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) (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)