foo/bar.txt").filename();   // yields "bar.txt"
+path("/foo/bar").filename();       // yields "bar"
+path("/foo/bar/").filename();      // yields ""
+path("/").filename();              // yields ""
+path("//host").filename();         // yields ""
+path(".").filename();              // yields "."
+path("..").filename();             // yields ".."
+```
+— *end example*]
+``` cpp
+path stem() const;
+```
+*Returns:* Let `f` be the generic format pathname of `filename()`.
+Returns a path whose pathname in the generic format is
+- `f`, if it contains no periods other than a leading period or consists
+  solely of one or two periods;
+- otherwise, the prefix of `f` ending before its last period.
+[*Example 7*:
+``` cpp
+std::cout << path("/foo/bar.txt").stem(); // outputs "bar"
+path p = "foo.bar.baz.tar";
+for (; !p.extension().empty(); p = p.stem())
+  std::cout << p.extension() << '\n';
+  // outputs: .tar
+  //          .baz
+  //          .bar
+```
+— *end example*]
+``` cpp
+path extension() const;
+```
+*Returns:* a path whose pathname in the generic format is the suffix of
+`filename()` not included in `stem()`.
+[*Example 8*:
+``` cpp
+path("/foo/bar.txt").extension();  // yields ".txt" and stem() is "bar"
+path("/foo/bar").extension();      // yields "" and stem() is "bar"
+path("/foo/.profile").extension(); // yields "" and stem() is ".profile"
+path(".bar").extension();          // yields "" and stem() is ".bar"
+path("..bar").extension();         // yields ".bar" and stem() is "."
+```
+— *end example*]
+[*Note 4*: The period is included in the return value so that it is
+possible to distinguish between no extension and an empty
+extension. — *end note*]
+[*Note 5*: On non-POSIX operating systems, for a path `p`, it may not
+be the case that `p.stem() + p.extension() == p.filename()`, even though
+the generic format pathnames are the same. — *end note*]
+##### `path` query <a id="fs.path.query">[[fs.path.query]]</a>
+``` cpp
+bool empty() const noexcept;
+```
+*Returns:* `true` if the pathname in the generic format is empty, else
+`false`.
+``` cpp
+bool has_root_path() const;
+```
+*Returns:* `!root_path().empty()`.
+``` cpp
+bool has_root_name() const;
+```
+*Returns:* `!root_name().empty()`.
+``` cpp
+bool has_root_directory() const;
+```
+*Returns:* `!root_directory().empty()`.
+``` cpp
+bool has_relative_path() const;
+```
+*Returns:* `!relative_path().empty()`.
+``` cpp
+bool has_parent_path() const;
+```
+*Returns:* `!parent_path().empty()`.
+``` cpp
+bool has_filename() const;
+```
+*Returns:* `!filename().empty()`.
+``` cpp
+bool has_stem() const;
+```
+*Returns:* `!stem().empty()`.
+``` cpp
+bool has_extension() const;
+```
+*Returns:* `!extension().empty()`.
+``` cpp
+bool is_absolute() const;
+```
+*Returns:* `true` if the pathname in the native format contains an
+absolute path ([[fs.def.absolute.path]]), else `false`.
+[*Example 9*: `path("/").is_absolute()` is `true` for POSIX-based
+operating systems, and `false` for Windows-based operating
+systems. — *end example*]
+``` cpp
+bool is_relative() const;
+```
+*Returns:* `!is_absolute()`.
+##### `path` generation <a id="fs.path.gen">[[fs.path.gen]]</a>
+``` cpp
+path lexically_normal() const;
+```
+*Returns:* A path whose pathname in the generic format is the normal
+form ([[fs.def.normal.form]]) of the pathname in the generic format of
+`*this`.
+[*Example 10*:
+``` cpp
+assert(path("foo/./bar/..").lexically_normal() == "foo/");
+assert(path("foo/.///bar/../").lexically_normal() == "foo/");
+```
+The above assertions will succeed. On Windows, the returned path’s
+*directory-separator* characters will be backslashes rather than
+slashes, but that does not affect `path` equality.
+— *end example*]
+``` cpp
+path lexically_relative(const path& base) const;
+```
+*Returns:* `*this` made relative to `base`. Does not
+resolve ([[fs.def.pathres]]) symlinks. Does not first
+normalize ([[fs.def.normal.form]]) `*this` or `base`.
+*Effects:* If `root_name() != base.root_name()` is `true` or
+`is_absolute() != base.is_absolute()` is `true` or
+`!has_root_directory() && base.has_root_directory()` is `true`, returns
+`path()`. Determines the first mismatched element of `*this` and `base`
+as if by:
+``` cpp
+auto [a, b] = mismatch(begin(), end(), base.begin(), base.end());
+```
+Then,
+- if `a == end()` and `b == base.end()`, returns `path(".")`; otherwise
+- let `n` be the number of *filename* elements in \[`b`, `base.end()`)
+  that are not *dot* or *dot-dot* minus the number that are *dot-dot*.
+  If `n<0,` returns `path()`; otherwise
+- returns an object of class `path` that is default-constructed,
+  followed by
+  - application of `operator/=(path(".."))` `n` times, and then
+  - application of `operator/=` for each element in \[`a`, `end()`).
+[*Example 11*:
+``` cpp
+assert(path("/a/d").lexically_relative("/a/b/c") == "../../d");
+assert(path("/a/b/c").lexically_relative("/a/d") == "../b/c");
+assert(path("a/b/c").lexically_relative("a") == "b/c");
+assert(path("a/b/c").lexically_relative("a/b/c/x/y") == "../..");
+assert(path("a/b/c").lexically_relative("a/b/c") == ".");
+assert(path("a/b").lexically_relative("c/d") == "../../a/b");
+```
+The above assertions will succeed. On Windows, the returned path’s
+*directory-separator* characters will be backslashes rather than
+slashes, but that does not affect `path` equality.
+— *end example*]
+[*Note 6*: If symlink following semantics are desired, use the
+operational function `relative()`. — *end note*]
+[*Note 7*: If normalization ([[fs.def.normal.form]]) is needed to
+ensure consistent matching of elements, apply `lexically_normal()` to
+`*this`, `base`, or both. — *end note*]
+``` cpp
+path lexically_proximate(const path& base) const;
+```
+*Returns:* If the value of `lexically_relative(base)` is not an empty
+path, return it. Otherwise return `*this`.
+[*Note 8*: If symlink following semantics are desired, use the
+operational function `proximate()`. — *end note*]
+[*Note 9*: If normalization ([[fs.def.normal.form]]) is needed to
+ensure consistent matching of elements, apply `lexically_normal()` to
+`*this`, `base`, or both. — *end note*]
+#### `path` iterators <a id="fs.path.itr">[[fs.path.itr]]</a>
+Path iterators iterate over the elements of the pathname in the generic
+format ([[fs.path.generic]]).
+A `path::iterator` is a constant iterator satisfying all the
+requirements of a bidirectional iterator ([[bidirectional.iterators]])
+except that, for dereferenceable iterators `a` and `b` of type
+`path::iterator` with `a == b`, there is no requirement that `*a` and
+`*b` are bound to the same object. Its `value_type` is `path`.
+Calling any non-const member function of a `path` object invalidates all
+iterators referring to elements of that object.
+For the elements of the pathname in the generic format, the forward
+traversal order is as follows:
+- The *root-name* element, if present.
+- The *root-directory* element, if present. \[*Note 1*: The generic
+  format is required to ensure lexicographical comparison works
+  correctly. — *end note*]
+- Each successive *filename* element, if present.
+- An empty element, if a trailing non-root *directory-separator* is
+  present.
+The backward traversal order is the reverse of forward traversal.
+``` cpp
+iterator begin() const;
+```
+*Returns:* An iterator for the first present element in the traversal
+list above. If no elements are present, the end iterator.
+``` cpp
+iterator end() const;
+```
+*Returns:* The end iterator.
+#### `path` non-member functions <a id="fs.path.nonmember">[[fs.path.nonmember]]</a>
+``` cpp
+void swap(path& lhs, path& rhs) noexcept;
+```
+*Effects:* Equivalent to: `lhs.swap(rhs);`
+``` cpp
+size_t hash_value (const path& p) noexcept;
+```
+*Returns:* A hash value for the path `p`. If for two paths, `p1 == p2`
+then `hash_value(p1) == hash_value(p2)`.
+``` cpp
+bool operator< (const path& lhs, const path& rhs) noexcept;
+```
+*Returns:* `lhs.compare(rhs) < 0`.
+``` cpp
+bool operator<=(const path& lhs, const path& rhs) noexcept;
+```
+*Returns:* `!(rhs < lhs)`.
+``` cpp
+bool operator> (const path& lhs, const path& rhs) noexcept;
+```
+*Returns:* `rhs < lhs`.
+``` cpp
+bool operator>=(const path& lhs, const path& rhs) noexcept;
+```
+*Returns:* `!(lhs < rhs)`.
+``` cpp
+bool operator==(const path& lhs, const path& rhs) noexcept;
+```
+*Returns:* `!(lhs < rhs) && !(rhs < lhs)`.
+[*Note 1*:
+Path equality and path equivalence have different semantics.
+- Equality is determined by the `path` non-member `operator==`, which
+  considers the two path’s lexical representations only.
+  \[*Example 1*: `path("foo") == "bar"` is never
+  `true`. — *end example*]
+- Equivalence is determined by the `equivalent()` non-member function,
+  which determines if two paths resolve ([[fs.def.pathres]]) to the
+  same file system entity. \[*Example 2*: `equivalent("foo", "bar")`
+  will be `true` when both paths resolve to the same
+  file. — *end example*]
+Programmers wishing to determine if two paths are “the same” must decide
+if “the same” means “the same representation” or “resolve to the same
+actual file”, and choose the appropriate function accordingly.
+— *end note*]
+``` cpp
+bool operator!=(const path& lhs, const path& rhs) noexcept;
+```
+*Returns:* `!(lhs == rhs)`.
+``` cpp
+path operator/ (const path& lhs, const path& rhs);
+```
+*Effects:* Equivalent to: `return path(lhs) /= rhs;`
+##### `path` inserter and extractor <a id="fs.path.io">[[fs.path.io]]</a>
+``` cpp
+template <class charT, class traits>
+  basic_ostream<charT, traits>&
+    operator<<(basic_ostream<charT, traits>& os, const path& p);
+```
+*Effects:* Equivalent to: `os << quoted(p.string<charT, traits>());`
+[*Note 2*: The `quoted` function is described
+in  [[quoted.manip]]. — *end note*]
+*Returns:* `os`.
+``` cpp
+template <class charT, class traits>
+  basic_istream<charT, traits>&
+    operator>>(basic_istream<charT, traits>& is, path& p);
+```
+*Effects:* Equivalent to:
+``` cpp
+basic_string<charT, traits> tmp;
+is >> quoted(tmp);
+p = tmp;
+```
+*Returns:* `is`.
+##### `path` factory functions <a id="fs.path.factory">[[fs.path.factory]]</a>
+``` cpp
+template <class Source>
+  path u8path(const Source& source);
+template <class InputIterator>
+  path u8path(InputIterator first, InputIterator last);
+```
+*Requires:* The `source` and \[`first`, `last`) sequences are UTF-8
+encoded. The value type of `Source` and `InputIterator` is `char`.
+*Returns:*
+- If `value_type` is `char` and the current native narrow
+  encoding ([[fs.def.native.encode]]) is UTF-8, return `path(source)`
+  or `path(first, last)`; otherwise,
+- if `value_type` is `wchar_t` and the native wide encoding is UTF-16,
+  or if `value_type` is `char16_t` or `char32_t`, convert `source` or
+  \[`first`, `last`) to a temporary, `tmp`, of type `string_type` and
+  return `path(tmp)`; otherwise,
+- convert `source` or \[`first`, `last`) to a temporary, `tmp`, of type
+  `u32string` and return `path(tmp)`.
+*Remarks:* Argument format conversion ([[fs.path.fmt.cvt]]) applies to
+the arguments for these functions. How Unicode encoding conversions are
+performed is unspecified.
+[*Example 1*:
+A string is to be read from a database that is encoded in UTF-8, and
+used to create a directory using the native encoding for filenames:
+``` cpp
+namespace fs = std::filesystem;
+std::string utf8_string = read_utf8_data();
+fs::create_directory(fs::u8path(utf8_string));
+```
+For POSIX-based operating systems with the native narrow encoding set to
+UTF-8, no encoding or type conversion occurs.
