52 lines
2.0 KiB
Markdown
52 lines
2.0 KiB
Markdown
[depr.variant]
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# Annex D (normative) Compatibility features [[depr]](./#depr)
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## D.16 Variant [depr.variant]
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L592)
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The header [<variant>](variant.syn#header:%3cvariant%3e "22.6.2 Header <variant> synopsis [variant.syn]") has the following additions:namespace std {template<class T> struct variant_size<volatile T>; template<class T> struct variant_size<const volatile T>; template<size_t I, class T> struct variant_alternative<I, volatile T>; template<size_t I, class T> struct variant_alternative<I, const volatile T>;}
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[ð](#itemdecl:1)
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`template<class T> struct variant_size<volatile T>;
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template<class T> struct variant_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#L610)
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Let VS denote variant_size<T> of the cv-unqualified type T[.](#2.sentence-1)
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Then specializations of each of the two templates meet
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the [*Cpp17UnaryTypeTrait*](meta.rqmts#:Cpp17UnaryTypeTrait "21.3.2 Requirements [meta.rqmts]") requirements
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with a base characteristic of integral_constant<size_t, VS::value>[.](#2.sentence-2)
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[ð](#itemdecl:2)
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`template<size_t I, class T> struct variant_alternative<I, volatile T>;
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template<size_t I, class T> struct variant_alternative<I, const volatile T>;
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`
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L624)
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Let VA denote variant_alternative<I, T> of the cv-unqualified type T[.](#3.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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- [(3.1)](#3.1)
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for the first specialization, add_volatile_t<VA::type>, and
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- [(3.2)](#3.2)
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for the second specialization, add_cv_t<VA::type>[.](#3.sentence-2)
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