[fs.class.path] - C++17 → C++20

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@@ -1,19 +1,46 @@
 ### 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;
@@ -44,11 +71,11 @@ namespace std::filesystem {
     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);
@@ -80,10 +107,16 @@ namespace std::filesystem {
     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;
@@ -91,22 +124,22 @@ namespace std::filesystem {
              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;
@@ -123,11 +156,11 @@ namespace std::filesystem {
     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;
@@ -146,21 +179,29 @@ namespace std::filesystem {
     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*]
@@ -208,31 +249,42 @@ preferred-separator:
 ``` 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
@@ -245,17 +297,42 @@ 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.
@@ -264,15 +341,15 @@ POSIX-based operating systems because on these systems:
 — *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
@@ -291,12 +368,12 @@ native-to-generic and generic-to-native formats respectively. If
 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
@@ -309,95 +386,101 @@ 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;
 ```
@@ -410,49 +493,48 @@ 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:
@@ -466,27 +548,27 @@ 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);
 ```
@@ -526,18 +608,18 @@ 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
@@ -560,26 +642,28 @@ Otherwise, modifies `*this` as if by these steps:
   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`.
@@ -598,22 +682,19 @@ 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
@@ -622,24 +703,32 @@ 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();
 ```
@@ -677,15 +766,15 @@ output is:
 ``` 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
@@ -723,12 +812,12 @@ path("/").replace_filename("bar");     // yields "/bar" on POSIX
 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);`.
@@ -740,14 +829,14 @@ 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;
 ```
@@ -755,11 +844,11 @@ const string_type& native() const noexcept;
 ``` cpp
 const value_type* c_str() const noexcept;
 ```
-*Returns:* Equivalent to `native().c_str()`.
 ``` cpp
 operator string_type() const;
 ```
@@ -783,26 +872,25 @@ 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*,
@@ -828,53 +916,51 @@ 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;
 ```
@@ -897,20 +983,21 @@ path root_path() const;
 ``` 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;
 ```
@@ -957,11 +1044,11 @@ for (; !p.extension().empty(); p = p.stem())
 ``` 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
@@ -980,18 +1067,18 @@ 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;
 ```
@@ -1042,11 +1129,11 @@ bool has_extension() const;
 ``` 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*]
@@ -1054,18 +1141,18 @@ systems. — *end example*]
 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
@@ -1082,29 +1169,40 @@ slashes, but that does not affect `path` equality.
 ``` 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()`).
@@ -1123,41 +1221,41 @@ 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
@@ -1184,165 +1282,88 @@ list above. If no elements are present, the end iterator.
 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 `path` <a id="fs.class.path">[[fs.class.path]]</a>
+An object of class `path` represents a path and contains a 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*]
+A *path* is 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 *filename*s
+[[fs.path.generic]]. The maximum number of elements in the sequence is
+operating system dependent [[fs.conform.os]].
+An *absolute path* is 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 *relative path* is a path that is not absolute, and as
+such, only unambiguously identifies the location of a file when resolved
+relative to an implied starting location. The elements of a path that
+determine if it is relative are operating system dependent.
+[*Note 2*: Pathnames “.” and “..” are relative paths. — *end note*]
+A *pathname* is a character string that represents the name of a path.
+Pathnames are formatted according to the generic pathname format grammar
+[[fs.path.generic]] or according to an operating system dependent
+*native pathname format* accepted by the host operating system.