+For POSIX-based operating systems with the native narrow encoding not
+set to UTF-8, a conversion to UTF-32 occurs, followed by a conversion to
+the current native narrow encoding. Some Unicode characters may have no
+native character set representation.
+For Windows-based operating systems a conversion from UTF-8 to UTF-16
+occurs.
+— *end example*]
+### Class `filesystem_error` <a id="fs.class.filesystem_error">[[fs.class.filesystem_error]]</a>
+``` cpp
+namespace std::filesystem {
+  class filesystem_error : public system_error {
+  public:
+    filesystem_error(const string& what_arg, error_code ec);
+    filesystem_error(const string& what_arg,
+                     const path& p1, error_code ec);
+    filesystem_error(const string& what_arg,
+                     const path& p1, const path& p2, error_code ec);
+    const path& path1() const noexcept;
+    const path& path2() const noexcept;
+    const char* what() const noexcept override;
+  };
+}
+```
+The class `filesystem_error` defines the type of objects thrown as
+exceptions to report file system errors from functions described in this
+subclause.
+#### `filesystem_error` members <a id="filesystem_error.members">[[filesystem_error.members]]</a>
+Constructors are provided that store zero, one, or two paths associated
+with an error.
+``` cpp
+filesystem_error(const string& what_arg, error_code ec);
+```
+*Postconditions:* The postconditions of this function are indicated in
+Table  [[tab:filesystem_error.1]].
+**Table: `filesystem_error(const string&, error_code)` effects** <a id="tab:filesystem_error.1">[tab:filesystem_error.1]</a>
+| Expression              | Value              |
+| ----------------------- | ------------------ |
+| `runtime_error::what()` | `what_arg.c_str()` |
+| `code()`                | `ec`               |
+| `path1().empty()`       | `true`             |
+| `path2().empty()`       | `true`             |
+``` cpp
+filesystem_error(const string& what_arg, const path& p1, error_code ec);
+```
+*Postconditions:* The postconditions of this function are indicated in
+Table  [[tab:filesystem_error.2]].
+**Table: `filesystem_error(const string&, const path&, error_code)` effects** <a id="tab:filesystem_error.2">[tab:filesystem_error.2]</a>
+| Expression              | Value                            |
+| ----------------------- | -------------------------------- |
+| `runtime_error::what()` | `what_arg.c_str()`               |
+| `code()`                | `ec`                             |
+| `path1()`               | Reference to stored copy of `p1` |
+| `path2().empty()`       | `true`                           |
+``` cpp
+filesystem_error(const string& what_arg, const path& p1, const path& p2, error_code ec);
+```
+*Postconditions:* The postconditions of this function are indicated in
+Table  [[tab:filesystem_error.3]].
+**Table: `filesystem_error(const string&, const path&, const path&, error_code)` effects** <a id="tab:filesystem_error.3">[tab:filesystem_error.3]</a>
+| Expression              | Value                            |
+| ----------------------- | -------------------------------- |
+| `runtime_error::what()` | `what_arg.c_str()`               |
+| `code()`                | `ec`                             |
+| `path1()`               | Reference to stored copy of `p1` |
+| `path2()`               | Reference to stored copy of `p2` |
+``` cpp
+const path& path1() const noexcept;
+```
+*Returns:* A reference to the copy of `p1` stored by the constructor,
+or, if none, an empty path.
+``` cpp
+const path& path2() const noexcept;
+```
+*Returns:* A reference to the copy of `p2` stored by the constructor,
+or, if none, an empty path.
+``` cpp
+const char* what() const noexcept override;
+```
+*Returns:* A string containing `runtime_error::what()`. The exact format
+is unspecified. Implementations are encouraged but not required to
+include `path1.native_string()` if not empty, `path2.native_string()` if
+not empty, and `system_error::what()` strings in the returned string.
+### Enumerations <a id="fs.enum">[[fs.enum]]</a>
+#### Enum `path::format` <a id="fs.enum.path.format">[[fs.enum.path.format]]</a>
+This enum specifies constants used to identify the format of the
+character sequence, with the meanings listed in Table
+[[tab:enum.path.format]].
+[*Note 1*: For POSIX-based systems, native and generic formats are
+equivalent and the character sequence should always be interpreted in
+the same way. — *end note*]
+#### Enum class `file_type` <a id="fs.enum.file_type">[[fs.enum.file_type]]</a>
+This enum class specifies constants used to identify file types, with
+the meanings listed in Table  [[tab:fs.enum.file_type]].
+[*Note 1*: The file not being found is not considered an error while
+determining the type of a file. — *end note*]
+#### Enum class `copy_options` <a id="fs.enum.copy.opts">[[fs.enum.copy.opts]]</a>
+The `enum class` type `copy_options` is a bitmask type (
+[[bitmask.types]]) that specifies bitmask constants used to control the
+semantics of copy operations. The constants are specified in option
+groups with the meanings listed in Table  [[tab:fs.enum.copy_options]].
+Constant `none` is shown in each option group for purposes of
+exposition; implementations shall provide only a single definition.
+**Table: Enum class `copy_options`** <a id="tab:fs.enum.copy_options">[tab:fs.enum.copy_options]</a>
+| Constant             | Meaning                                                                                                                                               |
+| -------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `none`               | (Default) Error; file already exists.                                                                                                                 |
+| `skip_existing`      | Do not overwrite existing file, do not report an error.                                                                                               |
+| `overwrite_existing` | Overwrite the existing file.                                                                                                                          |
+| `update_existing`    | Overwrite the existing file if it is older than the replacement file. \ohdrx{2}{Option group controlling `copy` function effects for sub-directories} |
+| `recursive`          | Recursively copy sub-directories and their contents. \ohdrx{2}{Option group controlling `copy` function effects for symbolic links}                   |
+| `copy_symlinks`      | Copy symbolic links as symbolic links rather than copying the files that they point to.                                                               |
+| `skip_symlinks`      | Ignore symbolic links. \ohdrx{2}{Option group controlling `copy` function effects for choosing the form of copying}                                   |
+| `directories_only`   | Copy directory structure only, do not copy non-directory files.                                                                                       |
+| `create_symlinks`    | Make symbolic links instead of copies of files. The source path shall be an absolute path unless the destination path is in the current directory.    |
+| `create_hard_links`  | Make hard links instead of copies of files.                                                                                                           |
+#### Enum class `perms` <a id="fs.enum.perms">[[fs.enum.perms]]</a>
+The `enum class` type `perms` is a bitmask type ([[bitmask.types]])
+that specifies bitmask constants used to identify file permissions, with
+the meanings listed in Table  [[tab:fs.enum.perms]].
+**Table: Enum class `perms`** <a id="tab:fs.enum.perms">[tab:fs.enum.perms]</a>
+| Name           | Value (octal) | POSIX macro | Definition or notes                                                                                              |
+| -------------- | ------------- | ----------- | ---------------------------------------------------------------------------------------------------------------- |
+| `none`         | `0`           |             | There are no permissions set for the file.                                                                       |
+| `owner_read`   | `0400`        | `S_IRUSR`   | Read permission, owner                                                                                           |
+| `owner_write`  | `0200`        | `S_IWUSR`   | Write permission, owner                                                                                          |
+| `owner_exec`   | `0100`        | `S_IXUSR`   | Execute/search permission, owner                                                                                 |
+| `owner_all`    | `0700`        | `S_IRWXU`   | Read, write, execute/search by owner;<br> `owner_read | owner_write | owner_exec`                                |
+| `group_read`   | `040`         | `S_IRGRP`   | Read permission, group                                                                                           |
+| `group_write`  | `020`         | `S_IWGRP`   | Write permission, group                                                                                          |
+| `group_exec`   | `010`         | `S_IXGRP`   | Execute/search permission, group                                                                                 |
+| `group_all`    | `070`         | `S_IRWXG`   | Read, write, execute/search by group;<br> `group_read | group_write | group_exec`                                |
+| `others_read`  | `04`          | `S_IROTH`   | Read permission, others                                                                                          |
+| `others_write` | `02`          | `S_IWOTH`   | Write permission, others                                                                                         |
+| `others_exec`  | `01`          | `S_IXOTH`   | Execute/search permission, others                                                                                |
+| `others_all`   | `07`          | `S_IRWXO`   | Read, write, execute/search by others;<br> `others_read | others_write | others_exec`                            |
+| `all`          | `0777`        |             | `owner_all | group_all | others_all`                                                                             |
+| `set_uid`      | `04000`       | `S_ISUID`   | Set-user-ID on execution                                                                                         |
+| `set_gid`      | `02000`       | `S_ISGID`   | Set-group-ID on execution                                                                                        |
+| `sticky_bit`   | `01000`       | `S_ISVTX`   | Operating system dependent.                                                                                      |
+| `mask`         | `07777`       |             | `all | set_uid | set_gid | sticky_bit`                                                                           |
+| `unknown`      | `0xFFFF`      |             | The permissions are not known, such as when a `file_status` object is created without specifying the permissions |
+#### Enum class `perm_options` <a id="fs.enum.perm.opts">[[fs.enum.perm.opts]]</a>
+The `enum class` type `perm_options` is a bitmask type (
+[[bitmask.types]]) that specifies bitmask constants used to control the
+semantics of permissions operations, with the meanings listed in Table
+[[tab:enum.perm_options]]. The bitmask constants are bitmask elements.
+In Table  [[tab:enum.perm_options]] `perm` denotes a value of type
+`perms` passed to `permissions`.
+**Table: Enum class `perm_options`** <a id="tab:enum.perm_options">[tab:enum.perm_options]</a>
+| Name       | Meaning                                                                                                                                         |
+| ---------- | ----------------------------------------------------------------------------------------------------------------------------------------------- |
+| `replace`  | `permissions` shall replace the file's permission bits with `perm`                                                                              |
+| `add`      | `permissions` shall replace the file's permission bits with the bitwise OR of `perm` and the file's current permission bits.                    |
+| `remove`   | `permissions` shall replace the file's permission bits with the bitwise AND of the complement of `perm` and the file's current permission bits. |
+| `nofollow` | `permissions` shall change the permissions of a symbolic link itself rather than the permissions of the file the link resolves to.              |
+#### Enum class `directory_options` <a id="fs.enum.dir.opts">[[fs.enum.dir.opts]]</a>
+The `enum class` type `directory_options` is a bitmask type (
+[[bitmask.types]]) that specifies bitmask constants used to identify
+directory traversal options, with the meanings listed in Table
+[[tab:fs.enum.directory_options]].
+**Table: Enum class `directory_options`** <a id="tab:fs.enum.directory_options">[tab:fs.enum.directory_options]</a>
+| Name                       | Meaning                                                            |
+| -------------------------- | ------------------------------------------------------------------ |
+| `none`                     | (Default) Skip directory symlinks, permission denied is an error.  |
+| `follow_directory_symlink` | Follow rather than skip directory symlinks.                        |
+| `skip_permission_denied`   | Skip directories that would otherwise result in permission denied. |
+### Class `file_status` <a id="fs.class.file_status">[[fs.class.file_status]]</a>
+``` cpp
+namespace std::filesystem {
+  class file_status {
+  public:
+    // [fs.file_status.cons], constructors and destructor
+    file_status() noexcept : file_status(file_type::none) {}
+    explicit file_status(file_type ft,
+                         perms prms = perms::unknown) noexcept;
+    file_status(const file_status&) noexcept = default;
+    file_status(file_status&&) noexcept = default;
+    ~file_status();
+    // assignments:
+    file_status& operator=(const file_status&) noexcept = default;
+    file_status& operator=(file_status&&) noexcept = default;
+    // [fs.file_status.mods], modifiers
+    void       type(file_type ft) noexcept;
+    void       permissions(perms prms) noexcept;
+    // [fs.file_status.obs], observers
+    file_type  type() const noexcept;
+    perms      permissions() const noexcept;
+  };
+}
+```
+#### `file_status` constructors <a id="fs.file_status.cons">[[fs.file_status.cons]]</a>
+``` cpp
+explicit file_status(file_type ft, perms prms = perms::unknown) noexcept;
+```
+*Postconditions:* `type() == ft` and `permissions() == prms`.
+#### `file_status` observers <a id="fs.file_status.obs">[[fs.file_status.obs]]</a>
+``` cpp
+file_type type() const noexcept;
+```
+*Returns:* The value of `type()` specified by the postconditions of the
+most recent call to a constructor, `operator=`, or `type(file_type)`
+function.
