tmp/tmpyklhd9pg/{from.md → to.md}
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| 1 |
+
#### General <a id="variant.variant.general">[[variant.variant.general]]</a>
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| 3 |
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``` cpp
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+
namespace std {
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template<class... Types>
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class variant {
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public:
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// [variant.ctor], constructors
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constexpr variant() noexcept(see below);
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constexpr variant(const variant&);
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constexpr variant(variant&&) noexcept(see below);
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template<class T>
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constexpr variant(T&&) noexcept(see below);
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template<class T, class... Args>
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constexpr explicit variant(in_place_type_t<T>, Args&&...);
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template<class T, class U, class... Args>
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constexpr explicit variant(in_place_type_t<T>, initializer_list<U>, Args&&...);
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template<size_t I, class... Args>
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constexpr explicit variant(in_place_index_t<I>, Args&&...);
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template<size_t I, class U, class... Args>
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constexpr explicit variant(in_place_index_t<I>, initializer_list<U>, Args&&...);
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// [variant.dtor], destructor
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constexpr ~variant();
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// [variant.assign], assignment
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constexpr variant& operator=(const variant&);
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constexpr variant& operator=(variant&&) noexcept(see below);
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template<class T> constexpr variant& operator=(T&&) noexcept(see below);
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// [variant.mod], modifiers
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template<class T, class... Args>
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constexpr T& emplace(Args&&...);
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| 38 |
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template<class T, class U, class... Args>
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constexpr T& emplace(initializer_list<U>, Args&&...);
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template<size_t I, class... Args>
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constexpr variant_alternative_t<I, variant<Types...>>& emplace(Args&&...);
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| 42 |
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template<size_t I, class U, class... Args>
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constexpr variant_alternative_t<I, variant<Types...>>&
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emplace(initializer_list<U>, Args&&...);
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// [variant.status], value status
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constexpr bool valueless_by_exception() const noexcept;
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constexpr size_t index() const noexcept;
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// [variant.swap], swap
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constexpr void swap(variant&) noexcept(see below);
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| 52 |
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};
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| 53 |
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}
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```
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Any instance of `variant` at any given time either holds a value of one
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| 57 |
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of its alternative types or holds no value. When an instance of
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| 58 |
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`variant` holds a value of alternative type `T`, it means that a value
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| 59 |
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of type `T`, referred to as the `variant` object’s *contained value*, is
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allocated within the storage of the `variant` object. Implementations
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| 61 |
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are not permitted to use additional storage, such as dynamic memory, to
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allocate the contained value.
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| 63 |
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All types in `Types` shall meet the *Cpp17Destructible* requirements (
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| 65 |
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[[cpp17.destructible]]).
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| 66 |
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A program that instantiates the definition of `variant` with no template
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| 68 |
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arguments is ill-formed.
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| 69 |
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