Re: Figure out why member function pointer doesn't work?

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sun, 3 Apr 2011 09:54:54 -0700 (PDT)
Message-ID:
<fdab21d7-7b3b-43d7-984e-7c8a664c461f@d19g2000yql.googlegroups.com>
On Apr 2, 2:15 am, Nephi Immortal <immortalne...@gmail.com> wrote:

Please look at my code below. You may notice operator->* with
comments. Figure out why it does not make any sense.

struct data;
typedef void ( data::*pGo )();

struct data {
        char x;
        char y;
        pGo Go;

        void Run() {
        }
};

struct storage {
        data *pData;

        data *operator->() {
                return pData;
        }

        storage &operator->*( pGo p ) {


Here you define an operator->* which takes a storage and a
data::*pGo, and returns a storage. Why? What are you trying to
achieve.

                ( pData->*p )();
                return *this;
        }
};

int main()
{
        data d; storage s;
        s.pData = &d;
        s->x = 1; s->y = 2; s->Go = &data::Run;

        ( d.* d.Go )(); // OK
        ( d.* s->Go )(); // OK

        s.operator->*( s->Go ); // ??? Works fine
        s->*( s->Go ); // ??? Works fine

        ( s->* s->Go )(); // Should be, but does not work!


s->*s->Go returns a storage&. You then try to call it as a
function. Since storage has no overloaded operator(), it fails.
What do you expect?

        return 0;
}


--
James Kanze

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