std::optional - Man Page

Class template for optional values.

Synopsis

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.

Definition at line 705 of file optional.

Member Typedef Documentation

template<typename _Tp > using std::optional< _Tp >::value_type =  _Tp

Definition at line 735 of file optional.

Constructor & Destructor Documentation

template<typename _Tp > constexpr std::optional< _Tp >::optional () [inline], [constexpr], [noexcept]

Definition at line 737 of file optional.

template<typename _Tp > constexpr std::optional< _Tp >::optional (nullopt_t) [inline], [constexpr], [noexcept]

Definition at line 739 of file optional.

template<typename _Tp > template<typename _Up  = _Tp, _Requires< __not_self< _Up >, __not_tag< _Up >, is_constructible< _Tp, _Up >, is_convertible< _Up, _Tp > >  = true> constexpr std::optional< _Tp >::optional (_Up && __t) [inline], [constexpr], [noexcept]

Definition at line 747 of file optional.

template<typename _Tp > template<typename _Up  = _Tp, _Requires< __not_self< _Up >, __not_tag< _Up >, is_constructible< _Tp, _Up >, __not_< is_convertible< _Up, _Tp > > >  = false> constexpr std::optional< _Tp >::optional (_Up && __t) [inline], [explicit], [constexpr], [noexcept]

Definition at line 756 of file optional.

template<typename _Tp > 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 std::optional< _Tp >::optional (const optional< _Up > & __t) [inline], [constexpr], [noexcept]

Definition at line 766 of file optional.

template<typename _Tp > 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 std::optional< _Tp >::optional (const optional< _Up > & __t) [inline], [explicit], [constexpr], [noexcept]

Definition at line 779 of file optional.

template<typename _Tp > 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 std::optional< _Tp >::optional (optional< _Up > && __t) [inline], [constexpr], [noexcept]

Definition at line 792 of file optional.

template<typename _Tp > 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 std::optional< _Tp >::optional (optional< _Up > && __t) [inline], [explicit], [constexpr], [noexcept]

Definition at line 805 of file optional.

template<typename _Tp > template<typename... _Args, _Requires< is_constructible< _Tp, _Args... > >  = false> constexpr std::optional< _Tp >::optional (in_place_t, _Args &&... __args) [inline], [explicit], [constexpr], [noexcept]

Definition at line 815 of file optional.

template<typename _Tp > template<typename _Up , typename... _Args, _Requires< is_constructible< _Tp, initializer_list< _Up > &, _Args... > >  = false> constexpr std::optional< _Tp >::optional (in_place_t, initializer_list< _Up > __il, _Args &&... __args) [inline], [explicit], [constexpr], [noexcept]

Definition at line 824 of file optional.

Member Function Documentation

template<typename _Tp > template<typename... _Args> constexpr enable_if_t< is_constructible_v< _Tp, _Args... >, _Tp & > std::optional< _Tp >::emplace (_Args &&... __args) [inline], [constexpr], [noexcept]

Definition at line 914 of file optional.

template<typename _Tp > template<typename _Up , typename... _Args> constexpr enable_if_t< is_constructible_v< _Tp, initializer_list< _Up > &, _Args... >, _Tp & > std::optional< _Tp >::emplace (initializer_list< _Up > __il, _Args &&... __args) [inline], [constexpr], [noexcept]

Definition at line 926 of file optional.

template<typename _Tp > constexpr bool std::optional< _Tp >::has_value () const [inline], [constexpr], [noexcept]

Definition at line 987 of file optional.

template<typename _Tp > constexpr std::optional< _Tp >::operator bool () const [inline], [explicit], [constexpr], [noexcept]

Definition at line 984 of file optional.

template<typename _Tp > constexpr _Tp && std::optional< _Tp >::operator* () && [inline], [constexpr], [noexcept]

Definition at line 977 of file optional.

template<typename _Tp > constexpr _Tp & std::optional< _Tp >::operator* () & [inline], [constexpr], [noexcept]

Definition at line 973 of file optional.

template<typename _Tp > constexpr const _Tp && std::optional< _Tp >::operator* () const && [inline], [constexpr], [noexcept]

Definition at line 981 of file optional.

template<typename _Tp > constexpr const _Tp & std::optional< _Tp >::operator* () const & [inline], [constexpr], [noexcept]

Definition at line 969 of file optional.

template<typename _Tp > constexpr const _Tp * std::optional< _Tp >::operator-> () const [inline], [constexpr], [noexcept]

Definition at line 961 of file optional.

template<typename _Tp > constexpr _Tp * std::optional< _Tp >::operator-> () [inline], [constexpr], [noexcept]

Definition at line 965 of file optional.

template<typename _Tp > 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 & > std::optional< _Tp >::operator= (_Up && __u) [inline], [constexpr], [noexcept]

Definition at line 846 of file optional.

template<typename _Tp > 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 & > std::optional< _Tp >::operator= (const optional< _Up > & __u) [inline], [constexpr], [noexcept]

Definition at line 866 of file optional.

template<typename _Tp > constexpr optional & std::optional< _Tp >::operator= (nullopt_t) [inline], [constexpr], [noexcept]

Definition at line 832 of file optional.

template<typename _Tp > 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 & > std::optional< _Tp >::operator= (optional< _Up > && __u) [inline], [constexpr], [noexcept]

Definition at line 892 of file optional.

template<typename _Tp > constexpr void std::optional< _Tp >::reset () [inline], [constexpr], [noexcept]

Definition at line 1170 of file optional.

template<typename _Tp > constexpr void std::optional< _Tp >::swap (optional< _Tp > & __other) [inline], [constexpr], [noexcept]

Definition at line 939 of file optional.

template<typename _Tp > constexpr _Tp & std::optional< _Tp >::value () & [inline], [constexpr]

Definition at line 999 of file optional.

template<typename _Tp > constexpr _Tp && std::optional< _Tp >::value () && [inline], [constexpr]

Definition at line 1007 of file optional.

template<typename _Tp > constexpr const _Tp & std::optional< _Tp >::value () const & [inline], [constexpr]

Definition at line 991 of file optional.

template<typename _Tp > constexpr const _Tp && std::optional< _Tp >::value () const && [inline], [constexpr]

Definition at line 1015 of file optional.

template<typename _Tp > template<typename _Up > constexpr _Tp std::optional< _Tp >::value_or (_Up && __u) && [inline], [constexpr]

Definition at line 1037 of file optional.

template<typename _Tp > template<typename _Up > constexpr _Tp std::optional< _Tp >::value_or (_Up && __u) const & [inline], [constexpr]

Definition at line 1024 of file optional.

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Mon Nov 21 2022 libstdc++