+``` cpp
+perms permissions() const noexcept;
+```
+*Returns:* The value of `permissions()` specified by the postconditions
+of the most recent call to a constructor, `operator=`, or
+`permissions(perms)` function.
+#### `file_status` modifiers <a id="fs.file_status.mods">[[fs.file_status.mods]]</a>
+``` cpp
+void type(file_type ft) noexcept;
+```
+*Postconditions:* `type() == ft`.
+``` cpp
+void permissions(perms prms) noexcept;
+```
+*Postconditions:* `permissions() == prms`.
+### Class `directory_entry` <a id="fs.class.directory_entry">[[fs.class.directory_entry]]</a>
+``` cpp
+namespace std::filesystem {
+  class directory_entry {
+  public:
+    // [fs.dir.entry.cons], constructors and destructor
+    directory_entry() noexcept = default;
+    directory_entry(const directory_entry&) = default;
+    directory_entry(directory_entry&&) noexcept = default;
+    explicit directory_entry(const path& p);
+    directory_entry(const path& p, error_code& ec);
+    ~directory_entry();
+    // assignments:
+    directory_entry& operator=(const directory_entry&) = default;
+    directory_entry& operator=(directory_entry&&) noexcept = default;
+    // [fs.dir.entry.mods], modifiers
+    void assign(const path& p);
+    void assign(const path& p, error_code& ec);
+    void replace_filename(const path& p);
+    void replace_filename(const path& p, error_code& ec);
+    void refresh();
+    void refresh(error_code& ec) noexcept;
+    // [fs.dir.entry.obs], observers
+    const path& path() const noexcept;
+    operator const path&() const noexcept;
+    bool exists() const;
+    bool exists(error_code& ec) const noexcept;
+    bool is_block_file() const;
+    bool is_block_file(error_code& ec) const noexcept;
+    bool is_character_file() const;
+    bool is_character_file(error_code& ec) const noexcept;
+    bool is_directory() const;
+    bool is_directory(error_code& ec) const noexcept;
+    bool is_fifo() const;
+    bool is_fifo(error_code& ec) const noexcept;
+    bool is_other() const;
+    bool is_other(error_code& ec) const noexcept;
+    bool is_regular_file() const;
+    bool is_regular_file(error_code& ec) const noexcept;
+    bool is_socket() const;
+    bool is_socket(error_code& ec) const noexcept;
+    bool is_symlink() const;
+    bool is_symlink(error_code& ec) const noexcept;
+    uintmax_t file_size() const;
+    uintmax_t file_size(error_code& ec) const noexcept;
+    uintmax_t hard_link_count() const;
+    uintmax_t hard_link_count(error_code& ec) const noexcept;
+    file_time_type last_write_time() const;
+    file_time_type last_write_time(error_code& ec) const noexcept;
+    file_status status() const;
+    file_status status(error_code& ec) const noexcept;
+    file_status symlink_status() const;
+    file_status symlink_status(error_code& ec) const noexcept;
+    bool operator< (const directory_entry& rhs) const noexcept;
+    bool operator==(const directory_entry& rhs) const noexcept;
+    bool operator!=(const directory_entry& rhs) const noexcept;
+    bool operator<=(const directory_entry& rhs) const noexcept;
+    bool operator> (const directory_entry& rhs) const noexcept;
+    bool operator>=(const directory_entry& rhs) const noexcept;
+  private:
+    path pathobject;                 // exposition only
+    friend class directory_iterator; // exposition only
+  };
+}
+```
+A `directory_entry` object stores a `path` object and may store
+additional objects for file attributes such as hard link count, status,
+symlink status, file size, and last write time.
+Implementations are encouraged to store such additional file attributes
+during directory iteration if their values are available and storing the
+values would allow the implementation to eliminate file system accesses
+by `directory_entry` observer functions ([[fs.op.funcs]]). Such stored
+file attribute values are said to be *cached*.
+[*Note 1*: For purposes of exposition, class `directory_iterator` (
+[[fs.class.directory_iterator]]) is shown above as a friend of class
+`directory_entry`. Friendship allows the `directory_iterator`
+implementation to cache already available attribute values directly into
+a `directory_entry` object without the cost of an unneeded call to
+`refresh()`. — *end note*]
+[*Example 1*:
+``` cpp
+using namespace std::filesystem;
+// use possibly cached last write time to minimize disk accesses
+for (auto&& x : directory_iterator("."))
+{
+  std::cout << x.path() << " " << x.last_write_time() << std::endl;
+}
+// call refresh() to refresh a stale cache
+for (auto&& x : directory_iterator("."))
+{
+  lengthy_function(x.path());  // cache becomes stale
+  x.refresh();
+  std::cout << x.path() << " " << x.last_write_time() << std::endl;
+}
+```
+On implementations that do not cache the last write time, both loops
+will result in a potentially expensive call to the
+`std::filesystem::last_write_time` function. On implementations that do
+cache the last write time, the first loop will use the cached value and
+so will not result in a potentially expensive call to the
+`std::filesystem::last_write_time` function. The code is portable to any
+implementation, regardless of whether or not it employs caching.
+— *end example*]
+#### `directory_entry` constructors <a id="fs.dir.entry.cons">[[fs.dir.entry.cons]]</a>
+``` cpp
+explicit directory_entry(const path& p);
+directory_entry(const path& p, error_code& ec);
+```
+*Effects:* Constructs an object of type `directory_entry`, then
+`refresh()` or `refresh(ec)`, respectively.
+*Postconditions:* `path() == p` if no error occurs, otherwise
+`path() == std::filesystem::path()`.
+*Throws:* As specified in  [[fs.err.report]].
+#### `directory_entry` modifiers <a id="fs.dir.entry.mods">[[fs.dir.entry.mods]]</a>
+``` cpp
+void assign(const path& p);
+void assign(const path& p, error_code& ec);
+```
+*Effects:* Equivalent to `pathobject = p`, then `refresh()` or
+`refresh(ec)`, respectively. If an error occurs, the values of any
+cached attributes are unspecified.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+void replace_filename(const path& p);
+void replace_filename(const path& p, error_code& ec);
+```
+*Effects:* Equivalent to `pathobject.replace_filename(p)`, then
+`refresh()` or `refresh(ec)`, respectively. If an error occurs, the
+values of any cached attributes are unspecified.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+void refresh();
+void refresh(error_code& ec) noexcept;
+```
+*Effects:* Stores the current values of any cached attributes of the
+file `p` resolves to. If an error occurs, an error is
+reported ([[fs.err.report]]) and the values of any cached attributes
+are unspecified.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: Implementations of
+`directory_iterator` ([[fs.class.directory_iterator]]) are prohibited
+from directly or indirectly calling the `refresh` function since it must
+access the external file system, and the objective of caching is to
+avoid unnecessary file system accesses. — *end note*]
+#### `directory_entry` observers <a id="fs.dir.entry.obs">[[fs.dir.entry.obs]]</a>
+Unqualified function names in the *Returns:* elements of the
+`directory_entry` observers described below refer to members of the
+`std::filesystem` namespace.
+``` cpp
+const path& path() const noexcept;
+operator const path&() const noexcept;
+```
+*Returns:* `pathobject`.
+``` cpp
+bool exists() const;
+bool exists(error_code& ec) const noexcept;
+```
+*Returns:* `exists(this->status())` or `exists(this->status(), ec)`,
+respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_block_file() const;
+bool is_block_file(error_code& ec) const noexcept;
+```
+*Returns:* `is_block_file(this->status())` or
+`is_block_file(this->status(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_character_file() const;
+bool is_character_file(error_code& ec) const noexcept;
+```
+*Returns:* `is_character_file(this->status())` or
+`is_character_file(this->status(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_directory() const;
+bool is_directory(error_code& ec) const noexcept;
+```
+*Returns:* `is_directory(this->status())` or
+`is_directory(this->status(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_fifo() const;
+bool is_fifo(error_code& ec) const noexcept;
+```
+*Returns:* `is_fifo(this->status())` or `is_fifo(this->status(), ec)`,
+respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_other() const;
+bool is_other(error_code& ec) const noexcept;
+```
+*Returns:* `is_other(this->status())` or `is_other(this->status(), ec)`,
+respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_regular_file() const;
+bool is_regular_file(error_code& ec) const noexcept;
+```
+*Returns:* `is_regular_file(this->status())` or
+`is_regular_file(this->status(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_socket() const;
+bool is_socket(error_code& ec) const noexcept;
+```
+*Returns:* `is_socket(this->status())` or
+`is_socket(this->status(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool is_symlink() const;
+bool is_symlink(error_code& ec) const noexcept;
+```
+*Returns:* `is_symlink(this->symlink_status())` or
+`is_symlink(this->symlink_status(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+uintmax_t file_size() const;
+uintmax_t file_size(error_code& ec) const noexcept;
+```
+*Returns:* If cached, the file size attribute value. Otherwise,
+`file_size(path())` or `file_size(path(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+uintmax_t hard_link_count() const;
+uintmax_t hard_link_count(error_code& ec) const noexcept;
+```
+*Returns:* If cached, the hard link count attribute value. Otherwise,
+`hard_link_count(path())` or `hard_link_count(path(), ec)`,
+respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+file_time_type last_write_time() const;
+file_time_type last_write_time(error_code& ec) const noexcept;
+```
+*Returns:* If cached, the last write time attribute value. Otherwise,
+`last_write_time(path())` or `last_write_time(path(), ec)`,
+respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+file_status status() const;
+file_status status(error_code& ec) const noexcept;
+```
+*Returns:* If cached, the status attribute value. Otherwise,
+`status(path())` or `status(path(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+file_status symlink_status() const;
+file_status symlink_status(error_code& ec) const noexcept;
+```
+*Returns:* If cached, the symlink status attribute value. Otherwise,
+`symlink_status(path())` or `symlink_status(path(), ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool operator==(const directory_entry& rhs) const noexcept;
+```
+*Returns:* `pathobject == rhs.pathobject`.
+``` cpp
+bool operator!=(const directory_entry& rhs) const noexcept;
+```
+*Returns:* `pathobject != rhs.pathobject`.
+``` cpp
+bool operator< (const directory_entry& rhs) const noexcept;
+```
+*Returns:* `pathobject < rhs.pathobject`.
+``` cpp
+bool operator<=(const directory_entry& rhs) const noexcept;
+```
+*Returns:* `pathobject <= rhs.pathobject`.
+``` cpp
+bool operator> (const directory_entry& rhs) const noexcept;
+```
+*Returns:* `pathobject > rhs.pathobject`.
+``` cpp
+bool operator>=(const directory_entry& rhs) const noexcept;
+```
+*Returns:* `pathobject >= rhs.pathobject`.
+### Class `directory_iterator` <a id="fs.class.directory_iterator">[[fs.class.directory_iterator]]</a>
+An object of type `directory_iterator` provides an iterator for a
+sequence of `directory_entry` elements representing the path and any
+cached attribute values ([[fs.class.directory_entry]]) for each file in
+a directory or in an *implementation-defined* directory-like file type.
+[*Note 1*: For iteration into sub-directories, see class
+`recursive_directory_iterator` (
+[[fs.class.rec.dir.itr]]). — *end note*]
+``` cpp
+namespace std::filesystem {
+  class directory_iterator {
+  public:
+    using iterator_category = input_iterator_tag;
+    using value_type        = directory_entry;
+    using difference_type   = ptrdiff_t;
+    using pointer           = const directory_entry*;
+    using reference         = const directory_entry&;
+    // [fs.dir.itr.members], member functions
+    directory_iterator() noexcept;
+    explicit directory_iterator(const path& p);
+    directory_iterator(const path& p, directory_options options);
+    directory_iterator(const path& p, error_code& ec) noexcept;
+    directory_iterator(const path& p, directory_options options,
+                       error_code& ec) noexcept;
+    directory_iterator(const directory_iterator& rhs);
+    directory_iterator(directory_iterator&& rhs) noexcept;
+    ~directory_iterator();
+    directory_iterator& operator=(const directory_iterator& rhs);
+    directory_iterator& operator=(directory_iterator&& rhs) noexcept;
+    const directory_entry& operator*() const;
+    const directory_entry* operator->() const;
+    directory_iterator&    operator++();
+    directory_iterator&    increment(error_code& ec) noexcept;
+    // other members as required by [input.iterators], input iterators
+  };
+}
+```
+`directory_iterator` satisfies the requirements of an input iterator (
+[[input.iterators]]).
