mem_fun_ref

template<class Result, class Ty>
    mem_fun_ref_t<Result, Ty> mem_fun_ref(Result (Ty::*pm)());
template<class Result, class Ty, class Arg>
    mem_fun1_ref_t<Result, Ty, Arg> mem_fun_ref(Result (Ty::*pm)(Arg));
template<class Result, class Ty>
    const_mem_fun_ref_t<Result, Ty> mem_fun_ref(Result (Ty::*pm)() const);
template<class Result, class Ty, class Arg>
    const_mem_fun1_ref_t<Result, Ty, Arg> mem_fun_ref(Result (Ty::*pm)(Arg) const);