- tmp/tmpfixp5gba/{from.md → to.md} +1177 -945
tmp/tmpfixp5gba/{from.md → to.md}
RENAMED
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@@ -1,32 +1,35 @@
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# Strings library <a id="strings">[[strings]]</a>
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## General <a id="strings.general">[[strings.general]]</a>
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This Clause describes components for manipulating sequences of any
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non-array trivial standard-layout [[
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called *char-like types*, and objects of char-like types
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*char-like objects* or simply *characters*.
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The following subclauses describe a character traits class, string
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classes, and null-terminated sequence utilities, as summarized in
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[[strings.summary]].
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## Character traits <a id="char.traits">[[char.traits]]</a>
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-
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`char_traits<
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Most classes specified in [[string.classes]], [[string.view]], and
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[[input.output]] need a set of related types and functions to complete
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the definition of their semantics. These types and functions are
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provided as a set of member *typedef-name*s and functions in the
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template parameter `traits` used by each such template.
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defines the semantics of these members.
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To specialize those templates to generate a string, string view, or
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iostream class to handle a particular character container type
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[[defns.character.container]] `C`, that and its related character traits
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class `X` are passed as a pair of parameters to the string, string view,
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@@ -38,12 +41,13 @@ or iostream template as parameters `charT` and `traits`. If
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In [[char.traits.req]], `X` denotes a traits class defining types and
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functions for the character container type `C`; `c` and `d` denote
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values of type `C`; `p` and `q` denote values of type `const C*`; `s`
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denotes a value of type `C*`; `n`, `i` and `j` denote values of type
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`size_t`; `e` and `f` denote values of type `X::int_type`; `pos` denotes
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a value of type `X::pos_type`; and `r` denotes an lvalue of type `C`.
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-
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The class template
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``` cpp
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template<class charT> struct char_traits;
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@@ -72,10 +76,12 @@ using state_type = see below;
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([[cpp17.copyconstructible]]), and *Cpp17DefaultConstructible*
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([[cpp17.defaultconstructible]]) requirements.
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### `char_traits` specializations <a id="char.traits.specializations">[[char.traits.specializations]]</a>
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``` cpp
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namespace std {
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template<> struct char_traits<char>;
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template<> struct char_traits<char8_t>;
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template<> struct char_traits<char16_t>;
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@@ -166,11 +172,11 @@ namespace std {
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```
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The two-argument members `assign`, `eq`, and `lt` are defined
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identically to the built-in operators `=`, `==`, and `<` respectively.
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The member `eof()` returns an implementation-defined constant that
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cannot appear as a valid UTF-8 code unit.
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#### `struct char_traits<char16_t>` <a id="char.traits.specializations.char16.t">[[char.traits.specializations.char16.t]]</a>
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``` cpp
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@@ -285,12 +291,894 @@ namespace std {
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The two-argument members `assign`, `eq`, and `lt` are defined
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identically to the built-in operators `=`, `==`, and `<`, respectively.
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The member `eof()` returns `WEOF`.
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|
| 290 |
## String classes <a id="string.classes">[[string.classes]]</a>
|
| 291 |
|
|
|
|
|
|
|
| 292 |
The header `<string>` defines the `basic_string` class template for
|
| 293 |
manipulating varying-length sequences of char-like objects and five
|
| 294 |
*typedef-name*s, `string`, `u8string`, `u16string`, `u32string`, and
|
| 295 |
`wstring`, that name the specializations `basic_string<char>`,
|
| 296 |
`basic_string<char8_t>`, `basic_string<char16_t>`,
|
|
@@ -420,11 +1308,11 @@ namespace std {
|
|
| 420 |
erase(basic_string<charT, traits, Allocator>& c, const U& value);
|
| 421 |
template<class charT, class traits, class Allocator, class Predicate>
|
| 422 |
constexpr typename basic_string<charT, traits, Allocator>::size_type
|
| 423 |
erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred);
|
| 424 |
|
| 425 |
-
// basic_string typedef
|
| 426 |
using string = basic_string<char>;
|
| 427 |
using u8string = basic_string<char8_t>;
|
| 428 |
using u16string = basic_string<char16_t>;
|
| 429 |
using u32string = basic_string<char32_t>;
|
| 430 |
using wstring = basic_string<wchar_t>;
|
|
@@ -477,20 +1365,15 @@ namespace std {
|
|
| 477 |
using wstring = basic_string<wchar_t>;
|
| 478 |
}
|
| 479 |
|
| 480 |
// [basic.string.hash], hash support
|
| 481 |
template<class T> struct hash;
|
| 482 |
-
template<> struct hash<
|
| 483 |
-
template<> struct hash<
|
| 484 |
-
template<> struct hash<
|
| 485 |
-
template<> struct hash<
|
| 486 |
-
template<> struct hash<
|
| 487 |
-
template<> struct hash<pmr::string>;
|
| 488 |
-
template<> struct hash<pmr::u8string>;
|
| 489 |
-
template<> struct hash<pmr::u16string>;
|
| 490 |
-
template<> struct hash<pmr::u32string>;
|
| 491 |
-
template<> struct hash<pmr::wstring>;
|
| 492 |
|
| 493 |
inline namespace literals {
|
| 494 |
inline namespace string_literals {
|
| 495 |
// [basic.string.literals], suffix for basic_string literals
|
| 496 |
constexpr string operator""s(const char* str, size_t len);
|
|
@@ -503,20 +1386,22 @@ namespace std {
|
|
| 503 |
}
|
| 504 |
```
|
| 505 |
|
| 506 |
### Class template `basic_string` <a id="basic.string">[[basic.string]]</a>
|
| 507 |
|
|
|
|
|
|
|
| 508 |
The class template `basic_string` describes objects that can store a
|
| 509 |
sequence consisting of a varying number of arbitrary char-like objects
|
| 510 |
with the first element of the sequence at position zero. Such a sequence
|
| 511 |
is also called a “string” if the type of the char-like objects that it
|
| 512 |
-
holds is clear from context. In the rest of
|
| 513 |
-
char-like objects held in a `basic_string` object is designated
|
| 514 |
-
`charT`.
|
| 515 |
|
| 516 |
A specialization of `basic_string` is a contiguous container
|
| 517 |
-
[[container.
|
| 518 |
|
| 519 |
In all cases, \[`data()`, `data() + size()`\] is a valid range,
|
| 520 |
`data() + size()` points at an object with value `charT()` (a “null
|
| 521 |
terminator”), and `size() <= capacity()` is `true`.
|
| 522 |
|
|
@@ -539,32 +1424,39 @@ namespace std {
|
|
| 539 |
|
| 540 |
using iterator = implementation-defined // type of basic_string::iterator; // see [container.requirements]
|
| 541 |
using const_iterator = implementation-defined // type of basic_string::const_iterator; // see [container.requirements]
|
| 542 |
using reverse_iterator = std::reverse_iterator<iterator>;
|
| 543 |
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
|
| 544 |
-
static
|
| 545 |
|
| 546 |
// [string.cons], construct/copy/destroy
|
| 547 |
constexpr basic_string() noexcept(noexcept(Allocator())) : basic_string(Allocator()) { }
|
| 548 |
constexpr explicit basic_string(const Allocator& a) noexcept;
|
| 549 |
constexpr basic_string(const basic_string& str);
|
| 550 |
constexpr basic_string(basic_string&& str) noexcept;
|
| 551 |
constexpr basic_string(const basic_string& str, size_type pos,
|
| 552 |
const Allocator& a = Allocator());
|
| 553 |
constexpr basic_string(const basic_string& str, size_type pos, size_type n,
|
| 554 |
const Allocator& a = Allocator());
|
|
|
|
|
|
|
|
|
|
|
|
|
| 555 |
template<class T>
|
| 556 |
constexpr basic_string(const T& t, size_type pos, size_type n,
|
| 557 |
const Allocator& a = Allocator());
|
| 558 |
template<class T>
|
| 559 |
constexpr explicit basic_string(const T& t, const Allocator& a = Allocator());
|
| 560 |
constexpr basic_string(const charT* s, size_type n, const Allocator& a = Allocator());
|
| 561 |
constexpr basic_string(const charT* s, const Allocator& a = Allocator());
|
|
|
|
| 562 |
constexpr basic_string(size_type n, charT c, const Allocator& a = Allocator());
|
| 563 |
template<class InputIterator>
|
| 564 |
constexpr basic_string(InputIterator begin, InputIterator end,
|
| 565 |
const Allocator& a = Allocator());
|
|
|
|
|
|
|
| 566 |
constexpr basic_string(initializer_list<charT>, const Allocator& = Allocator());
|
| 567 |
constexpr basic_string(const basic_string&, const Allocator&);
|
| 568 |
constexpr basic_string(basic_string&&, const Allocator&);
|
| 569 |
constexpr ~basic_string();
|
| 570 |
|
|
@@ -573,10 +1465,11 @@ namespace std {
|
|
| 573 |
noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
|
| 574 |
allocator_traits<Allocator>::is_always_equal::value);
|
| 575 |
template<class T>
|
| 576 |
constexpr basic_string& operator=(const T& t);
|
| 577 |
constexpr basic_string& operator=(const charT* s);
|
|
|
|
| 578 |
constexpr basic_string& operator=(charT c);
|
| 579 |
constexpr basic_string& operator=(initializer_list<charT>);
|
| 580 |
|
| 581 |
// [string.iterators], iterators
|
| 582 |
constexpr iterator begin() noexcept;
|
|
@@ -598,10 +1491,11 @@ namespace std {
|
|
| 598 |
constexpr size_type size() const noexcept;
|
| 599 |
constexpr size_type length() const noexcept;
|
| 600 |
constexpr size_type max_size() const noexcept;
|
| 601 |
constexpr void resize(size_type n, charT c);
|
| 602 |
constexpr void resize(size_type n);
|
|
|
|
| 603 |
constexpr size_type capacity() const noexcept;
|
| 604 |
constexpr void reserve(size_type res_arg);
|
| 605 |
constexpr void shrink_to_fit();
|
| 606 |
constexpr void clear() noexcept;
|
| 607 |
[[nodiscard]] constexpr bool empty() const noexcept;
|
|
@@ -633,10 +1527,12 @@ namespace std {
|
|
| 633 |
constexpr basic_string& append(const charT* s, size_type n);
|
| 634 |
constexpr basic_string& append(const charT* s);
|
| 635 |
constexpr basic_string& append(size_type n, charT c);
|
| 636 |
template<class InputIterator>
|
| 637 |
constexpr basic_string& append(InputIterator first, InputIterator last);
|
|
|
|
|
|
|
| 638 |
constexpr basic_string& append(initializer_list<charT>);
|
| 639 |
|
| 640 |
constexpr void push_back(charT c);
|
| 641 |
|
| 642 |
constexpr basic_string& assign(const basic_string& str);
|
|
@@ -651,10 +1547,12 @@ namespace std {
|
|
| 651 |
constexpr basic_string& assign(const charT* s, size_type n);
|
| 652 |
constexpr basic_string& assign(const charT* s);
|
| 653 |
constexpr basic_string& assign(size_type n, charT c);
|
| 654 |
template<class InputIterator>
|
| 655 |
constexpr basic_string& assign(InputIterator first, InputIterator last);
|
|
|
|
|
|
|
| 656 |
constexpr basic_string& assign(initializer_list<charT>);
|
| 657 |
|
| 658 |
constexpr basic_string& insert(size_type pos, const basic_string& str);
|
| 659 |
constexpr basic_string& insert(size_type pos1, const basic_string& str,
|
| 660 |
size_type pos2, size_type n = npos);
|
|
@@ -668,10 +1566,12 @@ namespace std {
|
|
| 668 |
constexpr basic_string& insert(size_type pos, size_type n, charT c);
|
| 669 |
constexpr iterator insert(const_iterator p, charT c);
|
| 670 |
constexpr iterator insert(const_iterator p, size_type n, charT c);
|
| 671 |
template<class InputIterator>
|
| 672 |
constexpr iterator insert(const_iterator p, InputIterator first, InputIterator last);
|
|
|
|
|
|
|
| 673 |
constexpr iterator insert(const_iterator p, initializer_list<charT>);
|
| 674 |
|
| 675 |
constexpr basic_string& erase(size_type pos = 0, size_type n = npos);
|
| 676 |
constexpr iterator erase(const_iterator p);
|
| 677 |
constexpr iterator erase(const_iterator first, const_iterator last);
|
|
@@ -698,10 +1598,12 @@ namespace std {
|
|
| 698 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, const charT* s);
|
| 699 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, size_type n, charT c);
|
| 700 |
template<class InputIterator>
|
| 701 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2,
|
| 702 |
InputIterator j1, InputIterator j2);
|
|
|
|
|
|
|
| 703 |
constexpr basic_string& replace(const_iterator, const_iterator, initializer_list<charT>);
|
| 704 |
|
| 705 |
constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
|
| 706 |
|
| 707 |
constexpr void swap(basic_string& str)
|
|
@@ -758,11 +1660,12 @@ namespace std {
|
|
| 758 |
size_type pos = npos) const noexcept;
|
| 759 |
constexpr size_type find_last_not_of(const charT* s, size_type pos, size_type n) const;
|
| 760 |
constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
|
| 761 |
constexpr size_type find_last_not_of(charT c, size_type pos = npos) const noexcept;
|
| 762 |
|
| 763 |
-
constexpr basic_string substr(size_type pos = 0, size_type n = npos) const;
|
|
|
|
| 764 |
|
| 765 |
template<class T>
|
| 766 |
constexpr int compare(const T& t) const noexcept(see below);
|
| 767 |
template<class T>
|
| 768 |
constexpr int compare(size_type pos1, size_type n1, const T& t) const;
|
|
@@ -781,19 +1684,29 @@ namespace std {
|
|
| 781 |
constexpr bool starts_with(charT x) const noexcept;
|
| 782 |
constexpr bool starts_with(const charT* x) const;
|
| 783 |
constexpr bool ends_with(basic_string_view<charT, traits> x) const noexcept;
|
| 784 |
constexpr bool ends_with(charT x) const noexcept;
|
| 785 |
constexpr bool ends_with(const charT* x) const;
|
|
|
|
|
|
|
|
|
|
|
|
|
| 786 |
};
|
| 787 |
|
| 788 |
template<class InputIterator,
|
| 789 |
class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
|
| 790 |
basic_string(InputIterator, InputIterator, Allocator = Allocator())
|
| 791 |
-> basic_string<typename iterator_traits<InputIterator>::value_type,
|
| 792 |
char_traits<typename iterator_traits<InputIterator>::value_type>,
|
| 793 |
Allocator>;
|
| 794 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 795 |
template<class charT,
|
| 796 |
class traits,
|
| 797 |
class Allocator = allocator<charT>>
|
| 798 |
explicit basic_string(basic_string_view<charT, traits>, const Allocator& = Allocator())
|
| 799 |
-> basic_string<charT, traits, Allocator>;
|
|
@@ -810,10 +1723,13 @@ namespace std {
|
|
| 810 |
|
| 811 |
A `size_type` parameter type in a `basic_string` deduction guide refers
|
| 812 |
to the `size_type` member type of the type deduced by the deduction
|
| 813 |
guide.
|
| 814 |
|
|
|
|
|
|
|
|
|
|
| 815 |
#### General requirements <a id="string.require">[[string.require]]</a>
|
| 816 |
|
| 817 |
If any operation would cause `size()` to exceed `max_size()`, that
|
| 818 |
operation throws an exception object of type `length_error`.
|
| 819 |
|
|
@@ -829,19 +1745,24 @@ as `charT`. Every object of type
|
|
| 829 |
objects as needed. The `Allocator` object used is obtained as described
|
| 830 |
in [[container.requirements.general]]. In every specialization
|
| 831 |
`basic_string<charT, traits, Allocator>`, the type `traits` shall meet
|
| 832 |
the character traits requirements [[char.traits]].
|
| 833 |
|
| 834 |
-
[*Note 1*:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 835 |
same type as `charT`. — *end note*]
|
| 836 |
|
| 837 |
References, pointers, and iterators referring to the elements of a
|
| 838 |
`basic_string` sequence may be invalidated by the following uses of that
|
| 839 |
`basic_string` object:
|
| 840 |
|
| 841 |
- Passing as an argument to any standard library function taking a
|
| 842 |
-
reference to non-const `basic_string` as an argument.[^
|
| 843 |
- Calling non-const member functions, except `operator[]`, `at`, `data`,
|
| 844 |
`front`, `back`, `begin`, `rbegin`, `end`, and `rend`.
|
| 845 |
|
| 846 |
#### Constructors and assignment operators <a id="string.cons">[[string.cons]]</a>
|
| 847 |
|
|
@@ -865,17 +1786,33 @@ state.
|
|
| 865 |
``` cpp
|
| 866 |
constexpr basic_string(const basic_string& str, size_type pos,
|
| 867 |
const Allocator& a = Allocator());
|
| 868 |
constexpr basic_string(const basic_string& str, size_type pos, size_type n,
|
| 869 |
const Allocator& a = Allocator());
|
|
|
|
|
|
|
|
|
|
|
|
|
| 870 |
```
|
| 871 |
|
| 872 |
-
|
| 873 |
|
| 874 |
-
```
|
| 875 |
-
|
| 876 |
-
```
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 877 |
|
| 878 |
``` cpp
|
| 879 |
template<class T>
|
| 880 |
constexpr basic_string(const T& t, size_type pos, size_type n, const Allocator& a = Allocator());
|
| 881 |
```
|
|
@@ -950,11 +1887,19 @@ template<class InputIterator>
|
|
| 950 |
|
| 951 |
*Constraints:* `InputIterator` is a type that qualifies as an input
|
| 952 |
iterator [[container.requirements.general]].
|
| 953 |
|
| 954 |
*Effects:* Constructs a string from the values in the range \[`begin`,
|
| 955 |
-
`end`), as
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 956 |
|
| 957 |
``` cpp
|
| 958 |
constexpr basic_string(initializer_list<charT> il, const Allocator& a = Allocator());
|
| 959 |
```
|
| 960 |
|
|
@@ -1140,10 +2085,45 @@ constexpr void resize(size_type n, charT c);
|
|
| 1140 |
constexpr void resize(size_type n);
|
| 1141 |
```
|
| 1142 |
|
| 1143 |
*Effects:* Equivalent to `resize(n, charT())`.
|
| 1144 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1145 |
``` cpp
|
| 1146 |
constexpr size_type capacity() const noexcept;
|
| 1147 |
```
|
| 1148 |
|
| 1149 |
*Returns:* The size of the allocated storage in the string.
|
|
@@ -1220,14 +2200,14 @@ undefined behavior.
|
|
| 1220 |
``` cpp
|
| 1221 |
constexpr const_reference at(size_type pos) const;
|
| 1222 |
constexpr reference at(size_type pos);
|
| 1223 |
```
|
| 1224 |
|
| 1225 |
-
*Throws:* `out_of_range` if `pos >= size()`.
|
| 1226 |
-
|
| 1227 |
*Returns:* `operator[](pos)`.
|
| 1228 |
|
|
|
|
|
|
|
| 1229 |
``` cpp
|
| 1230 |
constexpr const charT& front() const;
|
| 1231 |
constexpr charT& front();
|
| 1232 |
```
|
| 1233 |
|
|
@@ -1377,10 +2357,18 @@ template<class InputIterator>
|
|
| 1377 |
iterator [[container.requirements.general]].
|
| 1378 |
|
| 1379 |
*Effects:* Equivalent to:
|
| 1380 |
`return append(basic_string(first, last, get_allocator()));`
|
| 1381 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1382 |
``` cpp
|
| 1383 |
constexpr basic_string& append(initializer_list<charT> il);
|
| 1384 |
```
|
| 1385 |
|
| 1386 |
*Effects:* Equivalent to: `return append(il.begin(), il.size());`
|
|
@@ -1497,10 +2485,18 @@ template<class InputIterator>
|
|
| 1497 |
iterator [[container.requirements.general]].
|
| 1498 |
|
| 1499 |
*Effects:* Equivalent to:
|
| 1500 |
`return assign(basic_string(first, last, get_allocator()));`
|
| 1501 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1502 |
##### `basic_string::insert` <a id="string.insert">[[string.insert]]</a>
|
| 1503 |
|
| 1504 |
``` cpp
|
| 1505 |
constexpr basic_string& insert(size_type pos, const basic_string& str);
|
| 1506 |
```
|
|
@@ -1559,22 +2555,22 @@ return insert(pos1, sv.substr(pos2, n));
|
|
| 1559 |
constexpr basic_string& insert(size_type pos, const charT* s, size_type n);
|
| 1560 |
```
|
| 1561 |
|
| 1562 |
*Preconditions:* \[`s`, `s + n`) is a valid range.
|
| 1563 |
|
| 1564 |
-
*Throws:*
|
| 1565 |
-
|
| 1566 |
-
- `out_of_range` if `pos > size()`,
|
| 1567 |
-
- `length_error` if `n > max_size() - size()`, or
|
| 1568 |
-
- any exceptions thrown by `allocator_traits<Allocator>::allocate`.
|
| 1569 |
-
|
| 1570 |
*Effects:* Inserts a copy of the range \[`s`, `s + n`) immediately
|
| 1571 |
before the character at position `pos` if `pos < size()`, or otherwise
|
| 1572 |
at the end of the string.
|
| 1573 |
|
| 1574 |
*Returns:* `*this`.
|
| 1575 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1576 |
``` cpp
|
| 1577 |
constexpr basic_string& insert(size_type pos, const charT* s);
|
| 1578 |
```
|
| 1579 |
|
| 1580 |
*Effects:* Equivalent to: `return insert(pos, s, traits::length(s));`
|
|
@@ -1629,10 +2625,23 @@ iterator [[container.requirements.general]].
|
|
| 1629 |
`insert(p - begin(), basic_string(first, last, get_allocator()))`.
|
| 1630 |
|
| 1631 |
*Returns:* An iterator which refers to the first inserted character, or
|
| 1632 |
`p` if `first == last`.
|
| 1633 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1634 |
``` cpp
|
| 1635 |
constexpr iterator insert(const_iterator p, initializer_list<charT> il);
|
| 1636 |
```
|
| 1637 |
|
| 1638 |
*Effects:* Equivalent to: `return insert(p, il.begin(), il.end());`
|
|
@@ -1641,57 +2650,57 @@ constexpr iterator insert(const_iterator p, initializer_list<charT> il);
|
|
| 1641 |
|
| 1642 |
``` cpp
|
| 1643 |
constexpr basic_string& erase(size_type pos = 0, size_type n = npos);
|
| 1644 |
```
|
| 1645 |
|
| 1646 |
-
*Throws:* `out_of_range` if `pos` `> size()`.
|
| 1647 |
-
|
| 1648 |
*Effects:* Determines the effective length `xlen` of the string to be
|
| 1649 |
removed as the smaller of `n` and `size() - pos`. Removes the characters
|
| 1650 |
in the range \[`begin() + pos`, `begin() + pos + xlen`).
|
| 1651 |
|
| 1652 |
*Returns:* `*this`.
|
| 1653 |
|
|
|
|
|
|
|
| 1654 |
``` cpp
|
| 1655 |
constexpr iterator erase(const_iterator p);
|
| 1656 |
```
|
| 1657 |
|
| 1658 |
*Preconditions:* `p` is a valid dereferenceable iterator on `*this`.
|
| 1659 |
|
| 1660 |
-
*Throws:* Nothing.
|
| 1661 |
-
|
| 1662 |
*Effects:* Removes the character referred to by `p`.
|
| 1663 |
|
| 1664 |
*Returns:* An iterator which points to the element immediately following
|
| 1665 |
`p` prior to the element being erased. If no such element exists,
|
| 1666 |
`end()` is returned.
|
| 1667 |
|
|
|
|
|
|
|
| 1668 |
``` cpp
|
| 1669 |
constexpr iterator erase(const_iterator first, const_iterator last);
|
| 1670 |
```
|
| 1671 |
|
| 1672 |
*Preconditions:* `first` and `last` are valid iterators on `*this`.
|
| 1673 |
\[`first`, `last`) is a valid range.
|
| 1674 |
|
| 1675 |
-
*Throws:* Nothing.
|
| 1676 |
-
|
| 1677 |
*Effects:* Removes the characters in the range `[first, last)`.
|
| 1678 |
|
| 1679 |
*Returns:* An iterator which points to the element pointed to by `last`
|
| 1680 |
prior to the other elements being erased. If no such element exists,
|
| 1681 |
`end()` is returned.
|
| 1682 |
|
|
|
|
|
|
|
| 1683 |
``` cpp
|
| 1684 |
constexpr void pop_back();
|
| 1685 |
```
|
| 1686 |
|
| 1687 |
*Preconditions:* `!empty()`.
|
| 1688 |
|
| 1689 |
-
*Throws:* Nothing.
|
| 1690 |
-
|
| 1691 |
*Effects:* Equivalent to `erase(end() - 1)`.
|
| 1692 |
|
|
|
|
|
|
|
| 1693 |
##### `basic_string::replace` <a id="string.replace">[[string.replace]]</a>
|
| 1694 |
|
| 1695 |
``` cpp
|
| 1696 |
constexpr basic_string& replace(size_type pos1, size_type n1, const basic_string& str);
|
| 1697 |
```
|
|
@@ -1751,25 +2760,25 @@ return replace(pos1, n1, sv.substr(pos2, n2));
|
|
| 1751 |
constexpr basic_string& replace(size_type pos1, size_type n1, const charT* s, size_type n2);
|
| 1752 |
```
|
| 1753 |
|
| 1754 |
*Preconditions:* \[`s`, `s + n2`) is a valid range.
|
| 1755 |
|
| 1756 |
-
*Throws:*
|
| 1757 |
-
|
| 1758 |
-
- `out_of_range` if `pos1 > size()`,
|
| 1759 |
-
- `length_error` if the length of the resulting string would exceed
|
| 1760 |
-
`max_size()` (see below), or
|
| 1761 |
-
- any exceptions thrown by `allocator_traits<Allocator>::allocate`.
