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std::mem_fun_ref(3)	      C++ Standard Libary	   std::mem_fun_ref(3)

NAME
       std::mem_fun_ref	- std::mem_fun_ref

Synopsis
	  Defined in header <functional>
	  template< class Res, class T >			     (1) (dep-
       recated in C++11)
	  std::mem_fun_ref_t<Res,T>  mem_fun_ref( Res (T::*f)()	);	  (re-
       moved in	C++17)
	  template< class Res, class T >				 (dep-
       recated in C++11)
	  std::const_mem_fun_ref_t<Res,T> mem_fun_ref( Res (T::*f)() (1)  (re-
       moved in	C++17)
	  const	);
	  template< class Res, class T,	class Arg >			 (dep-
       recated in C++11)
	  std::mem_fun1_ref_t<Res,T,Arg>  mem_fun_ref( Res	      (2) (re-
       moved in	C++17)
	  (T::*f)(Arg) );
	  template< class Res, class T,	class Arg >			 (dep-
       recated in C++11)
	  std::const_mem_fun1_ref_t<Res,T,Arg> mem_fun_ref( Res	     (2)  (re-
       moved 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 re-
       moved 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
	  an 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 <functional>
	#include <vector>
	#include <string>
	#include <iterator>
	#include <algorithm>
	#include <iostream>

	int main()
	{
	    std::vector<std::string> v = {"once", "upon", "a", "time"};
	    std::transform(v.begin(), v.end(),
			   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)

http://cppreference.com		  2022.07.31		   std::mem_fun_ref(3)

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