This header is part of the general utility library.
[edit] Synopsis// mostly freestanding
#include <compare>
namespace std {
// class template variant
template<class... Types> class variant;
// variant helper classes
template<class T> struct variant_size; // not defined
template<class T> struct variant_size<const T>;
template<class T> constexpr size_t variant_size_v = variant_size<T>::value;
template<class... Types> struct variant_size<variant<Types...>>;
template<size_t I, class T> struct variant_alternative; // not defined
template<size_t I, class T> struct variant_alternative<I, const T>;
template<size_t I, class T>
using variant_alternative_t = typename variant_alternative<I, T>::type;
template<size_t I, class... Types> struct variant_alternative<I, variant<Types...>>;
inline constexpr size_t variant_npos = -1;
// value access
template<class T, class... Types>
constexpr bool holds_alternative(const variant<Types...>&) noexcept;
template<size_t I, class... Types>
constexpr variant_alternative_t<I, variant<Types...>>& get(
variant<Types...>&); // freestanding-deleted
template<size_t I, class... Types>
constexpr variant_alternative_t<I, variant<Types...>>&& get(
variant<Types...>&&); // freestanding-deleted
template<size_t I, class... Types>
constexpr const variant_alternative_t<I, variant<Types...>>& get(
const variant<Types...>&); // freestanding-deleted
template<size_t I, class... Types>
constexpr const variant_alternative_t<I, variant<Types...>>&& get(
const variant<Types...>&&); // freestanding-deleted
template<class T, class... Types>
constexpr T& get(variant<Types...>&); // freestanding-deleted
template<class T, class... Types>
constexpr T&& get(variant<Types...>&&); // freestanding-deleted
template<class T, class... Types>
constexpr const T& get(const variant<Types...>&); // freestanding-deleted
template<class T, class... Types>
constexpr const T&& get(const variant<Types...>&&); // freestanding-deleted
template<size_t I, class... Types>
constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>> get_if(
variant<Types...>*) noexcept;
template<size_t I, class... Types>
constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>> get_if(
const variant<Types...>*) noexcept;
template<class T, class... Types>
constexpr add_pointer_t<T> get_if(variant<Types...>*) noexcept;
template<class T, class... Types>
constexpr add_pointer_t<const T> get_if(const variant<Types...>*) noexcept;
// relational operators
template<class... Types>
constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
template<class... Types>
constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
template<class... Types>
constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
template<class... Types>
constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
template<class... Types>
constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
template<class... Types>
constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
template<class... Types>
requires(three_way_comparable<Types> && ...)
constexpr common_comparison_category_t<compare_three_way_result_t<Types>...>
operator<=>(const variant<Types...>&, const variant<Types...>&);
// visitation
template<class Visitor, class... Variants>
constexpr /* see description */ visit(Visitor&&, Variants&&...);
template<class R, class Visitor, class... Variants>
constexpr R visit(Visitor&&, Variants&&...);
// class monostate
struct monostate;
// monostate relational operators
constexpr bool operator==(monostate, monostate) noexcept;
constexpr strong_ordering operator<=>(monostate, monostate) noexcept;
// specialized algorithms
template<class... Types>
constexpr void swap(variant<Types...>&,
variant<Types...>&) noexcept(/* see description */);
// class bad_variant_access
class bad_variant_access;
// hash support
template<class T> struct hash;
template<class... Types> struct hash<variant<Types...>>;
template<> struct hash<monostate>;
}
// deprecated
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>;
}[edit] Class template std::variant
namespace std {
template<class... Types> class variant
{
public:
// constructors
constexpr variant() noexcept(/* see description */);
constexpr variant(const variant&);
constexpr variant(variant&&) noexcept(/* see description */);
template<class T> constexpr variant(T&&) noexcept(/* see description */);
template<class T, class... Args>
constexpr explicit variant(in_place_type_t<T>, Args&&...);
template<class T, class U, class... Args>
constexpr explicit variant(in_place_type_t<T>, initializer_list<U>, Args&&...);
template<size_t I, class... Args>
constexpr explicit variant(in_place_index_t<I>, Args&&...);
template<size_t I, class U, class... Args>
constexpr explicit variant(in_place_index_t<I>, initializer_list<U>, Args&&...);
// destructor
constexpr ~variant();
// assignment
constexpr variant& operator=(const variant&);
constexpr variant& operator=(variant&&) noexcept(/* see description */);
template<class T> constexpr variant& operator=(T&&) noexcept(/* see description */);
// modifiers
template<class T, class... Args> constexpr T& emplace(Args&&...);
template<class T, class U, class... Args>
constexpr T& emplace(initializer_list<U>, Args&&...);
template<size_t I, class... Args>
constexpr variant_alternative_t<I, variant<Types...>>& emplace(Args&&...);
template<size_t I, class U, class... Args>
constexpr variant_alternative_t<I, variant<Types...>>& emplace(initializer_list<U>,
Args&&...);
// value status
constexpr bool valueless_by_exception() const noexcept;
constexpr size_t index() const noexcept;
// swap
constexpr void swap(variant&) noexcept(/* see description */);
// visitation
template<class Self, class Visitor>
constexpr decltype(auto) visit(this Self&&, Visitor&&);
template<class R, class Self, class Visitor>
constexpr R visit(this Self&&, Visitor&&);
};
}[edit] Class std::monostate
namespace std {
struct monostate{};
constexpr bool
operator==(monostate, monostate) noexcept { return true; }
constexpr strong_ordering
operator<=>(monostate, monostate) noexcept
{
return strong_ordering::equal;
}
}[edit] Class std::bad_variant_access
namespace std {
class bad_variant_access : public exception
{
public:
// see description for the specification of the special member functions
constexpr const char* what() const noexcept override;
};
}
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4