+*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 1*: POSIX specifies the mechanism in section 4.11, Pathname
+resolution. — *end example*]
 ``` cpp
 namespace std::filesystem {
   class path {
   public:
     using value_type  = see below;
     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);
     path& remove_filename();
     path& replace_filename(const path& replacement);
     path& replace_extension(const path& replacement = path());
     void  swap(path& rhs) noexcept;
+    // [fs.path.nonmember], non-member operators
+    friend bool operator==(const path& lhs, const path& rhs) noexcept;
+    friend strong_ordering operator<=>(const path& lhs, const path& rhs) noexcept;
+    friend path operator/ (const path& lhs, const path& rhs);
     // [fs.path.native.obs], native format observers
     const string_type& native() const noexcept;
     const value_type*  c_str() const noexcept;
     operator string_type() const;
              class Allocator = allocator<EcharT>>
       basic_string<EcharT, traits, Allocator>
         string(const Allocator& a = Allocator()) const;
     std::string    string() const;
     std::wstring   wstring() const;
+    std::u8string  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::u8string  generic_u8string() const;
     std::u16string generic_u16string() const;
     std::u32string generic_u32string() const;
     // [fs.path.compare], compare
     int compare(const path& p) const noexcept;
     path filename() const;
     path stem() const;
     path extension() const;
     // [fs.path.query], query
+ [[nodiscard]] 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;
     class iterator;
     using const_iterator = iterator;
     iterator begin() const;
     iterator end() const;
+    // [fs.path.io], path inserter and extractor
+    template<class charT, class traits>
+      friend basic_ostream<charT, traits>&
+        operator<<(basic_ostream<charT, traits>& os, const path& p);
+    template<class charT, class traits>
+      friend basic_istream<charT, traits>&
+        operator>>(basic_istream<charT, traits>& is, path& p);
   };
 }
 ```
 `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 2*: 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*]
 ``` bnf
 fallback-separator:
     /, if *preferred-separator* is not /
 ```
+A *filename* is the name of a file. The *dot* and *dot-dot* filenames,
+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*] \[*Note 1*: 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*]
+- 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.
 Except in a *root-name*, multiple successive *directory-separator*
 characters are considered to be the same as one *directory-separator*
 character.
+The dot filename is treated as a reference to the current directory. The
+dot-dot filename is treated as a reference to the parent directory. What
+the dot-dot filename 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.class.path]]. 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
 [*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*]
+*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 4*: 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 5*: 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.
+The result of normalization is a path in *normal form*, which is said to
+be *normalized*.
+#### Conversions <a id="fs.path.cvt">[[fs.path.cvt]]</a>
+##### Argument format conversions <a id="fs.path.fmt.cvt">[[fs.path.fmt.cvt]]</a>
 [*Note 1*:
+The format conversions described in this subclause 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.
 — *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.class.path]]. 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
 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
 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*]
+##### Type and encoding conversions <a id="fs.path.type.cvt">[[fs.path.type.cvt]]</a>
+The *native encoding* of an ordinary character string is the operating
+system dependent current encoding for pathnames [[fs.class.path]]. The
+*native encoding* for wide character strings is the
+implementation-defined execution wide-character set encoding
+[[lex.charset]].
 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 ordinary encoding. 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 ordinary 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 ordinary 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. 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*]
+- `char8_t`: The encoding is UTF-8. The method of conversion is
+  unspecified.
 - `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`.
+#### 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 *Cpp17InputIterator* 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 `Source` denotes a type other
+than `path`, and 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.
+#### Members <a id="fs.path.member">[[fs.path.member]]</a>
+##### Constructors <a id="fs.path.construct">[[fs.path.construct]]</a>
 ``` cpp
 path() noexcept;
 ```
+*Ensures:* `empty() == true`.
 ``` cpp
 path(const path& p);
 path(path&& p) noexcept;
 ```
 ``` 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);
 ```
+*Mandates:* 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.path.type.cvt]] 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 ordinary 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:
 ```
 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.path.type.cvt]]. The resulting wide string is then
+converted to an ordinary character pathname string in the current native
+ordinary encoding. If the native wide encoding is UTF-16 or UTF-32, and
+the current native ordinary 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 ordinary 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*]
+##### Assignments <a id="fs.path.assign">[[fs.path.assign]]</a>
 ``` cpp
 path& operator=(const path& p);
 ```
   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`.
+##### 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
   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"`
+(although the former might use backslash as the preferred separator).
