std::in_place, std::in_place_type, std::in_place_index, std::in_place_t, std::in_place_type_t, std::
From cppreference.com
Defined in header <utility>
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struct in_place_t {
explicit in_place_t(
)
=
default
;
}
;
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(1) | (since C++17) |
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inline
constexpr std::
in_place_t in_place {
}
;
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(2) | (since C++17) |
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template
<
class T >
struct in_place_type_t { explicit in_place_type_t( ) = default ; } ; |
(3) | (since C++17) |
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template
<
class T >
constexpr std:: in_place_type_t <T> in_place_type { } ; |
(4) | (since C++17) |
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template
<
std::size_t I >
struct in_place_index_t { explicit in_place_index_t( ) = default ; } ; |
(5) | (since C++17) |
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template
<
std::size_t I >
constexpr std:: in_place_index_t <I> in_place_index { } ; |
(6) | (since C++17) |
1,3,5) The type/type templates
std::in_place_t, std::in_place_type_t and std::in_place_index_t
2,4,6) The corresponding
std::in_place, std::in_place_type, and std::in_place_index instances of (1,3,5)
Standard library
The following standard library types use (1-6) as disambiguation tags:
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(C++17) |
objects that hold instances of any CopyConstructible type (class) |
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(C++23)
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a wrapper that contains either an expected or error value (class template) |
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(C++23)
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move-only wrapper of any callable object that supports qualifiers in a given call signature (class template) |
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(C++17)
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a wrapper that may or may not hold an object (class template) |
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(C++17)
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a type-safe discriminated union (class template) |
See also
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(C++23)
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indicates that elements of a range are sorted and unique (tag) |
| indicates that elements of a range are sorted (uniqueness is not required) (tag) |