table of contents
std::_Optional_base< _Tp, bool, bool >(3cxx) | std::_Optional_base< _Tp, bool, bool >(3cxx) |
NAME¶
std::_Optional_base< _Tp, bool, bool > - Class template that provides copy/move constructors of optional.
SYNOPSIS¶
#include <optional>
Inherits std::_Optional_base_impl< _Tp, _Dp >.
Inherited by std::experimental::fundamentals_v1::optional< _Tp > [private], std::optional< _Tp > [private], and std::ranges::__detail::__non_propagating_cache< _Tp > [protected].
Public Member Functions¶
constexpr _Optional_base (_Optional_base
&&__other) noexcept(is_nothrow_move_constructible_v< _Tp >)
constexpr _Optional_base (const _Optional_base &__other)
template<typename... _Args, enable_if_t< is_constructible_v<
_Tp, _Args... >, bool > = false> constexpr _Optional_base
(in_place_t, _Args &&... __args)
template<typename _Up , typename... _Args, enable_if_t<
is_constructible_v< _Tp, initializer_list< _Up > &,
_Args... >, bool > = false> constexpr _Optional_base
(in_place_t, initializer_list< _Up > __il, _Args
&&... __args)
_Optional_base & operator= (_Optional_base
&&)=default
_Optional_base & operator= (const _Optional_base
&)=default
Public Attributes¶
_Optional_payload< _Tp > _M_payload
Protected Types¶
using _Stored_type = remove_const_t< _Tp
>
Protected Member Functions¶
template<typename... _Args> constexpr void
_M_construct (_Args &&... __args)
noexcept(is_nothrow_constructible_v< _Stored_type, _Args... >)
constexpr void _M_destruct () noexcept
constexpr const _Tp & _M_get () const noexcept
constexpr _Tp & _M_get () noexcept
constexpr bool _M_is_engaged () const noexcept
constexpr void _M_reset () noexcept
Detailed Description¶
template<typename _Tp, bool = is_trivially_copy_constructible_v<_Tp>, bool = is_trivially_move_constructible_v<_Tp>>¶
struct std::_Optional_base< _Tp, bool, bool >"Class template that provides copy/move constructors of optional.
Such a separate base class template is necessary in order to conditionally make copy/move constructors trivial.
When the contained value is trivially copy/move constructible, the copy/move constructors of _Optional_base will invoke the trivial copy/move constructor of _Optional_payload. Otherwise, they will invoke _Optional_payload(bool, const _Optional_payload&) or _Optional_payload(bool, _Optional_payload&&) to initialize the contained value, if copying/moving an engaged optional.
Whether the other special members are trivial is determined by the _Optional_payload<_Tp> specialization used for the _M_payload member.
See also
Author¶
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