std::has_unique_object_representations
Defined in header <type_traits>
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template< class T > struct has_unique_object_representations; |
(since C++17) | |
If T
is TriviallyCopyable
and if any two objects of type T
with the same value have the same object representation, provides the member constant value
equal true. For any other type, value
is false.
For the purpose of this trait, two arrays have the same value if their elements have the same values, two non-union classes have the same value if their direct subobjects have the same value, and two unions have the same value if they have the same active member and the value of that member are the same.
It is implementation-defined which scalar types satisfy this trait, but unsigned integer types that do not use padding bits are guaranteed to have unique object representations.
The behavior is undefined if T
is an incomplete type other than (possibly cv-qualified) void or array of unknown bound.
Template parameters
T | - | a type to check |
Helper variable template
template< class T > inline constexpr bool has_unique_object_representations_v = has_unique_object_representations<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
value [static] |
true if T has unique object representations , false otherwise (public static member constant) |
Member functions
operator bool |
converts the object to bool, returns value (public member function) |
operator() (C++14) |
returns value (public member function) |
Member types
Type | Definition |
value_type
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bool
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type
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std::integral_constant<bool, value> |
Notes
This trait was introduced to make it possible to determine whether a type can be correctly hashed by hashing its object representation as a byte array.
Example
This section is incomplete Reason: no example |
See also
(C++11) |
checks if a type is standard-layout type (class template) |
(C++11) |
hash function object (class template) |