+If an iterator of type `directory_iterator` reports an error or is
+advanced past the last directory element, that iterator shall become
+equal to the end iterator value. The `directory_iterator` default
+constructor shall create an iterator equal to the end iterator value,
+and this shall be the only valid iterator for the end condition.
+The end iterator is not dereferenceable.
+Two end iterators are always equal. An end iterator shall not be equal
+to a non-end iterator.
+The result of calling the `path()` member of the `directory_entry`
+object obtained by dereferencing a `directory_iterator` is a reference
+to a `path` object composed of the directory argument from which the
+iterator was constructed with filename of the directory entry appended
+as if by `operator/=`.
+Directory iteration shall not yield directory entries for the current
+(*dot*) and parent (*dot-dot*) directories.
+The order of directory entries obtained by dereferencing successive
+increments of a `directory_iterator` is unspecified.
+Constructors and non-const `directory_iterator` member functions store
+the values of any cached attributes ([[fs.class.directory_entry]]) in
+the `directory_entry` element returned by `operator*()`.
+`directory_iterator` member functions shall not directly or indirectly
+call any `directory_entry` `refresh` function.
+[*Note 2*: The exact mechanism for storing cached attribute values is
+not exposed to users. For exposition, class `directory_iterator` is
+shown in [[fs.class.directory_entry]] as a friend of class
+`directory_entry`. — *end note*]
+[*Note 3*: Programs performing directory iteration may wish to test if
+the path obtained by dereferencing a directory iterator actually exists.
+It could be a symbolic link to a non-existent file. Programs recursively
+walking directory trees for purposes of removing and renaming entries
+may wish to avoid following symbolic links. — *end note*]
+[*Note 4*: If a file is removed from or added to a directory after the
+construction of a `directory_iterator` for the directory, it is
+unspecified whether or not subsequently incrementing the iterator will
+ever result in an iterator referencing the removed or added directory
+entry. See POSIX `readdir_r`. — *end note*]
+#### `directory_iterator` members <a id="fs.dir.itr.members">[[fs.dir.itr.members]]</a>
+``` cpp
+directory_iterator() noexcept;
+```
+*Effects:* Constructs the end iterator.
+``` cpp
+explicit directory_iterator(const path& p);
+directory_iterator(const path& p, directory_options options);
+directory_iterator(const path& p, error_code& ec) noexcept;
+directory_iterator(const path& p, directory_options options, error_code& ec) noexcept;
+```
+*Effects:* For the directory that `p` resolves to, constructs an
+iterator for the first element in a sequence of `directory_entry`
+elements representing the files in the directory, if any; otherwise the
+end iterator. However, if
+``` cpp
+(options & directory_options::skip_permission_denied) != directory_options::none
+```
+and construction encounters an error indicating that permission to
+access `p` is denied, constructs the end iterator and does not report an
+error.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: To iterate over the current directory, use
+`directory_iterator(".")` rather than
+`directory_iterator("")`. — *end note*]
+``` cpp
+directory_iterator(const directory_iterator& rhs);
+directory_iterator(directory_iterator&& rhs) noexcept;
+```
+*Effects:* Constructs an object of class `directory_iterator`.
+*Postconditions:* `*this` has the original value of `rhs`.
+``` cpp
+directory_iterator& operator=(const directory_iterator& rhs);
+directory_iterator& operator=(directory_iterator&& rhs) noexcept;
+```
+*Effects:* If `*this` and `rhs` are the same object, the member has no
+effect.
+*Postconditions:* `*this` has the original value of `rhs`.
+*Returns:* `*this`.
+``` cpp
+directory_iterator& operator++();
+directory_iterator& increment(error_code& ec) noexcept;
+```
+*Effects:* As specified for the prefix increment operation of Input
+iterators ([[input.iterators]]).
+*Returns:* `*this`.
+*Throws:* As specified in  [[fs.err.report]].
+#### `directory_iterator` non-member functions <a id="fs.dir.itr.nonmembers">[[fs.dir.itr.nonmembers]]</a>
+These functions enable range access for `directory_iterator`.
+``` cpp
+directory_iterator begin(directory_iterator iter) noexcept;
+```
+*Returns:* `iter`.
+``` cpp
+directory_iterator end(const directory_iterator&) noexcept;
+```
+*Returns:* `directory_iterator()`.
+### Class `recursive_directory_iterator` <a id="fs.class.rec.dir.itr">[[fs.class.rec.dir.itr]]</a>
+An object of type `recursive_directory_iterator` provides an iterator
+for a sequence of `directory_entry` elements representing the files in a
+directory or in an *implementation-defined* directory-like file type,
+and its sub-directories.
+``` cpp
+namespace std::filesystem {
+  class recursive_directory_iterator {
+  public:
+    using iterator_category = input_iterator_tag;
+    using value_type        = directory_entry;
+    using difference_type   = ptrdiff_t;
+    using pointer           = const directory_entry*;
+    using reference         = const directory_entry&;
+    // [fs.rec.dir.itr.members], constructors and destructor
+    recursive_directory_iterator() noexcept;
+    explicit recursive_directory_iterator(const path& p);
+    recursive_directory_iterator(const path& p, directory_options options);
+    recursive_directory_iterator(const path& p, directory_options options,
+                                 error_code& ec) noexcept;
+    recursive_directory_iterator(const path& p, error_code& ec) noexcept;
+    recursive_directory_iterator(const recursive_directory_iterator& rhs);
+    recursive_directory_iterator(recursive_directory_iterator&& rhs) noexcept;
+    ~recursive_directory_iterator();
+    // [fs.rec.dir.itr.members], observers
+    directory_options  options() const;
+    int                depth() const;
+    bool               recursion_pending() const;
+    const directory_entry& operator*() const;
+    const directory_entry* operator->() const;
+    // [fs.rec.dir.itr.members], modifiers
+    recursive_directory_iterator&
+      operator=(const recursive_directory_iterator& rhs);
+    recursive_directory_iterator&
+      operator=(recursive_directory_iterator&& rhs) noexcept;
+    recursive_directory_iterator& operator++();
+    recursive_directory_iterator& increment(error_code& ec) noexcept;
+    void pop();
+    void pop(error_code& ec);
+    void disable_recursion_pending();
+    // other members as required by [input.iterators], input iterators
+  };
+}
+```
+Calling `options`, `depth`, `recursion_pending`, `pop` or
+`disable_recursion_pending` on an iterator that is not dereferenceable
+results in undefined behavior.
+The behavior of a `recursive_directory_iterator` is the same as a
+`directory_iterator` unless otherwise specified.
+[*Note 1*: If the directory structure being iterated over contains
+cycles then the end iterator may be unreachable. — *end note*]
+#### `recursive_directory_iterator` members <a id="fs.rec.dir.itr.members">[[fs.rec.dir.itr.members]]</a>
+``` cpp
+recursive_directory_iterator() noexcept;
+```
+*Effects:* Constructs the end iterator.
+``` cpp
+explicit recursive_directory_iterator(const path& p);
+recursive_directory_iterator(const path& p, directory_options options);
+recursive_directory_iterator(const path& p, directory_options options, error_code& ec) noexcept;
+recursive_directory_iterator(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Constructs a iterator representing the first entry in the
+directory `p` resolves to, if any; otherwise, the end iterator. However,
+if
+``` cpp
+(options & directory_options::skip_permission_denied) != directory_options::none
+```
+and construction encounters an error indicating that permission to
+access `p` is denied, constructs the end iterator and does not report an
+error.
+*Postconditions:* `options() == options` for the signatures with a
+`directory_options` argument, otherwise
+`options() == directory_options::none`.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: To iterate over the current directory, use
+`recursive_directory_iterator(".")` rather than
+`recursive_directory_iterator("")`. — *end note*]
+[*Note 2*: By default, `recursive_directory_iterator` does not follow
+directory symlinks. To follow directory symlinks, specify `options` as
+`directory_options::follow_directory_symlink` — *end note*]
+``` cpp
+recursive_directory_iterator(const recursive_directory_iterator& rhs);
+```
+*Effects:* Constructs an object of class `recursive_directory_iterator`.
+*Postconditions:*
+- `options() == rhs.options()`
+- `depth() == rhs.depth()`
+- `recursion_pending() == rhs.recursion_pending()`
+``` cpp
+recursive_directory_iterator(recursive_directory_iterator&& rhs) noexcept;
+```
+*Effects:* Constructs an object of class `recursive_directory_iterator`.
+*Postconditions:* `options()`, `depth()`, and `recursion_pending()` have
+the values that `rhs.options()`, `rhs.depth()`, and
+`rhs.recursion_pending()`, respectively, had before the function call.
+``` cpp
+recursive_directory_iterator& operator=(const recursive_directory_iterator& rhs);
+```
+*Effects:* If `*this` and `rhs` are the same object, the member has no
+effect.
+*Postconditions:*
+- `options() == rhs.options()`
+- `depth() == rhs.depth()`
+- `recursion_pending() == rhs.recursion_pending()`
+*Returns:* `*this`.
+``` cpp
+recursive_directory_iterator& operator=(recursive_directory_iterator&& rhs) noexcept;
+```
+*Effects:* If `*this` and `rhs` are the same object, the member has no
+effect.
+*Postconditions:* `options()`, `depth()`, and `recursion_pending()` have
+the values that `rhs.options()`, `rhs.depth()`, and
+`rhs.recursion_pending()`, respectively, had before the function call.
+*Returns:* `*this`.
+``` cpp
+directory_options options() const;
+```
+*Returns:* The value of the argument passed to the constructor for the
+`options` parameter, if present, otherwise `directory_options::none`.
+*Throws:* Nothing.
+``` cpp
+int depth() const;
+```
+*Returns:* The current depth of the directory tree being traversed.
+[*Note 3*: The initial directory is depth `0`, its immediate
+subdirectories are depth `1`, and so forth. — *end note*]
+*Throws:* Nothing.
+``` cpp
+bool recursion_pending() const;
+```
+*Returns:* `true` if `disable_recursion_pending()` has not been called
+subsequent to the prior construction or increment operation, otherwise
+`false`.
+*Throws:* Nothing.
+``` cpp
+recursive_directory_iterator& operator++();
+recursive_directory_iterator& increment(error_code& ec) noexcept;
+```
+*Effects:* As specified for the prefix increment operation of Input
+iterators ([[input.iterators]]), except that:
+- If there are no more entries at the current depth, then if
+  `depth() != 0` iteration over the parent directory resumes; otherwise
+  `*this = recursive_directory_iterator()`.
+- Otherwise if
+  ``` cpp
+  recursion_pending() && is_directory((*this)->status()) &&
+  (!is_symlink((*this)->symlink_status()) ||
+   (options() & directory_options::follow_directory_symlink) != directory_options::none)
+  ```
+  then either directory `(*this)->path()` is recursively iterated into
+  or, if
+  ``` cpp
+  (options() & directory_options::skip_permission_denied) != directory_options::none
+  ```
+  and an error occurs indicating that permission to access directory
+  `(*this)->path()` is denied, then directory `(*this)->path()` is
+  treated as an empty directory and no error is reported.
+*Returns:* `*this`.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+void pop();
+void pop(error_code& ec);
+```
+*Effects:* If `depth() == 0`, set `*this` to
+`recursive_directory_iterator()`. Otherwise, cease iteration of the
+directory currently being iterated over, and continue iteration over the
+parent directory.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+void disable_recursion_pending();
+```
+*Postconditions:* `recursion_pending() == false`.
+[*Note 4*: `disable_recursion_pending``()` is used to prevent unwanted
+recursion into a directory. — *end note*]
+#### `recursive_directory_iterator` non-member functions <a id="fs.rec.dir.itr.nonmembers">[[fs.rec.dir.itr.nonmembers]]</a>
+These functions enable use of `recursive_directory_iterator` with
+range-based for statements.
+``` cpp
+recursive_directory_iterator begin(recursive_directory_iterator iter) noexcept;
+```
+*Returns:* `iter`.
+``` cpp
+recursive_directory_iterator end(const recursive_directory_iterator&) noexcept;
+```
+*Returns:* `recursive_directory_iterator()`.
+### Filesystem operation functions <a id="fs.op.funcs">[[fs.op.funcs]]</a>
+Filesystem operation functions query or modify files, including
+directories, in external storage.
