std::optional< _Tp >(3cxx)

NAME
std::optional< _Tp > - Class template for optional values.

SYNOPSIS

#include <optional>

Inherits std::_Optional_base< _Tp, bool, bool >.

  Public Types

using value_type

  Public Member Functions

template<typename _Up = _Tp, _Requires< __not_self< _Up >, __not_tag< _Up >, is_constructible< _Tp, _Up >, __not_< is_convertible< _Up, _Tp > > > = false> constexpr optional (_Up &&__t) noexcept(is_nothrow_constructible_v< _Tp, _Up >)
template<typename _Up = _Tp, _Requires< __not_self< _Up >, __not_tag< _Up >, is_constructible< _Tp, _Up >, is_convertible< _Up, _Tp > > = true> constexpr optional (_Up &&__t) noexcept(is_nothrow_constructible_v< _Tp, _Up >)
template<typename _Up, _Requires< __not_< is_same< _Tp, _Up > >, is_constructible< _Tp, const _Up & >, __not_< is_convertible< const _Up &, _Tp > >, __not_< __converts_from_optional< _Tp, _Up > > > = false> constexpr optional (const optional< _Up > &__t) noexcept(is_nothrow_constructible_v< _Tp, const _Up & >)
template<typename _Up, _Requires< __not_< is_same< _Tp, _Up > >, is_constructible< _Tp, const _Up & >, is_convertible< const _Up &, _Tp >, __not_< __converts_from_optional< _Tp, _Up > > > = true> constexpr optional (const optional< _Up > &__t) noexcept(is_nothrow_constructible_v< _Tp, const _Up & >)
template<typename... _Args, _Requires< is_constructible< _Tp, _Args... > > = false> constexpr optional (in_place_t, _Args &&... __args) noexcept(is_nothrow_constructible_v< _Tp, _Args... >)
template<typename _Up, typename... _Args, _Requires< is_constructible< _Tp, initializer_list< _Up > &, _Args... > > = false> constexpr optional (in_place_t, initializer_list< _Up > __il, _Args &&... __args) noexcept(is_nothrow_constructible_v< _Tp, initializer_list< _Up > &, _Args... >)
constexpr optional (nullopt_t) noexcept
template<typename _Up, _Requires< __not_< is_same< _Tp, _Up > >, is_constructible< _Tp, _Up >, __not_< is_convertible< _Up, _Tp > >, __not_< __converts_from_optional< _Tp, _Up > > > = false> constexpr optional (optional< _Up > &&__t) noexcept(is_nothrow_constructible_v< _Tp, _Up >)
template<typename _Up, _Requires< __not_< is_same< _Tp, _Up > >, is_constructible< _Tp, _Up >, is_convertible< _Up, _Tp >, __not_< __converts_from_optional< _Tp, _Up > > > = true> constexpr optional (optional< _Up > &&__t) noexcept(is_nothrow_constructible_v< _Tp, _Up >)
template<typename... _Args> constexpr enable_if_t< is_constructible_v< _Tp, _Args... >, _Tp & > emplace (_Args &&... __args) noexcept(is_nothrow_constructible_v< _Tp, _Args... >)
template<typename _Up, typename... _Args> constexpr enable_if_t< is_constructible_v< _Tp, initializer_list< _Up > &, _Args... >, _Tp & > emplace (initializer_list< _Up > __il, _Args &&... __args) noexcept(is_nothrow_constructible_v< _Tp, initializer_list< _Up > &, _Args... >)
constexpr bool has_value () const noexcept
constexpr operator bool () const noexcept
constexpr _Tp && operator* () &&noexcept
constexpr _Tp & operator* () &noexcept
constexpr const _Tp && operator* () const &&noexcept
constexpr const _Tp & operator* () const &noexcept
constexpr const _Tp * operator-> () const noexcept
constexpr _Tp * operator-> () noexcept
template<typename _Up = _Tp> constexpr enable_if_t< __and_v< __not_self< _Up >, __not_< __and_< is_scalar< _Tp >, is_same< _Tp, decay_t< _Up > > > >, is_constructible< _Tp, _Up >, is_assignable< _Tp &, _Up > >, optional & > operator= (_Up &&__u) noexcept(__and_v< is_nothrow_constructible< _Tp, _Up >, is_nothrow_assignable< _Tp &, _Up > >)
template<typename _Up> constexpr enable_if_t< __and_v< __not_< is_same< _Tp, _Up > >, is_constructible< _Tp, const _Up & >, is_assignable< _Tp &, const _Up & >, __not_< __converts_from_optional< _Tp, _Up > >, __not_< __assigns_from_optional< _Tp, _Up > > >, optional & > operator= (const optional< _Up > &__u) noexcept(__and_v< is_nothrow_constructible< _Tp, const _Up & >, is_nothrow_assignable< _Tp &, const _Up & > >)
constexpr optional & operator= (nullopt_t) noexcept
template<typename _Up> constexpr enable_if_t< __and_v< __not_< is_same< _Tp, _Up > >, is_constructible< _Tp, _Up >, is_assignable< _Tp &, _Up >, __not_< __converts_from_optional< _Tp, _Up > >, __not_< __assigns_from_optional< _Tp, _Up > > >, optional & > operator= (optional< _Up > &&__u) noexcept(__and_v< is_nothrow_constructible< _Tp, _Up >, is_nothrow_assignable< _Tp &, _Up > >)
constexpr void reset () noexcept
constexpr void swap (optional &__other) noexcept(is_nothrow_move_constructible_v< _Tp > &&is_nothrow_swappable_v< _Tp >)
constexpr _Tp & value () &
constexpr _Tp && value () &&
constexpr const _Tp & value () const &
constexpr const _Tp && value () const &&
template<typename _Up> constexpr _Tp value_or (_Up &&__u) &&
template<typename _Up> constexpr _Tp value_or (_Up &&__u) const &

Detailed Description

  template<typename _Tp>
class std::optional< _Tp >"Class template for optional values.

Author

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