NAME¶

std::mem_fun_ref - std::mem_fun_ref

Synopsis¶

Defined in header <functional>
template< class Res, class T > (1) (deprecated in C++11)
std::mem_fun_ref_t<Res,T> mem_fun_ref( Res (T::*f)() ); (removed in C++17)
template< class Res, class T > (deprecated in C++11)
std::const_mem_fun_ref_t<Res,T> mem_fun_ref( Res (T::*f)() (1) (removed in C++17)
const );
template< class Res, class T, class Arg > (deprecated in C++11)
std::mem_fun1_ref_t<Res,T,Arg> mem_fun_ref( Res (2) (removed in C++17)
(T::*f)(Arg) );
template< class Res, class T, class Arg > (deprecated in C++11)
std::const_mem_fun1_ref_t<Res,T,Arg> mem_fun_ref( Res (2) (removed in C++17)
(T::*f)(Arg) const );

Creates a member function wrapper object, deducing the target type from the template
arguments. The wrapper object expects a reference to an object of type T as the
first parameter to its operator().

1) Effectively calls std::mem_fun_ref_t<S,T>(f) or std::const_mem_fun_ref_t<S,T>(f).
2) Effectively calls std::mem_fun1_ref_t<S,T>(f) or
std::const_mem_fun1_ref_t<S,T>(f).

This function and the related types were deprecated in C++11 and removed in C++17 in
favor of the more general std::mem_fn and std::bind, both of which create callable
adaptor-compatible function objects from member functions.

Parameters¶

f - pointer to a member function to create a wrapper for

Return value¶

A function object wrapping f.

Exceptions¶

May throw implementation-defined exceptions.

Notes¶

The difference between std::mem_fun and std::mem_fun_ref is that the former produces
a function wrapper that expects a pointer to an object, whereas the latter — a
reference.

Example¶

Uses std::mem_fun_ref to bind std::string's member function size().

// Run this code

#include <algorithm>
#include <functional>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

int main()
{
std::vector<std::string> v = {"once", "upon", "a", "time"};
std::transform(v.cbegin(), v.cend(),
std::ostream_iterator<std::size_t>(std::cout, " "),
std::mem_fun_ref(&std::string::size));
}

Output:¶

4 4 1 4

See also¶

mem_fun creates a wrapper from a pointer to member function, callable
(deprecated in C++11) with a pointer to object
(removed in C++17) (function template)