Re: function pointer class member ?

From:
Goran Pusic <goranp@cse-semaphore.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 16 Sep 2010 00:04:56 -0700 (PDT)
Message-ID:
<d8168fab-b72b-4ca8-bb48-f9883eb6c9f4@c32g2000vbq.googlegroups.com>
On Sep 16, 7:58 am, sledge <sunilk...@gmail.com> wrote:

Hi,
I am porting some legacy C code to C++.


If that is so, you should know first rule of porting, and that is:
"Don't". Porting is risky, and C++ is awesome enough that you can wrap
existing code (put a C++ fa=E7ade on it) virtually without impacting
performance. Did you try that first?

The code has a lot of member
function pointers like

class X {
               int (*a)(int,int);
               void (*b)(char t);
                int x;
               int f(int,int);

};

main()
{
// declare a pointer to member function
 void (X::*a) (int) = &X::f;
This does not seem to work. What is the right syntax to handle the
function pointer?


Obviously, this should be void (X::*a) (int, int) = &X::f; (note the
second "int").

On a more general note...

Your C function pointers do not seem to belong to X (logically, not
formally). If they "belonged", they would typically look like so:

int (*a)(X* this, int param1, int param2); (they would have "explicit"
this pointer.

That said, function pointers like these are normally a sign of an
attempt to get polymorphism in C (and if so, the above is not the best
version). If that is the purpose of the code, then you should just
switch to virtual functions.

Goran.

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