table of contents
| std::optional< _Tp >(3cxx) | std::optional< _Tp >(3cxx) |
NAME¶
std::optional< _Tp > - Class template for optional values.
SYNOPSIS¶
#include <optional>
Inherits std::_Optional_base< _Tp, bool, bool >, and _Enable_copy_move< is_copy_constructible_v< _Tp >, __and_v< is_copy_constructible< _Tp >, is_copy_assignable< _Tp > >, is_move_constructible_v< _Tp >, __and_v< is_move_constructible< _Tp >, is_move_assignable< _Tp > >, optional< _Tp > >.
Inherited by std::ranges::__detail::__box< _Pred >, std::ranges::__detail::__box< _Fp >, and std::ranges::__detail::__box< _Tp >.
Public Types¶
using value_type = _Tp
Public Member Functions¶
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 = _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 , _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 _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... _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
>, 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 _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... _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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