Init

cppdraft/variant/helper.md

@@ -0,0 +1,73 @@
+[variant.helper]
+
+# 22 General utilities library [[utilities]](./#utilities)
+
+## 22.6 Variants [[variant]](variant#helper)
+
+### 22.6.4 variant helper classes [variant.helper]
+
+[🔗](#lib:variant_size)
+
+`template<class T> struct variant_size;
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L6456)
+
+All specializations of variant_size meet the[*Cpp17UnaryTypeTrait*](meta.rqmts#:Cpp17UnaryTypeTrait "21.3.2 Requirements [meta.rqmts]") requirements ([[meta.rqmts]](meta.rqmts "21.3.2 Requirements"))
+with a base characteristic of integral_constant<size_t, N> for some N[.](#1.sentence-1)
+
+[🔗](#lib:variant_size_)
+
+`template<class T> struct variant_size<const T>;
+`
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L6468)
+
+Let VS denote variant_size<T> of the cv-unqualified
+type T[.](#2.sentence-1)
+
+Then each specialization of the template meets the[*Cpp17UnaryTypeTrait*](meta.rqmts#:Cpp17UnaryTypeTrait "21.3.2 Requirements [meta.rqmts]") requirements ([[meta.rqmts]](meta.rqmts "21.3.2 Requirements")) with a
+base characteristic of integral_constant<size_t, VS​::​value>[.](#2.sentence-2)
+
+[🔗](#lib:variant_size__)
+
+`template<class... Types>
+  struct variant_size<variant<Types...>> : integral_constant<size_t, sizeof...(Types)> { };
+`
+
+[🔗](#lib:variant_alternative)
+
+`template<size_t I, class T> struct variant_alternative<I, const T>;
+`
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L6488)
+
+Let VA denote variant_alternative<I, T> of the
+cv-unqualified type T[.](#3.sentence-1)
+
+Then each specialization of the template
+meets the [*Cpp17TransformationTrait*](meta.rqmts#:Cpp17TransformationTrait "21.3.2 Requirements [meta.rqmts]") requirements ([[meta.rqmts]](meta.rqmts "21.3.2 Requirements")) with a
+member typedef type that names the type add_const_t<VA​::​type>[.](#3.sentence-2)
+
+[🔗](#lib:variant_alternative_)
+
+`variant_alternative<I, variant<Types...>>::type
+`
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L6501)
+
+*Mandates*: I < sizeof...(Types)[.](#4.sentence-1)
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L6505)
+
+*Type*: The type TI[.](#5.sentence-1)