std::identity (3) - Linux Manuals
std::identity: std::identity
NAME
Synopsis
Defined in header <functional>
struct identity; (since C++20)
std::identity is a function object type whose operator() returns its argument unchanged.
Member types
Member type Definition
is_transparent /* unspecified */
Member functions
operator() (public member function)
std::identity::operator()
template< class T>
constexpr T&& operator()( T&& t ) const noexcept;
Returns std::forward<T>(t).
Parameters
t - argument to return
Return value
std::forward<T>(t).
Notes
The member type is_transparent indicates to the caller that this function object is a transparent function object: it accepts arguments of arbitrary types and uses perfect forwarding, which avoids unnecessary copying and conversion when the function object is used in heterogeneous context, or with rvalue arguments. In particular, template functions such as std::set::find and std::set::lower_bound make use of this member type on their Compare types.
Example
This section is incomplete
Reason: no example