whats wrong with pointer to member function

[Matthias Oltmanns]

Am Mit, 2003-05-07 um 10.28 schrieb Bhattiprolu Ravikumar-A18658:
> Hi Matthias,
> 
>    To my knowledge, in C++ to use function pointer to a member function, 
> the member function has to be static member function. Try making foo as static.
> 
No! Pointers to static member functions are *ordinary* pointers.
In this example, of course foo could be static. But in my real-life work
I must use non-static member functions.
Pointer to member functions are some kind of an offset used with the
operators: .* and ->*

Matthias

> regards,
> Ravi
> 
> -----Original Message-----
> From: Matthias Oltmanns
> [mailto:Mathias.Oltmanns.Oltmanns@sysde.eads.net]
> Sent: Wednesday, May 07, 2003 1:46 PM
> To: gcc-help@gcc.gnu.org
> Subject: whats wrong with pointer to member function
> 
> 
> Hi,
> 
> I'am confused while using pointer to member function. The compiler does
> not translate the following:
> 
> ---- foo.cpp ---------------------------
> 
> // Pointer to member function
> #include <iostream>
> 
> class A
> {
> public:
>   void foo()
>   {
>     std::cout << "Hi!" << std::endl;
>   }
> };
> 
> typedef void (A::*PMember) ();
> 
> // VARIANT 1
> class B
> {
> public:
>   void perform(A * pA)
>   {
>     PMember member = &A::foo;
>     pA->*member();
>   }
> };
> 
> // VARIANT 2
> void perform_func(A * pA)
> {
>   PMember member = &A::foo;
>   pA->*member();
> }
> int main(int, char**)
> {
>   A a;
>   PMember member = &A::foo;
> 
>   // direct call
>   a.foo();
> 
>   //VARIANT 3
>   // call through member pointer
>   a.*member();
> 
>   return 0;
> }
> 
> > g++ foo.cpp
> foo.cpp: In member function `void B::perform(A*)':
> foo.cpp:21: must use .* or ->* to call pointer-to-member function in
> `member
>    (...)'
> foo.cpp: In function `void perform_func(A*)':
> foo.cpp:28: pointer to member function called, but not in class scope
> foo.cpp: In function `int main(int, char**)':
> foo.cpp:40: pointer to member function called, but not in class scope
> 
> My current knowledge about pointers to members is based on Stroustroup 
> The C++ Programming Language, Third Edition, Chap. 15.5.
> 
> As far as I can see, the code above is correct and i cannot understand
> what the compiler tries to tell me.
> 
> Any help would be great.
> 
> cu
> Matthias
> 
> 
> -- 
> Matthias Oltmanns
> 
> Tel: 04421-1543-274
> mail: Mathias.Oltmanns.Oltmanns@sysde.eads.net
-- 
Matthias Oltmanns

Tel: 04421-1543-274
mail: Mathias.Oltmanns.Oltmanns@sysde.eads.net