|
| 1762 |
-
|
| 1763 |
*Effects:* Determines the effective length `xlen` of the string to be
|
| 1764 |
removed as the smaller of `n1` and `size() - pos1`. If
|
| 1765 |
`size() - xlen >= max_size() - n2` throws `length_error`. Otherwise, the
|
| 1766 |
function replaces the characters in the range \[`begin() + pos1`,
|
| 1767 |
`begin() + pos1 + xlen`) with a copy of the range \[`s`, `s + n2`).
|
| 1768 |
|
| 1769 |
*Returns:* `*this`.
|
| 1770 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1771 |
``` cpp
|
| 1772 |
constexpr basic_string& replace(size_type pos, size_type n, const charT* s);
|
| 1773 |
```
|
| 1774 |
|
| 1775 |
*Effects:* Equivalent to:
|
|
@@ -1777,25 +2786,25 @@ constexpr basic_string& replace(size_type pos, size_type n, const charT* s);
|
|
| 1777 |
|
| 1778 |
``` cpp
|
| 1779 |
constexpr basic_string& replace(size_type pos1, size_type n1, size_type n2, charT c);
|
| 1780 |
```
|
| 1781 |
|
| 1782 |
-
*Throws:*
|
| 1783 |
-
|
| 1784 |
-
- `out_of_range` if `pos1 > size()`,
|
| 1785 |
-
- `length_error` if the length of the resulting string would exceed
|
| 1786 |
-
`max_size()` (see below), or
|
| 1787 |
-
- any exceptions thrown by `allocator_traits<Allocator>::allocate.`
|
| 1788 |
-
|
| 1789 |
*Effects:* Determines the effective length `xlen` of the string to be
|
| 1790 |
removed as the smaller of `n1` and `size() - pos1`. If
|
| 1791 |
`size() - xlen >=` `max_size() - n2` throws `length_error`. Otherwise,
|
| 1792 |
the function replaces the characters in the range \[`begin() + pos1`,
|
| 1793 |
`begin() + pos1 + xlen`) with `n2` copies of `c`.
|
| 1794 |
|
| 1795 |
*Returns:* `*this`.
|
| 1796 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1797 |
``` cpp
|
| 1798 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, const basic_string& str);
|
| 1799 |
```
|
| 1800 |
|
| 1801 |
*Effects:* Equivalent to:
|
|
@@ -1853,10 +2862,21 @@ template<class InputIterator>
|
|
| 1853 |
iterator [[container.requirements.general]].
|
| 1854 |
|
| 1855 |
*Effects:* Equivalent to:
|
| 1856 |
`return replace(i1, i2, basic_string(j1, j2, get_allocator()));`
|
| 1857 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1858 |
``` cpp
|
| 1859 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, initializer_list<charT> il);
|
| 1860 |
```
|
| 1861 |
|
| 1862 |
*Effects:* Equivalent to:
|
|
@@ -1999,25 +3019,27 @@ template<class T>
|
|
| 1999 |
``` cpp
|
| 2000 |
basic_string_view<charT, traits> s = *this, sv = t;
|
| 2001 |
return s.G(sv, pos);
|
| 2002 |
```
|
| 2003 |
|
| 2004 |
-
*Remarks:* The
|
| 2005 |
`is_nothrow_convertible_v<const T&, basic_string_view<charT, traits>>`.
|
| 2006 |
|
| 2007 |
##### `basic_string::substr` <a id="string.substr">[[string.substr]]</a>
|
| 2008 |
|
| 2009 |
``` cpp
|
| 2010 |
-
constexpr basic_string substr(size_type pos = 0, size_type n = npos) const;
|
| 2011 |
```
|
| 2012 |
|
| 2013 |
-
*
|
| 2014 |
|
| 2015 |
-
|
| 2016 |
-
|
|
|
|
| 2017 |
|
| 2018 |
-
*
|
|
|
|
| 2019 |
|
| 2020 |
##### `basic_string::compare` <a id="string.compare">[[string.compare]]</a>
|
| 2021 |
|
| 2022 |
``` cpp
|
| 2023 |
template<class T>
|
|
@@ -2031,11 +3053,11 @@ template<class T>
|
|
| 2031 |
- `is_convertible_v<const T&, const charT*>` is `false`.
|
| 2032 |
|
| 2033 |
*Effects:* Equivalent to:
|
| 2034 |
`return basic_string_view<charT, traits>(*this).compare(t);`
|
| 2035 |
|
| 2036 |
-
*Remarks:* The
|
| 2037 |
`is_nothrow_convertible_v<const T&, basic_string_view<charT, traits>>`.
|
| 2038 |
|
| 2039 |
``` cpp
|
| 2040 |
template<class T>
|
| 2041 |
constexpr int compare(size_type pos1, size_type n1, const T& t) const;
|
|
@@ -2144,10 +3166,24 @@ constexpr bool ends_with(const charT* x) const;
|
|
| 2144 |
|
| 2145 |
``` cpp
|
| 2146 |
return basic_string_view<charT, traits>(data(), size()).ends_with(x);
|
| 2147 |
```
|
| 2148 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 2149 |
### Non-member functions <a id="string.nonmembers">[[string.nonmembers]]</a>
|
| 2150 |
|
| 2151 |
#### `operator+` <a id="string.op.plus">[[string.op.plus]]</a>
|
| 2152 |
|
| 2153 |
``` cpp
|
|
@@ -2201,11 +3237,11 @@ return std::move(lhs);
|
|
| 2201 |
|
| 2202 |
except that both `lhs` and `rhs` are left in valid but unspecified
|
| 2203 |
states.
|
| 2204 |
|
| 2205 |
[*Note 1*: If `lhs` and `rhs` have equal allocators, the implementation
|
| 2206 |
-
|
| 2207 |
|
| 2208 |
``` cpp
|
| 2209 |
template<class charT, class traits, class Allocator>
|
| 2210 |
constexpr basic_string<charT, traits, Allocator>
|
| 2211 |
operator+(const basic_string<charT, traits, Allocator>& lhs,
|
|
@@ -2288,11 +3324,11 @@ template<class charT, class traits, class Allocator>
|
|
| 2288 |
``` cpp
|
| 2289 |
lhs.push_back(rhs);
|
| 2290 |
return std::move(lhs);
|
| 2291 |
```
|
| 2292 |
|
| 2293 |
-
#### Non-member comparison functions <a id="string.cmp">[[string.cmp]]</a>
|
| 2294 |
|
| 2295 |
``` cpp
|
| 2296 |
template<class charT, class traits, class Allocator>
|
| 2297 |
constexpr bool
|
| 2298 |
operator==(const basic_string<charT, traits, Allocator>& lhs,
|
|
@@ -2335,28 +3371,27 @@ template<class charT, class traits, class Allocator>
|
|
| 2335 |
operator>>(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);
|
| 2336 |
```
|
| 2337 |
|
| 2338 |
*Effects:* Behaves as a formatted input
|
| 2339 |
function [[istream.formatted.reqmts]]. After constructing a `sentry`
|
| 2340 |
-
object, if the sentry
|
| 2341 |
-
|
| 2342 |
-
`str.append(1, c)`. If
|
| 2343 |
-
|
| 2344 |
-
`
|
| 2345 |
-
following occurs:
|
| 2346 |
|
| 2347 |
- *n* characters are stored;
|
| 2348 |
- end-of-file occurs on the input sequence;
|
| 2349 |
- `isspace(c, is.getloc())` is `true` for the next available input
|
| 2350 |
character *c*.
|
| 2351 |
|
| 2352 |
After the last character (if any) is extracted, `is.width(0)` is called
|
| 2353 |
and the `sentry` object is destroyed.
|
| 2354 |
|
| 2355 |
-
If the function extracts no characters,
|
| 2356 |
-
|
| 2357 |
-
[[iostate.flags]].
|
| 2358 |
|
| 2359 |
*Returns:* `is`.
|
| 2360 |
|
| 2361 |
``` cpp
|
| 2362 |
template<class charT, class traits, class Allocator>
|
|
@@ -2382,28 +3417,26 @@ template<class charT, class traits, class Allocator>
|
|
| 2382 |
```
|
| 2383 |
|
| 2384 |
*Effects:* Behaves as an unformatted input
|
| 2385 |
function [[istream.unformatted]], except that it does not affect the
|
| 2386 |
value returned by subsequent calls to `basic_istream<>::gcount()`. After
|
| 2387 |
-
constructing a `sentry` object, if the sentry
|
| 2388 |
-
|
| 2389 |
-
`
|
| 2390 |
-
occurs:
|
| 2391 |
|
| 2392 |
-
- end-of-file occurs on the input sequence
|
| 2393 |
-
function calls `is.setstate(ios_base::eofbit)`).
|
| 2394 |
- `traits::eq(c, delim)` for the next available input character *c* (in
|
| 2395 |
-
which case, *c* is extracted but not appended)
|
| 2396 |
-
- `str.max_size()` characters are stored (in which case,
|
| 2397 |
-
|
| 2398 |
|
| 2399 |
The conditions are tested in the order shown. In any case, after the
|
| 2400 |
last character is extracted, the `sentry` object is destroyed.
|
| 2401 |
|
| 2402 |
-
If the function extracts no characters,
|
| 2403 |
-
|
| 2404 |
-
[[iostate.flags]].
|
| 2405 |
|
| 2406 |
*Returns:* `is`.
|
| 2407 |
|
| 2408 |
``` cpp
|
| 2409 |
template<class charT, class traits, class Allocator>
|
|
@@ -2465,17 +3498,17 @@ unsigned long long stoull(const string& str, size_t* idx = nullptr, int base = 1
|
|
| 2465 |
`strtoul(str.c_str(), ptr, base)`, `strtoll(str.c_str(), ptr, base)`,
|
| 2466 |
and `strtoull(str.c_str(), ptr, base)`, respectively. Each function
|
| 2467 |
returns the converted result, if any. The argument `ptr` designates a
|
| 2468 |
pointer to an object internal to the function that is used to determine
|
| 2469 |
what to store at `*idx`. If the function does not throw an exception and
|
| 2470 |
-
`idx !=
|
| 2471 |
unconverted element of `str`.
|
| 2472 |
|
| 2473 |
*Returns:* The converted result.
|
| 2474 |
|
| 2475 |
*Throws:* `invalid_argument` if `strtol`, `strtoul`, `strtoll`, or
|
| 2476 |
-
`strtoull` reports that no conversion
|
| 2477 |
`out_of_range` if `strtol`, `strtoul`, `strtoll` or `strtoull` sets
|
| 2478 |
`errno` to `ERANGE`, or if the converted value is outside the range of
|
| 2479 |
representable values for the return type.
|
| 2480 |
|
| 2481 |
``` cpp
|
|
@@ -2487,20 +3520,19 @@ long double stold(const string& str, size_t* idx = nullptr);
|
|
| 2487 |
*Effects:* These functions call `strtof(str.c_str(), ptr)`,
|
| 2488 |
`strtod(str.c_str(), ptr)`, and `strtold(str.c_str(), ptr)`,
|
| 2489 |
respectively. Each function returns the converted result, if any. The
|
| 2490 |
argument `ptr` designates a pointer to an object internal to the
|
| 2491 |
function that is used to determine what to store at `*idx`. If the
|
| 2492 |
-
function does not throw an exception and `idx !=
|
| 2493 |
-
in `*idx` the index of the first unconverted element of `str`.
|
| 2494 |
|
| 2495 |
*Returns:* The converted result.
|
| 2496 |
|
| 2497 |
*Throws:* `invalid_argument` if `strtof`, `strtod`, or `strtold` reports
|
| 2498 |
-
that no conversion
|
| 2499 |
-
`
|
| 2500 |
-
|
| 2501 |
-
return type.
|
| 2502 |
|
| 2503 |
``` cpp
|
| 2504 |
string to_string(int val);
|
| 2505 |
string to_string(unsigned val);
|
| 2506 |
string to_string(long val);
|
|
@@ -2532,17 +3564,17 @@ unsigned long long stoull(const wstring& str, size_t* idx = nullptr, int base =
|
|
| 2532 |
`wcstoul(str.c_str(), ptr, base)`, `wcstoll(str.c_str(), ptr, base)`,
|
| 2533 |
and `wcstoull(str.c_str(), ptr, base)`, respectively. Each function
|
| 2534 |
returns the converted result, if any. The argument `ptr` designates a
|
| 2535 |
pointer to an object internal to the function that is used to determine
|
| 2536 |
what to store at `*idx`. If the function does not throw an exception and
|
| 2537 |
-
`idx !=
|
| 2538 |
unconverted element of `str`.
|
| 2539 |
|
| 2540 |
*Returns:* The converted result.
|
| 2541 |
|
| 2542 |
*Throws:* `invalid_argument` if `wcstol`, `wcstoul`, `wcstoll`, or
|
| 2543 |
-
`wcstoull` reports that no conversion
|
| 2544 |
`out_of_range` if the converted value is outside the range of
|
| 2545 |
representable values for the return type.
|
| 2546 |
|
| 2547 |
``` cpp
|
| 2548 |
float stof(const wstring& str, size_t* idx = nullptr);
|
|
@@ -2553,18 +3585,18 @@ long double stold(const wstring& str, size_t* idx = nullptr);
|
|
| 2553 |
*Effects:* These functions call `wcstof(str.c_str(), ptr)`,
|
| 2554 |
`wcstod(str.c_str(), ptr)`, and `wcstold(str.c_str(), ptr)`,
|
| 2555 |
respectively. Each function returns the converted result, if any. The
|
| 2556 |
argument `ptr` designates a pointer to an object internal to the
|
| 2557 |
function that is used to determine what to store at `*idx`. If the
|
| 2558 |
-
function does not throw an exception and `idx !=
|
| 2559 |
-
in `*idx` the index of the first unconverted element of `str`.
|
| 2560 |
|
| 2561 |
*Returns:* The converted result.
|
| 2562 |
|
| 2563 |
*Throws:* `invalid_argument` if `wcstof`, `wcstod`, or `wcstold` reports
|
| 2564 |
-
that no conversion
|
| 2565 |
-
`
|
| 2566 |
|
| 2567 |
``` cpp
|
| 2568 |
wstring to_wstring(int val);
|
| 2569 |
wstring to_wstring(unsigned val);
|
| 2570 |
wstring to_wstring(long val);
|
|
@@ -2584,20 +3616,15 @@ specifier of `L"%d"`, `L"%u"`, `L"%ld"`, `L"%lu"`, `L"%lld"`, `L"%llu"`,
|
|
| 2584 |
internal character buffer of sufficient size `buffsz`.
|
| 2585 |
|
| 2586 |
### Hash support <a id="basic.string.hash">[[basic.string.hash]]</a>
|
| 2587 |
|
| 2588 |
``` cpp
|
| 2589 |
-
template<> struct hash<
|
| 2590 |
-
template<> struct hash<
|
| 2591 |
-
template<> struct hash<
|
| 2592 |
-
template<> struct hash<
|
| 2593 |
-
template<> struct hash<
|
| 2594 |
-
template<> struct hash<pmr::string>;
|
| 2595 |
-
template<> struct hash<pmr::u8string>;
|
| 2596 |
-
template<> struct hash<pmr::u16string>;
|
| 2597 |
-
template<> struct hash<pmr::u32string>;
|
| 2598 |
-
template<> struct hash<pmr::wstring>;
|
| 2599 |
```
|
| 2600 |
|
| 2601 |
If `S` is one of these string types, `SV` is the corresponding string
|
| 2602 |
view type, and `s` is an object of type `S`, then
|
| 2603 |
`hash<S>()(s) == hash<SV>()(SV(s))`.
|
|
@@ -2637,822 +3664,10 @@ constexpr wstring operator""s(const wchar_t* str, size_t len);
|
|
| 2637 |
[*Note 1*: The same suffix `s` is used for `chrono::duration` literals
|
| 2638 |
denoting seconds but there is no conflict, since duration suffixes apply
|
| 2639 |
to numbers and string literal suffixes apply to character array
|
| 2640 |
literals. — *end note*]
|
| 2641 |
|
| 2642 |
-
## String view classes <a id="string.view">[[string.view]]</a>
|
| 2643 |
-
|
| 2644 |
-
The class template `basic_string_view` describes an object that can
|
| 2645 |
-
refer to a constant contiguous sequence of char-like [[strings.general]]
|
| 2646 |
-
objects with the first element of the sequence at position zero. In the
|
| 2647 |
-
rest of this subclause, the type of the char-like objects held in a
|
| 2648 |
-
`basic_string_view` object is designated by `charT`.
|
| 2649 |
-
|
| 2650 |
-
[*Note 1*: The library provides implicit conversions from
|
| 2651 |
-
`const charT*` and `std::basic_string<charT, ...>` to
|
| 2652 |
-
`std::basic_string_view<charT, ...>` so that user code can accept just
|
| 2653 |
-
`std::basic_string_view<charT>` as a non-templated parameter wherever a
|
| 2654 |
-
sequence of characters is expected. User-defined types should define
|
| 2655 |
-
their own implicit conversions to `std::basic_string_view` in order to
|
| 2656 |
-
interoperate with these functions. — *end note*]
|
| 2657 |
-
|
| 2658 |
-
### Header `<string_view>` synopsis <a id="string.view.synop">[[string.view.synop]]</a>
|
| 2659 |
-
|
| 2660 |
-
``` cpp
|
| 2661 |
-
#include <compare> // see [compare.syn]
|
| 2662 |
-
|
| 2663 |
-
namespace std {
|
| 2664 |
-
// [string.view.template], class template basic_string_view
|
| 2665 |
-
template<class charT, class traits = char_traits<charT>>
|
| 2666 |
-
class basic_string_view;
|
| 2667 |
-
|
| 2668 |
-
template<class charT, class traits>
|
| 2669 |
-
inline constexpr bool ranges::enable_view<basic_string_view<charT, traits>> = true;
|
| 2670 |
-
template<class charT, class traits>
|
| 2671 |
-
inline constexpr bool ranges::enable_borrowed_range<basic_string_view<charT, traits>> = true;
|
| 2672 |
-
|
| 2673 |
-
// [string.view.comparison], non-member comparison functions
|
| 2674 |
-
template<class charT, class traits>
|
| 2675 |
-
constexpr bool operator==(basic_string_view<charT, traits> x,
|
| 2676 |
-
basic_string_view<charT, traits> y) noexcept;
|
| 2677 |
-
template<class charT, class traits>
|
| 2678 |
-
constexpr see below operator<=>(basic_string_view<charT, traits> x,
|
| 2679 |
-
\itcorr basic_string_view<charT, traits> y) noexcept;
|
| 2680 |
-
|
| 2681 |
-
// see [string.view.comparison], sufficient additional overloads of comparison functions
|
| 2682 |
-
|
| 2683 |
-
// [string.view.io], inserters and extractors
|
| 2684 |
-
template<class charT, class traits>
|
| 2685 |
-
basic_ostream<charT, traits>&
|
| 2686 |
-
operator<<(basic_ostream<charT, traits>& os,
|
| 2687 |
-
basic_string_view<charT, traits> str);
|
| 2688 |
-
|
| 2689 |
-
// basic_string_view typedef names
|
| 2690 |
-
using string_view = basic_string_view<char>;
|
| 2691 |
-
using u8string_view = basic_string_view<char8_t>;
|
| 2692 |
-
using u16string_view = basic_string_view<char16_t>;
|
| 2693 |
-
using u32string_view = basic_string_view<char32_t>;
|
| 2694 |
-
using wstring_view = basic_string_view<wchar_t>;
|
| 2695 |
-
|
| 2696 |
-
// [string.view.hash], hash support
|
| 2697 |
-
template<class T> struct hash;
|
| 2698 |
-
template<> struct hash<string_view>;
|
| 2699 |
-
template<> struct hash<u8string_view>;
|
| 2700 |
-
template<> struct hash<u16string_view>;
|
| 2701 |
-
template<> struct hash<u32string_view>;
|
| 2702 |
-
template<> struct hash<wstring_view>;
|
| 2703 |
-
|
| 2704 |
-
inline namespace literals {
|
| 2705 |
-
inline namespace string_view_literals {
|
| 2706 |
-
// [string.view.literals], suffix for basic_string_view literals
|
| 2707 |
-
constexpr string_view operator""sv(const char* str, size_t len) noexcept;
|
| 2708 |
-
constexpr u8string_view operator""sv(const char8_t* str, size_t len) noexcept;
|
| 2709 |
-
constexpr u16string_view operator""sv(const char16_t* str, size_t len) noexcept;
|
| 2710 |
-
constexpr u32string_view operator""sv(const char32_t* str, size_t len) noexcept;
|
| 2711 |
-
constexpr wstring_view operator""sv(const wchar_t* str, size_t len) noexcept;
|
| 2712 |
-
}
|
| 2713 |
-
}
|
| 2714 |
-
}
|
| 2715 |
-
```
|
| 2716 |
-
|
| 2717 |
-
The function templates defined in [[utility.swap]] and
|
| 2718 |
-
[[iterator.range]] are available when `<string_view>` is included.
|
| 2719 |
-
|
| 2720 |
-
### Class template `basic_string_view` <a id="string.view.template">[[string.view.template]]</a>
|
| 2721 |
-
|
| 2722 |
-
``` cpp
|
| 2723 |
-
template<class charT, class traits = char_traits<charT>>
|
| 2724 |
-
class basic_string_view {
|
| 2725 |
-
public:
|
| 2726 |
-
// types
|
| 2727 |
-
using traits_type = traits;
|
| 2728 |
-
using value_type = charT;
|
| 2729 |
-
using pointer = value_type*;
|
| 2730 |
-
using const_pointer = const value_type*;
|
| 2731 |
-
using reference = value_type&;
|
| 2732 |
-
using const_reference = const value_type&;
|
| 2733 |
-
using const_iterator = implementation-defined // type of basic_string_view::const_iterator; // see [string.view.iterators]
|
| 2734 |
-
using iterator = const_iterator;\footnote{Because basic_string_view refers to a constant sequence, iterator and const_iterator are the same type.}
|
| 2735 |
-
using const_reverse_iterator = reverse_iterator<const_iterator>;
|
| 2736 |
-
using reverse_iterator = const_reverse_iterator;
|
| 2737 |
-
using size_type = size_t;
|
| 2738 |
-
using difference_type = ptrdiff_t;
|
| 2739 |
-
static constexpr size_type npos = size_type(-1);
|
| 2740 |
-
|
| 2741 |
-
// [string.view.cons], construction and assignment
|
| 2742 |
-
constexpr basic_string_view() noexcept;
|
| 2743 |
-
constexpr basic_string_view(const basic_string_view&) noexcept = default;
|
| 2744 |
-
constexpr basic_string_view& operator=(const basic_string_view&) noexcept = default;
|
| 2745 |
-
constexpr basic_string_view(const charT* str);
|
| 2746 |
-
constexpr basic_string_view(const charT* str, size_type len);
|
| 2747 |
-
template<class It, class End>
|
| 2748 |
-
constexpr basic_string_view(It begin, End end);
|
| 2749 |
-
|
| 2750 |
-
// [string.view.iterators], iterator support
|
| 2751 |
-
constexpr const_iterator begin() const noexcept;
|
| 2752 |
-
constexpr const_iterator end() const noexcept;
|
| 2753 |
-
constexpr const_iterator cbegin() const noexcept;
|
| 2754 |
-
constexpr const_iterator cend() const noexcept;
|
| 2755 |
-
constexpr const_reverse_iterator rbegin() const noexcept;
|
| 2756 |
-
constexpr const_reverse_iterator rend() const noexcept;
|
| 2757 |
-
constexpr const_reverse_iterator crbegin() const noexcept;
|
| 2758 |
-
constexpr const_reverse_iterator crend() const noexcept;
|
| 2759 |
-
|
| 2760 |
-
// [string.view.capacity], capacity
|
| 2761 |
-
constexpr size_type size() const noexcept;
|
| 2762 |
-
constexpr size_type length() const noexcept;
|
| 2763 |
-
constexpr size_type max_size() const noexcept;
|
| 2764 |
-
[[nodiscard]] constexpr bool empty() const noexcept;
|
| 2765 |
-
|
| 2766 |
-
// [string.view.access], element access
|
| 2767 |
-
constexpr const_reference operator[](size_type pos) const;
|
| 2768 |
-
constexpr const_reference at(size_type pos) const;
|
| 2769 |
-
constexpr const_reference front() const;
|
| 2770 |
-
constexpr const_reference back() const;
|
| 2771 |
-
constexpr const_pointer data() const noexcept;
|
| 2772 |
-
|
| 2773 |
-
// [string.view.modifiers], modifiers
|
| 2774 |
-
constexpr void remove_prefix(size_type n);
|
| 2775 |
-
constexpr void remove_suffix(size_type n);
|
| 2776 |
-
constexpr void swap(basic_string_view& s) noexcept;
|
| 2777 |
-
|
| 2778 |
-
// [string.view.ops], string operations
|
| 2779 |
-
constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
|
| 2780 |
-
|
| 2781 |
-
constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
|
| 2782 |
-
|
| 2783 |
-
constexpr int compare(basic_string_view s) const noexcept;
|
| 2784 |
-
constexpr int compare(size_type pos1, size_type n1, basic_string_view s) const;
|
| 2785 |
-
constexpr int compare(size_type pos1, size_type n1, basic_string_view s,
|
| 2786 |
-
size_type pos2, size_type n2) const;
|
| 2787 |
-
constexpr int compare(const charT* s) const;
|
| 2788 |
-
constexpr int compare(size_type pos1, size_type n1, const charT* s) const;
|
| 2789 |
-
constexpr int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const;
|
| 2790 |
-
|
| 2791 |
-
constexpr bool starts_with(basic_string_view x) const noexcept;
|
| 2792 |
-
constexpr bool starts_with(charT x) const noexcept;
|
| 2793 |
-
constexpr bool starts_with(const charT* x) const;
|
| 2794 |
-
constexpr bool ends_with(basic_string_view x) const noexcept;
|
| 2795 |
-
constexpr bool ends_with(charT x) const noexcept;
|
| 2796 |
-
constexpr bool ends_with(const charT* x) const;
|
| 2797 |
-
|
| 2798 |
-
// [string.view.find], searching
|
| 2799 |
-
constexpr size_type find(basic_string_view s, size_type pos = 0) const noexcept;
|
| 2800 |
-
constexpr size_type find(charT c, size_type pos = 0) const noexcept;
|
| 2801 |
-
constexpr size_type find(const charT* s, size_type pos, size_type n) const;
|
| 2802 |
-
constexpr size_type find(const charT* s, size_type pos = 0) const;
|
| 2803 |
-
constexpr size_type rfind(basic_string_view s, size_type pos = npos) const noexcept;
|
| 2804 |
-
constexpr size_type rfind(charT c, size_type pos = npos) const noexcept;
|
| 2805 |
-
constexpr size_type rfind(const charT* s, size_type pos, size_type n) const;
|
| 2806 |
-
constexpr size_type rfind(const charT* s, size_type pos = npos) const;
|
| 2807 |
-
|
| 2808 |
-
constexpr size_type find_first_of(basic_string_view s, size_type pos = 0) const noexcept;
|
| 2809 |
-
constexpr size_type find_first_of(charT c, size_type pos = 0) const noexcept;
|
| 2810 |
-
constexpr size_type find_first_of(const charT* s, size_type pos, size_type n) const;
|
| 2811 |
-
constexpr size_type find_first_of(const charT* s, size_type pos = 0) const;
|
| 2812 |
-
constexpr size_type find_last_of(basic_string_view s, size_type pos = npos) const noexcept;
|
| 2813 |
-
constexpr size_type find_last_of(charT c, size_type pos = npos) const noexcept;
|
| 2814 |
-
constexpr size_type find_last_of(const charT* s, size_type pos, size_type n) const;
|
| 2815 |
-
constexpr size_type find_last_of(const charT* s, size_type pos = npos) const;
|
| 2816 |
-
constexpr size_type find_first_not_of(basic_string_view s, size_type pos = 0) const noexcept;
|
| 2817 |
-
constexpr size_type find_first_not_of(charT c, size_type pos = 0) const noexcept;
|
| 2818 |
-
constexpr size_type find_first_not_of(const charT* s, size_type pos,
|
| 2819 |
-
size_type n) const;
|
| 2820 |
-
constexpr size_type find_first_not_of(const charT* s, size_type pos = 0) const;
|
| 2821 |
-
constexpr size_type find_last_not_of(basic_string_view s,
|
| 2822 |
-
size_type pos = npos) const noexcept;
|
| 2823 |
-
constexpr size_type find_last_not_of(charT c, size_type pos = npos) const noexcept;
|
| 2824 |
-
constexpr size_type find_last_not_of(const charT* s, size_type pos,
|
| 2825 |
-
size_type n) const;
|
| 2826 |
-
constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
|
| 2827 |
-
|
| 2828 |
-
private:
|
| 2829 |
-
const_pointer data_; // exposition only
|
| 2830 |
-
size_type size_; // exposition only
|
| 2831 |
-
};
|
| 2832 |
-
|
| 2833 |
-
// [string.view.deduct], deduction guide
|
| 2834 |
-
template<class It, class End>
|
| 2835 |
-
basic_string_view(It, End) -> basic_string_view<iter_value_t<It>>;
|
| 2836 |
-
```
|
| 2837 |
-
|
| 2838 |
-
In every specialization `basic_string_view<charT, traits>`, the type
|
| 2839 |
-
`traits` shall meet the character traits requirements [[char.traits]].
