传递给 C++ STL mem_fun_t 的对象如何调用其名称在 mem_fun_t 中定义的函数

Question

This the code from GNU STL:

template<typename _Ret, typename _Tp>
    class mem_fun_t : public unary_function<_Tp*, _Ret>
    {
    public:
      explicit
      mem_fun_t(_Ret (_Tp::*__pf)())
      : _M_f(__pf) { }

      _Ret
      operator()(_Tp* __p) const
      { return (__p->*_M_f)(); }

    private:
      _Ret (_Tp::*_M_f)();
    };

Although __p has a member function that has the same type with _M_f ,how could __p call _M_f , __p don't have a member named _M_f .

Answer 1

_M_f is a pointer to member function, of type _Ret(_Tp::*)() .

It is called through the pointer: __p->*_M_f)() . The dereference operator * is very significant there.