78 lines
3.7 KiB
Markdown
78 lines
3.7 KiB
Markdown
[depr.tuple]
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# Annex D (normative) Compatibility features [[depr]](./#depr)
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## D.15 Tuple [depr.tuple]
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L523)
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The header [<tuple>](tuple.syn#header:%3ctuple%3e "22.4.2 Header <tuple> synopsis [tuple.syn]") has the following additions:namespace std {template<class T> struct tuple_size<volatile T>; template<class T> struct tuple_size<const volatile T>; template<size_t I, class T> struct tuple_element<I, volatile T>; template<size_t I, class T> struct tuple_element<I, const volatile T>;}
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[ð](#itemdecl:1)
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`template<class T> struct tuple_size<volatile T>;
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template<class T> struct tuple_size<const volatile T>;
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`
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L541)
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Let TS denote tuple_size<T> of the cv-unqualified type T[.](#2.sentence-1)
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If the expression TS::value is well-formed
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when treated as an [unevaluated operand](expr.context#def:unevaluated_operand "7.2.3 Context dependence [expr.context]"),
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then specializations of each of the two templates meet
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the [*Cpp17TransformationTrait*](meta.rqmts#:Cpp17TransformationTrait "21.3.2 Requirements [meta.rqmts]") requirements with a base characteristic ofintegral_constant<size_t, TS::value>[.](#2.sentence-2)
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Otherwise, they have no member value[.](#2.sentence-3)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L550)
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Access checking is performed as if
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in a context unrelated to TS and T[.](#3.sentence-1)
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Only the validity of the immediate context of the expression is considered[.](#3.sentence-2)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L555)
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In addition to being available via inclusion of the [<tuple>](tuple.syn#header:%3ctuple%3e "22.4.2 Header <tuple> synopsis [tuple.syn]") header,
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the two templates are available when any of the headers[<array>](array.syn#header:%3carray%3e "23.3.2 Header <array> synopsis [array.syn]"),[<ranges>](ranges.syn#header:%3cranges%3e "25.2 Header <ranges> synopsis [ranges.syn]"), or[<utility>](utility.syn#header:%3cutility%3e "22.2.1 Header <utility> synopsis [utility.syn]") are included[.](#4.sentence-1)
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[ð](#itemdecl:2)
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`template<size_t I, class T> struct tuple_element<I, volatile T>;
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template<size_t I, class T> struct tuple_element<I, const volatile T>;
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`
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L570)
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Let TE denote tuple_element_t<I, T> of the cv-unqualified type T[.](#5.sentence-1)
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Then specializations of each of the two templates meet
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the [*Cpp17TransformationTrait*](meta.rqmts#:Cpp17TransformationTrait "21.3.2 Requirements [meta.rqmts]") requirements
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with a member typedef type that names the following type:
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- [(5.1)](#5.1)
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for the first specialization, add_volatile_t<TE>, and
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- [(5.2)](#5.2)
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for the second specialization, add_cv_t<TE>[.](#5.sentence-2)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L581)
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In addition to being available via inclusion of the [<tuple>](tuple.syn#header:%3ctuple%3e "22.4.2 Header <tuple> synopsis [tuple.syn]") header,
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the two templates are available when any of the headers[<array>](array.syn#header:%3carray%3e "23.3.2 Header <array> synopsis [array.syn]"),[<ranges>](ranges.syn#header:%3cranges%3e "25.2 Header <ranges> synopsis [ranges.syn]"), or[<utility>](utility.syn#header:%3cutility%3e "22.2.1 Header <utility> synopsis [utility.syn]") are included[.](#6.sentence-1)
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