|
| 2840 |
-
|
| 2841 |
-
[*Note 1*: The program is ill-formed if `traits::char_type` is not the
|
| 2842 |
-
same type as `charT`. — *end note*]
|
| 2843 |
-
|
| 2844 |
-
For a `basic_string_view str`, any operation that invalidates a pointer
|
| 2845 |
-
in the range \[`str.data()`, `str.data() + str.size()`) invalidates
|
| 2846 |
-
pointers, iterators, and references returned from `str`’s member
|
| 2847 |
-
functions.
|
| 2848 |
-
|
| 2849 |
-
The complexity of `basic_string_view` member functions is 𝑂(1) unless
|
| 2850 |
-
otherwise specified.
|
| 2851 |
-
|
| 2852 |
-
#### Construction and assignment <a id="string.view.cons">[[string.view.cons]]</a>
|
| 2853 |
-
|
| 2854 |
-
``` cpp
|
| 2855 |
-
constexpr basic_string_view() noexcept;
|
| 2856 |
-
```
|
| 2857 |
-
|
| 2858 |
-
*Ensures:* `size_ == 0` and `data_ == nullptr`.
|
| 2859 |
-
|
| 2860 |
-
``` cpp
|
| 2861 |
-
constexpr basic_string_view(const charT* str);
|
| 2862 |
-
```
|
| 2863 |
-
|
| 2864 |
-
*Preconditions:* \[`str`, `str + traits::length(str)`) is a valid range.
|
| 2865 |
-
|
| 2866 |
-
*Effects:* Constructs a `basic_string_view`, initializing `data_` with
|
| 2867 |
-
`str` and initializing `size_` with `traits::length(str)`.
|
| 2868 |
-
|
| 2869 |
-
*Complexity:* 𝑂(`traits::length(str)`).
|
| 2870 |
-
|
| 2871 |
-
``` cpp
|
| 2872 |
-
constexpr basic_string_view(const charT* str, size_type len);
|
| 2873 |
-
```
|
| 2874 |
-
|
| 2875 |
-
*Preconditions:* \[`str`, `str + len`) is a valid range.
|
| 2876 |
-
|
| 2877 |
-
*Effects:* Constructs a `basic_string_view`, initializing `data_` with
|
| 2878 |
-
`str` and initializing `size_` with `len`.
|
| 2879 |
-
|
| 2880 |
-
``` cpp
|
| 2881 |
-
template<class It, class End>
|
| 2882 |
-
constexpr basic_string_view(It begin, End end);
|
| 2883 |
-
```
|
| 2884 |
-
|
| 2885 |
-
*Constraints:*
|
| 2886 |
-
|
| 2887 |
-
- `It` satisfies `contiguous_iterator`.
|
| 2888 |
-
- `End` satisfies `sized_sentinel_for<It>`.
|
| 2889 |
-
- `is_same_v<iter_value_t<It>, charT>` is `true`.
|
| 2890 |
-
- `is_convertible_v<End, size_type>` is `false`.
|
| 2891 |
-
|
| 2892 |
-
*Preconditions:*
|
| 2893 |
-
|
| 2894 |
-
- \[`begin`, `end`) is a valid range.
|
| 2895 |
-
- `It` models `contiguous_iterator`.
|
| 2896 |
-
- `End` models `sized_sentinel_for<It>`.
|
| 2897 |
-
|
| 2898 |
-
*Effects:* Initializes `data_` with `to_address(begin)` and initializes
|
| 2899 |
-
`size_` with `end - begin`.
|
| 2900 |
-
|
| 2901 |
-
#### Iterator support <a id="string.view.iterators">[[string.view.iterators]]</a>
|
| 2902 |
-
|
| 2903 |
-
``` cpp
|
| 2904 |
-
using const_iterator = implementation-defined // type of basic_string_view::const_iterator;
|
| 2905 |
-
```
|
| 2906 |
-
|
| 2907 |
-
A type that meets the requirements of a constant
|
| 2908 |
-
*Cpp17RandomAccessIterator*[[random.access.iterators]], models
|
| 2909 |
-
`contiguous_iterator` [[iterator.concept.contiguous]], and meets the
|
| 2910 |
-
constexpr iterator requirements [[iterator.requirements.general]], whose
|
| 2911 |
-
`value_type` is the template parameter `charT`.
|
| 2912 |
-
|
| 2913 |
-
All requirements on container iterators [[container.requirements]] apply
|
| 2914 |
-
to `basic_string_view::const_iterator` as well.
|
| 2915 |
-
|
| 2916 |
-
``` cpp
|
| 2917 |
-
constexpr const_iterator begin() const noexcept;
|
| 2918 |
-
constexpr const_iterator cbegin() const noexcept;
|
| 2919 |
-
```
|
| 2920 |
-
|
| 2921 |
-
*Returns:* An iterator such that
|
| 2922 |
-
|
| 2923 |
-
- if `!empty()`, `addressof(*begin()) == data_`,
|
| 2924 |
-
- otherwise, an unspecified value such that \[`begin()`, `end()`) is a
|
| 2925 |
-
valid range.
|
| 2926 |
-
|
| 2927 |
-
``` cpp
|
| 2928 |
-
constexpr const_iterator end() const noexcept;
|
| 2929 |
-
constexpr const_iterator cend() const noexcept;
|
| 2930 |
-
```
|
| 2931 |
-
|
| 2932 |
-
*Returns:* `begin() + size()`.
|
| 2933 |
-
|
| 2934 |
-
``` cpp
|
| 2935 |
-
constexpr const_reverse_iterator rbegin() const noexcept;
|
| 2936 |
-
constexpr const_reverse_iterator crbegin() const noexcept;
|
| 2937 |
-
```
|
| 2938 |
-
|
| 2939 |
-
*Returns:* `const_reverse_iterator(end())`.
|
| 2940 |
-
|
| 2941 |
-
``` cpp
|
| 2942 |
-
constexpr const_reverse_iterator rend() const noexcept;
|
| 2943 |
-
constexpr const_reverse_iterator crend() const noexcept;
|
| 2944 |
-
```
|
| 2945 |
-
|
| 2946 |
-
*Returns:* `const_reverse_iterator(begin())`.
|
| 2947 |
-
|
| 2948 |
-
#### Capacity <a id="string.view.capacity">[[string.view.capacity]]</a>
|
| 2949 |
-
|
| 2950 |
-
``` cpp
|
| 2951 |
-
constexpr size_type size() const noexcept;
|
| 2952 |
-
constexpr size_type length() const noexcept;
|
| 2953 |
-
```
|
| 2954 |
-
|
| 2955 |
-
*Returns:* `size_`.
|
| 2956 |
-
|
| 2957 |
-
``` cpp
|
| 2958 |
-
constexpr size_type max_size() const noexcept;
|
| 2959 |
-
```
|
| 2960 |
-
|
| 2961 |
-
*Returns:* The largest possible number of char-like objects that can be
|
| 2962 |
-
referred to by a `basic_string_view`.
|
| 2963 |
-
|
| 2964 |
-
``` cpp
|
| 2965 |
-
[[nodiscard]] constexpr bool empty() const noexcept;
|
| 2966 |
-
```
|
| 2967 |
-
|
| 2968 |
-
*Returns:* `size_ == 0`.
|
| 2969 |
-
|
| 2970 |
-
#### Element access <a id="string.view.access">[[string.view.access]]</a>
|
| 2971 |
-
|
| 2972 |
-
``` cpp
|
| 2973 |
-
constexpr const_reference operator[](size_type pos) const;
|
| 2974 |
-
```
|
| 2975 |
-
|
| 2976 |
-
*Preconditions:* `pos < size()`.
|
| 2977 |
-
|
| 2978 |
-
*Returns:* `data_[pos]`.
|
| 2979 |
-
|
| 2980 |
-
*Throws:* Nothing.
|
| 2981 |
-
|
| 2982 |
-
[*Note 1*: Unlike `basic_string::operator[]`,
|
| 2983 |
-
`basic_string_view::operator[](size())` has undefined behavior instead
|
| 2984 |
-
of returning `charT()`. — *end note*]
|
| 2985 |
-
|
| 2986 |
-
``` cpp
|
| 2987 |
-
constexpr const_reference at(size_type pos) const;
|
| 2988 |
-
```
|
| 2989 |
-
|
| 2990 |
-
*Throws:* `out_of_range` if `pos >= size()`.
|
| 2991 |
-
|
| 2992 |
-
*Returns:* `data_[pos]`.
|
| 2993 |
-
|
| 2994 |
-
``` cpp
|
| 2995 |
-
constexpr const_reference front() const;
|
| 2996 |
-
```
|
| 2997 |
-
|
| 2998 |
-
*Preconditions:* `!empty()`.
|
| 2999 |
-
|
| 3000 |
-
*Returns:* `data_[0]`.
|
| 3001 |
-
|
| 3002 |
-
*Throws:* Nothing.
|
| 3003 |
-
|
| 3004 |
-
``` cpp
|
| 3005 |
-
constexpr const_reference back() const;
|
| 3006 |
-
```
|
| 3007 |
-
|
| 3008 |
-
*Preconditions:* `!empty()`.
|
| 3009 |
-
|
| 3010 |
-
*Returns:* `data_[size() - 1]`.
|
| 3011 |
-
|
| 3012 |
-
*Throws:* Nothing.
|
| 3013 |
-
|
| 3014 |
-
``` cpp
|
| 3015 |
-
constexpr const_pointer data() const noexcept;
|
| 3016 |
-
```
|
| 3017 |
-
|
| 3018 |
-
*Returns:* `data_`.
|
| 3019 |
-
|
| 3020 |
-
[*Note 2*: Unlike `basic_string::data()` and *string-literal*s,
|
| 3021 |
-
`data()` may return a pointer to a buffer that is not null-terminated.
|
| 3022 |
-
Therefore it is typically a mistake to pass `data()` to a function that
|
| 3023 |
-
takes just a `const charT*` and expects a null-terminated
|
| 3024 |
-
string. — *end note*]
|
| 3025 |
-
|
| 3026 |
-
#### Modifiers <a id="string.view.modifiers">[[string.view.modifiers]]</a>
|
| 3027 |
-
|
| 3028 |
-
``` cpp
|
| 3029 |
-
constexpr void remove_prefix(size_type n);
|
| 3030 |
-
```
|
| 3031 |
-
|
| 3032 |
-
*Preconditions:* `n <= size()`.
|
| 3033 |
-
|
| 3034 |
-
*Effects:* Equivalent to: `data_ += n; size_ -= n;`
|
| 3035 |
-
|
| 3036 |
-
``` cpp
|
| 3037 |
-
constexpr void remove_suffix(size_type n);
|
| 3038 |
-
```
|
| 3039 |
-
|
| 3040 |
-
*Preconditions:* `n <= size()`.
|
| 3041 |
-
|
| 3042 |
-
*Effects:* Equivalent to: `size_ -= n;`
|
| 3043 |
-
|
| 3044 |
-
``` cpp
|
| 3045 |
-
constexpr void swap(basic_string_view& s) noexcept;
|
| 3046 |
-
```
|
| 3047 |
-
|
| 3048 |
-
*Effects:* Exchanges the values of `*this` and `s`.
|
| 3049 |
-
|
| 3050 |
-
#### String operations <a id="string.view.ops">[[string.view.ops]]</a>
|
| 3051 |
-
|
| 3052 |
-
``` cpp
|
| 3053 |
-
constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
|
| 3054 |
-
```
|
| 3055 |
-
|
| 3056 |
-
Let `rlen` be the smaller of `n` and `size() - pos`.
|
| 3057 |
-
|
| 3058 |
-
*Throws:* `out_of_range` if `pos > size()`.
|
| 3059 |
-
|
| 3060 |
-
*Preconditions:* \[`s`, `s + rlen`) is a valid range.
|
| 3061 |
-
|
| 3062 |
-
*Effects:* Equivalent to `traits::copy(s, data() + pos, rlen)`.
|
| 3063 |
-
|
| 3064 |
-
*Returns:* `rlen`.
|
| 3065 |
-
|
| 3066 |
-
*Complexity:* 𝑂(`rlen`).
|
| 3067 |
-
|
| 3068 |
-
``` cpp
|
| 3069 |
-
constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
|
| 3070 |
-
```
|
| 3071 |
-
|
| 3072 |
-
Let `rlen` be the smaller of `n` and `size() - pos`.
|
| 3073 |
-
|
| 3074 |
-
*Throws:* `out_of_range` if `pos > size()`.
|
| 3075 |
-
|
| 3076 |
-
*Effects:* Determines `rlen`, the effective length of the string to
|
| 3077 |
-
reference.
|
| 3078 |
-
|
| 3079 |
-
*Returns:* `basic_string_view(data() + pos, rlen)`.
|
| 3080 |
-
|
| 3081 |
-
``` cpp
|
| 3082 |
-
constexpr int compare(basic_string_view str) const noexcept;
|
| 3083 |
-
```
|
| 3084 |
-
|
| 3085 |
-
Let `rlen` be the smaller of `size()` and `str.size()`.
|
| 3086 |
-
|
| 3087 |
-
*Effects:* Determines `rlen`, the effective length of the strings to
|
| 3088 |
-
compare. The function then compares the two strings by calling
|
| 3089 |
-
`traits::compare(data(), str.data(), rlen)`.
|
| 3090 |
-
|
| 3091 |
-
*Complexity:* 𝑂(`rlen`).
|
| 3092 |
-
|
| 3093 |
-
*Returns:* The nonzero result if the result of the comparison is
|
| 3094 |
-
nonzero. Otherwise, returns a value as indicated in
|
| 3095 |
-
[[string.view.compare]].
|
| 3096 |
-
|
| 3097 |
-
**Table: `compare()` results** <a id="string.view.compare">[string.view.compare]</a>
|
| 3098 |
-
|
| 3099 |
-
| Condition | Return Value |
|
| 3100 |
-
| ---------------------- | ------------ |
|
| 3101 |
-
| `size() < str.size()` | `< 0` |
|
| 3102 |
-
| `size() == str.size()` | ` 0` |
|
| 3103 |
-
| `size() > str.size()` | `> 0` |
|
| 3104 |
-
|
| 3105 |
-
``` cpp
|
| 3106 |
-
constexpr int compare(size_type pos1, size_type n1, basic_string_view str) const;
|
| 3107 |
-
```
|
| 3108 |
-
|
| 3109 |
-
*Effects:* Equivalent to: `return substr(pos1, n1).compare(str);`
|
| 3110 |
-
|
| 3111 |
-
``` cpp
|
| 3112 |
-
constexpr int compare(size_type pos1, size_type n1, basic_string_view str,
|
| 3113 |
-
size_type pos2, size_type n2) const;
|
| 3114 |
-
```
|
| 3115 |
-
|
| 3116 |
-
*Effects:* Equivalent to:
|
| 3117 |
-
`return substr(pos1, n1).compare(str.substr(pos2, n2));`
|
| 3118 |
-
|
| 3119 |
-
``` cpp
|
| 3120 |
-
constexpr int compare(const charT* s) const;
|
| 3121 |
-
```
|
| 3122 |
-
|
| 3123 |
-
*Effects:* Equivalent to: `return compare(basic_string_view(s));`
|
| 3124 |
-
|
| 3125 |
-
``` cpp
|
| 3126 |
-
constexpr int compare(size_type pos1, size_type n1, const charT* s) const;
|
| 3127 |
-
```
|
| 3128 |
-
|
| 3129 |
-
*Effects:* Equivalent to:
|
| 3130 |
-
`return substr(pos1, n1).compare(basic_string_view(s));`
|
| 3131 |
-
|
| 3132 |
-
``` cpp
|
| 3133 |
-
constexpr int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const;
|
| 3134 |
-
```
|
| 3135 |
-
|
| 3136 |
-
*Effects:* Equivalent to:
|
| 3137 |
-
`return substr(pos1, n1).compare(basic_string_view(s, n2));`
|
| 3138 |
-
|
| 3139 |
-
``` cpp
|
| 3140 |
-
constexpr bool starts_with(basic_string_view x) const noexcept;
|
| 3141 |
-
```
|
| 3142 |
-
|
| 3143 |
-
*Effects:* Equivalent to: `return substr(0, x.size()) == x;`
|
| 3144 |
-
|
| 3145 |
-
``` cpp
|
| 3146 |
-
constexpr bool starts_with(charT x) const noexcept;
|
| 3147 |
-
```
|
| 3148 |
-
|
| 3149 |
-
*Effects:* Equivalent to: `return !empty() && traits::eq(front(), x);`
|
| 3150 |
-
|
| 3151 |
-
``` cpp
|
| 3152 |
-
constexpr bool starts_with(const charT* x) const;
|
| 3153 |
-
```
|
| 3154 |
-
|
| 3155 |
-
*Effects:* Equivalent to: `return starts_with(basic_string_view(x));`
|
| 3156 |
-
|
| 3157 |
-
``` cpp
|
| 3158 |
-
constexpr bool ends_with(basic_string_view x) const noexcept;
|
| 3159 |
-
```
|
| 3160 |
-
|
| 3161 |
-
*Effects:* Equivalent to:
|
| 3162 |
-
|
| 3163 |
-
``` cpp
|
| 3164 |
-
return size() >= x.size() && compare(size() - x.size(), npos, x) == 0;
|
| 3165 |
-
```
|
| 3166 |
-
|
| 3167 |
-
``` cpp
|
| 3168 |
-
constexpr bool ends_with(charT x) const noexcept;
|
| 3169 |
-
```
|
| 3170 |
-
|
| 3171 |
-
*Effects:* Equivalent to: `return !empty() && traits::eq(back(), x);`
|
| 3172 |
-
|
| 3173 |
-
``` cpp
|
| 3174 |
-
constexpr bool ends_with(const charT* x) const;
|
| 3175 |
-
```
|
| 3176 |
-
|
| 3177 |
-
*Effects:* Equivalent to: `return ends_with(basic_string_view(x));`
|
| 3178 |
-
|
| 3179 |
-
#### Searching <a id="string.view.find">[[string.view.find]]</a>
|
| 3180 |
-
|
| 3181 |
-
Member functions in this subclause have complexity
|
| 3182 |
-
𝑂(`size() * str.size()`) at worst, although implementations should do
|
| 3183 |
-
better.
|
| 3184 |
-
|
| 3185 |
-
Let *F* be one of `find`, `rfind`, `find_first_of`, `find_last_of`,
|
| 3186 |
-
`find_first_not_of`, and `find_last_not_of`.
|
| 3187 |
-
|
| 3188 |
-
- Each member function of the form
|
| 3189 |
-
``` cpp
|
| 3190 |
-
constexpr return-type F(const charT* s, size_type pos) const;
|
| 3191 |
-
```
|
| 3192 |
-
|
| 3193 |
-
has effects equivalent to: `return F(basic_string_view(s), pos);`
|
| 3194 |
-
- Each member function of the form
|
| 3195 |
-
``` cpp
|
| 3196 |
-
constexpr return-type F(const charT* s, size_type pos, size_type n) const;
|
| 3197 |
-
```
|
| 3198 |
-
|
| 3199 |
-
has effects equivalent to: `return F(basic_string_view(s, n), pos);`
|
| 3200 |
-
- Each member function of the form
|
| 3201 |
-
``` cpp
|
| 3202 |
-
constexpr return-type F(charT c, size_type pos) const noexcept;
|
| 3203 |
-
```
|
| 3204 |
-
|
| 3205 |
-
has effects equivalent to:
|
| 3206 |
-
`return F(basic_string_view(addressof(c), 1), pos);`
|
| 3207 |
-
|
| 3208 |
-
``` cpp
|
| 3209 |
-
constexpr size_type find(basic_string_view str, size_type pos = 0) const noexcept;
|
| 3210 |
-
```
|
| 3211 |
-
|
| 3212 |
-
Let `xpos` be the lowest position, if possible, such that the following
|
| 3213 |
-
conditions hold:
|
| 3214 |
-
|
| 3215 |
-
- `pos <= xpos`
|
| 3216 |
-
- `xpos + str.size() <= size()`
|
| 3217 |
-
- `traits::eq(at(xpos + I), str.at(I))` for all elements `I` of the
|
| 3218 |
-
string referenced by `str`.
|
| 3219 |
-
|
| 3220 |
-
*Effects:* Determines `xpos`.
|
| 3221 |
-
|
| 3222 |
-
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 3223 |
-
Otherwise, returns `npos`.
|
| 3224 |
-
|
| 3225 |
-
``` cpp
|
| 3226 |
-
constexpr size_type rfind(basic_string_view str, size_type pos = npos) const noexcept;
|
| 3227 |
-
```
|
| 3228 |
-
|
| 3229 |
-
Let `xpos` be the highest position, if possible, such that the following
|
| 3230 |
-
conditions hold:
|
| 3231 |
-
|
| 3232 |
-
- `xpos <= pos`
|
| 3233 |
-
- `xpos + str.size() <= size()`
|
| 3234 |
-
- `traits::eq(at(xpos + I), str.at(I))` for all elements `I` of the
|
| 3235 |
-
string referenced by `str`.
|
| 3236 |
-
|
| 3237 |
-
*Effects:* Determines `xpos`.
|
| 3238 |
-
|
| 3239 |
-
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 3240 |
-
Otherwise, returns `npos`.
|
| 3241 |
-
|
| 3242 |
-
``` cpp
|
| 3243 |
-
constexpr size_type find_first_of(basic_string_view str, size_type pos = 0) const noexcept;
|
| 3244 |
-
```
|
| 3245 |
-
|
| 3246 |
-
Let `xpos` be the lowest position, if possible, such that the following
|
| 3247 |
-
conditions hold:
|
| 3248 |
-
|
| 3249 |
-
- `pos <= xpos`
|
| 3250 |
-
- `xpos < size()`
|
| 3251 |
-
- `traits::eq(at(xpos), str.at(I))` for some element `I` of the string
|
| 3252 |
-
referenced by `str`.
|
| 3253 |
-
|
| 3254 |
-
*Effects:* Determines `xpos`.
|
| 3255 |
-
|
| 3256 |
-
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 3257 |
-
Otherwise, returns `npos`.
|
| 3258 |
-
|
| 3259 |
-
``` cpp
|
| 3260 |
-
constexpr size_type find_last_of(basic_string_view str, size_type pos = npos) const noexcept;
|
| 3261 |
-
```
|
| 3262 |
-
|
| 3263 |
-
Let `xpos` be the highest position, if possible, such that the following
|
| 3264 |
-
conditions hold:
|
| 3265 |
-
|
| 3266 |
-
- `xpos <= pos`
|
| 3267 |
-
- `xpos < size()`
|
| 3268 |
-
- `traits::eq(at(xpos), str.at(I))` for some element `I` of the string
|
| 3269 |
-
referenced by `str`.
|
| 3270 |
-
|
| 3271 |
-
*Effects:* Determines `xpos`.
|
| 3272 |
-
|
| 3273 |
-
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 3274 |
-
Otherwise, returns `npos`.
