std::mem_fun_ref
<functional>
std::mem_fun_ref_t <Res,T> mem_fun_ref( Res (T::*f)() );
(removed in C++17)
std::const_mem_fun_ref_t <Res,T> mem_fun_ref( Res (T::*f)() const );
(removed in C++17)
std::mem_fun1_ref_t <Res,T,Arg> mem_fun_ref( Res (T::*f)(Arg) );
(removed in C++17)
std::const_mem_fun1_ref_t <Res,T,Arg> mem_fun_ref( Res (T::*f)(Arg) const );
(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().
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.
[edit] Parameters
[edit] Return value
A function object wrapping f.
[edit] Exceptions
May throw implementation-defined exceptions.
[edit] 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.
[edit] Example
Uses std::mem_fun_ref to bind std::string 's member function size() .
#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