Difference between revisions of "cpp/utility/in place"
From cppreference.com
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explicit in_place_t() = default; | explicit in_place_t() = default; | ||
}; | }; | ||
| − | inline constexpr | + | inline constexpr in_place_t in_place{}; |
}} | }} | ||
{{dcl | since=c++17 | 1= | {{dcl | since=c++17 | 1= | ||
Revision as of 14:07, 15 October 2017
| 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 <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) |
