5.2 KiB
[variant.get]
22 General utilities library [utilities]
22.6 Variants [variant]
22.6.5 Value access [variant.get]
template<class T, class... Types> constexpr bool holds_alternative(const variant<Types...>& v) noexcept;
Mandates: The type T occurs exactly once in Types.
Returns: true if index() is equal to the zero-based index of T in Types.
template<size_t I, class... Types> constexpr variant_alternative_t<I, variant<Types...>>& GET(variant<Types...>& v); // exposition only template<size_t I, class... Types> constexpr variant_alternative_t<I, variant<Types...>>&& GET(variant<Types...>&& v); // exposition only template<size_t I, class... Types> constexpr const variant_alternative_t<I, variant<Types...>>& GET(const variant<Types...>& v); // exposition only template<size_t I, class... Types> constexpr const variant_alternative_t<I, variant<Types...>>&& GET(const variant<Types...>&& v); // exposition only
Mandates: I < sizeof...(Types).
Preconditions: v.index() is I.
Returns: A reference to the object stored in the variant.
template<size_t I, class... Types> constexpr variant_alternative_t<I, variant<Types...>>& get(variant<Types...>& v); template<size_t I, class... Types> constexpr variant_alternative_t<I, variant<Types...>>&& get(variant<Types...>&& v); template<size_t I, class... Types> constexpr const variant_alternative_t<I, variant<Types...>>& get(const variant<Types...>& v); template<size_t I, class... Types> constexpr const variant_alternative_t<I, variant<Types...>>&& get(const variant<Types...>&& v);
Mandates: I < sizeof...(Types).
Effects: If v.index() is I, returns a reference to the object stored in the variant.
Otherwise, throws an exception of type bad_variant_access.
template<class T, class... Types> constexpr T& get(variant<Types...>& v); template<class T, class... Types> constexpr T&& get(variant<Types...>&& v); template<class T, class... Types> constexpr const T& get(const variant<Types...>& v); template<class T, class... Types> constexpr const T&& get(const variant<Types...>&& v);
Mandates: The type T occurs exactly once in Types.
Effects: If v holds a value of type T, returns a reference to that value.
Otherwise, throws an exception of type bad_variant_access.
template<size_t I, class... Types> constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>> get_if(variant<Types...>* v) noexcept; template<size_t I, class... Types> constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>> get_if(const variant<Types...>* v) noexcept;
Mandates: I < sizeof...(Types).
Returns: A pointer to the value stored in the variant, if v != nullptr and v->index() == I.
Otherwise, returns nullptr.
template<class T, class... Types> constexpr add_pointer_t<T> get_if(variant<Types...>* v) noexcept; template<class T, class... Types> constexpr add_pointer_t<const T> get_if(const variant<Types...>* v) noexcept;
Mandates: The type T occurs exactly once in Types.
Effects: Equivalent to: return get_if(v); with i being the zero-based index of T in Types.