 Expression examples:
 ``` cpp
 // On POSIX,
+path("foo") /= path(""); // yields path("foo/")
+path("foo") /= path("/bar"); // yields path("/bar")
 // On Windows,
+path("foo") /= path(""); // yields path("foo\{")}
+path("foo") /= path("/bar"); // yields path("/bar")
+path("foo") /= path("c:/bar"); // yields path("c:/bar")
+path("foo") /= path("c:"); // yields path("c:")
+path("c:") /= path(""); // yields path("c:")
+path("c:foo") /= path("/bar");  // yields path("c:/bar")
+path("c:foo") /= path("c:bar"); // yields path("c:foo\{bar")}
 ```
 — *end example*]
 *Returns:* `*this`.
   path& append(InputIterator first, InputIterator last);
 ```
 *Effects:* Equivalent to: `return operator/=(path(first, last));`
+##### 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);
 template<class Source>
   path& operator+=(const Source& x);
 template<class Source>
   path& concat(const Source& x);
 ```
 *Effects:* Appends `path(x).native()` to the pathname in the native
 [*Note 2*: This directly manipulates the value of `native()` and may
 not be portable between operating systems. — *end note*]
 *Returns:* `*this`.
+``` cpp
+path& operator+=(value_type x);
+template<class EcharT>
+  path& operator+=(EcharT x);
+```
+*Effects:* Equivalent to: `return *this += basic_string_view(&x, 1);`
 ``` cpp
 template<class InputIterator>
   path& concat(InputIterator first, InputIterator last);
 ```
+*Effects:* Equivalent to: `return *this += path(first, last);`
+##### Modifiers <a id="fs.path.modifiers">[[fs.path.modifiers]]</a>
 ``` cpp
 void clear() noexcept;
 ```
+*Ensures:* `empty() == true`.
 ``` cpp
 path& make_preferred();
 ```
 ``` cpp
 path& remove_filename();
 ```
 *Effects:* Remove the generic format pathname of `filename()` from the
 generic format pathname.
+*Ensures:* `!has_filename()`.
 *Returns:* `*this`.
 [*Example 4*:
 ``` 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);`.
 *Effects:* Swaps the contents (in all formats) of the two paths.
 *Complexity:* Constant time.
+##### 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.class.path]].
 ``` cpp
 const string_type& native() const noexcept;
 ```
 ``` cpp
 const value_type* c_str() const noexcept;
 ```
+*Effects:* Equivalent to: `return native().c_str();`
 ``` cpp
 operator string_type() const;
 ```
 [[fs.path.cvt]].
 ``` cpp
 std::string string() const;
 std::wstring wstring() const;
+std::u8string u8string() const;
 std::u16string u16string() const;
 std::u32string u32string() const;
 ```
+*Returns:* `native()`.
 *Remarks:* Conversion, if any, is performed as specified by
+[[fs.path.cvt]].
+##### 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*,
 [[fs.path.cvt]].
 ``` cpp
 std::string generic_string() const;
 std::wstring generic_wstring() const;
+std::u8string 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]].
+##### Compare <a id="fs.path.compare">[[fs.path.compare]]</a>
 ``` cpp
 int compare(const path& p) const noexcept;
 ```
 *Returns:*
+- Let `rootNameComparison` be the result of
+  `this->root_name().native().compare(p.root_name().native())`. If
+ `rootNameComparison` is not `0`, `rootNameComparison`.
+- Otherwise, if `!this->has_root_directory()` and
+  `p.has_root_directory()`, a value less than `0`.
+- Otherwise, if `this->has_root_directory()` and
+  `!p.has_root_directory()`, a value greater than `0`.
+- Otherwise, if `native()` for the elements of `this->relative_path()`
+ are lexicographically less than `native()` for the elements of
+ `p.relative_path()`, a value less than `0`.
+- Otherwise, if `native()` for the elements of `this->relative_path()`
+  are lexicographically greater than `native()` for the elements of
+  `p.relative_path()`, a value greater than `0`.
+- Otherwise, `0`.
