From Jason Turner

[variant.helper]

C++17 → C++20 2.3 KB 31 lines
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Archived: C++17 | C++20
Markdown: C++17 | C++20
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  1. tmp/tmp4d16onw1/{from.md → to.md} +10 -18
tmp/tmp4d16onw1/{from.md → to.md} RENAMED
@@ -2,48 +2,40 @@
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  ``` cpp
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  template<class T> struct variant_size;
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  ```
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- *Remarks:* All specializations of `variant_size` shall meet the
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- `UnaryTypeTrait` requirements ([[meta.rqmts]]) with a base
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- characteristic of `integral_constant<size_t, N>` for some `N`.
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  ``` cpp
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  template<class T> class variant_size<const T>;
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- template <class T> class variant_size<volatile T>;
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- template <class T> class variant_size<const volatile T>;
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  ```
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  Let `VS` denote `variant_size<T>` of the cv-unqualified type `T`. Then
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- each of the three templates shall meet the `UnaryTypeTrait`
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- requirements ([[meta.rqmts]]) with a base characteristic of
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  `integral_constant<size_t, VS::value>`.
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  ``` cpp
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  template<class... Types>
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  struct variant_size<variant<Types...>> : integral_constant<size_t, sizeof...(Types)> { };
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  ```
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  ``` cpp
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  template<size_t I, class T> class variant_alternative<I, const T>;
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- template <size_t I, class T> class variant_alternative<I, volatile T>;
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- template <size_t I, class T> class variant_alternative<I, const volatile T>;
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  ```
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  Let `VA` denote `variant_alternative<I, T>` of the cv-unqualified type
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- `T`. Then each of the three templates shall meet the
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- `TransformationTrait` requirements ([[meta.rqmts]]) with a member
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- typedef `type` that names the following type:
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-
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- - for the first specialization, `add_const_t<VA::type>`,
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- - for the second specialization, `add_volatile_t<VA::type>`, and
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- - for the third specialization, `add_cv_t<VA::type>`.
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  ``` cpp
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  variant_alternative<I, variant<Types...>>::type
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  ```
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- *Requires:* `I < sizeof...(Types)`.
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- *Value:* The type `T_I`.
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  ``` cpp
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  template<class T> struct variant_size;
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  ```
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+ All specializations of `variant_size` meet the *Cpp17UnaryTypeTrait*
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+ requirements [[meta.rqmts]] with a base characteristic of
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+ `integral_constant<size_t, N>` for some `N`.
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  ``` cpp
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  template<class T> class variant_size<const T>;
 
 
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  ```
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  Let `VS` denote `variant_size<T>` of the cv-unqualified type `T`. Then
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+ each specialization of the template meets the *Cpp17UnaryTypeTrait*
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+ requirements [[meta.rqmts]] with a base characteristic of
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  `integral_constant<size_t, VS::value>`.
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  ``` cpp
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  template<class... Types>
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  struct variant_size<variant<Types...>> : integral_constant<size_t, sizeof...(Types)> { };
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  ```
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  ``` cpp
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  template<size_t I, class T> class variant_alternative<I, const T>;
 
 
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  ```
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  Let `VA` denote `variant_alternative<I, T>` of the cv-unqualified type
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+ `T`. Then each specialization of the template meets the
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+ *Cpp17TransformationTrait* requirements [[meta.rqmts]] with a member
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+ typedef `type` that names the type `add_const_t<VA::type>`.
 
 
 
 
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  ``` cpp
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  variant_alternative<I, variant<Types...>>::type
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  ```
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+ *Mandates:* `I` < `sizeof...(Types)`.
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+ *Type:* The type `T_I`.
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