std::in_place, std::in_place_type, std::in_place_index, std::in_place_t, std::in_place_type_t, std::in_place_index_t
Defined in header <utility>
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struct in_place_t { explicit in_place_t() = default; |
(since C++17) | |
template <class T> struct in_place_type_t { explicit in_place_type_t() = default; |
(since C++17) | |
template <std::size_t I> struct in_place_index_t { explicit in_place_index_t() = default; |
(since C++17) | |
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
(C++17) |
a wrapper that may or may not hold an object (class template) |
(C++17) |
a type-safe discriminated union (class template) |
(C++17) |
Objects that hold instances of any CopyConstructible type. (class) |