|
| 3275 |
-
|
| 3276 |
-
``` cpp
|
| 3277 |
-
constexpr size_type find_first_not_of(basic_string_view str, size_type pos = 0) const noexcept;
|
| 3278 |
-
```
|
| 3279 |
-
|
| 3280 |
-
Let `xpos` be the lowest position, if possible, such that the following
|
| 3281 |
-
conditions hold:
|
| 3282 |
-
|
| 3283 |
-
- `pos <= xpos`
|
| 3284 |
-
- `xpos < size()`
|
| 3285 |
-
- `traits::eq(at(xpos), str.at(I))` for no element `I` of the string
|
| 3286 |
-
referenced by `str`.
|
| 3287 |
-
|
| 3288 |
-
*Effects:* Determines `xpos`.
|
| 3289 |
-
|
| 3290 |
-
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 3291 |
-
Otherwise, returns `npos`.
|
| 3292 |
-
|
| 3293 |
-
``` cpp
|
| 3294 |
-
constexpr size_type find_last_not_of(basic_string_view str, size_type pos = npos) const noexcept;
|
| 3295 |
-
```
|
| 3296 |
-
|
| 3297 |
-
Let `xpos` be the highest position, if possible, such that the following
|
| 3298 |
-
conditions hold:
|
| 3299 |
-
|
| 3300 |
-
- `xpos <= pos`
|
| 3301 |
-
- `xpos < size()`
|
| 3302 |
-
- `traits::eq(at(xpos), str.at(I))` for no element `I` of the string
|
| 3303 |
-
referenced by `str`.
|
| 3304 |
-
|
| 3305 |
-
*Effects:* Determines `xpos`.
|
| 3306 |
-
|
| 3307 |
-
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 3308 |
-
Otherwise, returns `npos`.
|
| 3309 |
-
|
| 3310 |
-
### Deduction guide <a id="string.view.deduct">[[string.view.deduct]]</a>
|
| 3311 |
-
|
| 3312 |
-
``` cpp
|
| 3313 |
-
template<class It, class End>
|
| 3314 |
-
basic_string_view(It, End) -> basic_string_view<iter_value_t<It>>;
|
| 3315 |
-
```
|
| 3316 |
-
|
| 3317 |
-
*Constraints:*
|
| 3318 |
-
|
| 3319 |
-
- `It` satisfies `contiguous_iterator`.
|
| 3320 |
-
- `End` satisfies `sized_sentinel_for<It>`.
|
| 3321 |
-
|
| 3322 |
-
### Non-member comparison functions <a id="string.view.comparison">[[string.view.comparison]]</a>
|
| 3323 |
-
|
| 3324 |
-
Let `S` be `basic_string_view<charT, traits>`, and `sv` be an instance
|
| 3325 |
-
of `S`. Implementations shall provide sufficient additional overloads
|
| 3326 |
-
marked `constexpr` and `noexcept` so that an object `t` with an implicit
|
| 3327 |
-
conversion to `S` can be compared according to
|
| 3328 |
-
[[string.view.comparison.overloads]].
|
| 3329 |
-
|
| 3330 |
-
**Table: Additional `basic_string_view` comparison overloads** <a id="string.view.comparison.overloads">[string.view.comparison.overloads]</a>
|
| 3331 |
-
|
| 3332 |
-
| Expression | Equivalent to |
|
| 3333 |
-
| ---------- | ------------- |
|
| 3334 |
-
| `t == sv` | `S(t) == sv` |
|
| 3335 |
-
| `sv == t` | `sv == S(t)` |
|
| 3336 |
-
| `t != sv` | `S(t) != sv` |
|
| 3337 |
-
| `sv != t` | `sv != S(t)` |
|
| 3338 |
-
| `t < sv` | `S(t) < sv` |
|
| 3339 |
-
| `sv < t` | `sv < S(t)` |
|
| 3340 |
-
| `t > sv` | `S(t) > sv` |
|
| 3341 |
-
| `sv > t` | `sv > S(t)` |
|
| 3342 |
-
| `t <= sv` | `S(t) <= sv` |
|
| 3343 |
-
| `sv <= t` | `sv <= S(t)` |
|
| 3344 |
-
| `t >= sv` | `S(t) >= sv` |
|
| 3345 |
-
| `sv >= t` | `sv >= S(t)` |
|
| 3346 |
-
| `t <=> sv` | `S(t) <=> sv` |
|
| 3347 |
-
| `sv <=> t` | `sv <=> S(t)` |
|
| 3348 |
-
|
| 3349 |
-
|
| 3350 |
-
[*Example 1*:
|
| 3351 |
-
|
| 3352 |
-
A sample conforming implementation for `operator==` would be:
|
| 3353 |
-
|
| 3354 |
-
``` cpp
|
| 3355 |
-
template<class charT, class traits>
|
| 3356 |
-
constexpr bool operator==(basic_string_view<charT, traits> lhs,
|
| 3357 |
-
basic_string_view<charT, traits> rhs) noexcept {
|
| 3358 |
-
return lhs.compare(rhs) == 0;
|
| 3359 |
-
}
|
| 3360 |
-
template<class charT, class traits>
|
| 3361 |
-
constexpr bool operator==(basic_string_view<charT, traits> lhs,
|
| 3362 |
-
type_identity_t<basic_string_view<charT, traits>> rhs) noexcept {
|
| 3363 |
-
return lhs.compare(rhs) == 0;
|
| 3364 |
-
}
|
| 3365 |
-
```
|
| 3366 |
-
|
| 3367 |
-
— *end example*]
|
| 3368 |
-
|
| 3369 |
-
``` cpp
|
| 3370 |
-
template<class charT, class traits>
|
| 3371 |
-
constexpr bool operator==(basic_string_view<charT, traits> lhs,
|
| 3372 |
-
basic_string_view<charT, traits> rhs) noexcept;
|
| 3373 |
-
```
|
| 3374 |
-
|
| 3375 |
-
*Returns:* `lhs.compare(rhs) == 0`.
|
| 3376 |
-
|
| 3377 |
-
``` cpp
|
| 3378 |
-
template<class charT, class traits>
|
| 3379 |
-
constexpr see below operator<=>(basic_string_view<charT, traits> lhs,
|
| 3380 |
-
\itcorr basic_string_view<charT, traits> rhs) noexcept;
|
| 3381 |
-
```
|
| 3382 |
-
|
| 3383 |
-
Let `R` denote the type `traits::comparison_category` if it exists,
|
| 3384 |
-
otherwise `R` is `weak_ordering`.
|
| 3385 |
-
|
| 3386 |
-
*Returns:* `static_cast<R>(lhs.compare(rhs) <=> 0)`.
|
| 3387 |
-
|
| 3388 |
-
### Inserters and extractors <a id="string.view.io">[[string.view.io]]</a>
|
| 3389 |
-
|
| 3390 |
-
``` cpp
|
| 3391 |
-
template<class charT, class traits>
|
| 3392 |
-
basic_ostream<charT, traits>&
|
| 3393 |
-
operator<<(basic_ostream<charT, traits>& os, basic_string_view<charT, traits> str);
|
| 3394 |
-
```
|
| 3395 |
-
|
| 3396 |
-
*Effects:* Behaves as a formatted output
|
| 3397 |
-
function [[ostream.formatted.reqmts]] of `os`. Forms a character
|
| 3398 |
-
sequence `seq`, initially consisting of the elements defined by the
|
| 3399 |
-
range \[`str.begin()`, `str.end()`). Determines padding for `seq` as
|
| 3400 |
-
described in [[ostream.formatted.reqmts]]. Then inserts `seq` as if by
|
| 3401 |
-
calling `os.rdbuf()->sputn(seq, n)`, where `n` is the larger of
|
| 3402 |
-
`os.width()` and `str.size()`; then calls `os.width(0)`.
|
| 3403 |
-
|
| 3404 |
-
*Returns:* `os`
|
| 3405 |
-
|
| 3406 |
-
### Hash support <a id="string.view.hash">[[string.view.hash]]</a>
|
| 3407 |
-
|
| 3408 |
-
``` cpp
|
| 3409 |
-
template<> struct hash<string_view>;
|
| 3410 |
-
template<> struct hash<u8string_view>;
|
| 3411 |
-
template<> struct hash<u16string_view>;
|
| 3412 |
-
template<> struct hash<u32string_view>;
|
| 3413 |
-
template<> struct hash<wstring_view>;
|
| 3414 |
-
```
|
| 3415 |
-
|
| 3416 |
-
The specialization is enabled [[unord.hash]].
|
| 3417 |
-
|
| 3418 |
-
[*Note 1*: The hash value of a string view object is equal to the hash
|
| 3419 |
-
value of the corresponding string
|
| 3420 |
-
object [[basic.string.hash]]. — *end note*]
|
| 3421 |
-
|
| 3422 |
-
### Suffix for `basic_string_view` literals <a id="string.view.literals">[[string.view.literals]]</a>
|
| 3423 |
-
|
| 3424 |
-
``` cpp
|
| 3425 |
-
constexpr string_view operator""sv(const char* str, size_t len) noexcept;
|
| 3426 |
-
```
|
| 3427 |
-
|
| 3428 |
-
*Returns:* `string_view{str, len}`.
|
| 3429 |
-
|
| 3430 |
-
``` cpp
|
| 3431 |
-
constexpr u8string_view operator""sv(const char8_t* str, size_t len) noexcept;
|
| 3432 |
-
```
|
| 3433 |
-
|
| 3434 |
-
*Returns:* `u8string_view{str, len}`.
|
| 3435 |
-
|
| 3436 |
-
``` cpp
|
| 3437 |
-
constexpr u16string_view operator""sv(const char16_t* str, size_t len) noexcept;
|
| 3438 |
-
```
|
| 3439 |
-
|
| 3440 |
-
*Returns:* `u16string_view{str, len}`.
|
| 3441 |
-
|
| 3442 |
-
``` cpp
|
| 3443 |
-
constexpr u32string_view operator""sv(const char32_t* str, size_t len) noexcept;
|
| 3444 |
-
```
|
| 3445 |
-
|
| 3446 |
-
*Returns:* `u32string_view{str, len}`.
|
| 3447 |
-
|
| 3448 |
-
``` cpp
|
| 3449 |
-
constexpr wstring_view operator""sv(const wchar_t* str, size_t len) noexcept;
|
| 3450 |
-
```
|
| 3451 |
-
|
| 3452 |
-
*Returns:* `wstring_view{str, len}`.
|
| 3453 |
-
|
| 3454 |
## Null-terminated sequence utilities <a id="c.strings">[[c.strings]]</a>
|
| 3455 |
|
| 3456 |
### Header `<cctype>` synopsis <a id="cctype.syn">[[cctype.syn]]</a>
|
| 3457 |
|
| 3458 |
``` cpp
|
|
@@ -3633,11 +3848,11 @@ namespace std {
|
|
| 3633 |
wchar_t* wcstok(wchar_t* s1, const wchar_t* s2, wchar_t** ptr);
|
| 3634 |
const wchar_t* wmemchr(const wchar_t* s, wchar_t c, size_t n); // see [library.c]
|
| 3635 |
wchar_t* wmemchr(wchar_t* s, wchar_t c, size_t n); // see [library.c]
|
| 3636 |
size_t wcslen(const wchar_t* s);
|
| 3637 |
wchar_t* wmemset(wchar_t* s, wchar_t c, size_t n);
|
| 3638 |
-
size_t wcsftime(wchar_t* s, size_t maxsize, const wchar_t* format, const
|
| 3639 |
wint_t btowc(int c);
|
| 3640 |
int wctob(wint_t c);
|
| 3641 |
|
| 3642 |
// [c.mb.wcs], multibyte / wide string and character conversion functions
|
| 3643 |
int mbsinit(const mbstate_t* ps);
|
|
@@ -3748,22 +3963,24 @@ next multibyte character is complete and valid, it determines the values
|
|
| 3748 |
of the corresponding UTF-8 code units and then, if `pc8` is not a null
|
| 3749 |
pointer, stores the value of the first (or only) such code unit in the
|
| 3750 |
object pointed to by `pc8`. Subsequent calls will store successive UTF-8
|
| 3751 |
code units without consuming any additional input until all the code
|
| 3752 |
units have been stored. If the corresponding Unicode character is
|
| 3753 |
-
U+0000, the resulting state described is the initial conversion
|
|
|
|
| 3754 |
|
| 3755 |
*Returns:* The first of the following that applies (given the current
|
| 3756 |
conversion state):
|
| 3757 |
|
| 3758 |
- `0`, if the next `n` or fewer bytes complete the multibyte character
|
| 3759 |
-
that corresponds to the U+0000 Unicode character (which is the
|
| 3760 |
-
stored).
|
| 3761 |
- between `1` and `n` (inclusive), if the next n or fewer bytes complete
|
| 3762 |
-
a valid multibyte character (
|
| 3763 |
-
returned is the number of bytes that complete the
|
| 3764 |
-
|
|
|
|
| 3765 |
has been stored (no bytes from the input have been consumed by this
|
| 3766 |
call).
|
| 3767 |
- `(size_t)(-2)`, if the next `n` bytes contribute to an incomplete (but
|
| 3768 |
potentially valid) multibyte character, and all `n` bytes have been
|
| 3769 |
processed (no value is stored).
|
|
@@ -3796,62 +4013,69 @@ conversion state is unspecified.
|
|
| 3796 |
*Remarks:* Calls to `c8rtomb` with a null pointer argument for `s` may
|
| 3797 |
introduce a data race [[res.on.data.races]] with other calls to
|
| 3798 |
`c8rtomb` with a null pointer argument for `s`.
|
| 3799 |
|
| 3800 |
<!-- Link reference definitions -->
|
|
|
|
| 3801 |
[basic.string]: #basic.string
|
|
|
|
| 3802 |
[basic.string.hash]: #basic.string.hash
|
| 3803 |
[basic.string.literals]: #basic.string.literals
|
| 3804 |
-
[basic.types]: basic.md#basic.types
|
| 3805 |
[c.mb.wcs]: #c.mb.wcs
|
| 3806 |
[c.strings]: #c.strings
|
| 3807 |
[cctype.syn]: #cctype.syn
|
| 3808 |
[char.traits]: #char.traits
|
|
|
|
| 3809 |
[char.traits.req]: #char.traits.req
|
| 3810 |
[char.traits.require]: #char.traits.require
|
| 3811 |
[char.traits.specializations]: #char.traits.specializations
|
| 3812 |
[char.traits.specializations.char]: #char.traits.specializations.char
|
| 3813 |
[char.traits.specializations.char16.t]: #char.traits.specializations.char16.t
|
| 3814 |
[char.traits.specializations.char32.t]: #char.traits.specializations.char32.t
|
| 3815 |
[char.traits.specializations.char8.t]: #char.traits.specializations.char8.t
|
|
|
|
| 3816 |
[char.traits.specializations.wchar.t]: #char.traits.specializations.wchar.t
|
| 3817 |
[char.traits.typedefs]: #char.traits.typedefs
|
|
|
|
|
|
|
| 3818 |
[container.requirements]: containers.md#container.requirements
|
| 3819 |
[container.requirements.general]: containers.md#container.requirements.general
|
| 3820 |
-
[container.seq.req]: containers.md#container.seq.req
|
| 3821 |
[cpp17.copyassignable]: #cpp17.copyassignable
|
| 3822 |
[cpp17.copyconstructible]: #cpp17.copyconstructible
|
| 3823 |
[cpp17.defaultconstructible]: #cpp17.defaultconstructible
|
| 3824 |
[cpp17.destructible]: #cpp17.destructible
|
| 3825 |
[cstring.syn]: #cstring.syn
|
| 3826 |
[cuchar.syn]: #cuchar.syn
|
| 3827 |
[cwchar.syn]: #cwchar.syn
|
| 3828 |
[cwctype.syn]: #cwctype.syn
|
| 3829 |
-
[defns.character.container]:
|
| 3830 |
[input.output]: input.md#input.output
|
| 3831 |
[intro.object]: basic.md#intro.object
|
| 3832 |
-
[iostate.flags]: input.md#iostate.flags
|
| 3833 |
[iostream.forward]: input.md#iostream.forward
|
| 3834 |
[iostreams.limits.pos]: input.md#iostreams.limits.pos
|
| 3835 |
[istream.formatted.reqmts]: input.md#istream.formatted.reqmts
|
| 3836 |
[istream.unformatted]: input.md#istream.unformatted
|
| 3837 |
[iterator.concept.contiguous]: iterators.md#iterator.concept.contiguous
|
|
|
|
| 3838 |
[iterator.range]: iterators.md#iterator.range
|
| 3839 |
[iterator.requirements.general]: iterators.md#iterator.requirements.general
|
| 3840 |
[library.c]: library.md#library.c
|
| 3841 |
[ostream.formatted.reqmts]: input.md#ostream.formatted.reqmts
|
| 3842 |
[random.access.iterators]: iterators.md#random.access.iterators
|
| 3843 |
[res.on.data.races]: library.md#res.on.data.races
|
|
|
|
| 3844 |
[string.access]: #string.access
|
| 3845 |
[string.accessors]: #string.accessors
|
| 3846 |
[string.append]: #string.append
|
| 3847 |
[string.assign]: #string.assign
|
| 3848 |
[string.capacity]: #string.capacity
|
| 3849 |
[string.classes]: #string.classes
|
|
|
|
| 3850 |
[string.cmp]: #string.cmp
|
| 3851 |
[string.compare]: #string.compare
|
| 3852 |
[string.cons]: #string.cons
|
|
|
|
| 3853 |
[string.conversions]: #string.conversions
|
| 3854 |
[string.copy]: #string.copy
|
| 3855 |
[string.ends.with]: #string.ends.with
|
| 3856 |
[string.erase]: #string.erase
|
| 3857 |
[string.erasure]: #string.erasure
|
|
@@ -3878,26 +4102,34 @@ introduce a data race [[res.on.data.races]] with other calls to
|
|
| 3878 |
[string.view.comparison]: #string.view.comparison
|
| 3879 |
[string.view.comparison.overloads]: #string.view.comparison.overloads
|
| 3880 |
[string.view.cons]: #string.view.cons
|
| 3881 |
[string.view.deduct]: #string.view.deduct
|
| 3882 |
[string.view.find]: #string.view.find
|
|
|
|
| 3883 |
[string.view.hash]: #string.view.hash
|
| 3884 |
[string.view.io]: #string.view.io
|
| 3885 |
[string.view.iterators]: #string.view.iterators
|
| 3886 |
[string.view.literals]: #string.view.literals
|
| 3887 |
[string.view.modifiers]: #string.view.modifiers
|
| 3888 |
[string.view.ops]: #string.view.ops
|
| 3889 |
[string.view.synop]: #string.view.synop
|
| 3890 |
[string.view.template]: #string.view.template
|
|
|
|
| 3891 |
[strings]: #strings
|
| 3892 |
[strings.general]: #strings.general
|
| 3893 |
[strings.summary]: #strings.summary
|
| 3894 |
[support.signal]: support.md#support.signal
|
|
|
|
|
|
|
|
|
|
| 3895 |
[unord.hash]: utilities.md#unord.hash
|
| 3896 |
[utility.swap]: utilities.md#utility.swap
|
| 3897 |
|
| 3898 |
[^1]: If `eof()` can be held in `char_type` then some iostreams
|
| 3899 |
operations can give surprising results.
|
| 3900 |
|
| 3901 |
-
[^2]:
|
|
|
|
|
|
|
|
|
|
| 3902 |
[[string.special]], `operator>{}>()` [[string.io]], and `getline()`
|
| 3903 |
[[string.io]], or as an argument to `basic_string::swap()`.
|
|
|
|
| 1 |
# Strings library <a id="strings">[[strings]]</a>
|
| 2 |
|
| 3 |
## General <a id="strings.general">[[strings.general]]</a>
|
| 4 |
|
| 5 |
This Clause describes components for manipulating sequences of any
|
| 6 |
+
non-array trivial standard-layout [[term.standard.layout.type]] type.
|
| 7 |
+
Such types are called *char-like types*, and objects of char-like types
|
| 8 |
+
are called *char-like objects* or simply *characters*.
|
| 9 |
|
| 10 |
The following subclauses describe a character traits class, string
|
| 11 |
classes, and null-terminated sequence utilities, as summarized in
|
| 12 |
[[strings.summary]].
|
| 13 |
|
| 14 |
## Character traits <a id="char.traits">[[char.traits]]</a>
|
| 15 |
|
| 16 |
+
### General <a id="char.traits.general">[[char.traits.general]]</a>
|
| 17 |
+
|
| 18 |
+
Subclause [[char.traits]] defines requirements on classes representing
|
| 19 |
+
*character traits*, and defines a class template `char_traits<charT>`,
|
| 20 |
+
along with five specializations, `char_traits<char>`,
|
| 21 |
+
`char_traits<char8_t>`, `char_traits<char16_t>`,
|
| 22 |
+
`char_traits<char32_t>`, and `char_traits<wchar_t>`, that meet those
|
| 23 |
+
requirements.
|
| 24 |
|
| 25 |
Most classes specified in [[string.classes]], [[string.view]], and
|
| 26 |
[[input.output]] need a set of related types and functions to complete
|
| 27 |
the definition of their semantics. These types and functions are
|
| 28 |
provided as a set of member *typedef-name*s and functions in the
|
| 29 |
+
template parameter `traits` used by each such template. Subclause
|
| 30 |
+
[[char.traits]] defines the semantics of these members.
|
| 31 |
|
| 32 |
To specialize those templates to generate a string, string view, or
|
| 33 |
iostream class to handle a particular character container type
|
| 34 |
[[defns.character.container]] `C`, that and its related character traits
|
| 35 |
class `X` are passed as a pair of parameters to the string, string view,
|
|
|
|
| 41 |
In [[char.traits.req]], `X` denotes a traits class defining types and
|
| 42 |
functions for the character container type `C`; `c` and `d` denote
|
| 43 |
values of type `C`; `p` and `q` denote values of type `const C*`; `s`
|
| 44 |
denotes a value of type `C*`; `n`, `i` and `j` denote values of type
|
| 45 |
`size_t`; `e` and `f` denote values of type `X::int_type`; `pos` denotes
|
| 46 |
+
a value of type `X::pos_type`; and `r` denotes an lvalue of type `C`. No
|
| 47 |
+
expression which is part of the character traits requirements specified
|
| 48 |
+
in this subclause [[char.traits.require]] shall exit via an exception.
|
| 49 |
|
| 50 |
The class template
|
| 51 |
|
| 52 |
``` cpp
|
| 53 |
template<class charT> struct char_traits;
|
|
|
|
| 76 |
([[cpp17.copyconstructible]]), and *Cpp17DefaultConstructible*
|
| 77 |
([[cpp17.defaultconstructible]]) requirements.
|
| 78 |
|
| 79 |
### `char_traits` specializations <a id="char.traits.specializations">[[char.traits.specializations]]</a>
|
| 80 |
|
| 81 |
+
#### General <a id="char.traits.specializations.general">[[char.traits.specializations.general]]</a>
|
| 82 |
+
|
| 83 |
``` cpp
|
| 84 |
namespace std {
|
| 85 |
template<> struct char_traits<char>;
|
| 86 |
template<> struct char_traits<char8_t>;
|
| 87 |
template<> struct char_traits<char16_t>;
|
|
|
|
| 172 |
```
|
| 173 |
|
| 174 |
The two-argument members `assign`, `eq`, and `lt` are defined
|
| 175 |
identically to the built-in operators `=`, `==`, and `<` respectively.
|
| 176 |
|
| 177 |
+
The member `eof()` returns an *implementation-defined* constant that
|
| 178 |
cannot appear as a valid UTF-8 code unit.
|
| 179 |
|
| 180 |
#### `struct char_traits<char16_t>` <a id="char.traits.specializations.char16.t">[[char.traits.specializations.char16.t]]</a>
|
| 181 |
|
| 182 |
``` cpp
|
|
|
|
| 291 |
The two-argument members `assign`, `eq`, and `lt` are defined
|
| 292 |
identically to the built-in operators `=`, `==`, and `<`, respectively.
|
| 293 |
|
| 294 |
The member `eof()` returns `WEOF`.
|
| 295 |
|
| 296 |
+
## String view classes <a id="string.view">[[string.view]]</a>
|
| 297 |
+
|
| 298 |
+
### General <a id="string.view.general">[[string.view.general]]</a>
|
| 299 |
+
|
| 300 |
+
The class template `basic_string_view` describes an object that can
|
| 301 |
+
refer to a constant contiguous sequence of char-like [[strings.general]]
|
| 302 |
+
objects with the first element of the sequence at position zero. In the
|
| 303 |
+
rest of [[string.view]], the type of the char-like objects held in a
|
| 304 |
+
`basic_string_view` object is designated by `charT`.