+[*Note 1*: Because hardware failures, network failures, file system
+races ([[fs.def.race]]), and many other kinds of errors occur
+frequently in file system operations, users should be aware that any
+filesystem operation function, no matter how apparently innocuous, may
+encounter an error; see  [[fs.err.report]]. — *end note*]
+#### Absolute <a id="fs.op.absolute">[[fs.op.absolute]]</a>
+``` cpp
+path absolute(const path& p);
+path absolute(const path& p, error_code& ec);
+```
+*Effects:* Composes an absolute path referencing the same file system
+location as `p` according to the operating system ([[fs.conform.os]]).
+*Returns:* The composed path. The signature with argument `ec` returns
+`path()` if an error occurs.
+[*Note 1*: For the returned path, `rp`, `rp.is_absolute()` is `true`
+unless an error occurs. — *end note*]
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 2*: To resolve symlinks, or perform other sanitization which
+might require queries to secondary storage, such as hard disks, consider
+`canonical` ([[fs.op.canonical]]). — *end note*]
+[*Note 3*: Implementations are strongly encouraged to not query
+secondary storage, and not consider `!exists(p)` an
+error. — *end note*]
+[*Example 1*: For POSIX-based operating systems, `absolute(p)` is
+simply `current_path()/p`. For Windows-based operating systems,
+`absolute` might have the same semantics as
+`GetFullPathNameW`. — *end example*]
+#### Canonical <a id="fs.op.canonical">[[fs.op.canonical]]</a>
+``` cpp
+path canonical(const path& p, const path& base = current_path());
+path canonical(const path& p, error_code& ec);
+path canonical(const path& p, const path& base, error_code& ec);
+```
+*Effects:* Converts `p`, which must exist, to an absolute path that has
+no symbolic link, *dot*, or *dot-dot* elements in its pathname in the
+generic format.
+*Returns:* A path that refers to the same file system object as
+`absolute(p, base)`. For the overload without a `base` argument, `base`
+is `current_path()`. Signatures with argument `ec` return `path()` if an
+error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+*Remarks:* `!exists(p)` is an error.
+#### Copy <a id="fs.op.copy">[[fs.op.copy]]</a>
+``` cpp
+void copy(const path& from, const path& to);
+```
+*Effects:* Equivalent to `copy(from, to, copy_options::none)`.
+``` cpp
+void copy(const path& from, const path& to, error_code& ec) noexcept;
+```
+*Effects:* Equivalent to `copy(from, to, copy_options::none, ec)`.
+``` cpp
+void copy(const path& from, const path& to, copy_options options);
+void copy(const path& from, const path& to, copy_options options,
+          error_code& ec) noexcept;
+```
+*Requires:* At most one element from each option group
+([[fs.enum.copy.opts]]) is set in `options`.
+*Effects:* Before the first use of `f` and `t`:
+- If
+  ``` cpp
+  (options & copy_options::create_symlinks) != copy_options::none ||
+  (options & copy_options::skip_symlinks) != copy_options::none
+  ```
+  then `auto f = symlink_status(from)` and if needed
+  `auto t = symlink_status(to)`.
+- Otherwise, if
+  ``` cpp
+  (options & copy_options::copy_symlinks) != copy_options::none
+  ```
+  then `auto f = symlink_status(from)` and if needed
+  `auto t = status(to)`.
+- Otherwise, `auto f = status(from)` and if needed
+  `auto t = status(to)`.
+Effects are then as follows:
+- If `f.type()` or `t.type()` is an implementation-defined file
+  type ([[fs.enum.file_type]]), then the effects are
+  *implementation-defined*.
+- Otherwise, an error is reported as specified in  [[fs.err.report]] if:
+  - `!exists(f)`, or
+  - `equivalent(from, to)`, or
+  - `is_other(f) || is_other(t)`, or
+  - `is_directory(f) && is_regular_file(t)`.
+- Otherwise, if `is_symlink(f)`, then:
+  - If `(options & copy_options::skip_symlinks) != copy_options::none`
+    then return.
+  - Otherwise if
+    ``` cpp
+    !exists(t) && (options & copy_options::copy_symlinks) != copy_options::none
+    ```
+    then `copy_symlink(from, to)`.
+  - Otherwise report an error as specified in  [[fs.err.report]].
+- Otherwise, if `is_regular_file(f)`, then:
+  - If
+    `(options & copy_options::directories_only) != copy_options::none`,
+    then return.
+  - Otherwise, if
+    `(options & copy_options::create_symlinks) `` != copy_options::none`,
+    then create a symbolic link to the source file.
+  - Otherwise, if
+    `(options & copy_options::create_hard_links) != copy_options::none`,
+    then create a hard link to the source file.
+  - Otherwise, if `is_directory(t)`, then
+    `copy_file(from, to/from.filename(), options)`.
+  - Otherwise, `copy_file(from, to, options)`.
+- Otherwise, if
+  ``` cpp
+  is_directory(f) &&
+  ((options & copy_options::recursive) != copy_options::none ||
+   options == copy_options::none)
+  ```
+  then:
+  - If `!exists(t)`, then `create_directory(to, from)`.
+  - Then, iterate over the files in `from`, as if by
+    ``` cpp
+    for (const directory_entry& x : directory_iterator(from))
+      copy(x.path(), to/x.path().filename(), options | copy_options::unspecified)
+    ```
+- Otherwise, for the signature with argument `ec`, `ec.clear()`.
+- Otherwise, no effects.
+*Throws:* As specified in  [[fs.err.report]].
+*Remarks:* For the signature with argument `ec`, any library functions
+called by the implementation shall have an `error_code` argument if
+applicable.
+[*Example 1*:
+Given this directory structure:
+``` cpp
+/dir1
+  file1
+  file2
+  dir2
+    file3
+```
+Calling `copy("/dir1", "/dir3")` would result in:
+``` cpp
+/dir1
+  file1
+  file2
+  dir2
+    file3
+/dir3
+  file1
+  file2
+```
+Alternatively, calling `copy("/dir1", "/dir3", copy_options::recursive)`
+would result in:
+``` cpp
+/dir1
+  file1
+  file2
+  dir2
+    file3
+/dir3
+  file1
+  file2
+  dir2
+    file3
+```
+— *end example*]
+#### Copy file <a id="fs.op.copy_file">[[fs.op.copy_file]]</a>
+``` cpp
+bool copy_file(const path& from, const path& to);
+bool copy_file(const path& from, const path& to, error_code& ec) noexcept;
+```
+*Returns:* `copy_file(from, to, copy_options::none)` or
+`copy_file(from, to, copy_options::none, ec)`, respectively.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool copy_file(const path& from, const path& to, copy_options options);
+bool copy_file(const path& from, const path& to, copy_options options,
+               error_code& ec) noexcept;
+```
+*Requires:* At most one element from each option group
+([[fs.enum.copy.opts]]) is set in `options`.
+*Effects:* As follows:
+- Report a file already exists error as specified in  [[fs.err.report]]
+  if:
+  - `!is_regular_file(from)`, or
+  - `exists(to)` and `!is_regular_file(to)`, or
+  - `exists(to)` and `equivalent(from, to)`, or
+  - `exists(to)` and
+    ``` cpp
+    (options & (copy_options::skip_existing |
+                copy_options::overwrite_existing |
+                copy_options::update_existing)) == copy_options::none
+    ```
+- Otherwise, copy the contents and attributes of the file `from`
+  resolves to, to the file `to` resolves to, if:
+  - `!exists(to)`, or
+  - `(options & copy_options::overwrite_existing) != copy_options::none`,
+    or
+  - `(options & copy_options::update_existing) `` `` != copy_options::none`
+    and `from` is more recent than `to`, determined as if by use of the
+    `last_write_time` function ([[fs.op.last_write_time]]).
+- Otherwise, no effects.
+*Returns:* `true` if the `from` file was copied, otherwise `false`. The
+signature with argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+*Complexity:* At most one direct or indirect invocation of `status(to)`.
+#### Copy symlink <a id="fs.op.copy_symlink">[[fs.op.copy_symlink]]</a>
+``` cpp
+void copy_symlink(const path& existing_symlink, const path& new_symlink);
+void copy_symlink(const path& existing_symlink, const path& new_symlink,
+                  error_code& ec) noexcept;
+```
+*Effects:* Equivalent to
+*`function`*`(read_symlink(existing_symlink), new_symlink)` or
+*`function`*`(read_symlink(existing_symlink, ec), new_symlink, ec)`,
+respectively, where in each case *`function`* is `create_symlink` or
+`create_directory_symlink` as appropriate.
+*Throws:* As specified in  [[fs.err.report]].
+#### Create directories <a id="fs.op.create_directories">[[fs.op.create_directories]]</a>
+``` cpp
+bool create_directories(const path& p);
+bool create_directories(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition by calling `create_directory()`
+for any element of `p` that does not exist.
+*Postconditions:* `is_directory(p)`.
+*Returns:* `true` if a new directory was created, otherwise `false`. The
+signature with argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+*Complexity:* 𝑂(n) where *n* is the number of elements of `p` that do
+not exist.
+#### Create directory <a id="fs.op.create_directory">[[fs.op.create_directory]]</a>
+``` cpp
+bool create_directory(const path& p);
+bool create_directory(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition by attempting to create the
+directory `p` resolves to, as if by POSIX `mkdir()` with a second
+argument of `static_cast<int>(perms::all)`. Creation failure because `p`
+resolves to an existing directory shall not be treated as an error.
+*Postconditions:* `is_directory(p)`.
+*Returns:* `true` if a new directory was created, otherwise `false`. The
+signature with argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+bool create_directory(const path& p, const path& existing_p);
+bool create_directory(const path& p, const path& existing_p, error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition by attempting to create the
+directory `p` resolves to, with attributes copied from directory
+`existing_p`. The set of attributes copied is operating system
+dependent. Creation failure because `p` resolves to an existing
+directory shall not be treated as an error.
+[*Note 1*: For POSIX-based operating systems, the attributes are those
+copied by native API `stat(existing_p.c_str(), &attributes_stat)`
+followed by `mkdir(p.c_str(), attributes_stat.st_mode)`. For
+Windows-based operating systems, the attributes are those copied by
+native API
+`CreateDirectoryExW(existing_p.c_str(), p.c_str(), 0)`. — *end note*]
+*Postconditions:* `is_directory(p)`.
+*Returns:* `true` if a new directory was created, otherwise `false`. The
+signature with argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Create directory symlink <a id="fs.op.create_dir_symlk">[[fs.op.create_dir_symlk]]</a>
+``` cpp
+void create_directory_symlink(const path& to, const path& new_symlink);
+void create_directory_symlink(const path& to, const path& new_symlink,
+                              error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition, as if by POSIX `symlink()`.
+*Postconditions:* `new_symlink` resolves to a symbolic link file that
+contains an unspecified representation of `to`.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: Some operating systems require symlink creation to identify
+that the link is to a directory. Portable code should use
+`create_directory_symlink()` to create directory symlinks rather than
+`create_symlink()` — *end note*]
+[*Note 2*: Some operating systems do not support symbolic links at all
+or support them only for regular files. Some file systems (such as the
+FAT file system) do not support symbolic links regardless of the
+operating system. — *end note*]
+#### Create hard link <a id="fs.op.create_hard_lk">[[fs.op.create_hard_lk]]</a>
+``` cpp
+void create_hard_link(const path& to, const path& new_hard_link);
+void create_hard_link(const path& to, const path& new_hard_link,
+                                      error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition, as if by POSIX `link()`.
+*Postconditions:*
+- `exists(to) && exists(new_hard_link) && equivalent(to, new_hard_link)`
+- The contents of the file or directory `to` resolves to are unchanged.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: Some operating systems do not support hard links at all or
+support them only for regular files. Some file systems (such as the FAT
+file system) do not support hard links regardless of the operating
+system. Some file systems limit the number of links per
+file. — *end note*]
+#### Create symlink <a id="fs.op.create_symlink">[[fs.op.create_symlink]]</a>
+``` cpp
+void create_symlink(const path& to, const path& new_symlink);
+void create_symlink(const path& to, const path& new_symlink,
+                    error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition, as if by POSIX `symlink()`.
+*Postconditions:* `new_symlink` resolves to a symbolic link file that
+contains an unspecified representation of `to`.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: Some operating systems do not support symbolic links at all
+or support them only for regular files. Some file systems (such as the
+FAT file system) do not support symbolic links regardless of the
+operating system. — *end note*]
+#### Current path <a id="fs.op.current_path">[[fs.op.current_path]]</a>
+``` cpp
+path current_path();
+path current_path(error_code& ec);
+```
+*Returns:* The absolute path of the current working directory, whose
+pathname in the native format is obtained as if by POSIX `getcwd()`. The
+signature with argument `ec` returns `path()` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+*Remarks:* The current working directory is the directory, associated
+with the process, that is used as the starting location in pathname
+resolution for relative paths.
