RET_TYPE operator() (PAR1 p1, PAR2 p2, PAR3 p3, PAR4 p4) const { return (_binder.exec()->*(_binder.get_mem_ptr()))(p1, p2, p3, p4); }
RET_TYPE operator() (PAR1 p1) const { return (_binder.exec()->*(_binder.get_mem_ptr()))(p1); }