|
| 305 |
+
|
| 306 |
+
[*Note 1*: The library provides implicit conversions from
|
| 307 |
+
`const charT*` and `std::basic_string<charT, ...>` to
|
| 308 |
+
`std::basic_string_view<charT, ...>` so that user code can accept just
|
| 309 |
+
`std::basic_string_view<charT>` as a non-templated parameter wherever a
|
| 310 |
+
sequence of characters is expected. User-defined types can define their
|
| 311 |
+
own implicit conversions to `std::basic_string_view<charT>` in order to
|
| 312 |
+
interoperate with these functions. — *end note*]
|
| 313 |
+
|
| 314 |
+
### Header `<string_view>` synopsis <a id="string.view.synop">[[string.view.synop]]</a>
|
| 315 |
+
|
| 316 |
+
``` cpp
|
| 317 |
+
#include <compare> // see [compare.syn]
|
| 318 |
+
|
| 319 |
+
namespace std {
|
| 320 |
+
// [string.view.template], class template basic_string_view
|
| 321 |
+
template<class charT, class traits = char_traits<charT>>
|
| 322 |
+
class basic_string_view;
|
| 323 |
+
|
| 324 |
+
template<class charT, class traits>
|
| 325 |
+
constexpr bool ranges::enable_view<basic_string_view<charT, traits>> = true;
|
| 326 |
+
template<class charT, class traits>
|
| 327 |
+
constexpr bool ranges::enable_borrowed_range<basic_string_view<charT, traits>> = true;
|
| 328 |
+
|
| 329 |
+
// [string.view.comparison], non-member comparison functions
|
| 330 |
+
template<class charT, class traits>
|
| 331 |
+
constexpr bool operator==(basic_string_view<charT, traits> x,
|
| 332 |
+
basic_string_view<charT, traits> y) noexcept;
|
| 333 |
+
template<class charT, class traits>
|
| 334 |
+
constexpr see below operator<=>(basic_string_view<charT, traits> x,
|
| 335 |
+
\itcorr basic_string_view<charT, traits> y) noexcept;
|
| 336 |
+
|
| 337 |
+
// see [string.view.comparison], sufficient additional overloads of comparison functions
|
| 338 |
+
|
| 339 |
+
// [string.view.io], inserters and extractors
|
| 340 |
+
template<class charT, class traits>
|
| 341 |
+
basic_ostream<charT, traits>&
|
| 342 |
+
operator<<(basic_ostream<charT, traits>& os,
|
| 343 |
+
basic_string_view<charT, traits> str);
|
| 344 |
+
|
| 345 |
+
// basic_string_view typedef-names
|
| 346 |
+
using string_view = basic_string_view<char>;
|
| 347 |
+
using u8string_view = basic_string_view<char8_t>;
|
| 348 |
+
using u16string_view = basic_string_view<char16_t>;
|
| 349 |
+
using u32string_view = basic_string_view<char32_t>;
|
| 350 |
+
using wstring_view = basic_string_view<wchar_t>;
|
| 351 |
+
|
| 352 |
+
// [string.view.hash], hash support
|
| 353 |
+
template<class T> struct hash;
|
| 354 |
+
template<> struct hash<string_view>;
|
| 355 |
+
template<> struct hash<u8string_view>;
|
| 356 |
+
template<> struct hash<u16string_view>;
|
| 357 |
+
template<> struct hash<u32string_view>;
|
| 358 |
+
template<> struct hash<wstring_view>;
|
| 359 |
+
|
| 360 |
+
inline namespace literals {
|
| 361 |
+
inline namespace string_view_literals {
|
| 362 |
+
// [string.view.literals], suffix for basic_string_view literals
|
| 363 |
+
constexpr string_view operator""sv(const char* str, size_t len) noexcept;
|
| 364 |
+
constexpr u8string_view operator""sv(const char8_t* str, size_t len) noexcept;
|
| 365 |
+
constexpr u16string_view operator""sv(const char16_t* str, size_t len) noexcept;
|
| 366 |
+
constexpr u32string_view operator""sv(const char32_t* str, size_t len) noexcept;
|
| 367 |
+
constexpr wstring_view operator""sv(const wchar_t* str, size_t len) noexcept;
|
| 368 |
+
}
|
| 369 |
+
}
|
| 370 |
+
}
|
| 371 |
+
```
|
| 372 |
+
|
| 373 |
+
The function templates defined in [[utility.swap]] and
|
| 374 |
+
[[iterator.range]] are available when `<string_view>` is included.
|
| 375 |
+
|
| 376 |
+
### Class template `basic_string_view` <a id="string.view.template">[[string.view.template]]</a>
|
| 377 |
+
|
| 378 |
+
#### General <a id="string.view.template.general">[[string.view.template.general]]</a>
|
| 379 |
+
|
| 380 |
+
``` cpp
|
| 381 |
+
namespace std {
|
| 382 |
+
template<class charT, class traits = char_traits<charT>>
|
| 383 |
+
class basic_string_view {
|
| 384 |
+
public:
|
| 385 |
+
// types
|
| 386 |
+
using traits_type = traits;
|
| 387 |
+
using value_type = charT;
|
| 388 |
+
using pointer = value_type*;
|
| 389 |
+
using const_pointer = const value_type*;
|
| 390 |
+
using reference = value_type&;
|
| 391 |
+
using const_reference = const value_type&;
|
| 392 |
+
using const_iterator = implementation-defined // type of basic_string_view::const_iterator; // see [string.view.iterators]
|
| 393 |
+
using iterator = const_iterator;
|
| 394 |
+
using const_reverse_iterator = reverse_iterator<const_iterator>;
|
| 395 |
+
using reverse_iterator = const_reverse_iterator;
|
| 396 |
+
using size_type = size_t;
|
| 397 |
+
using difference_type = ptrdiff_t;
|
| 398 |
+
static constexpr size_type npos = size_type(-1);
|
| 399 |
+
|
| 400 |
+
// [string.view.cons], construction and assignment
|
| 401 |
+
constexpr basic_string_view() noexcept;
|
| 402 |
+
constexpr basic_string_view(const basic_string_view&) noexcept = default;
|
| 403 |
+
constexpr basic_string_view& operator=(const basic_string_view&) noexcept = default;
|
| 404 |
+
constexpr basic_string_view(const charT* str);
|
| 405 |
+
basic_string_view(nullptr_t) = delete;
|
| 406 |
+
constexpr basic_string_view(const charT* str, size_type len);
|
| 407 |
+
template<class It, class End>
|
| 408 |
+
constexpr basic_string_view(It begin, End end);
|
| 409 |
+
template<class R>
|
| 410 |
+
constexpr explicit basic_string_view(R&& r);
|
| 411 |
+
|
| 412 |
+
// [string.view.iterators], iterator support
|
| 413 |
+
constexpr const_iterator begin() const noexcept;
|
| 414 |
+
constexpr const_iterator end() const noexcept;
|
| 415 |
+
constexpr const_iterator cbegin() const noexcept;
|
| 416 |
+
constexpr const_iterator cend() const noexcept;
|
| 417 |
+
constexpr const_reverse_iterator rbegin() const noexcept;
|
| 418 |
+
constexpr const_reverse_iterator rend() const noexcept;
|
| 419 |
+
constexpr const_reverse_iterator crbegin() const noexcept;
|
| 420 |
+
constexpr const_reverse_iterator crend() const noexcept;
|
| 421 |
+
|
| 422 |
+
// [string.view.capacity], capacity
|
| 423 |
+
constexpr size_type size() const noexcept;
|
| 424 |
+
constexpr size_type length() const noexcept;
|
| 425 |
+
constexpr size_type max_size() const noexcept;
|
| 426 |
+
[[nodiscard]] constexpr bool empty() const noexcept;
|
| 427 |
+
|
| 428 |
+
// [string.view.access], element access
|
| 429 |
+
constexpr const_reference operator[](size_type pos) const;
|
| 430 |
+
constexpr const_reference at(size_type pos) const;
|
| 431 |
+
constexpr const_reference front() const;
|
| 432 |
+
constexpr const_reference back() const;
|
| 433 |
+
constexpr const_pointer data() const noexcept;
|
| 434 |
+
|
| 435 |
+
// [string.view.modifiers], modifiers
|
| 436 |
+
constexpr void remove_prefix(size_type n);
|
| 437 |
+
constexpr void remove_suffix(size_type n);
|
| 438 |
+
constexpr void swap(basic_string_view& s) noexcept;
|
| 439 |
+
|
| 440 |
+
// [string.view.ops], string operations
|
| 441 |
+
constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
|
| 442 |
+
|
| 443 |
+
constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
|
| 444 |
+
|
| 445 |
+
constexpr int compare(basic_string_view s) const noexcept;
|
| 446 |
+
constexpr int compare(size_type pos1, size_type n1, basic_string_view s) const;
|
| 447 |
+
constexpr int compare(size_type pos1, size_type n1, basic_string_view s,
|
| 448 |
+
size_type pos2, size_type n2) const;
|
| 449 |
+
constexpr int compare(const charT* s) const;
|
| 450 |
+
constexpr int compare(size_type pos1, size_type n1, const charT* s) const;
|
| 451 |
+
constexpr int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const;
|
| 452 |
+
|
| 453 |
+
constexpr bool starts_with(basic_string_view x) const noexcept;
|
| 454 |
+
constexpr bool starts_with(charT x) const noexcept;
|
| 455 |
+
constexpr bool starts_with(const charT* x) const;
|
| 456 |
+
constexpr bool ends_with(basic_string_view x) const noexcept;
|
| 457 |
+
constexpr bool ends_with(charT x) const noexcept;
|
| 458 |
+
constexpr bool ends_with(const charT* x) const;
|
| 459 |
+
|
| 460 |
+
constexpr bool contains(basic_string_view x) const noexcept;
|
| 461 |
+
constexpr bool contains(charT x) const noexcept;
|
| 462 |
+
constexpr bool contains(const charT* x) const;
|
| 463 |
+
|
| 464 |
+
// [string.view.find], searching
|
| 465 |
+
constexpr size_type find(basic_string_view s, size_type pos = 0) const noexcept;
|
| 466 |
+
constexpr size_type find(charT c, size_type pos = 0) const noexcept;
|
| 467 |
+
constexpr size_type find(const charT* s, size_type pos, size_type n) const;
|
| 468 |
+
constexpr size_type find(const charT* s, size_type pos = 0) const;
|
| 469 |
+
constexpr size_type rfind(basic_string_view s, size_type pos = npos) const noexcept;
|
| 470 |
+
constexpr size_type rfind(charT c, size_type pos = npos) const noexcept;
|
| 471 |
+
constexpr size_type rfind(const charT* s, size_type pos, size_type n) const;
|
| 472 |
+
constexpr size_type rfind(const charT* s, size_type pos = npos) const;
|
| 473 |
+
|
| 474 |
+
constexpr size_type find_first_of(basic_string_view s, size_type pos = 0) const noexcept;
|
| 475 |
+
constexpr size_type find_first_of(charT c, size_type pos = 0) const noexcept;
|
| 476 |
+
constexpr size_type find_first_of(const charT* s, size_type pos, size_type n) const;
|
| 477 |
+
constexpr size_type find_first_of(const charT* s, size_type pos = 0) const;
|
| 478 |
+
constexpr size_type find_last_of(basic_string_view s, size_type pos = npos) const noexcept;
|
| 479 |
+
constexpr size_type find_last_of(charT c, size_type pos = npos) const noexcept;
|
| 480 |
+
constexpr size_type find_last_of(const charT* s, size_type pos, size_type n) const;
|
| 481 |
+
constexpr size_type find_last_of(const charT* s, size_type pos = npos) const;
|
| 482 |
+
constexpr size_type find_first_not_of(basic_string_view s, size_type pos = 0) const noexcept;
|
| 483 |
+
constexpr size_type find_first_not_of(charT c, size_type pos = 0) const noexcept;
|
| 484 |
+
constexpr size_type find_first_not_of(const charT* s, size_type pos,
|
| 485 |
+
size_type n) const;
|
| 486 |
+
constexpr size_type find_first_not_of(const charT* s, size_type pos = 0) const;
|
| 487 |
+
constexpr size_type find_last_not_of(basic_string_view s,
|
| 488 |
+
size_type pos = npos) const noexcept;
|
| 489 |
+
constexpr size_type find_last_not_of(charT c, size_type pos = npos) const noexcept;
|
| 490 |
+
constexpr size_type find_last_not_of(const charT* s, size_type pos,
|
| 491 |
+
size_type n) const;
|
| 492 |
+
constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
|
| 493 |
+
|
| 494 |
+
private:
|
| 495 |
+
const_pointer data_; // exposition only
|
| 496 |
+
size_type size_; // exposition only
|
| 497 |
+
};
|
| 498 |
+
|
| 499 |
+
// [string.view.deduct], deduction guides
|
| 500 |
+
template<class It, class End>
|
| 501 |
+
basic_string_view(It, End) -> basic_string_view<iter_value_t<It>>;
|
| 502 |
+
template<class R>
|
| 503 |
+
basic_string_view(R&&) -> basic_string_view<ranges::range_value_t<R>>;
|
| 504 |
+
}
|
| 505 |
+
```
|
| 506 |
+
|
| 507 |
+
[^2]
|
| 508 |
+
|
| 509 |
+
In every specialization `basic_string_view<charT, traits>`, the type
|
| 510 |
+
`traits` shall meet the character traits requirements [[char.traits]].
|
| 511 |
+
|
| 512 |
+
[*Note 1*: The program is ill-formed if `traits::char_type` is not the
|
| 513 |
+
same type as `charT`. — *end note*]
|
| 514 |
+
|
| 515 |
+
For a `basic_string_view str`, any operation that invalidates a pointer
|
| 516 |
+
in the range
|
| 517 |
+
|
| 518 |
+
``` cpp
|
| 519 |
+
{[}str.data(), {str.data() + str.size()}{)}
|
| 520 |
+
```
|
| 521 |
+
|
| 522 |
+
invalidates pointers, iterators, and references returned from `str`’s
|
| 523 |
+
member functions.
|
| 524 |
+
|
| 525 |
+
The complexity of `basic_string_view` member functions is 𝑂(1) unless
|
| 526 |
+
otherwise specified.
|
| 527 |
+
|
| 528 |
+
`basic_string_view<charT, traits>` is a trivially copyable type
|
| 529 |
+
[[term.trivially.copyable.type]].
|
| 530 |
+
|
| 531 |
+
#### Construction and assignment <a id="string.view.cons">[[string.view.cons]]</a>
|
| 532 |
+
|
| 533 |
+
``` cpp
|
| 534 |
+
constexpr basic_string_view() noexcept;
|
| 535 |
+
```
|
| 536 |
+
|
| 537 |
+
*Ensures:* `size_ == 0` and `data_ == nullptr`.
|
| 538 |
+
|
| 539 |
+
``` cpp
|
| 540 |
+
constexpr basic_string_view(const charT* str);
|
| 541 |
+
```
|
| 542 |
+
|
| 543 |
+
*Preconditions:* \[`str`, `str + traits::length(str)`) is a valid range.
|
| 544 |
+
|
| 545 |
+
*Effects:* Constructs a `basic_string_view`, initializing `data_` with
|
| 546 |
+
`str` and initializing `size_` with `traits::length(str)`.
|
| 547 |
+
|
| 548 |
+
*Complexity:* 𝑂(`traits::length(str)`).
|
| 549 |
+
|
| 550 |
+
``` cpp
|
| 551 |
+
constexpr basic_string_view(const charT* str, size_type len);
|
| 552 |
+
```
|
| 553 |
+
|
| 554 |
+
*Preconditions:* \[`str`, `str + len`) is a valid range.
|
| 555 |
+
|
| 556 |
+
*Effects:* Constructs a `basic_string_view`, initializing `data_` with
|
| 557 |
+
`str` and initializing `size_` with `len`.
|
| 558 |
+
|
| 559 |
+
``` cpp
|
| 560 |
+
template<class It, class End>
|
| 561 |
+
constexpr basic_string_view(It begin, End end);
|
| 562 |
+
```
|
| 563 |
+
|
| 564 |
+
*Constraints:*
|
| 565 |
+
|
| 566 |
+
- `It` satisfies `contiguous_iterator`.
|
| 567 |
+
- `End` satisfies `sized_sentinel_for<It>`.
|
| 568 |
+
- `is_same_v<iter_value_t<It>, charT>` is `true`.
|
| 569 |
+
- `is_convertible_v<End, size_type>` is `false`.
|
| 570 |
+
|
| 571 |
+
*Preconditions:*
|
| 572 |
+
|
| 573 |
+
- \[`begin`, `end`) is a valid range.
|
| 574 |
+
- `It` models `contiguous_iterator`.
|
| 575 |
+
- `End` models `sized_sentinel_for<It>`.
|
| 576 |
+
|
| 577 |
+
*Effects:* Initializes `data_` with `to_address(begin)` and initializes
|
| 578 |
+
`size_` with `end - begin`.
|
| 579 |
+
|
| 580 |
+
*Throws:* When and what `end - begin` throws.
|
| 581 |
+
|
| 582 |
+
``` cpp
|
| 583 |
+
template<class R>
|
| 584 |
+
constexpr explicit basic_string_view(R&& r);
|
| 585 |
+
```
|
| 586 |
+
|
| 587 |
+
Let `d` be an lvalue of type `remove_cvref_t<R>`.
|
| 588 |
+
|
| 589 |
+
*Constraints:*
|
| 590 |
+
|
| 591 |
+
- `remove_cvref_t<R>` is not the same type as `basic_string_view`,
|
| 592 |
+
- `R` models `ranges::contiguous_range` and `ranges::sized_range`,
|
| 593 |
+
- `is_same_v<ranges::range_value_t<R>, charT>` is `true`,
|
| 594 |
+
- `is_convertible_v<R, const charT*>` is `false`, and
|
| 595 |
+
- `d.operator ::std::basic_string_view<charT, traits>()` is not a valid
|
| 596 |
+
expression.
|
| 597 |
+
|
| 598 |
+
*Effects:* Initializes `data_` with `ranges::data(r)` and `size_` with
|
| 599 |
+
`ranges::size(r)`.
|
| 600 |
+
|
| 601 |
+
*Throws:* Any exception thrown by `ranges::data(r)` and
|
| 602 |
+
`ranges::size(r)`.
|
| 603 |
+
|
| 604 |
+
#### Deduction guides <a id="string.view.deduct">[[string.view.deduct]]</a>
|
| 605 |
+
|
| 606 |
+
``` cpp
|
| 607 |
+
template<class It, class End>
|
| 608 |
+
basic_string_view(It, End) -> basic_string_view<iter_value_t<It>>;
|
| 609 |
+
```
|
| 610 |
+
|
| 611 |
+
*Constraints:*
|
| 612 |
+
|
| 613 |
+
- `It` satisfies `contiguous_iterator`.
|
| 614 |
+
- `End` satisfies `sized_sentinel_for<It>`.
|
| 615 |
+
|
| 616 |
+
``` cpp
|
| 617 |
+
template<class R>
|
| 618 |
+
basic_string_view(R&&) -> basic_string_view<ranges::range_value_t<R>>;
|
| 619 |
+
```
|
| 620 |
+
|
| 621 |
+
*Constraints:* `R` satisfies `ranges::contiguous_range`.
|
| 622 |
+
|
| 623 |
+
#### Iterator support <a id="string.view.iterators">[[string.view.iterators]]</a>
|
| 624 |
+
|
| 625 |
+
``` cpp
|
| 626 |
+
using const_iterator = implementation-defined // type of basic_string_view::const_iterator;
|
| 627 |
+
```
|
| 628 |
+
|
| 629 |
+
A type that meets the requirements of a constant
|
| 630 |
+
*Cpp17RandomAccessIterator*[[random.access.iterators]], models
|
| 631 |
+
`contiguous_iterator` [[iterator.concept.contiguous]], and meets the
|
| 632 |
+
constexpr iterator requirements [[iterator.requirements.general]], whose
|
| 633 |
+
`value_type` is the template parameter `charT`.
|
| 634 |
+
|
| 635 |
+
All requirements on container iterators [[container.requirements]] apply
|
| 636 |
+
to `basic_string_view::const_iterator` as well.
|
| 637 |
+
|
| 638 |
+
``` cpp
|
| 639 |
+
constexpr const_iterator begin() const noexcept;
|
| 640 |
+
constexpr const_iterator cbegin() const noexcept;
|
| 641 |
+
```
|
| 642 |
+
|
| 643 |
+
*Returns:* An iterator such that
|
| 644 |
+
|
| 645 |
+
- if `!empty()`, `addressof(*begin()) == data_`,
|
| 646 |
+
- otherwise, an unspecified value such that \[`begin()`, `end()`) is a
|
| 647 |
+
valid range.
|
| 648 |
+
|
| 649 |
+
``` cpp
|
| 650 |
+
constexpr const_iterator end() const noexcept;
|
| 651 |
+
constexpr const_iterator cend() const noexcept;
|
| 652 |
+
```
|
| 653 |
+
|
| 654 |
+
*Returns:* `begin() + size()`.
|
| 655 |
+
|
| 656 |
+
``` cpp
|
| 657 |
+
constexpr const_reverse_iterator rbegin() const noexcept;
|
| 658 |
+
constexpr const_reverse_iterator crbegin() const noexcept;
|
| 659 |
+
```
|
| 660 |
+
|
| 661 |
+
*Returns:* `const_reverse_iterator(end())`.
|
| 662 |
+
|
| 663 |
+
``` cpp
|
| 664 |
+
constexpr const_reverse_iterator rend() const noexcept;
|
| 665 |
+
constexpr const_reverse_iterator crend() const noexcept;
|
| 666 |
+
```
|
| 667 |
+
|
| 668 |
+
*Returns:* `const_reverse_iterator(begin())`.
|
| 669 |
+
|
| 670 |
+
#### Capacity <a id="string.view.capacity">[[string.view.capacity]]</a>
|
| 671 |
+
|
| 672 |
+
``` cpp
|
| 673 |
+
constexpr size_type size() const noexcept;
|
| 674 |
+
constexpr size_type length() const noexcept;
|
| 675 |
+
```
|
| 676 |
+
|
| 677 |
+
*Returns:* `size_`.
|
| 678 |
+
|
| 679 |
+
``` cpp
|
| 680 |
+
constexpr size_type max_size() const noexcept;
|
| 681 |
+
```
|
| 682 |
+
|
| 683 |
+
*Returns:* The largest possible number of char-like objects that can be
|
| 684 |
+
referred to by a `basic_string_view`.
|
| 685 |
+
|
| 686 |
+
``` cpp
|
| 687 |
+
[[nodiscard]] constexpr bool empty() const noexcept;
|
| 688 |
+
```
|
| 689 |
+
|
| 690 |
+
*Returns:* `size_ == 0`.
|
| 691 |
+
|
| 692 |
+
#### Element access <a id="string.view.access">[[string.view.access]]</a>
|
| 693 |
+
|
| 694 |
+
``` cpp
|
| 695 |
+
constexpr const_reference operator[](size_type pos) const;
|
| 696 |
+
```
|
| 697 |
+
|
| 698 |
+
*Preconditions:* `pos < size()`.
|
| 699 |
+
|
| 700 |
+
*Returns:* `data_[pos]`.
|
| 701 |
+
|
| 702 |
+
*Throws:* Nothing.
|
| 703 |
+
|
| 704 |
+
[*Note 1*: Unlike `basic_string::operator[]`,
|
| 705 |
+
`basic_string_view::operator[](size())` has undefined behavior instead
|
| 706 |
+
of returning `charT()`. — *end note*]
|
| 707 |
+
|
| 708 |
+
``` cpp
|
| 709 |
+
constexpr const_reference at(size_type pos) const;
|
| 710 |
+
```
|
| 711 |
+
|
| 712 |
+
*Returns:* `data_[pos]`.
|
| 713 |
+
|
| 714 |
+
*Throws:* `out_of_range` if `pos >= size()`.
|
| 715 |
+
|
| 716 |
+
``` cpp
|
| 717 |
+
constexpr const_reference front() const;
|
| 718 |
+
```
|
| 719 |
+
|
| 720 |
+
*Preconditions:* `!empty()`.
|
| 721 |
+
|
| 722 |
+
*Returns:* `data_[0]`.
|
| 723 |
+
|
| 724 |
+
*Throws:* Nothing.
|
| 725 |
+
|
| 726 |
+
``` cpp
|
| 727 |
+
constexpr const_reference back() const;
|
| 728 |
+
```
|
| 729 |
+
|
| 730 |
+
*Preconditions:* `!empty()`.
|
| 731 |
+
|
| 732 |
+
*Returns:* `data_[size() - 1]`.
|
| 733 |
+
|
| 734 |
+
*Throws:* Nothing.
|
| 735 |
+
|
| 736 |
+
``` cpp
|
| 737 |
+
constexpr const_pointer data() const noexcept;
|
| 738 |
+
```
|
| 739 |
+
|
| 740 |
+
*Returns:* `data_`.
|
| 741 |
+
|
| 742 |
+
[*Note 2*: Unlike `basic_string::data()` and *string-literal*s,
|
| 743 |
+
`data()` can return a pointer to a buffer that is not null-terminated.
|
| 744 |
+
Therefore it is typically a mistake to pass `data()` to a function that
|
| 745 |
+
takes just a `const charT*` and expects a null-terminated
|
| 746 |
+
string. — *end note*]
|
| 747 |
+
|
| 748 |
+
#### Modifiers <a id="string.view.modifiers">[[string.view.modifiers]]</a>
|
| 749 |
+
|
| 750 |
+
``` cpp
|
| 751 |
+
constexpr void remove_prefix(size_type n);
|
| 752 |
+
```
|
| 753 |
+
|
| 754 |
+
*Preconditions:* `n <= size()`.
|
| 755 |
+
|
| 756 |
+
*Effects:* Equivalent to: `data_ += n; size_ -= n;`
|
| 757 |
+
|
| 758 |
+
``` cpp
|
| 759 |
+
constexpr void remove_suffix(size_type n);
|
| 760 |
+
```
|
| 761 |
+
|
| 762 |
+
*Preconditions:* `n <= size()`.
|
| 763 |
+
|
| 764 |
+
*Effects:* Equivalent to: `size_ -= n;`
|
| 765 |
+
|
| 766 |
+
``` cpp
|
| 767 |
+
constexpr void swap(basic_string_view& s) noexcept;
|
| 768 |
+
```
|
| 769 |
+
|
| 770 |
+
*Effects:* Exchanges the values of `*this` and `s`.
|
| 771 |
+
|
| 772 |
+
#### String operations <a id="string.view.ops">[[string.view.ops]]</a>
|
| 773 |
+
|
| 774 |
+
``` cpp
|
| 775 |
+
constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
|
| 776 |
+
```
|
| 777 |
+
|
| 778 |
+
Let `rlen` be the smaller of `n` and `size() - pos`.
|
| 779 |
+
|
| 780 |
+
*Preconditions:* \[`s`, `s + rlen`) is a valid range.
|
| 781 |
+
|
| 782 |
+
*Effects:* Equivalent to `traits::copy(s, data() + pos, rlen)`.
|
| 783 |
+
|
| 784 |
+
*Returns:* `rlen`.
|
| 785 |
+
|
| 786 |
+
*Throws:* `out_of_range` if `pos > size()`.
|
| 787 |
+
|
| 788 |
+
*Complexity:* 𝑂(`rlen`).
|
| 789 |
+
|
| 790 |
+
``` cpp
|
| 791 |
+
constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
|
| 792 |
+
```
|
| 793 |
+
|
| 794 |
+
Let `rlen` be the smaller of `n` and `size() - pos`.