+[*Note 1*: The `current_path()` name was chosen to emphasize that the
+returned value is a path, not just a single directory
+name. — *end note*]
+[*Note 2*: The current path as returned by many operating systems is a
+dangerous global variable. It may be changed unexpectedly by a
+third-party or system library functions, or by another
+thread. — *end note*]
+``` cpp
+void current_path(const path& p);
+void current_path(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Establishes the postcondition, as if by POSIX `chdir()`.
+*Postconditions:* `equivalent(p, current_path())`.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 3*: The current path for many operating systems is a dangerous
+global state. It may be changed unexpectedly by a third-party or system
+library functions, or by another thread. — *end note*]
+#### Equivalent <a id="fs.op.equivalent">[[fs.op.equivalent]]</a>
+``` cpp
+bool equivalent(const path& p1, const path& p2);
+bool equivalent(const path& p1, const path& p2, error_code& ec) noexcept;
+```
+Let `s1` and `s2` be `file_status`s, determined as if by `status(p1)`
+and `status(p2)`, respectively.
+*Effects:* Determines `s1` and `s2`. If
+`(!exists(s1) && !exists(s2)) || (is_other(s1) && is_other(s2))` an
+error is reported ([[fs.err.report]]).
+*Returns:* `true`, if `s1 == s2` and `p1` and `p2` resolve to the same
+file system entity, else `false`. The signature with argument `ec`
+returns `false` if an error occurs.
+Two paths are considered to resolve to the same file system entity if
+two candidate entities reside on the same device at the same location.
+This is determined as if by the values of the POSIX `stat` structure,
+obtained as if by `stat()` for the two paths, having equal `st_dev`
+values and equal `st_ino` values.
+*Throws:* As specified in  [[fs.err.report]].
+#### Exists <a id="fs.op.exists">[[fs.op.exists]]</a>
+``` cpp
+bool exists(file_status s) noexcept;
+```
+*Returns:* `status_known(s) && s.type() != file_type::not_found`.
+``` cpp
+bool exists(const path& p);
+bool exists(const path& p, error_code& ec) noexcept;
+```
+Let `s` be a `file_status`, determined as if by `status(p)` or
+`status(p, ec)`, respectively.
+*Effects:* The signature with argument `ec` calls `ec.clear()` if
+`status_known(s)`.
+*Returns:* `exists(s)`.
+*Throws:* As specified in  [[fs.err.report]].
+#### File size <a id="fs.op.file_size">[[fs.op.file_size]]</a>
+``` cpp
+uintmax_t file_size(const path& p);
+uintmax_t file_size(const path& p, error_code& ec) noexcept;
+```
+*Returns:*
+- If `!exists(p)` an error is reported ([[fs.err.report]]).
+- Otherwise, if `is_regular_file(p)`, the size in bytes of the file `p`
+  resolves to, determined as if by the value of the POSIX `stat`
+  structure member `st_size` obtained as if by POSIX `stat()`.
+- Otherwise, the result is *implementation-defined*.
+The signature with argument `ec` returns `static_cast<uintmax_t>(-1)` if
+an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Hard link count <a id="fs.op.hard_lk_ct">[[fs.op.hard_lk_ct]]</a>
+``` cpp
+uintmax_t hard_link_count(const path& p);
+uintmax_t hard_link_count(const path& p, error_code& ec) noexcept;
+```
+*Returns:* The number of hard links for `p`. The signature with argument
+`ec` returns `static_cast<uintmax_t>(-1)` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is block file <a id="fs.op.is_block_file">[[fs.op.is_block_file]]</a>
+``` cpp
+bool is_block_file(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::block`.
+``` cpp
+bool is_block_file(const path& p);
+bool is_block_file(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_block_file(status(p))` or `is_block_file(status(p, ec))`,
+respectively. The signature with argument `ec` returns `false` if an
+error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is character file <a id="fs.op.is_char_file">[[fs.op.is_char_file]]</a>
+``` cpp
+bool is_character_file(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::character`.
+``` cpp
+bool is_character_file(const path& p);
+bool is_character_file(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_character_file(status(p))` or
+`is_character_file(status(p, ec))`, respectively.
+The signature with argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is directory <a id="fs.op.is_directory">[[fs.op.is_directory]]</a>
+``` cpp
+bool is_directory(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::directory`.
+``` cpp
+bool is_directory(const path& p);
+bool is_directory(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_directory(status(p))` or `is_directory(status(p, ec))`,
+respectively. The signature with argument `ec` returns `false` if an
+error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is empty <a id="fs.op.is_empty">[[fs.op.is_empty]]</a>
+``` cpp
+bool is_empty(const path& p);
+bool is_empty(const path& p, error_code& ec) noexcept;
+```
+*Effects:*
+- Determine `file_status s`, as if by `status(p)` or `status(p, ec)`,
+  respectively.
+- For the signature with argument `ec`, return `false` if an error
+  occurred.
+- Otherwise, if `is_directory(s)`:
+  - Create a variable `itr`, as if by `directory_iterator itr(p)` or
+    `directory_iterator itr(p, ec)`, respectively.
+  - For the signature with argument `ec`, return `false` if an error
+    occurred.
+  - Otherwise, return `itr == directory_iterator()`.
+- Otherwise:
+  - Determine `uintmax_t sz`, as if by `file_size(p)` or
+    `file_size(p, ec)`, respectively.
+  - For the signature with argument `ec`, return `false` if an error
+    occurred.
+  - Otherwise, return `sz == 0`.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is fifo <a id="fs.op.is_fifo">[[fs.op.is_fifo]]</a>
+``` cpp
+bool is_fifo(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::fifo`.
+``` cpp
+bool is_fifo(const path& p);
+bool is_fifo(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_fifo(status(p))` or `is_fifo(status(p, ec))`,
+respectively. The signature with argument `ec` returns `false` if an
+error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is other <a id="fs.op.is_other">[[fs.op.is_other]]</a>
+``` cpp
+bool is_other(file_status s) noexcept;
+```
+*Returns:*
+`exists(s) && !is_regular_file(s) && !is_directory(s) && !is_symlink(s)`.
+``` cpp
+bool is_other(const path& p);
+bool is_other(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_other(status(p))` or `is_other(status(p, ec))`,
+respectively. The signature with argument `ec` returns `false` if an
+error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is regular file <a id="fs.op.is_regular_file">[[fs.op.is_regular_file]]</a>
+``` cpp
+bool is_regular_file(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::regular`.
+``` cpp
+bool is_regular_file(const path& p);
+```
+*Returns:* `is_regular_file(status(p))`.
+*Throws:* `filesystem_error` if `status(p)` would throw
+`filesystem_error.`
+``` cpp
+bool is_regular_file(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Sets `ec` as if by `status(p, ec)`.
+[*Note 1*: `file_type::none`, `file_type::not_found` and
+`file_type::unknown` cases set `ec` to error values. To distinguish
+between cases, call the `status` function directly. — *end note*]
+*Returns:* `is_regular_file(status(p, ec))`. Returns `false` if an error
+occurs.
+#### Is socket <a id="fs.op.is_socket">[[fs.op.is_socket]]</a>
+``` cpp
+bool is_socket(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::socket`.
+``` cpp
+bool is_socket(const path& p);
+bool is_socket(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_socket(status(p))` or `is_socket(status(p, ec))`,
+respectively. The signature with argument `ec` returns `false` if an
+error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Is symlink <a id="fs.op.is_symlink">[[fs.op.is_symlink]]</a>
+``` cpp
+bool is_symlink(file_status s) noexcept;
+```
+*Returns:* `s.type() == file_type::symlink`.
+``` cpp
+bool is_symlink(const path& p);
+bool is_symlink(const path& p, error_code& ec) noexcept;
+```
+*Returns:* `is_symlink(symlink_status(p))` or
+`is_symlink(symlink_status(p, ec))`, respectively. The signature with
+argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Last write time <a id="fs.op.last_write_time">[[fs.op.last_write_time]]</a>
+``` cpp
+file_time_type last_write_time(const path& p);
+file_time_type last_write_time(const path& p, error_code& ec) noexcept;
+```
+*Returns:* The time of last data modification of `p`, determined as if
+by the value of the POSIX `stat` structure member `st_mtime` obtained as
+if by POSIX `stat()`. The signature with argument `ec` returns
+`file_time_type::min()` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+void last_write_time(const path& p, file_time_type new_time);
+void last_write_time(const path& p, file_time_type new_time,
+                     error_code& ec) noexcept;
+```
+*Effects:* Sets the time of last data modification of the file resolved
+to by `p` to `new_time`, as if by POSIX `futimens()`.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: A postcondition of `last_write_time(p) == new_time` is not
+specified since it might not hold for file systems with coarse time
+granularity. — *end note*]
+#### Permissions <a id="fs.op.permissions">[[fs.op.permissions]]</a>
+``` cpp
+void permissions(const path& p, perms prms, perm_options opts=perm_options::replace);
+void permissions(const path& p, perms prms, error_code& ec) noexcept;
+void permissions(const path& p, perms prms, perm_options opts, error_code& ec);
+```
+*Requires:* Exactly one of the `perm_options` constants `replace`,
+`add`, or `remove` is present in `opts`.
+*Remarks:* The second signature behaves as if it had an additional
+parameter `perm_options` `opts` with an argument of
+`perm_options::replace`.
+*Effects:* Applies the action specified by `opts` to the file `p`
+resolves to, or to file `p` itself if `p` is a symbolic link and
+`perm_options::nofollow` is set in `opts`. The action is applied as if
+by POSIX `fchmodat()`.
+[*Note 1*: Conceptually permissions are viewed as bits, but the actual
+implementation may use some other mechanism. — *end note*]
+*Throws:* As specified in  [[fs.err.report]].
+#### Proximate <a id="fs.op.proximate">[[fs.op.proximate]]</a>
+``` cpp
+path proximate(const path& p, error_code& ec);
+```
+*Returns:* `proximate(p, current_path(), ec)`.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+path proximate(const path& p, const path& base = current_path());
+path proximate(const path& p, const path& base, error_code& ec);
+```
+*Returns:* For the first form:
+``` cpp
+weakly_canonical(p).lexically_proximate(weakly_canonical(base));
+```
+For the second form:
+``` cpp
+weakly_canonical(p, ec).lexically_proximate(weakly_canonical(base, ec));
+```
+or `path()` at the first error occurrence, if any.
+*Throws:* As specified in  [[fs.err.report]].
+#### Read symlink <a id="fs.op.read_symlink">[[fs.op.read_symlink]]</a>
+``` cpp
+path read_symlink(const path& p);
+path read_symlink(const path& p, error_code& ec);
+```
+*Returns:* If `p` resolves to a symbolic link, a `path` object
+containing the contents of that symbolic link. The signature with
+argument `ec` returns `path()` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+[*Note 1*: It is an error if `p` does not resolve to a symbolic
+link. — *end note*]
+#### Relative <a id="fs.op.relative">[[fs.op.relative]]</a>
+``` cpp
+path relative(const path& p, error_code& ec);
+```
+*Returns:* `relative(p, current_path(), ec)`.
+*Throws:* As specified in  [[fs.err.report]].
+``` cpp
+path relative(const path& p, const path& base = current_path());
+path relative(const path& p, const path& base, error_code& ec);
+```
+*Returns:* For the first form:
+``` cpp
+weakly_canonical(p).lexically_relative(weakly_canonical(base));
+```
+For the second form:
+``` cpp
+weakly_canonical(p, ec).lexically_relative(weakly_canonical(base, ec));
+```
+or `path()` at the first error occurrence, if any.
+*Throws:* As specified in  [[fs.err.report]].
+#### Remove <a id="fs.op.remove">[[fs.op.remove]]</a>
+``` cpp
+bool remove(const path& p);
+bool remove(const path& p, error_code& ec) noexcept;
+```
+*Effects:* If `exists(symlink_status(p, ec))`, the file `p` is removed
+as if by POSIX `remove()`.
+[*Note 1*: A symbolic link is itself removed, rather than the file it
+resolves to. — *end note*]
+*Postconditions:* `!exists(symlink_status(p))`.
+*Returns:* `false` if `p` did not exist, otherwise `true`. The signature
+with argument `ec` returns `false` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Remove all <a id="fs.op.remove_all">[[fs.op.remove_all]]</a>
+``` cpp
+uintmax_t remove_all(const path& p);
+uintmax_t remove_all(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Recursively deletes the contents of `p` if it exists, then
+deletes file `p` itself, as if by POSIX `remove()`.
