std::mem_fun_ref (3) - Linux Manuals

std::mem_fun_ref: std::mem_fun_ref

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 > (1) (deprecated in C++11)
std::const_mem_fun_ref_t<Res,T> mem_fun_ref( Res (T::*f)() ); (removed in C++17)
template< class Res, class T, class Arg > (2) (deprecated in C++11)
std::mem_fun1_ref_t<Res,T,Arg> mem_fun_ref( Res (T::*f)(Arg) ); (removed in C++17)
template< class Res, class T, class Arg > (2) (deprecated in C++11)
std::const_mem_fun1_ref_t<Res,T,Arg> mem_fun_ref( S (T::*f)(Arg) ); (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 adapter-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

(none)

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