|
| 795 |
+
|
| 796 |
+
*Effects:* Determines `rlen`, the effective length of the string to
|
| 797 |
+
reference.
|
| 798 |
+
|
| 799 |
+
*Returns:* `basic_string_view(data() + pos, rlen)`.
|
| 800 |
+
|
| 801 |
+
*Throws:* `out_of_range` if `pos > size()`.
|
| 802 |
+
|
| 803 |
+
``` cpp
|
| 804 |
+
constexpr int compare(basic_string_view str) const noexcept;
|
| 805 |
+
```
|
| 806 |
+
|
| 807 |
+
Let `rlen` be the smaller of `size()` and `str.size()`.
|
| 808 |
+
|
| 809 |
+
*Effects:* Determines `rlen`, the effective length of the strings to
|
| 810 |
+
compare. The function then compares the two strings by calling
|
| 811 |
+
`traits::compare(data(), str.data(), rlen)`.
|
| 812 |
+
|
| 813 |
+
*Returns:* The nonzero result if the result of the comparison is
|
| 814 |
+
nonzero. Otherwise, returns a value as indicated in
|
| 815 |
+
[[string.view.compare]].
|
| 816 |
+
|
| 817 |
+
**Table: `compare()` results** <a id="string.view.compare">[string.view.compare]</a>
|
| 818 |
+
|
| 819 |
+
| Condition | Return Value |
|
| 820 |
+
| ---------------------- | ------------ |
|
| 821 |
+
| `size() < str.size()` | `< 0` |
|
| 822 |
+
| `size() == str.size()` | ` 0` |
|
| 823 |
+
| `size() > str.size()` | `> 0` |
|
| 824 |
+
|
| 825 |
+
|
| 826 |
+
*Complexity:* 𝑂(`rlen`).
|
| 827 |
+
|
| 828 |
+
``` cpp
|
| 829 |
+
constexpr int compare(size_type pos1, size_type n1, basic_string_view str) const;
|
| 830 |
+
```
|
| 831 |
+
|
| 832 |
+
*Effects:* Equivalent to: `return substr(pos1, n1).compare(str);`
|
| 833 |
+
|
| 834 |
+
``` cpp
|
| 835 |
+
constexpr int compare(size_type pos1, size_type n1, basic_string_view str,
|
| 836 |
+
size_type pos2, size_type n2) const;
|
| 837 |
+
```
|
| 838 |
+
|
| 839 |
+
*Effects:* Equivalent to:
|
| 840 |
+
`return substr(pos1, n1).compare(str.substr(pos2, n2));`
|
| 841 |
+
|
| 842 |
+
``` cpp
|
| 843 |
+
constexpr int compare(const charT* s) const;
|
| 844 |
+
```
|
| 845 |
+
|
| 846 |
+
*Effects:* Equivalent to: `return compare(basic_string_view(s));`
|
| 847 |
+
|
| 848 |
+
``` cpp
|
| 849 |
+
constexpr int compare(size_type pos1, size_type n1, const charT* s) const;
|
| 850 |
+
```
|
| 851 |
+
|
| 852 |
+
*Effects:* Equivalent to:
|
| 853 |
+
`return substr(pos1, n1).compare(basic_string_view(s));`
|
| 854 |
+
|
| 855 |
+
``` cpp
|
| 856 |
+
constexpr int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const;
|
| 857 |
+
```
|
| 858 |
+
|
| 859 |
+
*Effects:* Equivalent to:
|
| 860 |
+
`return substr(pos1, n1).compare(basic_string_view(s, n2));`
|
| 861 |
+
|
| 862 |
+
``` cpp
|
| 863 |
+
constexpr bool starts_with(basic_string_view x) const noexcept;
|
| 864 |
+
```
|
| 865 |
+
|
| 866 |
+
*Effects:* Equivalent to: `return substr(0, x.size()) == x;`
|
| 867 |
+
|
| 868 |
+
``` cpp
|
| 869 |
+
constexpr bool starts_with(charT x) const noexcept;
|
| 870 |
+
```
|
| 871 |
+
|
| 872 |
+
*Effects:* Equivalent to: `return !empty() && traits::eq(front(), x);`
|
| 873 |
+
|
| 874 |
+
``` cpp
|
| 875 |
+
constexpr bool starts_with(const charT* x) const;
|
| 876 |
+
```
|
| 877 |
+
|
| 878 |
+
*Effects:* Equivalent to: `return starts_with(basic_string_view(x));`
|
| 879 |
+
|
| 880 |
+
``` cpp
|
| 881 |
+
constexpr bool ends_with(basic_string_view x) const noexcept;
|
| 882 |
+
```
|
| 883 |
+
|
| 884 |
+
*Effects:* Equivalent to:
|
| 885 |
+
|
| 886 |
+
``` cpp
|
| 887 |
+
return size() >= x.size() && compare(size() - x.size(), npos, x) == 0;
|
| 888 |
+
```
|
| 889 |
+
|
| 890 |
+
``` cpp
|
| 891 |
+
constexpr bool ends_with(charT x) const noexcept;
|
| 892 |
+
```
|
| 893 |
+
|
| 894 |
+
*Effects:* Equivalent to: `return !empty() && traits::eq(back(), x);`
|
| 895 |
+
|
| 896 |
+
``` cpp
|
| 897 |
+
constexpr bool ends_with(const charT* x) const;
|
| 898 |
+
```
|
| 899 |
+
|
| 900 |
+
*Effects:* Equivalent to: `return ends_with(basic_string_view(x));`
|
| 901 |
+
|
| 902 |
+
``` cpp
|
| 903 |
+
constexpr bool contains(basic_string_view x) const noexcept;
|
| 904 |
+
constexpr bool contains(charT x) const noexcept;
|
| 905 |
+
constexpr bool contains(const charT* x) const;
|
| 906 |
+
```
|
| 907 |
+
|
| 908 |
+
*Effects:* Equivalent to: `return find(x) != npos;`
|
| 909 |
+
|
| 910 |
+
#### Searching <a id="string.view.find">[[string.view.find]]</a>
|
| 911 |
+
|
| 912 |
+
Member functions in this subclause have complexity
|
| 913 |
+
𝑂(`size() * str.size()`) at worst, although implementations should do
|
| 914 |
+
better.
|
| 915 |
+
|
| 916 |
+
Let *F* be one of `find`, `rfind`, `find_first_of`, `find_last_of`,
|
| 917 |
+
`find_first_not_of`, and `find_last_not_of`.
|
| 918 |
+
|
| 919 |
+
- Each member function of the form
|
| 920 |
+
``` cpp
|
| 921 |
+
constexpr return-type F(const charT* s, size_type pos) const;
|
| 922 |
+
```
|
| 923 |
+
|
| 924 |
+
has effects equivalent to: `return F(basic_string_view(s), pos);`
|
| 925 |
+
- Each member function of the form
|
| 926 |
+
``` cpp
|
| 927 |
+
constexpr return-type F(const charT* s, size_type pos, size_type n) const;
|
| 928 |
+
```
|
| 929 |
+
|
| 930 |
+
has effects equivalent to: `return F(basic_string_view(s, n), pos);`
|
| 931 |
+
- Each member function of the form
|
| 932 |
+
``` cpp
|
| 933 |
+
constexpr return-type F(charT c, size_type pos) const noexcept;
|
| 934 |
+
```
|
| 935 |
+
|
| 936 |
+
has effects equivalent to:
|
| 937 |
+
`return F(basic_string_view(addressof(c), 1), pos);`
|
| 938 |
+
|
| 939 |
+
``` cpp
|
| 940 |
+
constexpr size_type find(basic_string_view str, size_type pos = 0) const noexcept;
|
| 941 |
+
```
|
| 942 |
+
|
| 943 |
+
Let `xpos` be the lowest position, if possible, such that the following
|
| 944 |
+
conditions hold:
|
| 945 |
+
|
| 946 |
+
- `pos <= xpos`
|
| 947 |
+
- `xpos + str.size() <= size()`
|
| 948 |
+
- `traits::eq(at(xpos + I), str.at(I))` for all elements `I` of the
|
| 949 |
+
string referenced by `str`.
|
| 950 |
+
|
| 951 |
+
*Effects:* Determines `xpos`.
|
| 952 |
+
|
| 953 |
+
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 954 |
+
Otherwise, returns `npos`.
|
| 955 |
+
|
| 956 |
+
``` cpp
|
| 957 |
+
constexpr size_type rfind(basic_string_view str, size_type pos = npos) const noexcept;
|
| 958 |
+
```
|
| 959 |
+
|
| 960 |
+
Let `xpos` be the highest position, if possible, such that the following
|
| 961 |
+
conditions hold:
|
| 962 |
+
|
| 963 |
+
- `xpos <= pos`
|
| 964 |
+
- `xpos + str.size() <= size()`
|
| 965 |
+
- `traits::eq(at(xpos + I), str.at(I))` for all elements `I` of the
|
| 966 |
+
string referenced by `str`.
|
| 967 |
+
|
| 968 |
+
*Effects:* Determines `xpos`.
|
| 969 |
+
|
| 970 |
+
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 971 |
+
Otherwise, returns `npos`.
|
| 972 |
+
|
| 973 |
+
``` cpp
|
| 974 |
+
constexpr size_type find_first_of(basic_string_view str, size_type pos = 0) const noexcept;
|
| 975 |
+
```
|
| 976 |
+
|
| 977 |
+
Let `xpos` be the lowest position, if possible, such that the following
|
| 978 |
+
conditions hold:
|
| 979 |
+
|
| 980 |
+
- `pos <= xpos`
|
| 981 |
+
- `xpos < size()`
|
| 982 |
+
- `traits::eq(at(xpos), str.at(I))` for some element `I` of the string
|
| 983 |
+
referenced by `str`.
|
| 984 |
+
|
| 985 |
+
*Effects:* Determines `xpos`.
|
| 986 |
+
|
| 987 |
+
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 988 |
+
Otherwise, returns `npos`.
|
| 989 |
+
|
| 990 |
+
``` cpp
|
| 991 |
+
constexpr size_type find_last_of(basic_string_view str, size_type pos = npos) const noexcept;
|
| 992 |
+
```
|
| 993 |
+
|
| 994 |
+
Let `xpos` be the highest position, if possible, such that the following
|
| 995 |
+
conditions hold:
|
| 996 |
+
|
| 997 |
+
- `xpos <= pos`
|
| 998 |
+
- `xpos < size()`
|
| 999 |
+
- `traits::eq(at(xpos), str.at(I))` for some element `I` of the string
|
| 1000 |
+
referenced by `str`.
|
| 1001 |
+
|
| 1002 |
+
*Effects:* Determines `xpos`.
|
| 1003 |
+
|
| 1004 |
+
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 1005 |
+
Otherwise, returns `npos`.
|
| 1006 |
+
|
| 1007 |
+
``` cpp
|
| 1008 |
+
constexpr size_type find_first_not_of(basic_string_view str, size_type pos = 0) const noexcept;
|
| 1009 |
+
```
|
| 1010 |
+
|
| 1011 |
+
Let `xpos` be the lowest position, if possible, such that the following
|
| 1012 |
+
conditions hold:
|
| 1013 |
+
|
| 1014 |
+
- `pos <= xpos`
|
| 1015 |
+
- `xpos < size()`
|
| 1016 |
+
- `traits::eq(at(xpos), str.at(I))` for no element `I` of the string
|
| 1017 |
+
referenced by `str`.
|
| 1018 |
+
|
| 1019 |
+
*Effects:* Determines `xpos`.
|
| 1020 |
+
|
| 1021 |
+
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 1022 |
+
Otherwise, returns `npos`.
|
| 1023 |
+
|
| 1024 |
+
``` cpp
|
| 1025 |
+
constexpr size_type find_last_not_of(basic_string_view str, size_type pos = npos) const noexcept;
|
| 1026 |
+
```
|
| 1027 |
+
|
| 1028 |
+
Let `xpos` be the highest position, if possible, such that the following
|
| 1029 |
+
conditions hold:
|
| 1030 |
+
|
| 1031 |
+
- `xpos <= pos`
|
| 1032 |
+
- `xpos < size()`
|
| 1033 |
+
- `traits::eq(at(xpos), str.at(I))` for no element `I` of the string
|
| 1034 |
+
referenced by `str`.
|
| 1035 |
+
|
| 1036 |
+
*Effects:* Determines `xpos`.
|
| 1037 |
+
|
| 1038 |
+
*Returns:* `xpos` if the function can determine such a value for `xpos`.
|
| 1039 |
+
Otherwise, returns `npos`.
|
| 1040 |
+
|
| 1041 |
+
### Non-member comparison functions <a id="string.view.comparison">[[string.view.comparison]]</a>
|
| 1042 |
+
|
| 1043 |
+
Let `S` be `basic_string_view<charT, traits>`, and `sv` be an instance
|
| 1044 |
+
of `S`. Implementations shall provide sufficient additional overloads
|
| 1045 |
+
marked `constexpr` and `noexcept` so that an object `t` with an implicit
|
| 1046 |
+
conversion to `S` can be compared according to
|
| 1047 |
+
[[string.view.comparison.overloads]].
|
| 1048 |
+
|
| 1049 |
+
**Table: Additional `basic_string_view` comparison overloads** <a id="string.view.comparison.overloads">[string.view.comparison.overloads]</a>
|
| 1050 |
+
|
| 1051 |
+
| Expression | Equivalent to |
|
| 1052 |
+
| ---------- | ------------- |
|
| 1053 |
+
| `t == sv` | `S(t) == sv` |
|
| 1054 |
+
| `sv == t` | `sv == S(t)` |
|
| 1055 |
+
| `t != sv` | `S(t) != sv` |
|
| 1056 |
+
| `sv != t` | `sv != S(t)` |
|
| 1057 |
+
| `t < sv` | `S(t) < sv` |
|
| 1058 |
+
| `sv < t` | `sv < S(t)` |
|
| 1059 |
+
| `t > sv` | `S(t) > sv` |
|
| 1060 |
+
| `sv > t` | `sv > S(t)` |
|
| 1061 |
+
| `t <= sv` | `S(t) <= sv` |
|
| 1062 |
+
| `sv <= t` | `sv <= S(t)` |
|
| 1063 |
+
| `t >= sv` | `S(t) >= sv` |
|
| 1064 |
+
| `sv >= t` | `sv >= S(t)` |
|
| 1065 |
+
| `t <=> sv` | `S(t) <=> sv` |
|
| 1066 |
+
| `sv <=> t` | `sv <=> S(t)` |
|
| 1067 |
+
|
| 1068 |
+
|
| 1069 |
+
[*Example 1*:
|
| 1070 |
+
|
| 1071 |
+
A sample conforming implementation for `operator==` would be:
|
| 1072 |
+
|
| 1073 |
+
``` cpp
|
| 1074 |
+
template<class charT, class traits>
|
| 1075 |
+
constexpr bool operator==(basic_string_view<charT, traits> lhs,
|
| 1076 |
+
basic_string_view<charT, traits> rhs) noexcept {
|
| 1077 |
+
return lhs.compare(rhs) == 0;
|
| 1078 |
+
}
|
| 1079 |
+
template<class charT, class traits>
|
| 1080 |
+
constexpr bool operator==(basic_string_view<charT, traits> lhs,
|
| 1081 |
+
type_identity_t<basic_string_view<charT, traits>> rhs) noexcept {
|
| 1082 |
+
return lhs.compare(rhs) == 0;
|
| 1083 |
+
}
|
| 1084 |
+
```
|
| 1085 |
+
|
| 1086 |
+
— *end example*]
|
| 1087 |
+
|
| 1088 |
+
``` cpp
|
| 1089 |
+
template<class charT, class traits>
|
| 1090 |
+
constexpr bool operator==(basic_string_view<charT, traits> lhs,
|
| 1091 |
+
basic_string_view<charT, traits> rhs) noexcept;
|
| 1092 |
+
```
|
| 1093 |
+
|
| 1094 |
+
*Returns:* `lhs.compare(rhs) == 0`.
|
| 1095 |
+
|
| 1096 |
+
``` cpp
|
| 1097 |
+
template<class charT, class traits>
|
| 1098 |
+
constexpr see below operator<=>(basic_string_view<charT, traits> lhs,
|
| 1099 |
+
\itcorr basic_string_view<charT, traits> rhs) noexcept;
|
| 1100 |
+
```
|
| 1101 |
+
|
| 1102 |
+
Let `R` denote the type `traits::comparison_category` if that
|
| 1103 |
+
*qualified-id* is valid and denotes a type [[temp.deduct]], otherwise
|
| 1104 |
+
`R` is `weak_ordering`.
|
| 1105 |
+
|
| 1106 |
+
*Mandates:* `R` denotes a comparison category type [[cmp.categories]].
|
| 1107 |
+
|
| 1108 |
+
*Returns:* `static_cast<R>(lhs.compare(rhs) <=> 0)`.
|
| 1109 |
+
|
| 1110 |
+
### Inserters and extractors <a id="string.view.io">[[string.view.io]]</a>
|
| 1111 |
+
|
| 1112 |
+
``` cpp
|
| 1113 |
+
template<class charT, class traits>
|
| 1114 |
+
basic_ostream<charT, traits>&
|
| 1115 |
+
operator<<(basic_ostream<charT, traits>& os, basic_string_view<charT, traits> str);
|
| 1116 |
+
```
|
| 1117 |
+
|
| 1118 |
+
*Effects:* Behaves as a formatted output
|
| 1119 |
+
function [[ostream.formatted.reqmts]] of `os`. Forms a character
|
| 1120 |
+
sequence `seq`, initially consisting of the elements defined by the
|
| 1121 |
+
range \[`str.begin()`, `str.end()`). Determines padding for `seq` as
|
| 1122 |
+
described in [[ostream.formatted.reqmts]]. Then inserts `seq` as if by
|
| 1123 |
+
calling `os.rdbuf()->sputn(seq, n)`, where `n` is the larger of
|
| 1124 |
+
`os.width()` and `str.size()`; then calls `os.width(0)`.
|
| 1125 |
+
|
| 1126 |
+
*Returns:* `os`
|
| 1127 |
+
|
| 1128 |
+
### Hash support <a id="string.view.hash">[[string.view.hash]]</a>
|
| 1129 |
+
|
| 1130 |
+
``` cpp
|
| 1131 |
+
template<> struct hash<string_view>;
|
| 1132 |
+
template<> struct hash<u8string_view>;
|
| 1133 |
+
template<> struct hash<u16string_view>;
|
| 1134 |
+
template<> struct hash<u32string_view>;
|
| 1135 |
+
template<> struct hash<wstring_view>;
|
| 1136 |
+
```
|
| 1137 |
+
|
| 1138 |
+
The specialization is enabled [[unord.hash]].
|
| 1139 |
+
|
| 1140 |
+
[*Note 1*: The hash value of a string view object is equal to the hash
|
| 1141 |
+
value of the corresponding string
|
| 1142 |
+
object [[basic.string.hash]]. — *end note*]
|
| 1143 |
+
|
| 1144 |
+
### Suffix for `basic_string_view` literals <a id="string.view.literals">[[string.view.literals]]</a>
|
| 1145 |
+
|
| 1146 |
+
``` cpp
|
| 1147 |
+
constexpr string_view operator""sv(const char* str, size_t len) noexcept;
|
| 1148 |
+
```
|
| 1149 |
+
|
| 1150 |
+
*Returns:* `string_view{str, len}`.
|
| 1151 |
+
|
| 1152 |
+
``` cpp
|
| 1153 |
+
constexpr u8string_view operator""sv(const char8_t* str, size_t len) noexcept;
|
| 1154 |
+
```
|
| 1155 |
+
|
| 1156 |
+
*Returns:* `u8string_view{str, len}`.
|
| 1157 |
+
|
| 1158 |
+
``` cpp
|
| 1159 |
+
constexpr u16string_view operator""sv(const char16_t* str, size_t len) noexcept;
|
| 1160 |
+
```
|
| 1161 |
+
|
| 1162 |
+
*Returns:* `u16string_view{str, len}`.
|
| 1163 |
+
|
| 1164 |
+
``` cpp
|
| 1165 |
+
constexpr u32string_view operator""sv(const char32_t* str, size_t len) noexcept;
|
| 1166 |
+
```
|
| 1167 |
+
|
| 1168 |
+
*Returns:* `u32string_view{str, len}`.
|
| 1169 |
+
|
| 1170 |
+
``` cpp
|
| 1171 |
+
constexpr wstring_view operator""sv(const wchar_t* str, size_t len) noexcept;
|
| 1172 |
+
```
|
| 1173 |
+
|
| 1174 |
+
*Returns:* `wstring_view{str, len}`.
|
| 1175 |
+
|
| 1176 |
## String classes <a id="string.classes">[[string.classes]]</a>
|
| 1177 |
|
| 1178 |
+
### General <a id="string.classes.general">[[string.classes.general]]</a>
|
| 1179 |
+
|
| 1180 |
The header `<string>` defines the `basic_string` class template for
|
| 1181 |
manipulating varying-length sequences of char-like objects and five
|
| 1182 |
*typedef-name*s, `string`, `u8string`, `u16string`, `u32string`, and
|
| 1183 |
`wstring`, that name the specializations `basic_string<char>`,
|
| 1184 |
`basic_string<char8_t>`, `basic_string<char16_t>`,
|
|
|
|
| 1308 |
erase(basic_string<charT, traits, Allocator>& c, const U& value);
|
| 1309 |
template<class charT, class traits, class Allocator, class Predicate>
|
| 1310 |
constexpr typename basic_string<charT, traits, Allocator>::size_type
|
| 1311 |
erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred);
|
| 1312 |
|
| 1313 |
+
// basic_string typedef-names
|
| 1314 |
using string = basic_string<char>;
|
| 1315 |
using u8string = basic_string<char8_t>;
|
| 1316 |
using u16string = basic_string<char16_t>;
|
| 1317 |
using u32string = basic_string<char32_t>;
|
| 1318 |
using wstring = basic_string<wchar_t>;
|
|
|
|
| 1365 |
using wstring = basic_string<wchar_t>;
|
| 1366 |
}
|
| 1367 |
|
| 1368 |
// [basic.string.hash], hash support
|
| 1369 |
template<class T> struct hash;
|
| 1370 |
+
template<class A> struct hash<basic_string<char, char_traits<char>, A>>;
|
| 1371 |
+
template<class A> struct hash<basic_string<char8_t, char_traits<char8_t>, A>>;
|
| 1372 |
+
template<class A> struct hash<basic_string<char16_t, char_traits<char16_t>, A>>;
|
| 1373 |
+
template<class A> struct hash<basic_string<char32_t, char_traits<char32_t>, A>>;
|
| 1374 |
+
template<class A> struct hash<basic_string<wchar_t, char_traits<wchar_t>, A>>;
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1375 |
|
| 1376 |
inline namespace literals {
|
| 1377 |
inline namespace string_literals {
|
| 1378 |
// [basic.string.literals], suffix for basic_string literals
|
| 1379 |
constexpr string operator""s(const char* str, size_t len);
|
|
|
|
| 1386 |
}
|
| 1387 |
```
|
| 1388 |
|
| 1389 |
### Class template `basic_string` <a id="basic.string">[[basic.string]]</a>
|
| 1390 |
|
| 1391 |
+
#### General <a id="basic.string.general">[[basic.string.general]]</a>
|
| 1392 |
+
|
| 1393 |
The class template `basic_string` describes objects that can store a
|
| 1394 |
sequence consisting of a varying number of arbitrary char-like objects
|
| 1395 |
with the first element of the sequence at position zero. Such a sequence
|
| 1396 |
is also called a “string” if the type of the char-like objects that it
|
| 1397 |
+
holds is clear from context. In the rest of [[basic.string]], the type
|
| 1398 |
+
of the char-like objects held in a `basic_string` object is designated
|
| 1399 |
+
by `charT`.
|
| 1400 |
|
| 1401 |
A specialization of `basic_string` is a contiguous container
|
| 1402 |
+
[[container.reqmts]].
|
| 1403 |
|
| 1404 |
In all cases, \[`data()`, `data() + size()`\] is a valid range,
|
| 1405 |
`data() + size()` points at an object with value `charT()` (a “null
|
| 1406 |
terminator”), and `size() <= capacity()` is `true`.