+[*Note 1*: A symbolic link is itself removed, rather than the file it
+resolves to. — *end note*]
+*Postconditions:* `!exists(symlink_status(p))`.
+*Returns:* The number of files removed. The signature with argument `ec`
+returns `static_cast< uintmax_t>(-1)` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+#### Rename <a id="fs.op.rename">[[fs.op.rename]]</a>
+``` cpp
+void rename(const path& old_p, const path& new_p);
+void rename(const path& old_p, const path& new_p, error_code& ec) noexcept;
+```
+*Effects:* Renames `old_p` to `new_p`, as if by POSIX `rename()`.
+[*Note 1*:
+- If `old_p` and `new_p` resolve to the same existing file, no action is
+  taken.
+- Otherwise, the rename may include the following effects:
+  - if `new_p` resolves to an existing non-directory file, `new_p` is
+    removed; otherwise,
+  - if `new_p` resolves to an existing directory, `new_p` is removed if
+    empty on POSIX compliant operating systems but may be an error on
+    other operating systems.
+A symbolic link is itself renamed, rather than the file it resolves to.
+— *end note*]
+*Throws:* As specified in  [[fs.err.report]].
+#### Resize file <a id="fs.op.resize_file">[[fs.op.resize_file]]</a>
+``` cpp
+void resize_file(const path& p, uintmax_t new_size);
+void resize_file(const path& p, uintmax_t new_size, error_code& ec) noexcept;
+```
+*Postconditions:* `file_size(p) == new_size`.
+*Throws:* As specified in  [[fs.err.report]].
+*Remarks:* Achieves its postconditions as if by POSIX `truncate()`.
+#### Space <a id="fs.op.space">[[fs.op.space]]</a>
+``` cpp
+space_info space(const path& p);
+space_info space(const path& p, error_code& ec) noexcept;
+```
+*Returns:* An object of type `space_info`. The value of the `space_info`
+object is determined as if by using POSIX `statvfs` to obtain a POSIX
+`struct statvfs`, and then multiplying its `f_blocks`, `f_bfree`, and
+`f_bavail` members by its `f_frsize` member, and assigning the results
+to the `capacity`, `free`, and `available` members respectively. Any
+members for which the value cannot be determined shall be set to
+`static_cast<uintmax_t>(-1)`. For the signature with argument `ec`, all
+members are set to `static_cast<uintmax_t>(-1)` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+*Remarks:* The value of member `space_info::available` is operating
+system dependent.
+[*Note 1*: `available` may be less than `free`. — *end note*]
+#### Status <a id="fs.op.status">[[fs.op.status]]</a>
+``` cpp
+file_status status(const path& p);
+```
+*Effects:* As if:
+``` cpp
+error_code ec;
+file_status result = status(p, ec);
+if (result.type() == file_type::none)
+  throw filesystem_error(implementation-supplied-message, p, ec);
+return result;
+```
+*Returns:* See above.
+*Throws:* `filesystem_error`.
+[*Note 1*: `result` values of `file_status(file_type::not_found)` and
+`file_status(file_type::unknown)` are not considered failures and do not
+cause an exception to be thrown. — *end note*]
+``` cpp
+file_status status(const path& p, error_code& ec) noexcept;
+```
+*Effects:* If possible, determines the attributes of the file `p`
+resolves to, as if by using POSIX `stat()` to obtain a POSIX
+`struct stat`. If, during attribute determination, the underlying file
+system API reports an error, sets `ec` to indicate the specific error
+reported. Otherwise, `ec.clear()`.
+[*Note 2*: This allows users to inspect the specifics of underlying API
+errors even when the value returned by `status()` is not
+`file_status(file_type::none)`. — *end note*]
+Let `prms` denote the result of `(m & perms::mask)`, where `m` is
+determined as if by converting the `st_mode` member of the obtained
+`struct stat` to the type `perms`.
+*Returns:*
+- If `ec != error_code()`:
+  - If the specific error indicates that `p` cannot be resolved because
+    some element of the path does not exist, returns
+    `file_status(file_type::not_found)`.
+  - Otherwise, if the specific error indicates that `p` can be resolved
+    but the attributes cannot be determined, returns
+    `file_status(file_type::unknown)`.
+  - Otherwise, returns `file_status(file_type::none)`.
+  \[*Note 1*: These semantics distinguish between `p` being known not to
+  exist, `p` existing but not being able to determine its attributes,
+  and there being an error that prevents even knowing if `p` exists.
+  These distinctions are important to some use cases. — *end note*]
+- Otherwise,
+  - If the attributes indicate a regular file, as if by POSIX `S_ISREG`,
+    returns `file_status(file_type::regular, prms)`.
+    \[*Note 2*: `file_type::regular` implies appropriate `<fstream>`
+    operations would succeed, assuming no hardware, permission, access,
+    or file system race errors. Lack of `file_type::regular` does not
+    necessarily imply `<fstream>` operations would fail on a
+    directory. — *end note*]
+  - Otherwise, if the attributes indicate a directory, as if by POSIX
+    `S_ISDIR`, returns `file_status(file_type::directory, prms)`.
+    \[*Note 3*: `file_type::directory` implies that calling
+    `directory_iterator(p)` would succeed. — *end note*]
+  - Otherwise, if the attributes indicate a block special file, as if by
+    POSIX `S_ISBLK`, returns `file_status(file_type::block, prms)`.
+  - Otherwise, if the attributes indicate a character special file, as
+    if by POSIX `S_ISCHR`, returns
+    `file_status(file_type::character, prms)`.
+  - Otherwise, if the attributes indicate a fifo or pipe file, as if by
+    POSIX `S_ISFIFO`, returns `file_status(file_type::fifo, prms)`.
+  - Otherwise, if the attributes indicate a socket, as if by POSIX
+    `S_ISSOCK`, returns `file_status(file_type::socket, prms)`.
+  - Otherwise, if the attributes indicate an implementation-defined file
+    type ([[fs.enum.file_type]]), returns
+    `file_status(file_type::`*`A`*`, prms)`, where *A* is the constant
+    for the *implementation-defined* file type.
+  - Otherwise, returns `file_status(file_type::unknown, prms)`.
+*Remarks:* If a symbolic link is encountered during pathname resolution,
+pathname resolution continues using the contents of the symbolic link.
+#### Status known <a id="fs.op.status_known">[[fs.op.status_known]]</a>
+``` cpp
+bool status_known(file_status s) noexcept;
+```
+*Returns:* `s.type() != file_type::none`.
+#### Symlink status <a id="fs.op.symlink_status">[[fs.op.symlink_status]]</a>
+``` cpp
+file_status symlink_status(const path& p);
+file_status symlink_status(const path& p, error_code& ec) noexcept;
+```
+*Effects:* Same as `status()`, above, except that the attributes of `p`
+are determined as if by using POSIX `lstat()` to obtain a POSIX
+`struct stat`.
+Let `prms` denote the result of `(m & perms::mask)`, where `m` is
+determined as if by converting the `st_mode` member of the obtained
+`struct stat` to the type `perms`.
+*Returns:* Same as `status()`, above, except that if the attributes
+indicate a symbolic link, as if by POSIX `S_ISLNK`, returns
+`file_status(file_type::symlink, prms)`. The signature with argument
+`ec` returns `file_status(file_type::none)` if an error occurs.
+*Remarks:* Pathname resolution terminates if `p` names a symbolic link.
+*Throws:* As specified in  [[fs.err.report]].
+#### Temporary directory path <a id="fs.op.temp_dir_path">[[fs.op.temp_dir_path]]</a>
+``` cpp
+path temp_directory_path();
+path temp_directory_path(error_code& ec);
+```
+*Returns:* An unspecifed directory path suitable for temporary files. An
+error shall be reported if `!exists(p) || !is_directory(p)`, where `p`
+is the path to be returned. The signature with argument `ec` returns
+`path()` if an error occurs.
+*Throws:* As specified in  [[fs.err.report]].
+[*Example 1*: For POSIX-based operating systems, an implementation
+might return the path supplied by the first environment variable found
+in the list TMPDIR, TMP, TEMP, TEMPDIR, or if none of these are found,
+`"/tmp"`. For Windows-based operating systems, an implementation might
+return the path reported by the Windows `GetTempPath` API
+function. — *end example*]
+#### Weakly canonical <a id="fs.op.weakly_canonical">[[fs.op.weakly_canonical]]</a>
+``` cpp
+path weakly_canonical(const path& p);
+path weakly_canonical(const path& p, error_code& ec);
+```
+*Returns:* `p` with symlinks resolved and the result
+normalized ([[fs.def.normal.form]]).
+*Effects:* Using `status(p)` or `status(p, ec)`, respectively, to
+determine existence, return a path composed by `operator/=` from the
+result of calling `canonical()` without a `base` argument and with a
+path argument composed of the leading elements of `p` that exist, if
+any, followed by the elements of `p` that do not exist, if any. For the
+first form, `canonical()` is called without an `error_code` argument.
+For the second form, `canonical()` is called with `ec` as an
+`error_code` argument, and `path()` is returned at the first error
+occurrence, if any.
+*Postconditions:* The returned path is in normal
+form ([[fs.def.normal.form]]).
+*Remarks:* Implementations are encouraged to avoid unnecessary
+normalization such as when `canonical` has already been called on the
+entirety of `p`.
+*Throws:* As specified in  [[fs.err.report]].
+## C library files <a id="c.files">[[c.files]]</a>
+### Header `<cstdio>` synopsis <a id="cstdio.syn">[[cstdio.syn]]</a>
+``` cpp
+namespace std {
+  using size_t = see [support.types.layout];
+  using FILE = see below;
+  using fpos_t = see below;
+}
+#define NULL see [support.types.nullptr]
+#define _IOFBF see below
+#define _IOLBF see below
+#define _IONBF see below
+#define BUFSIZ see below
+#define EOF see below
+#define FOPEN_MAX see below
+#define FILENAME_MAX see below
+#define L_tmpnam see below
+#define SEEK_CUR see below
+#define SEEK_END see below
+#define SEEK_SET see below
+#define TMP_MAX see below
+#define stderr see below
+#define stdin see below
+#define stdout see below
+namespace std {
+  int remove(const char* filename);
+  int rename(const char* old, const char* new);
+  FILE* tmpfile();
+  char* tmpnam(char* s);
+  int fclose(FILE* stream);
+  int fflush(FILE* stream);
+  FILE* fopen(const char* filename, const char* mode);
+  FILE* freopen(const char* filename, const char* mode, FILE* stream);
+  void setbuf(FILE* stream, char* buf);
+  int setvbuf(FILE* stream, char* buf, int mode, size_t size);
+  int fprintf(FILE* stream, const char* format, ...);
+  int fscanf(FILE* stream, const char* format, ...);
+  int printf(const char* format, ...);
+  int scanf(const char* format, ...);
+  int snprintf(char* s, size_t n, const char* format, ...);
+  int sprintf(char* s, const char* format, ...);
+  int sscanf(const char* s, const char* format, ...);
+  int vfprintf(FILE* stream, const char* format, va_list arg);
+  int vfscanf(FILE* stream, const char* format, va_list arg);
+  int vprintf(const char* format, va_list arg);
+  int vscanf(const char* format, va_list arg);
+  int vsnprintf(char* s, size_t n, const char* format, va_list arg);
+  int vsprintf(char* s, const char* format, va_list arg);
+  int vsscanf(const char* s, const char* format, va_list arg);
+  int fgetc(FILE* stream);
+  char* fgets(char* s, int n, FILE* stream);
+  int fputc(int c, FILE* stream);
+  int fputs(const char* s, FILE* stream);
+  int getc(FILE* stream);
+  int getchar();
+  int putc(int c, FILE* stream);
+  int putchar(int c);
+  int puts(const char* s);
+  int ungetc(int c, FILE* stream);
+  size_t fread(void* ptr, size_t size, size_t nmemb, FILE* stream);
+  size_t fwrite(const void* ptr, size_t size, size_t nmemb, FILE* stream);
+  int fgetpos(FILE* stream, fpos_t* pos);
+  int fseek(FILE* stream, long int offset, int whence);
+  int fsetpos(FILE* stream, const fpos_t* pos);
+  long int ftell(FILE* stream);
+  void rewind(FILE* stream);
+  void clearerr(FILE* stream);
+  int feof(FILE* stream);
+  int ferror(FILE* stream);
+  void perror(const char* s);
+}
+```
+The contents and meaning of the header `<cstdio>` are the same as the C
+standard library header `<stdio.h>`.
