The function template mem_fn creates an unspecified callable wrapper [cw] which calls through the callable target (provided as argument).It provides a big improvement over the std::mem_fun and std::mem_fun_ref, in that at the instantiation point it's not required to decide which argument the callable wrapper will be passed: an object, a pointer or a shared pointer.

#include <tr1/functional>

using std::tr1::mem_fn;

template <class R, class Ty>

unspecified mem_fn(R Ty::*pm);

struct object

{

    int method()

    { return 0; }

    int method_int()

    { return 0; }

    int method_int(int n)

    { return n; }

    int method_cv()

    { return 1; }

    int method_cv() const

    { return 2; }

};

object obj;

object * ptr = &obj;

mem_fn(&object::method)(obj);

mem_fn(&object::method)(ptr);

mem_fn(static_cast<int(object::*)()>(&object::method_int))(obj);

mem_fn(static_cast<int(object::*)(int)>(&object::method_int))(obj,1);

 

mem_fn(static_cast<int(object::*)()>(&object::method_cv))(obj);

mem_fn(static_cast<int(object::*)() const>(&object::method_cv))(obj);

note: the callable wrappers are highlighted.

example:

std::vector<object> vec;

std::for_each(vec.begin(), vec.end(), mem_fn(&object::method)); // that is equivalent to...

                                                                // std::for_each(vec.begin(), vec.end(), bind(&object::method, _1));

std::for_each(vec.begin(), vec.end(), bind(mem_fn(static_cast<int(object::*)(int)>(&object::method_int),_1,0xcafebabe));