 ``` cpp
+int compare(const string_type& s) const;
 int compare(basic_string_view<value_type> s) const;
+int compare(const value_type* s) const;
 ```
+*Effects:* Equivalent to: `return compare(path(s));`
+##### Decomposition <a id="fs.path.decompose">[[fs.path.decompose]]</a>
 ``` cpp
 path root_name() const;
 ```
 ``` cpp
 path relative_path() const;
 ```
 *Returns:* A `path` composed from the pathname in the generic format, if
+`empty()` is `false`, beginning with the first *filename* after
+`root_path()`. Otherwise, `path()`.
 ``` cpp
 path parent_path() const;
 ```
+*Returns:* `*this` if `has_relative_path()` is `false`, 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;
 ```
 ``` 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
 [*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*]
+##### Query <a id="fs.path.query">[[fs.path.query]]</a>
 ``` cpp
+[[nodiscard]] bool empty() const noexcept;
 ```
+*Returns:* `true` if the pathname in the generic format is empty,
+otherwise `false`.
 ``` cpp
 bool has_root_path() const;
 ```
 ``` cpp
 bool is_absolute() const;
 ```
 *Returns:* `true` if the pathname in the native format contains an
+absolute path [[fs.class.path]], otherwise `false`.
 [*Example 9*: `path("/").is_absolute()` is `true` for POSIX-based
 operating systems, and `false` for Windows-based operating
 systems. — *end example*]
 bool is_relative() const;
 ```
 *Returns:* `!is_absolute()`.
+##### 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.path.generic]] of the pathname in the generic format of
 `*this`.
 [*Example 10*:
 ``` cpp
 ``` cpp
 path lexically_relative(const path& base) const;
 ```
 *Returns:* `*this` made relative to `base`. Does not
+resolve [[fs.class.path]] symlinks. Does not first
+normalize [[fs.path.generic]] `*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`, or
+- any *filename* in `relative_path()` or `base.relative_path()` can be
+  interpreted as a *root-name*,
+returns `path()`.
+[*Note 6*: On a POSIX implementation, no *filename* in a
+*relative-path* is acceptable as a *root-name*. — *end note*]
+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 or empty, minus the number that are
+ dot-dot. If `n<0,` returns `path()`; otherwise
+- if `n == 0` and `(a == end() || a->empty())`, 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()`).
 *directory-separator* characters will be backslashes rather than
 slashes, but that does not affect `path` equality.
 — *end example*]
+[*Note 7*: If symlink following semantics are desired, use the
 operational function `relative()`. — *end note*]
+[*Note 8*: If normalization [[fs.path.generic]] 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 9*: If symlink following semantics are desired, use the
 operational function `proximate()`. — *end note*]
+[*Note 10*: If normalization [[fs.path.generic]] is needed to ensure
+consistent matching of elements, apply `lexically_normal()` to `*this`,
+`base`, or both. — *end note*]
+#### 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 meeting 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
 iterator end() const;
 ```
 *Returns:* The end iterator.
+#### Inserter and extractor <a id="fs.path.io">[[fs.path.io]]</a>
+``` cpp
+template<class charT, class traits>
+  friend basic_ostream<charT, traits>&
+    operator<<(basic_ostream<charT, traits>& os, const path& p);
+```
+*Effects:* Equivalent to `os << quoted(p.string<charT, traits>())`.
+[*Note 1*: The `quoted` function is described
+in  [[quoted.manip]]. — *end note*]
+*Returns:* `os`.
+``` cpp
+template<class charT, class traits>
+  friend 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`.
+#### 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
+friend bool operator==(const path& lhs, const path& rhs) noexcept;
 ```
+*Returns:* `lhs.compare(rhs) == 0`.
 [*Note 1*:
 Path equality and path equivalence have different semantics.
 - Equality is determined by the `path` non-member `operator==`, which
+  considers the two paths’ 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.class.path]] 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
+friend strong_ordering operator<=>(const path& lhs, const path& rhs) noexcept;
 ```
+*Returns:* `lhs.compare(rhs) <=> 0`.
 ``` cpp
+friend path operator/ (const path& lhs, const path& rhs);
 ```
 *Effects:* Equivalent to: `return path(lhs) /= rhs;`

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