+Calls to the function `tmpnam` with an argument that is a null pointer
+value may introduce a data race ([[res.on.data.races]]) with other
+calls to `tmpnam` with an argument that is a null pointer value.
+ISO C 7.21.
+### Header `<cinttypes>` synopsis <a id="cinttypes.syn">[[cinttypes.syn]]</a>
+``` cpp
+#include <cstdint>  // see [cstdint.syn]
+namespace std {
+  using imaxdiv_t = see below;
+  intmax_t imaxabs(intmax_t j);
+  imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
+  intmax_t strtoimax(const char* nptr, char** endptr, int base);
+  uintmax_t strtoumax(const char* nptr, char** endptr, int base);
+  intmax_t wcstoimax(const wchar_t* nptr, wchar_t** endptr, int base);
+  uintmax_t wcstoumax(const wchar_t* nptr, wchar_t** endptr, int base);
+  intmax_t abs(intmax_t);  // optional, see below
+  imaxdiv_t div(intmax_t, intmax_t);  // optional, see below
+}
+#define PRIdN see below
+#define PRIiN see below
+#define PRIoN see below
+#define PRIuN see below
+#define PRIxN see below
+#define PRIXN see below
+#define SCNdN see below
+#define SCNiN see below
+#define SCNoN see below
+#define SCNuN see below
+#define SCNxN see below
+#define PRIdLEASTN see below
+#define PRIiLEASTN see below
+#define PRIoLEASTN see below
+#define PRIuLEASTN see below
+#define PRIxLEASTN see below
+#define PRIXLEASTN see below
+#define SCNdLEASTN see below
+#define SCNiLEASTN see below
+#define SCNoLEASTN see below
+#define SCNuLEASTN see below
+#define SCNxLEASTN see below
+#define PRIdFASTN see below
+#define PRIiFASTN see below
+#define PRIoFASTN see below
+#define PRIuFASTN see below
+#define PRIxFASTN see below
+#define PRIXFASTN see below
+#define SCNdFASTN see below
+#define SCNiFASTN see below
+#define SCNoFASTN see below
+#define SCNuFASTN see below
+#define SCNxFASTN see below
+#define PRIdMAX see below
+#define PRIiMAX see below
+#define PRIoMAX see below
+#define PRIuMAX see below
+#define PRIxMAX see below
+#define PRIXMAX see below
+#define SCNdMAX see below
+#define SCNiMAX see below
+#define SCNoMAX see below
+#define SCNuMAX see below
+#define SCNxMAX see below
+#define PRIdPTR see below
+#define PRIiPTR see below
+#define PRIoPTR see below
+#define PRIuPTR see below
+#define PRIxPTR see below
+#define PRIXPTR see below
+#define SCNdPTR see below
+#define SCNiPTR see below
+#define SCNoPTR see below
+#define SCNuPTR see below
+#define SCNxPTR see below
+```
+The contents and meaning of the header `<cinttypes>` are the same as the
+C standard library header `<inttypes.h>`, with the following changes:
+- The header `<cinttypes>` includes the header `<cstdint>` instead of
   `<stdint.h>`, and
 - if and only if the type `intmax_t` designates an extended integer
   type ([[basic.fundamental]]), the following function signatures are
   added:
   ``` cpp
   which shall have the same semantics as the function signatures
   `intmax_t imaxabs(intmax_t)` and
   `imaxdiv_t imaxdiv(intmax_t, intmax_t)`, respectively.
+ISO C 7.8.
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 [istringstream.members]: #istringstream.members
+[lex.charset]: lex.md#lex.charset
 [locale.codecvt.virtuals]: localization.md#locale.codecvt.virtuals
 [locale.num.get]: localization.md#locale.num.get
 [narrow.stream.objects]: #narrow.stream.objects
+[numeric.limits]: language.md#numeric.limits
 [ofstream]: #ofstream
 [ofstream.assign]: #ofstream.assign
 [ofstream.cons]: #ofstream.cons
 [ofstream.members]: #ofstream.members
 [ostream]: #ostream
 [ostream.inserters.arithmetic]: #ostream.inserters.arithmetic
 [ostream.inserters.character]: #ostream.inserters.character
 [ostream.manip]: #ostream.manip
 [ostream.rvalue]: #ostream.rvalue
 [ostream.seeks]: #ostream.seeks
+[ostream.syn]: #ostream.syn
 [ostream.unformatted]: #ostream.unformatted
 [ostream::sentry]: #ostream::sentry
 [ostringstream]: #ostringstream
 [ostringstream.assign]: #ostringstream.assign
 [ostringstream.cons]: #ostringstream.cons
 [ostringstream.members]: #ostringstream.members
 [output.streams]: #output.streams
 [quoted.manip]: #quoted.manip
 [res.on.data.races]: library.md#res.on.data.races
 [res.on.exception.handling]: library.md#res.on.exception.handling
+[sstream.syn]: #sstream.syn
 [std.ios.manip]: #std.ios.manip
 [std.manip]: #std.manip
 [stream.buffers]: #stream.buffers
 [stream.types]: #stream.types
 [streambuf]: #streambuf
 [streambuf.assign]: #streambuf.assign
 [streambuf.buffer]: #streambuf.buffer
 [streambuf.cons]: #streambuf.cons
 [streambuf.pub.get]: #streambuf.pub.get
 [streambuf.pub.pback]: #streambuf.pub.pback
 [streambuf.pub.put]: #streambuf.pub.put
 [streambuf.put.area]: #streambuf.put.area
 [streambuf.reqts]: #streambuf.reqts
+[streambuf.syn]: #streambuf.syn
 [streambuf.virt.buffer]: #streambuf.virt.buffer
 [streambuf.virt.get]: #streambuf.virt.get
 [streambuf.virt.locales]: #streambuf.virt.locales
 [streambuf.virt.pback]: #streambuf.virt.pback
 [streambuf.virt.put]: #streambuf.virt.put
 [streambuf.virtuals]: #streambuf.virtuals
 [string.classes]: strings.md#string.classes
 [string.streams]: #string.streams
 [stringbuf]: #stringbuf
 [stringbuf.assign]: #stringbuf.assign
 [stringbuf.cons]: #stringbuf.cons
 [stringbuf.members]: #stringbuf.members
 [stringbuf.virtuals]: #stringbuf.virtuals
 [strings]: strings.md#strings
 [stringstream]: #stringstream
 [stringstream.assign]: #stringstream.assign
 [stringstream.cons]: #stringstream.cons
 [stringstream.members]: #stringstream.members
+[tab:enum.path.format]: #tab:enum.path.format
+[tab:enum.perm_options]: #tab:enum.perm_options
+[tab:filesystem_error.1]: #tab:filesystem_error.1
+[tab:filesystem_error.2]: #tab:filesystem_error.2
+[tab:filesystem_error.3]: #tab:filesystem_error.3
+[tab:fs.enum.copy_options]: #tab:fs.enum.copy_options
+[tab:fs.enum.directory_options]: #tab:fs.enum.directory_options
+[tab:fs.enum.file_type]: #tab:fs.enum.file_type
+[tab:fs.enum.perms]: #tab:fs.enum.perms
 [tab:iostreams.basicios.init.effects]: #tab:iostreams.basicios.init.effects
 [tab:iostreams.copyfmt.effects]: #tab:iostreams.copyfmt.effects
 [tab:iostreams.file.open.modes]: #tab:iostreams.file.open.modes
 [tab:iostreams.fmtflags.constants]: #tab:iostreams.fmtflags.constants
 [tab:iostreams.fmtflags.effects]: #tab:iostreams.fmtflags.effects
 [tab:iostreams.iostate.effects]: #tab:iostreams.iostate.effects
 [tab:iostreams.lib.summary]: #tab:iostreams.lib.summary
 [tab:iostreams.newoff.values]: #tab:iostreams.newoff.values
 [tab:iostreams.openmode.effects]: #tab:iostreams.openmode.effects
 [tab:iostreams.position.requirements]: #tab:iostreams.position.requirements
 [tab:iostreams.seekdir.effects]: #tab:iostreams.seekdir.effects
 [tab:iostreams.seekoff.effects]: #tab:iostreams.seekoff.effects
 [tab:iostreams.seekoff.positioning]: #tab:iostreams.seekoff.positioning
+[temp.deduct]: temp.md#temp.deduct
+[time.clock.req]: utilities.md#time.clock.req
 [wide.stream.objects]: #wide.stream.objects
 [^1]: It is the implementation’s responsibility to implement headers so
     that including `<iosfwd>` and other headers does not violate the
     rules about multiple occurrences of default arguments.
 [^9]: for example, because it cannot allocate space.
 [^10]: This suggests an infinite amount of copying, but the
     implementation can keep track of the maximum element of the arrays
+    that is nonzero.
 [^11]: Checking `badbit` also for `fail()` is historical practice.
 [^12]: The function signature `dec(ios_base&)` can be called by the
     function signature
     to assure that only objects for classes derived from this class may
     be constructed.
 [^14]: `underflow` or `uflow` might fail by throwing an exception
     prematurely. The intention is not only that the calls will not
+    return `eof()` but that they will return “immediately”.
 [^15]: Classes derived from `basic_streambuf` can provide more efficient
     ways to implement `xsgetn()` and `xsputn()` by overriding these
     definitions from the base class.
+[^16]: That is, for each class derived from an instance of
+    `basic_streambuf` in this Clause ([[stringbuf]],
+ [[filebuf]]), a specification of how consuming a character
+    effects the associated output sequence is given. There is no
+    requirement on a program-defined class.
+[^17]: Typically, `overflow` returns `c` to indicate success, except
+    when `traits::eq_int_type(c, traits::eof())` returns `true`, in
+    which case it returns `traits::not_eof(c)`.
+[^18]: This will be possible only in functions that are part of the
     library. The semantics of the constructor used in user code is as
     specified.
+[^19]: The sentry constructor and destructor can also perform additional
     implementation-dependent operations.
+[^20]: This is done without causing an `ios::failure` to be thrown.
 [^21]: See, for example, the function signature
+    `ws(basic_istream&)` ([[istream.manip]]).
+[^22]: See, for example, the function signature
     `dec(ios_base&)` ([[basefield.manip]]).
+[^23]: This is done without causing an `ios::failure` to be thrown.
 [^24]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
 [^25]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
+[^26]: Note that this function is not overloaded on types `signed char`
+    and `unsigned char`.
+[^27]: Since the final input character is “extracted”, it is counted in
     the `gcount()`, even though it is not stored.
+[^28]: This allows an input line which exactly fills the buffer, without
     setting `failbit`. This is different behavior than the historical
     AT&T implementation.
+[^29]: This implies an empty input line will not cause `failbit` to be
     set.
+[^30]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
+[^31]: The call `os.tie()->flush()` does not necessarily occur if the
     function can determine that no synchronization is necessary.
+[^32]: The `sentry` constructor and destructor can also perform
     additional implementation-dependent operations.
+[^33]: without causing an `ios::failure` to be thrown.
 [^34]: See, for example, the function signature
+    `endl(basic_ostream&)` ([[ostream.manip]]).
+[^35]: See, for example, the function signature
     `dec(ios_base&)` ([[basefield.manip]]).
+[^36]: without causing an `ios::failure` to be thrown.
 [^37]: Note that this function is not overloaded on types `signed char`
     and `unsigned char`.
+[^38]: Note that this function is not overloaded on types `signed char`
+    and `unsigned char`.
+[^39]: The expression `cin >> resetiosflags(ios_base::skipws)` clears
     `ios_base::skipws` in the format flags stored in the
     `basic_istream<charT, traits>` object `cin` (the same as
     `cin >> noskipws`), and the expression
     `cout << resetiosflags(ios_base::showbase)` clears
     `ios_base::showbase` in the format flags stored in the
     `basic_ostream<charT, traits>` object `cout` (the same as
     `cout << noshowbase`).
+[^40]: The macro `SEEK_END` is defined, and the function signatures
     `fopen(const char*, const char*)` and `fseek(FILE*, long, int)` are
+    declared, in `<cstdio>` ([[cstdio.syn]]).
+[^41]: POSIX® is a registered trademark of The IEEE. Windows® is a
+ registered trademark of Microsoft Corporation. This information is
+    given for the convenience of users of this document and does not
+    constitute an endorsement by ISO or IEC of these products.

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