|
| 1407 |
|
|
|
|
| 1424 |
|
| 1425 |
using iterator = implementation-defined // type of basic_string::iterator; // see [container.requirements]
|
| 1426 |
using const_iterator = implementation-defined // type of basic_string::const_iterator; // see [container.requirements]
|
| 1427 |
using reverse_iterator = std::reverse_iterator<iterator>;
|
| 1428 |
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
|
| 1429 |
+
static constexpr size_type npos = size_type(-1);
|
| 1430 |
|
| 1431 |
// [string.cons], construct/copy/destroy
|
| 1432 |
constexpr basic_string() noexcept(noexcept(Allocator())) : basic_string(Allocator()) { }
|
| 1433 |
constexpr explicit basic_string(const Allocator& a) noexcept;
|
| 1434 |
constexpr basic_string(const basic_string& str);
|
| 1435 |
constexpr basic_string(basic_string&& str) noexcept;
|
| 1436 |
constexpr basic_string(const basic_string& str, size_type pos,
|
| 1437 |
const Allocator& a = Allocator());
|
| 1438 |
constexpr basic_string(const basic_string& str, size_type pos, size_type n,
|
| 1439 |
const Allocator& a = Allocator());
|
| 1440 |
+
constexpr basic_string(basic_string&& str, size_type pos,
|
| 1441 |
+
const Allocator& a = Allocator());
|
| 1442 |
+
constexpr basic_string(basic_string&& str, size_type pos, size_type n,
|
| 1443 |
+
const Allocator& a = Allocator());
|
| 1444 |
template<class T>
|
| 1445 |
constexpr basic_string(const T& t, size_type pos, size_type n,
|
| 1446 |
const Allocator& a = Allocator());
|
| 1447 |
template<class T>
|
| 1448 |
constexpr explicit basic_string(const T& t, const Allocator& a = Allocator());
|
| 1449 |
constexpr basic_string(const charT* s, size_type n, const Allocator& a = Allocator());
|
| 1450 |
constexpr basic_string(const charT* s, const Allocator& a = Allocator());
|
| 1451 |
+
basic_string(nullptr_t) = delete;
|
| 1452 |
constexpr basic_string(size_type n, charT c, const Allocator& a = Allocator());
|
| 1453 |
template<class InputIterator>
|
| 1454 |
constexpr basic_string(InputIterator begin, InputIterator end,
|
| 1455 |
const Allocator& a = Allocator());
|
| 1456 |
+
template<container-compatible-range<charT> R>
|
| 1457 |
+
constexpr basic_string(from_range_t, R&& rg, const Allocator& a = Allocator());
|
| 1458 |
constexpr basic_string(initializer_list<charT>, const Allocator& = Allocator());
|
| 1459 |
constexpr basic_string(const basic_string&, const Allocator&);
|
| 1460 |
constexpr basic_string(basic_string&&, const Allocator&);
|
| 1461 |
constexpr ~basic_string();
|
| 1462 |
|
|
|
|
| 1465 |
noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
|
| 1466 |
allocator_traits<Allocator>::is_always_equal::value);
|
| 1467 |
template<class T>
|
| 1468 |
constexpr basic_string& operator=(const T& t);
|
| 1469 |
constexpr basic_string& operator=(const charT* s);
|
| 1470 |
+
basic_string& operator=(nullptr_t) = delete;
|
| 1471 |
constexpr basic_string& operator=(charT c);
|
| 1472 |
constexpr basic_string& operator=(initializer_list<charT>);
|
| 1473 |
|
| 1474 |
// [string.iterators], iterators
|
| 1475 |
constexpr iterator begin() noexcept;
|
|
|
|
| 1491 |
constexpr size_type size() const noexcept;
|
| 1492 |
constexpr size_type length() const noexcept;
|
| 1493 |
constexpr size_type max_size() const noexcept;
|
| 1494 |
constexpr void resize(size_type n, charT c);
|
| 1495 |
constexpr void resize(size_type n);
|
| 1496 |
+
template<class Operation> constexpr void resize_and_overwrite(size_type n, Operation op);
|
| 1497 |
constexpr size_type capacity() const noexcept;
|
| 1498 |
constexpr void reserve(size_type res_arg);
|
| 1499 |
constexpr void shrink_to_fit();
|
| 1500 |
constexpr void clear() noexcept;
|
| 1501 |
[[nodiscard]] constexpr bool empty() const noexcept;
|
|
|
|
| 1527 |
constexpr basic_string& append(const charT* s, size_type n);
|
| 1528 |
constexpr basic_string& append(const charT* s);
|
| 1529 |
constexpr basic_string& append(size_type n, charT c);
|
| 1530 |
template<class InputIterator>
|
| 1531 |
constexpr basic_string& append(InputIterator first, InputIterator last);
|
| 1532 |
+
template<container-compatible-range<charT> R>
|
| 1533 |
+
constexpr basic_string& append_range(R&& rg);
|
| 1534 |
constexpr basic_string& append(initializer_list<charT>);
|
| 1535 |
|
| 1536 |
constexpr void push_back(charT c);
|
| 1537 |
|
| 1538 |
constexpr basic_string& assign(const basic_string& str);
|
|
|
|
| 1547 |
constexpr basic_string& assign(const charT* s, size_type n);
|
| 1548 |
constexpr basic_string& assign(const charT* s);
|
| 1549 |
constexpr basic_string& assign(size_type n, charT c);
|
| 1550 |
template<class InputIterator>
|
| 1551 |
constexpr basic_string& assign(InputIterator first, InputIterator last);
|
| 1552 |
+
template<container-compatible-range<charT> R>
|
| 1553 |
+
constexpr basic_string& assign_range(R&& rg);
|
| 1554 |
constexpr basic_string& assign(initializer_list<charT>);
|
| 1555 |
|
| 1556 |
constexpr basic_string& insert(size_type pos, const basic_string& str);
|
| 1557 |
constexpr basic_string& insert(size_type pos1, const basic_string& str,
|
| 1558 |
size_type pos2, size_type n = npos);
|
|
|
|
| 1566 |
constexpr basic_string& insert(size_type pos, size_type n, charT c);
|
| 1567 |
constexpr iterator insert(const_iterator p, charT c);
|
| 1568 |
constexpr iterator insert(const_iterator p, size_type n, charT c);
|
| 1569 |
template<class InputIterator>
|
| 1570 |
constexpr iterator insert(const_iterator p, InputIterator first, InputIterator last);
|
| 1571 |
+
template<container-compatible-range<charT> R>
|
| 1572 |
+
constexpr iterator insert_range(const_iterator p, R&& rg);
|
| 1573 |
constexpr iterator insert(const_iterator p, initializer_list<charT>);
|
| 1574 |
|
| 1575 |
constexpr basic_string& erase(size_type pos = 0, size_type n = npos);
|
| 1576 |
constexpr iterator erase(const_iterator p);
|
| 1577 |
constexpr iterator erase(const_iterator first, const_iterator last);
|
|
|
|
| 1598 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, const charT* s);
|
| 1599 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, size_type n, charT c);
|
| 1600 |
template<class InputIterator>
|
| 1601 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2,
|
| 1602 |
InputIterator j1, InputIterator j2);
|
| 1603 |
+
template<container-compatible-range<charT> R>
|
| 1604 |
+
constexpr basic_string& replace_with_range(const_iterator i1, const_iterator i2, R&& rg);
|
| 1605 |
constexpr basic_string& replace(const_iterator, const_iterator, initializer_list<charT>);
|
| 1606 |
|
| 1607 |
constexpr size_type copy(charT* s, size_type n, size_type pos = 0) const;
|
| 1608 |
|
| 1609 |
constexpr void swap(basic_string& str)
|
|
|
|
| 1660 |
size_type pos = npos) const noexcept;
|
| 1661 |
constexpr size_type find_last_not_of(const charT* s, size_type pos, size_type n) const;
|
| 1662 |
constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
|
| 1663 |
constexpr size_type find_last_not_of(charT c, size_type pos = npos) const noexcept;
|
| 1664 |
|
| 1665 |
+
constexpr basic_string substr(size_type pos = 0, size_type n = npos) const &;
|
| 1666 |
+
constexpr basic_string substr(size_type pos = 0, size_type n = npos) &&;
|
| 1667 |
|
| 1668 |
template<class T>
|
| 1669 |
constexpr int compare(const T& t) const noexcept(see below);
|
| 1670 |
template<class T>
|
| 1671 |
constexpr int compare(size_type pos1, size_type n1, const T& t) const;
|
|
|
|
| 1684 |
constexpr bool starts_with(charT x) const noexcept;
|
| 1685 |
constexpr bool starts_with(const charT* x) const;
|
| 1686 |
constexpr bool ends_with(basic_string_view<charT, traits> x) const noexcept;
|
| 1687 |
constexpr bool ends_with(charT x) const noexcept;
|
| 1688 |
constexpr bool ends_with(const charT* x) const;
|
| 1689 |
+
|
| 1690 |
+
constexpr bool contains(basic_string_view<charT, traits> x) const noexcept;
|
| 1691 |
+
constexpr bool contains(charT x) const noexcept;
|
| 1692 |
+
constexpr bool contains(const charT* x) const;
|
| 1693 |
};
|
| 1694 |
|
| 1695 |
template<class InputIterator,
|
| 1696 |
class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
|
| 1697 |
basic_string(InputIterator, InputIterator, Allocator = Allocator())
|
| 1698 |
-> basic_string<typename iterator_traits<InputIterator>::value_type,
|
| 1699 |
char_traits<typename iterator_traits<InputIterator>::value_type>,
|
| 1700 |
Allocator>;
|
| 1701 |
|
| 1702 |
+
template<ranges::input_range R,
|
| 1703 |
+
class Allocator = allocator<ranges::range_value_t<R>>>
|
| 1704 |
+
basic_string(from_range_t, R&&, Allocator = Allocator())
|
| 1705 |
+
-> basic_string<ranges::range_value_t<R>, char_traits<ranges::range_value_t<R>>,
|
| 1706 |
+
Allocator>;
|
| 1707 |
+
|
| 1708 |
template<class charT,
|
| 1709 |
class traits,
|
| 1710 |
class Allocator = allocator<charT>>
|
| 1711 |
explicit basic_string(basic_string_view<charT, traits>, const Allocator& = Allocator())
|
| 1712 |
-> basic_string<charT, traits, Allocator>;
|
|
|
|
| 1723 |
|
| 1724 |
A `size_type` parameter type in a `basic_string` deduction guide refers
|
| 1725 |
to the `size_type` member type of the type deduced by the deduction
|
| 1726 |
guide.
|
| 1727 |
|
| 1728 |
+
The types `iterator` and `const_iterator` meet the constexpr iterator
|
| 1729 |
+
requirements [[iterator.requirements.general]].
|
| 1730 |
+
|
| 1731 |
#### General requirements <a id="string.require">[[string.require]]</a>
|
| 1732 |
|
| 1733 |
If any operation would cause `size()` to exceed `max_size()`, that
|
| 1734 |
operation throws an exception object of type `length_error`.
|
| 1735 |
|
|
|
|
| 1745 |
objects as needed. The `Allocator` object used is obtained as described
|
| 1746 |
in [[container.requirements.general]]. In every specialization
|
| 1747 |
`basic_string<charT, traits, Allocator>`, the type `traits` shall meet
|
| 1748 |
the character traits requirements [[char.traits]].
|
| 1749 |
|
| 1750 |
+
[*Note 1*: Every specialization
|
| 1751 |
+
`basic_string<charT, traits, Allocator>` is an allocator-aware
|
| 1752 |
+
container, but does not use the allocator’s `construct` and `destroy`
|
| 1753 |
+
member functions [[container.requirements.general]]. — *end note*]
|
| 1754 |
+
|
| 1755 |
+
[*Note 2*: The program is ill-formed if `traits::char_type` is not the
|
| 1756 |
same type as `charT`. — *end note*]
|
| 1757 |
|
| 1758 |
References, pointers, and iterators referring to the elements of a
|
| 1759 |
`basic_string` sequence may be invalidated by the following uses of that
|
| 1760 |
`basic_string` object:
|
| 1761 |
|
| 1762 |
- Passing as an argument to any standard library function taking a
|
| 1763 |
+
reference to non-const `basic_string` as an argument.[^3]
|
| 1764 |
- Calling non-const member functions, except `operator[]`, `at`, `data`,
|
| 1765 |
`front`, `back`, `begin`, `rbegin`, `end`, and `rend`.
|
| 1766 |
|
| 1767 |
#### Constructors and assignment operators <a id="string.cons">[[string.cons]]</a>
|
| 1768 |
|
|
|
|
| 1786 |
``` cpp
|
| 1787 |
constexpr basic_string(const basic_string& str, size_type pos,
|
| 1788 |
const Allocator& a = Allocator());
|
| 1789 |
constexpr basic_string(const basic_string& str, size_type pos, size_type n,
|
| 1790 |
const Allocator& a = Allocator());
|
| 1791 |
+
constexpr basic_string(basic_string&& str, size_type pos,
|
| 1792 |
+
const Allocator& a = Allocator());
|
| 1793 |
+
constexpr basic_string(basic_string&& str, size_type pos, size_type n,
|
| 1794 |
+
const Allocator& a = Allocator());
|
| 1795 |
```
|
| 1796 |
|
| 1797 |
+
Let
|
| 1798 |
|
| 1799 |
+
- `s` be the value of `str` prior to this call and
|
| 1800 |
+
- `rlen` be `pos + min(n, s.size() - pos)` for the overloads with
|
| 1801 |
+
parameter `n`, and `s.size()` otherwise.
|
| 1802 |
+
|
| 1803 |
+
*Effects:* Constructs an object whose initial value is the range
|
| 1804 |
+
\[`s.data() + pos`, `s.data() + rlen`).
|
| 1805 |
+
|
| 1806 |
+
*Throws:* `out_of_range` if `pos > s.size()`.
|
| 1807 |
+
|
| 1808 |
+
*Remarks:* For the overloads with a `basic_string&&` parameter, `str` is
|
| 1809 |
+
left in a valid but unspecified state.
|
| 1810 |
+
|
| 1811 |
+
*Recommended practice:* For the overloads with a `basic_string&&`
|
| 1812 |
+
parameter, implementations should avoid allocation if
|
| 1813 |
+
`s.get_allocator() == a` is `true`.
|
| 1814 |
|
| 1815 |
``` cpp
|
| 1816 |
template<class T>
|
| 1817 |
constexpr basic_string(const T& t, size_type pos, size_type n, const Allocator& a = Allocator());
|
| 1818 |
```
|
|
|
|
| 1887 |
|
| 1888 |
*Constraints:* `InputIterator` is a type that qualifies as an input
|
| 1889 |
iterator [[container.requirements.general]].
|
| 1890 |
|
| 1891 |
*Effects:* Constructs a string from the values in the range \[`begin`,
|
| 1892 |
+
`end`), as specified in [[sequence.reqmts]].
|
| 1893 |
+
|
| 1894 |
+
``` cpp
|
| 1895 |
+
template<container-compatible-range<charT> R>
|
| 1896 |
+
constexpr basic_string(from_range_t, R&& rg, const Allocator& = Allocator());
|
| 1897 |
+
```
|
| 1898 |
+
|
| 1899 |
+
*Effects:* Constructs a string from the values in the range `rg`, as
|
| 1900 |
+
specified in [[sequence.reqmts]].
|
| 1901 |
|
| 1902 |
``` cpp
|
| 1903 |
constexpr basic_string(initializer_list<charT> il, const Allocator& a = Allocator());
|
| 1904 |
```
|
| 1905 |
|
|
|
|
| 2085 |
constexpr void resize(size_type n);
|
| 2086 |
```
|
| 2087 |
|
| 2088 |
*Effects:* Equivalent to `resize(n, charT())`.
|
| 2089 |
|
| 2090 |
+
``` cpp
|
| 2091 |
+
template<class Operation> constexpr void resize_and_overwrite(size_type n, Operation op);
|
| 2092 |
+
```
|
| 2093 |
+
|
| 2094 |
+
Let
|
| 2095 |
+
|
| 2096 |
+
- `o = size()` before the call to `resize_and_overwrite`.
|
| 2097 |
+
- `k` be `min(o, n)`.
|
| 2098 |
+
- `p` be a value of type `charT*` or `charT* const`, such that the range
|
| 2099 |
+
\[`p`, `p + n`\] is valid and `this->compare(0, k, p, k) == 0` is
|
| 2100 |
+
`true` before the call. The values in the range \[`p + k`, `p + n`\]
|
| 2101 |
+
may be indeterminate [[basic.indet]].
|
| 2102 |
+
- `m` be a value of type `size_type` or `const size_type` equal to `n`.
|
| 2103 |
+
- *`OP`* be the expression `std::move(op)(p, m)`.
|
| 2104 |
+
- `r` = *`OP`*.
|
| 2105 |
+
|
| 2106 |
+
*Mandates:* *`OP`* has an integer-like type [[iterator.concept.winc]].
|
| 2107 |
+
|
| 2108 |
+
*Preconditions:*
|
| 2109 |
+
|
| 2110 |
+
- *`OP`* does not throw an exception or modify `p` or `m`.
|
| 2111 |
+
- `r` ≥ 0.
|
| 2112 |
+
- `r` ≤ `m`.
|
| 2113 |
+
- After evaluating *`OP`* there are no indeterminate values in the range
|
| 2114 |
+
\[`p`, `p + r`).
|
| 2115 |
+
|
| 2116 |
+
*Effects:* Evaluates *`OP`*, replaces the contents of `*this` with
|
| 2117 |
+
\[`p`, `p + r`), and invalidates all pointers and references to the
|
| 2118 |
+
range \[`p`, `p + n`\].
|
| 2119 |
+
|
| 2120 |
+
*Recommended practice:* Implementations should avoid unnecessary copies
|
| 2121 |
+
and allocations by, for example, making `p` a pointer into internal
|
| 2122 |
+
storage and by restoring `*(p + r)` to `charT()` after evaluating
|
| 2123 |
+
*`OP`*.
|
| 2124 |
+
|
| 2125 |
``` cpp
|
| 2126 |
constexpr size_type capacity() const noexcept;
|
| 2127 |
```
|
| 2128 |
|
| 2129 |
*Returns:* The size of the allocated storage in the string.
|
|
|
|
| 2200 |
``` cpp
|
| 2201 |
constexpr const_reference at(size_type pos) const;
|
| 2202 |
constexpr reference at(size_type pos);
|
| 2203 |
```
|
| 2204 |
|
|
|
|
|
|
|
| 2205 |
*Returns:* `operator[](pos)`.
|
| 2206 |
|
| 2207 |
+
*Throws:* `out_of_range` if `pos >= size()`.
|
| 2208 |
+
|
| 2209 |
``` cpp
|
| 2210 |
constexpr const charT& front() const;
|
| 2211 |
constexpr charT& front();
|
| 2212 |
```
|
| 2213 |
|
|
|
|
| 2357 |
iterator [[container.requirements.general]].
|
| 2358 |
|
| 2359 |
*Effects:* Equivalent to:
|
| 2360 |
`return append(basic_string(first, last, get_allocator()));`
|
| 2361 |
|
| 2362 |
+
``` cpp
|
| 2363 |
+
template<container-compatible-range<charT> R>
|
| 2364 |
+
constexpr basic_string& append_range(R&& rg);
|
| 2365 |
+
```
|
| 2366 |
+
|
| 2367 |
+
*Effects:* Equivalent to:
|
| 2368 |
+
`return append(basic_string(from_range, std::forward<R>(rg), get_allocator()));`
|
| 2369 |
+
|
| 2370 |
``` cpp
|
| 2371 |
constexpr basic_string& append(initializer_list<charT> il);
|
| 2372 |
```
|
| 2373 |
|
| 2374 |
*Effects:* Equivalent to: `return append(il.begin(), il.size());`
|
|
|
|
| 2485 |
iterator [[container.requirements.general]].
|
| 2486 |
|
| 2487 |
*Effects:* Equivalent to:
|
| 2488 |
`return assign(basic_string(first, last, get_allocator()));`
|
| 2489 |
|
| 2490 |
+
``` cpp
|
| 2491 |
+
template<container-compatible-range<charT> R>
|
| 2492 |
+
constexpr basic_string& assign_range(R&& rg);
|
| 2493 |
+
```
|
| 2494 |
+
|
| 2495 |
+
*Effects:* Equivalent to:
|
| 2496 |
+
`return assign(basic_string(from_range, std::forward<R>(rg), get_allocator()));`
|
| 2497 |
+
|
| 2498 |
##### `basic_string::insert` <a id="string.insert">[[string.insert]]</a>
|
| 2499 |
|
| 2500 |
``` cpp
|
| 2501 |
constexpr basic_string& insert(size_type pos, const basic_string& str);
|
| 2502 |
```
|
|
|
|
| 2555 |
constexpr basic_string& insert(size_type pos, const charT* s, size_type n);
|
| 2556 |
```
|
| 2557 |
|
| 2558 |
*Preconditions:* \[`s`, `s + n`) is a valid range.
|
| 2559 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 2560 |
*Effects:* Inserts a copy of the range \[`s`, `s + n`) immediately
|
| 2561 |
before the character at position `pos` if `pos < size()`, or otherwise
|
| 2562 |
at the end of the string.
|
| 2563 |
|
| 2564 |
*Returns:* `*this`.
|
| 2565 |
|
| 2566 |
+
*Throws:*
|
| 2567 |
+
|
| 2568 |
+
- `out_of_range` if `pos > size()`,
|
| 2569 |
+
- `length_error` if `n > max_size() - size()`, or
|
| 2570 |
+
- any exceptions thrown by `allocator_traits<Allocator>::allocate`.
|
| 2571 |
+
|
| 2572 |
``` cpp
|
| 2573 |
constexpr basic_string& insert(size_type pos, const charT* s);
|
| 2574 |
```
|
| 2575 |
|
| 2576 |
*Effects:* Equivalent to: `return insert(pos, s, traits::length(s));`
|
|
|
|
| 2625 |
`insert(p - begin(), basic_string(first, last, get_allocator()))`.
|
| 2626 |
|
| 2627 |
*Returns:* An iterator which refers to the first inserted character, or
|
| 2628 |
`p` if `first == last`.
|
| 2629 |
|
| 2630 |
+
``` cpp
|
| 2631 |
+
template<container-compatible-range<charT> R>
|
| 2632 |
+
constexpr iterator insert_range(const_iterator p, R&& rg);
|
| 2633 |
+
```
|
| 2634 |
+
|
| 2635 |
+
*Preconditions:* `p` is a valid iterator on `*this`.
|
| 2636 |
+
|
| 2637 |
+
*Effects:* Equivalent to
|
| 2638 |
+
`insert(p - begin(), basic_string(from_range, std::forward<R>(rg), get_allocator()))`.
|
| 2639 |
+
|
| 2640 |
+
*Returns:* An iterator which refers to the first inserted character, or
|
| 2641 |
+
`p` if `rg` is empty.
|
| 2642 |
+
|
| 2643 |
``` cpp
|
| 2644 |
constexpr iterator insert(const_iterator p, initializer_list<charT> il);
|
| 2645 |
```
|
| 2646 |
|
| 2647 |
*Effects:* Equivalent to: `return insert(p, il.begin(), il.end());`
|
|
|
|
| 2650 |
|
| 2651 |
``` cpp
|
| 2652 |
constexpr basic_string& erase(size_type pos = 0, size_type n = npos);
|
| 2653 |
```
|
| 2654 |
|
|
|
|
|
|
|
| 2655 |
*Effects:* Determines the effective length `xlen` of the string to be
|
| 2656 |
removed as the smaller of `n` and `size() - pos`. Removes the characters
|
| 2657 |
in the range \[`begin() + pos`, `begin() + pos + xlen`).
|
| 2658 |
|
| 2659 |
*Returns:* `*this`.
|
| 2660 |
|
| 2661 |
+
*Throws:* `out_of_range` if `pos` `> size()`.
|
| 2662 |
+
|
| 2663 |
``` cpp
|
| 2664 |
constexpr iterator erase(const_iterator p);
|
| 2665 |
```
|
| 2666 |
|
| 2667 |
*Preconditions:* `p` is a valid dereferenceable iterator on `*this`.
|
| 2668 |
|
|
|
|
|
|
|
| 2669 |
*Effects:* Removes the character referred to by `p`.
|
| 2670 |
|
| 2671 |
*Returns:* An iterator which points to the element immediately following
|
| 2672 |
`p` prior to the element being erased. If no such element exists,
|
| 2673 |
`end()` is returned.
|
| 2674 |
|
| 2675 |
+
*Throws:* Nothing.
|
| 2676 |
+
|
| 2677 |
``` cpp
|
| 2678 |
constexpr iterator erase(const_iterator first, const_iterator last);
|
| 2679 |
```
|
| 2680 |
|
| 2681 |
*Preconditions:* `first` and `last` are valid iterators on `*this`.
|
| 2682 |
\[`first`, `last`) is a valid range.
|
| 2683 |
|
|
|
|
|
|
|
| 2684 |
*Effects:* Removes the characters in the range `[first, last)`.
|
| 2685 |
|
| 2686 |
*Returns:* An iterator which points to the element pointed to by `last`
|
| 2687 |
prior to the other elements being erased. If no such element exists,
|
| 2688 |
`end()` is returned.
|
| 2689 |
|
| 2690 |
+
*Throws:* Nothing.
|
| 2691 |
+
|
| 2692 |
``` cpp
|
| 2693 |
constexpr void pop_back();
|
| 2694 |
```
|
| 2695 |
|
| 2696 |
*Preconditions:* `!empty()`.
|
| 2697 |
|
|
|
|
|
|
|
| 2698 |
*Effects:* Equivalent to `erase(end() - 1)`.
|
| 2699 |
|
| 2700 |
+
*Throws:* Nothing.
|
| 2701 |
+
|
| 2702 |
##### `basic_string::replace` <a id="string.replace">[[string.replace]]</a>
|
| 2703 |
|
| 2704 |
``` cpp
|
| 2705 |
constexpr basic_string& replace(size_type pos1, size_type n1, const basic_string& str);
|
| 2706 |
```
|
|
|
|
| 2760 |
constexpr basic_string& replace(size_type pos1, size_type n1, const charT* s, size_type n2);
|
| 2761 |
```
|
| 2762 |
|
| 2763 |
*Preconditions:* \[`s`, `s + n2`) is a valid range.
|
| 2764 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 2765 |
*Effects:* Determines the effective length `xlen` of the string to be
|
| 2766 |
removed as the smaller of `n1` and `size() - pos1`. If
|
| 2767 |
`size() - xlen >= max_size() - n2` throws `length_error`. Otherwise, the
|
| 2768 |
function replaces the characters in the range \[`begin() + pos1`,
|
| 2769 |
`begin() + pos1 + xlen`) with a copy of the range \[`s`, `s + n2`).
|
| 2770 |
|
| 2771 |
*Returns:* `*this`.
|
| 2772 |
|
| 2773 |
+
*Throws:*
|
| 2774 |
+
|
| 2775 |
+
- `out_of_range` if `pos1 > size()`,
|
| 2776 |
+
- `length_error` if the length of the resulting string would exceed
|
| 2777 |
+
`max_size()`, or
|
| 2778 |
+
- any exceptions thrown by `allocator_traits<Allocator>::allocate`.
|
| 2779 |
+
|
| 2780 |
``` cpp
|
| 2781 |
constexpr basic_string& replace(size_type pos, size_type n, const charT* s);
|
| 2782 |
```
|
| 2783 |
|
| 2784 |
*Effects:* Equivalent to:
|
|
|
|
| 2786 |
|
| 2787 |
``` cpp
|
| 2788 |
constexpr basic_string& replace(size_type pos1, size_type n1, size_type n2, charT c);
|
| 2789 |
```
|
| 2790 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 2791 |
*Effects:* Determines the effective length `xlen` of the string to be
|
| 2792 |
removed as the smaller of `n1` and `size() - pos1`. If
|
| 2793 |
`size() - xlen >=` `max_size() - n2` throws `length_error`. Otherwise,
|
| 2794 |
the function replaces the characters in the range \[`begin() + pos1`,
|
| 2795 |
`begin() + pos1 + xlen`) with `n2` copies of `c`.
