94 lines
2.9 KiB
Markdown
94 lines
2.9 KiB
Markdown
[pairs.spec]
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# 22 General utilities library [[utilities]](./#utilities)
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## 22.3 Pairs [[pairs]](pairs#spec)
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### 22.3.3 Specialized algorithms [pairs.spec]
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[ð](#lib:operator==,pair)
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`template<class T1, class T2, class U1, class U2>
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constexpr bool operator==(const pair<T1, T2>& x, const pair<U1, U2>& y);
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1305)
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*Constraints*: x.first == y.first and x.second == y.second are
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valid expressions and
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each of decltype(x.first == y.first) anddecltype(x.second == y.second) models *boolean-
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testable*[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1312)
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*Returns*: x.first == y.first && x.second == y.second[.](#2.sentence-1)
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[ð](#lib:operator%3c=%3e,pair)
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`template<class T1, class T2, class U1, class U2>
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constexpr common_comparison_category_t<synth-three-way-result<T1, U1>,
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synth-three-way-result<T2, U2>>
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operator<=>(const pair<T1, T2>& x, const pair<U1, U2>& y);
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`
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1326)
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*Effects*: Equivalent to:if (auto c = *synth-three-way*(x.first, y.first); c != 0) return c;return *synth-three-way*(x.second, y.second);
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[ð](#lib:swap,pair)
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`template<class T1, class T2>
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constexpr void swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
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template<class T1, class T2>
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constexpr void swap(const pair<T1, T2>& x, const pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
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`
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1344)
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*Constraints*:
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- [(4.1)](#4.1)
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For the first overload,is_swappable_v<T1> is true andis_swappable_v<T2> is true[.](#4.1.sentence-1)
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- [(4.2)](#4.2)
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For the second overload,is_swappable_v<const T1> is true andis_swappable_v<const T2> is true[.](#4.2.sentence-1)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1357)
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*Effects*: Equivalent to x.swap(y)[.](#5.sentence-1)
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[ð](#lib:make_pair)
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`template<class T1, class T2>
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constexpr pair<unwrap_ref_decay_t<T1>, unwrap_ref_decay_t<T2>> make_pair(T1&& x, T2&& y);
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`
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1369)
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*Returns*: pair<unwrap_ref_decay_t<T1>,
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unwrap_ref_decay_t<T2>>(std::forward<T1>(x), std::forward<T2>(y))
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1377)
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[*Example [1](#example-1)*:
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In place of:return pair<int, double>(5, 3.1415926); // explicit types a C++ program may contain:return make_pair(5, 3.1415926); // types are deduced
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â *end example*]
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