std::mem_fun_ref

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

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

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