std::in_place,std::in_place_type,std::in_place_index,std::in_place_t,(3) | C++ Standard Libary | std::in_place,std::in_place_type,std::in_place_index,std::in_place_t,(3) |
NAME¶
std::in_place,std::in_place_type,std::in_place_index,std::in_place_t, - std::in_place,std::in_place_type,std::in_place_index,std::in_place_t,
Synopsis¶
Defined in header <utility>
struct in_place_t {
explicit in_place_t() = default; (since C++17)
};
inline constexpr in_place_t in_place{};
template <class T> struct in_place_type_t {
explicit in_place_type_t() = default;
}; (since C++17)
template <class T>
inline constexpr in_place_type_t<T> in_place_type{};
template <std::size_t I> struct in_place_index_t {
explicit in_place_index_t() = default;
}; (since C++17)
template <std::size_t I>
inline constexpr in_place_index_t<I> in_place_index{};
std::in_place, std::in_place_type, and std::in_place_index are disambiguation
tags
that can be passed to the constructors of std::optional, std::variant, and
std::any
to indicate that the contained object should be constructed in-place, and
(for the
latter two) the type of the object to be constructed.
The corresponding type/type templates std::in_place_t, std::in_place_type_t
and
std::in_place_index_t can be used in the constructor's parameter list to
match the
intended tag.
See also¶
optional a wrapper that may or may not hold an object
(C++17) (class template)
variant a type-safe discriminated union
(C++17) (class template)
any Objects that hold instances of any CopyConstructible type.
(C++17) (class)
2022.07.31 | http://cppreference.com |