114 lines
3.1 KiB
Markdown
114 lines
3.1 KiB
Markdown
[pair.astuple]
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# 22 General utilities library [[utilities]](./#utilities)
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## 22.3 Pairs [[pairs]](pairs#pair.astuple)
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### 22.3.4 Tuple-like access to pair [pair.astuple]
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[ð](#lib:tuple_size)
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`template<class T1, class T2>
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struct tuple_size<pair<T1, T2>> : integral_constant<size_t, 2> { };
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`
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[ð](#lib:tuple_element)
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`template<size_t I, class T1, class T2>
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struct tuple_element<I, pair<T1, T2>> {
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using type = see below ;
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};
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1405)
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*Mandates*: I<2[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1409)
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*Type*: The type T1 if I is 0, otherwise the type T2[.](#2.sentence-1)
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[ð](#lib:get,pair)
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`template<size_t I, class T1, class T2>
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constexpr tuple_element_t<I, pair<T1, T2>>& get(pair<T1, T2>& p) noexcept;
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template<size_t I, class T1, class T2>
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constexpr const tuple_element_t<I, pair<T1, T2>>& get(const pair<T1, T2>& p) noexcept;
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template<size_t I, class T1, class T2>
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constexpr tuple_element_t<I, pair<T1, T2>>&& get(pair<T1, T2>&& p) noexcept;
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template<size_t I, class T1, class T2>
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constexpr const tuple_element_t<I, pair<T1, T2>>&& get(const pair<T1, T2>&& p) noexcept;
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`
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1427)
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*Mandates*: I<2[.](#3.sentence-1)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1431)
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*Returns*:
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- [(4.1)](#4.1)
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If I is 0, returns a reference to p.first[.](#4.1.sentence-1)
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- [(4.2)](#4.2)
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If I is 1, returns a reference to p.second[.](#4.2.sentence-1)
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[ð](#lib:get,pair_)
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`template<class T1, class T2>
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constexpr T1& get(pair<T1, T2>& p) noexcept;
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template<class T1, class T2>
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constexpr const T1& get(const pair<T1, T2>& p) noexcept;
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template<class T1, class T2>
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constexpr T1&& get(pair<T1, T2>&& p) noexcept;
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template<class T1, class T2>
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constexpr const T1&& get(const pair<T1, T2>&& p) noexcept;
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`
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1455)
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*Mandates*: T1 and T2 are distinct types[.](#5.sentence-1)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1459)
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*Returns*: A reference to p.first[.](#6.sentence-1)
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[ð](#lib:get,pair__)
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`template<class T2, class T1>
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constexpr T2& get(pair<T1, T2>& p) noexcept;
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template<class T2, class T1>
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constexpr const T2& get(const pair<T1, T2>& p) noexcept;
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template<class T2, class T1>
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constexpr T2&& get(pair<T1, T2>&& p) noexcept;
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template<class T2, class T1>
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constexpr const T2&& get(const pair<T1, T2>&& p) noexcept;
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`
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1477)
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*Mandates*: T1 and T2 are distinct types[.](#7.sentence-1)
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[8](#8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L1481)
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*Returns*: A reference to p.second[.](#8.sentence-1)
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