|
| 2796 |
|
| 2797 |
*Returns:* `*this`.
|
| 2798 |
|
| 2799 |
+
*Throws:*
|
| 2800 |
+
|
| 2801 |
+
- `out_of_range` if `pos1 > size()`,
|
| 2802 |
+
- `length_error` if the length of the resulting string would
|
| 2803 |
+
exceed`max_size()`, or
|
| 2804 |
+
- any exceptions thrown by `allocator_traits<Allocator>::allocate.`
|
| 2805 |
+
|
| 2806 |
``` cpp
|
| 2807 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, const basic_string& str);
|
| 2808 |
```
|
| 2809 |
|
| 2810 |
*Effects:* Equivalent to:
|
|
|
|
| 2862 |
iterator [[container.requirements.general]].
|
| 2863 |
|
| 2864 |
*Effects:* Equivalent to:
|
| 2865 |
`return replace(i1, i2, basic_string(j1, j2, get_allocator()));`
|
| 2866 |
|
| 2867 |
+
``` cpp
|
| 2868 |
+
template<container-compatible-range<charT> R>
|
| 2869 |
+
constexpr basic_string& replace_with_range(const_iterator i1, const_iterator i2, R&& rg);
|
| 2870 |
+
```
|
| 2871 |
+
|
| 2872 |
+
*Effects:* Equivalent to:
|
| 2873 |
+
|
| 2874 |
+
``` cpp
|
| 2875 |
+
return replace(i1, i2, basic_string(from_range, std::forward<R>(rg), get_allocator()));
|
| 2876 |
+
```
|
| 2877 |
+
|
| 2878 |
``` cpp
|
| 2879 |
constexpr basic_string& replace(const_iterator i1, const_iterator i2, initializer_list<charT> il);
|
| 2880 |
```
|
| 2881 |
|
| 2882 |
*Effects:* Equivalent to:
|
|
|
|
| 3019 |
``` cpp
|
| 3020 |
basic_string_view<charT, traits> s = *this, sv = t;
|
| 3021 |
return s.G(sv, pos);
|
| 3022 |
```
|
| 3023 |
|
| 3024 |
+
*Remarks:* The exception specification is equivalent to
|
| 3025 |
`is_nothrow_convertible_v<const T&, basic_string_view<charT, traits>>`.
|
| 3026 |
|
| 3027 |
##### `basic_string::substr` <a id="string.substr">[[string.substr]]</a>
|
| 3028 |
|
| 3029 |
``` cpp
|
| 3030 |
+
constexpr basic_string substr(size_type pos = 0, size_type n = npos) const &;
|
| 3031 |
```
|
| 3032 |
|
| 3033 |
+
*Effects:* Equivalent to: `return basic_string(*this, pos, n);`
|
| 3034 |
|
| 3035 |
+
``` cpp
|
| 3036 |
+
constexpr basic_string substr(size_type pos = 0, size_type n = npos) &&;
|
| 3037 |
+
```
|
| 3038 |
|
| 3039 |
+
*Effects:* Equivalent to:
|
| 3040 |
+
`return basic_string(std::move(*this), pos, n);`
|
| 3041 |
|
| 3042 |
##### `basic_string::compare` <a id="string.compare">[[string.compare]]</a>
|
| 3043 |
|
| 3044 |
``` cpp
|
| 3045 |
template<class T>
|
|
|
|
| 3053 |
- `is_convertible_v<const T&, const charT*>` is `false`.
|
| 3054 |
|
| 3055 |
*Effects:* Equivalent to:
|
| 3056 |
`return basic_string_view<charT, traits>(*this).compare(t);`
|
| 3057 |
|
| 3058 |
+
*Remarks:* The exception specification is equivalent to
|
| 3059 |
`is_nothrow_convertible_v<const T&, basic_string_view<charT, traits>>`.
|
| 3060 |
|
| 3061 |
``` cpp
|
| 3062 |
template<class T>
|
| 3063 |
constexpr int compare(size_type pos1, size_type n1, const T& t) const;
|
|
|
|
| 3166 |
|
| 3167 |
``` cpp
|
| 3168 |
return basic_string_view<charT, traits>(data(), size()).ends_with(x);
|
| 3169 |
```
|
| 3170 |
|
| 3171 |
+
##### `basic_string::contains` <a id="string.contains">[[string.contains]]</a>
|
| 3172 |
+
|
| 3173 |
+
``` cpp
|
| 3174 |
+
constexpr bool contains(basic_string_view<charT, traits> x) const noexcept;
|
| 3175 |
+
constexpr bool contains(charT x) const noexcept;
|
| 3176 |
+
constexpr bool contains(const charT* x) const;
|
| 3177 |
+
```
|
| 3178 |
+
|
| 3179 |
+
*Effects:* Equivalent to:
|
| 3180 |
+
|
| 3181 |
+
``` cpp
|
| 3182 |
+
return basic_string_view<charT, traits>(data(), size()).contains(x);
|
| 3183 |
+
```
|
| 3184 |
+
|
| 3185 |
### Non-member functions <a id="string.nonmembers">[[string.nonmembers]]</a>
|
| 3186 |
|
| 3187 |
#### `operator+` <a id="string.op.plus">[[string.op.plus]]</a>
|
| 3188 |
|
| 3189 |
``` cpp
|
|
|
|
| 3237 |
|
| 3238 |
except that both `lhs` and `rhs` are left in valid but unspecified
|
| 3239 |
states.
|
| 3240 |
|
| 3241 |
[*Note 1*: If `lhs` and `rhs` have equal allocators, the implementation
|
| 3242 |
+
can move from either. — *end note*]
|
| 3243 |
|
| 3244 |
``` cpp
|
| 3245 |
template<class charT, class traits, class Allocator>
|
| 3246 |
constexpr basic_string<charT, traits, Allocator>
|
| 3247 |
operator+(const basic_string<charT, traits, Allocator>& lhs,
|
|
|
|
| 3324 |
``` cpp
|
| 3325 |
lhs.push_back(rhs);
|
| 3326 |
return std::move(lhs);
|
| 3327 |
```
|
| 3328 |
|
| 3329 |
+
#### Non-member comparison operator functions <a id="string.cmp">[[string.cmp]]</a>
|
| 3330 |
|
| 3331 |
``` cpp
|
| 3332 |
template<class charT, class traits, class Allocator>
|
| 3333 |
constexpr bool
|
| 3334 |
operator==(const basic_string<charT, traits, Allocator>& lhs,
|
|
|
|
| 3371 |
operator>>(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);
|
| 3372 |
```
|
| 3373 |
|
| 3374 |
*Effects:* Behaves as a formatted input
|
| 3375 |
function [[istream.formatted.reqmts]]. After constructing a `sentry`
|
| 3376 |
+
object, if the `sentry` object returns `true` when converted to a value
|
| 3377 |
+
of type `bool`, calls `str.erase()` and then extracts characters from
|
| 3378 |
+
`is` and appends them to `str` as if by calling `str.append(1, c)`. If
|
| 3379 |
+
`is.width()` is greater than zero, the maximum number `n` of characters
|
| 3380 |
+
appended is `is.width()`; otherwise `n` is `str.max_size()`. Characters
|
| 3381 |
+
are extracted and appended until any of the following occurs:
|
| 3382 |
|
| 3383 |
- *n* characters are stored;
|
| 3384 |
- end-of-file occurs on the input sequence;
|
| 3385 |
- `isspace(c, is.getloc())` is `true` for the next available input
|
| 3386 |
character *c*.
|
| 3387 |
|
| 3388 |
After the last character (if any) is extracted, `is.width(0)` is called
|
| 3389 |
and the `sentry` object is destroyed.
|
| 3390 |
|
| 3391 |
+
If the function extracts no characters, `ios_base::failbit` is set in
|
| 3392 |
+
the input function’s local error state before `setstate` is called.
|
|
|
|
| 3393 |
|
| 3394 |
*Returns:* `is`.
|
| 3395 |
|
| 3396 |
``` cpp
|
| 3397 |
template<class charT, class traits, class Allocator>
|
|
|
|
| 3417 |
```
|
| 3418 |
|
| 3419 |
*Effects:* Behaves as an unformatted input
|
| 3420 |
function [[istream.unformatted]], except that it does not affect the
|
| 3421 |
value returned by subsequent calls to `basic_istream<>::gcount()`. After
|
| 3422 |
+
constructing a `sentry` object, if the `sentry` object returns `true`
|
| 3423 |
+
when converted to a value of type `bool`, calls `str.erase()` and then
|
| 3424 |
+
extracts characters from `is` and appends them to `str` as if by calling
|
| 3425 |
+
`str.append(1, c)` until any of the following occurs:
|
| 3426 |
|
| 3427 |
+
- end-of-file occurs on the input sequence;
|
|
|
|
| 3428 |
- `traits::eq(c, delim)` for the next available input character *c* (in
|
| 3429 |
+
which case, *c* is extracted but not appended);
|
| 3430 |
+
- `str.max_size()` characters are stored (in which case,
|
| 3431 |
+
`ios_base::failbit` is set in the input function’s local error state).
|
| 3432 |
|
| 3433 |
The conditions are tested in the order shown. In any case, after the
|
| 3434 |
last character is extracted, the `sentry` object is destroyed.
|
| 3435 |
|
| 3436 |
+
If the function extracts no characters, `ios_base::failbit` is set in
|
| 3437 |
+
the input function’s local error state before `setstate` is called.
|
|
|
|
| 3438 |
|
| 3439 |
*Returns:* `is`.
|
| 3440 |
|
| 3441 |
``` cpp
|
| 3442 |
template<class charT, class traits, class Allocator>
|
|
|
|
| 3498 |
`strtoul(str.c_str(), ptr, base)`, `strtoll(str.c_str(), ptr, base)`,
|
| 3499 |
and `strtoull(str.c_str(), ptr, base)`, respectively. Each function
|
| 3500 |
returns the converted result, if any. The argument `ptr` designates a
|
| 3501 |
pointer to an object internal to the function that is used to determine
|
| 3502 |
what to store at `*idx`. If the function does not throw an exception and
|
| 3503 |
+
`idx != nullptr`, the function stores in `*idx` the index of the first
|
| 3504 |
unconverted element of `str`.
|
| 3505 |
|
| 3506 |
*Returns:* The converted result.
|
| 3507 |
|
| 3508 |
*Throws:* `invalid_argument` if `strtol`, `strtoul`, `strtoll`, or
|
| 3509 |
+
`strtoull` reports that no conversion can be performed. Throws
|
| 3510 |
`out_of_range` if `strtol`, `strtoul`, `strtoll` or `strtoull` sets
|
| 3511 |
`errno` to `ERANGE`, or if the converted value is outside the range of
|
| 3512 |
representable values for the return type.
|
| 3513 |
|
| 3514 |
``` cpp
|
|
|
|
| 3520 |
*Effects:* These functions call `strtof(str.c_str(), ptr)`,
|
| 3521 |
`strtod(str.c_str(), ptr)`, and `strtold(str.c_str(), ptr)`,
|
| 3522 |
respectively. Each function returns the converted result, if any. The
|
| 3523 |
argument `ptr` designates a pointer to an object internal to the
|
| 3524 |
function that is used to determine what to store at `*idx`. If the
|
| 3525 |
+
function does not throw an exception and `idx != nullptr`, the function
|
| 3526 |
+
stores in `*idx` the index of the first unconverted element of `str`.
|
| 3527 |
|
| 3528 |
*Returns:* The converted result.
|
| 3529 |
|
| 3530 |
*Throws:* `invalid_argument` if `strtof`, `strtod`, or `strtold` reports
|
| 3531 |
+
that no conversion can be performed. Throws `out_of_range` if `strtof`,
|
| 3532 |
+
`strtod`, or `strtold` sets `errno` to `ERANGE` or if the converted
|
| 3533 |
+
value is outside the range of representable values for the return type.
|
|
|
|
| 3534 |
|
| 3535 |
``` cpp
|
| 3536 |
string to_string(int val);
|
| 3537 |
string to_string(unsigned val);
|
| 3538 |
string to_string(long val);
|
|
|
|
| 3564 |
`wcstoul(str.c_str(), ptr, base)`, `wcstoll(str.c_str(), ptr, base)`,
|
| 3565 |
and `wcstoull(str.c_str(), ptr, base)`, respectively. Each function
|
| 3566 |
returns the converted result, if any. The argument `ptr` designates a
|
| 3567 |
pointer to an object internal to the function that is used to determine
|
| 3568 |
what to store at `*idx`. If the function does not throw an exception and
|
| 3569 |
+
`idx != nullptr`, the function stores in `*idx` the index of the first
|
| 3570 |
unconverted element of `str`.
|
| 3571 |
|
| 3572 |
*Returns:* The converted result.
|
| 3573 |
|
| 3574 |
*Throws:* `invalid_argument` if `wcstol`, `wcstoul`, `wcstoll`, or
|
| 3575 |
+
`wcstoull` reports that no conversion can be performed. Throws
|
| 3576 |
`out_of_range` if the converted value is outside the range of
|
| 3577 |
representable values for the return type.
|
| 3578 |
|
| 3579 |
``` cpp
|
| 3580 |
float stof(const wstring& str, size_t* idx = nullptr);
|
|
|
|
| 3585 |
*Effects:* These functions call `wcstof(str.c_str(), ptr)`,
|
| 3586 |
`wcstod(str.c_str(), ptr)`, and `wcstold(str.c_str(), ptr)`,
|
| 3587 |
respectively. Each function returns the converted result, if any. The
|
| 3588 |
argument `ptr` designates a pointer to an object internal to the
|
| 3589 |
function that is used to determine what to store at `*idx`. If the
|
| 3590 |
+
function does not throw an exception and `idx != nullptr`, the function
|
| 3591 |
+
stores in `*idx` the index of the first unconverted element of `str`.
|
| 3592 |
|
| 3593 |
*Returns:* The converted result.
|
| 3594 |
|
| 3595 |
*Throws:* `invalid_argument` if `wcstof`, `wcstod`, or `wcstold` reports
|
| 3596 |
+
that no conversion can be performed. Throws `out_of_range` if `wcstof`,
|
| 3597 |
+
`wcstod`, or `wcstold` sets `errno` to `ERANGE`.
|
| 3598 |
|
| 3599 |
``` cpp
|
| 3600 |
wstring to_wstring(int val);
|
| 3601 |
wstring to_wstring(unsigned val);
|
| 3602 |
wstring to_wstring(long val);
|
|
|
|
| 3616 |
internal character buffer of sufficient size `buffsz`.
|
| 3617 |
|
| 3618 |
### Hash support <a id="basic.string.hash">[[basic.string.hash]]</a>
|
| 3619 |
|
| 3620 |
``` cpp
|
| 3621 |
+
template<class A> struct hash<basic_string<char, char_traits<char>, A>>;
|
| 3622 |
+
template<class A> struct hash<basic_string<char8_t, char_traits<char8_t>, A>>;
|
| 3623 |
+
template<class A> struct hash<basic_string<char16_t, char_traits<char16_t>, A>>;
|
| 3624 |
+
template<class A> struct hash<basic_string<char32_t, char_traits<char32_t>, A>>;
|
| 3625 |
+
template<class A> struct hash<basic_string<wchar_t, char_traits<wchar_t>, A>>;
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 3626 |
```
|
| 3627 |
|
| 3628 |
If `S` is one of these string types, `SV` is the corresponding string
|
| 3629 |
view type, and `s` is an object of type `S`, then
|
| 3630 |
`hash<S>()(s) == hash<SV>()(SV(s))`.
|
|
|
|
| 3664 |
[*Note 1*: The same suffix `s` is used for `chrono::duration` literals
|
| 3665 |
denoting seconds but there is no conflict, since duration suffixes apply
|
| 3666 |
to numbers and string literal suffixes apply to character array
|
| 3667 |
literals. — *end note*]
|
| 3668 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
| 3669 |
## Null-terminated sequence utilities <a id="c.strings">[[c.strings]]</a>
|
| 3670 |
|
| 3671 |
### Header `<cctype>` synopsis <a id="cctype.syn">[[cctype.syn]]</a>
|
| 3672 |
|
| 3673 |
``` cpp
|
|
|
|
| 3848 |
wchar_t* wcstok(wchar_t* s1, const wchar_t* s2, wchar_t** ptr);
|
| 3849 |
const wchar_t* wmemchr(const wchar_t* s, wchar_t c, size_t n); // see [library.c]
|
| 3850 |
wchar_t* wmemchr(wchar_t* s, wchar_t c, size_t n); // see [library.c]
|
| 3851 |
size_t wcslen(const wchar_t* s);
|
| 3852 |
wchar_t* wmemset(wchar_t* s, wchar_t c, size_t n);
|
| 3853 |
+
size_t wcsftime(wchar_t* s, size_t maxsize, const wchar_t* format, const tm* timeptr);
|
| 3854 |
wint_t btowc(int c);
|
| 3855 |
int wctob(wint_t c);
|
| 3856 |
|
| 3857 |
// [c.mb.wcs], multibyte / wide string and character conversion functions
|
| 3858 |
int mbsinit(const mbstate_t* ps);
|
|
|
|
| 3963 |
of the corresponding UTF-8 code units and then, if `pc8` is not a null
|
| 3964 |
pointer, stores the value of the first (or only) such code unit in the
|
| 3965 |
object pointed to by `pc8`. Subsequent calls will store successive UTF-8
|
| 3966 |
code units without consuming any additional input until all the code
|
| 3967 |
units have been stored. If the corresponding Unicode character is
|
| 3968 |
+
U+0000 (null), the resulting state described is the initial conversion
|
| 3969 |
+
state.
|
| 3970 |
|
| 3971 |
*Returns:* The first of the following that applies (given the current
|
| 3972 |
conversion state):
|
| 3973 |
|
| 3974 |
- `0`, if the next `n` or fewer bytes complete the multibyte character
|
| 3975 |
+
that corresponds to the U+0000 (null) Unicode character (which is the
|
| 3976 |
+
value stored).
|
| 3977 |
- between `1` and `n` (inclusive), if the next n or fewer bytes complete
|
| 3978 |
+
a valid multibyte character (whose first (or only) code unit is
|
| 3979 |
+
stored); the value returned is the number of bytes that complete the
|
| 3980 |
+
multibyte character.
|
| 3981 |
+
- `(size_t)(-3)`, if the next code unit resulting from a previous call
|
| 3982 |
has been stored (no bytes from the input have been consumed by this
|
| 3983 |
call).
|
| 3984 |
- `(size_t)(-2)`, if the next `n` bytes contribute to an incomplete (but
|
| 3985 |
potentially valid) multibyte character, and all `n` bytes have been
|
| 3986 |
processed (no value is stored).
|
|
|
|
| 4013 |
*Remarks:* Calls to `c8rtomb` with a null pointer argument for `s` may
|
| 4014 |
introduce a data race [[res.on.data.races]] with other calls to
|
| 4015 |
`c8rtomb` with a null pointer argument for `s`.
|
| 4016 |
|
| 4017 |
<!-- Link reference definitions -->
|
| 4018 |
+
[basic.indet]: basic.md#basic.indet
|
| 4019 |
[basic.string]: #basic.string
|
| 4020 |
+
[basic.string.general]: #basic.string.general
|
| 4021 |
[basic.string.hash]: #basic.string.hash
|
| 4022 |
[basic.string.literals]: #basic.string.literals
|
|
|
|
| 4023 |
[c.mb.wcs]: #c.mb.wcs
|
| 4024 |
[c.strings]: #c.strings
|
| 4025 |
[cctype.syn]: #cctype.syn
|
| 4026 |
[char.traits]: #char.traits
|
| 4027 |
+
[char.traits.general]: #char.traits.general
|
| 4028 |
[char.traits.req]: #char.traits.req
|
| 4029 |
[char.traits.require]: #char.traits.require
|
| 4030 |
[char.traits.specializations]: #char.traits.specializations
|
| 4031 |
[char.traits.specializations.char]: #char.traits.specializations.char
|
| 4032 |
[char.traits.specializations.char16.t]: #char.traits.specializations.char16.t
|
| 4033 |
[char.traits.specializations.char32.t]: #char.traits.specializations.char32.t
|
| 4034 |
[char.traits.specializations.char8.t]: #char.traits.specializations.char8.t
|
| 4035 |
+
[char.traits.specializations.general]: #char.traits.specializations.general
|
| 4036 |
[char.traits.specializations.wchar.t]: #char.traits.specializations.wchar.t
|
| 4037 |
[char.traits.typedefs]: #char.traits.typedefs
|
| 4038 |
+
[cmp.categories]: support.md#cmp.categories
|
| 4039 |
+
[container.reqmts]: containers.md#container.reqmts
|
| 4040 |
[container.requirements]: containers.md#container.requirements
|
| 4041 |
[container.requirements.general]: containers.md#container.requirements.general
|
|
|
|
| 4042 |
[cpp17.copyassignable]: #cpp17.copyassignable
|
| 4043 |
[cpp17.copyconstructible]: #cpp17.copyconstructible
|
| 4044 |
[cpp17.defaultconstructible]: #cpp17.defaultconstructible
|
| 4045 |
[cpp17.destructible]: #cpp17.destructible
|
| 4046 |
[cstring.syn]: #cstring.syn
|
| 4047 |
[cuchar.syn]: #cuchar.syn
|
| 4048 |
[cwchar.syn]: #cwchar.syn
|
| 4049 |
[cwctype.syn]: #cwctype.syn
|
| 4050 |
+
[defns.character.container]: intro.md#defns.character.container
|
| 4051 |
[input.output]: input.md#input.output
|
| 4052 |
[intro.object]: basic.md#intro.object
|
|
|
|
| 4053 |
[iostream.forward]: input.md#iostream.forward
|
| 4054 |
[iostreams.limits.pos]: input.md#iostreams.limits.pos
|
| 4055 |
[istream.formatted.reqmts]: input.md#istream.formatted.reqmts
|
| 4056 |
[istream.unformatted]: input.md#istream.unformatted
|
| 4057 |
[iterator.concept.contiguous]: iterators.md#iterator.concept.contiguous
|
| 4058 |
+
[iterator.concept.winc]: iterators.md#iterator.concept.winc
|
| 4059 |
[iterator.range]: iterators.md#iterator.range
|
| 4060 |
[iterator.requirements.general]: iterators.md#iterator.requirements.general
|
| 4061 |
[library.c]: library.md#library.c
|
| 4062 |
[ostream.formatted.reqmts]: input.md#ostream.formatted.reqmts
|
| 4063 |
[random.access.iterators]: iterators.md#random.access.iterators
|
| 4064 |
[res.on.data.races]: library.md#res.on.data.races
|
| 4065 |
+
[sequence.reqmts]: containers.md#sequence.reqmts
|
| 4066 |
[string.access]: #string.access
|
| 4067 |
[string.accessors]: #string.accessors
|
| 4068 |
[string.append]: #string.append
|
| 4069 |
[string.assign]: #string.assign
|
| 4070 |
[string.capacity]: #string.capacity
|
| 4071 |
[string.classes]: #string.classes
|
| 4072 |
+
[string.classes.general]: #string.classes.general
|
| 4073 |
[string.cmp]: #string.cmp
|
| 4074 |
[string.compare]: #string.compare
|
| 4075 |
[string.cons]: #string.cons
|
| 4076 |
+
[string.contains]: #string.contains
|
| 4077 |
[string.conversions]: #string.conversions
|
| 4078 |
[string.copy]: #string.copy
|
| 4079 |
[string.ends.with]: #string.ends.with
|
| 4080 |
[string.erase]: #string.erase
|
| 4081 |
[string.erasure]: #string.erasure
|
|
|
|
| 4102 |
[string.view.comparison]: #string.view.comparison
|
| 4103 |
[string.view.comparison.overloads]: #string.view.comparison.overloads
|
| 4104 |
[string.view.cons]: #string.view.cons
|
| 4105 |
[string.view.deduct]: #string.view.deduct
|
| 4106 |
[string.view.find]: #string.view.find
|
| 4107 |
+
[string.view.general]: #string.view.general
|
| 4108 |
[string.view.hash]: #string.view.hash
|
| 4109 |
[string.view.io]: #string.view.io
|
| 4110 |
[string.view.iterators]: #string.view.iterators
|
| 4111 |
[string.view.literals]: #string.view.literals
|
| 4112 |
[string.view.modifiers]: #string.view.modifiers
|
| 4113 |
[string.view.ops]: #string.view.ops
|
| 4114 |
[string.view.synop]: #string.view.synop
|
| 4115 |
[string.view.template]: #string.view.template
|
| 4116 |
+
[string.view.template.general]: #string.view.template.general
|
| 4117 |
[strings]: #strings
|
| 4118 |
[strings.general]: #strings.general
|
| 4119 |
[strings.summary]: #strings.summary
|
| 4120 |
[support.signal]: support.md#support.signal
|
| 4121 |
+
[temp.deduct]: temp.md#temp.deduct
|
| 4122 |
+
[term.standard.layout.type]: basic.md#term.standard.layout.type
|
| 4123 |
+
[term.trivially.copyable.type]: basic.md#term.trivially.copyable.type
|
| 4124 |
[unord.hash]: utilities.md#unord.hash
|
| 4125 |
[utility.swap]: utilities.md#utility.swap
|
| 4126 |
|
| 4127 |
[^1]: If `eof()` can be held in `char_type` then some iostreams
|
| 4128 |
operations can give surprising results.
|
| 4129 |
|
| 4130 |
+
[^2]: Because `basic_string_view` refers to a constant sequence,
|
| 4131 |
+
`iterator` and `const_iterator` are the same type.
|
| 4132 |
+
|
| 4133 |
+
[^3]: For example, as an argument to non-member functions `swap()`
|
| 4134 |
[[string.special]], `operator>{}>()` [[string.io]], and `getline()`
|
| 4135 |
[[string.io]], or as an argument to `basic_string::swap()`.
|