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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) (depre-
     cated 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 >				 (depre-
     cated 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 >			 (depre-
     cated 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 >			 (depre-
     cated 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 cre-
     ate 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 lat-
     ter a 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 func-
     tion, callable
	(deprecated in C++11) with a pointer to object
	(removed in C++17)    (function template)

http://cppreference.com 	   2024.06.10		     std::mem_fun_ref(3)
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