template< class T >
struct type_identity;
Provides the member typedef type that names T (i.e., the identity transformation).
If the program adds specializations for std::type_identity, the behavior is undefined.
template< class T >
using type_identity_t = type_identity<T>::type;
template<class T>
struct type_identity { using type = T; };[edit] Notes
std::type_identity can be used to establish non-deduced contexts in template argument deduction.
#include <iostream>
#include <type_traits>
template<class T>
T foo(T a, T b) { return a + b; }
template<class T>
T bar(T a, std::type_identity_t<T> b) { return a + b; }
int main()
{
// foo(4.2, 1); // error, deduced conflicting types for 'T'
std::cout << bar(4.2, 1) << '\n'; // OK, calls bar<double>
}
Output:
[edit] See also function object that returns its argument unchangedRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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