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On 2003-10-13, some one <> wrote:
> I know that C++ lets you overload functions, but how do I overload
> functions in C?

You cannot do so arbitrarily, all C solutions require some form of
trickery. Several have been offered to you.

One trickery not yet suggested is to employ a polymorphic interface.

typedef struct polymorph polymorph;
struct polymorph {
void (* const foo)(polymorph *);
};

void foo(polymorph *p) { p->foo(p); }


Now, you get a form of function overloading when you create instances
of polymorph.

struct A {
polymorph interface;
int a;
};

static void A_foo(polymorph *p) {
struct A *me = (void *)p;
printf("a:%d\n", a++);
}

static const polymorph A_interface = { A_foo };

polymorph * create_A(void) {
struct A *i = malloc(sizeof(struct A));
i->interface = A_interface;
i->a = 0;
}

struct B {
polymorph interface;
int b;
};

static void B_foo(polymorph *p) {
struct B *me = (void *)p;
printf("b:%d\n", b--);
}

static const polymorph B_interface = { B_foo };

polymorph * create_B(void) {
struct B *i = malloc(sizeof(struct B));
i->interface = B_interface;
i->b = 0;
}

Now, you can get a form of overloading with the foo() function.

polymorph *a = create_A(); /* a points to a struct A */
polymorph *b = create_B(); /* b points to a struct B */

foo(a); /* will output "a:0" */
foo(b); /* will output "b:0" */
foo(a); /* will output "a:1" */
foo(b); /* will output "b:-1" */

-- James

jacob navia wrote:
> With lcc-win32 you write:
[stuff that isn't C and isn't topical in comp.lang.c]



--
Martin Ambuhl

"Arthur J. O'Dwyer" <> wrote in message
newsine.LNX.4.58-...
>
> On Mon, 13 Oct 2003, jacob navia wrote:
> >
> > "some one" <> wrote [...]
> > > I know that C++ lets you overload functions, but how do
> > > I overload functions in C?
> >
> > With lcc-win32 you write:
> > int overloaded fn(struct a*arg);
> > int overloaded fn(struct b *arg);
> >
> > and when you pass to fn an "a" it will call the first, and when you
> > pass it the second it will call the second.
> >
> > http://www.cs.virginia.edu/~lcc-win32
>
> That's very interesting, Jacob, but the OP did ask about
> the C language, not about lcc-win32.
>
> Oh, and *please* don't top-post.
>
> -Arthur
>
OK OK True, this is an lcc-win32 evil extension...
Sorry, I couldn't resist
If this question arises it is because people need that isn't it?

"jacob navia" <> wrote in message news:<bmgs55$frt$>...
> "Arthur J. O'Dwyer" <> wrote in message
> newsine.LNX.4.58-...
> >
> > That's very interesting, Jacob, but the OP did ask about
> > the C language, not about lcc-win32.
> >
> > Oh, and *please* don't top-post.
> >
> > -Arthur
> >
> OK OK True, this is an lcc-win32 evil extension...

Not evil, just off-topic. It isn't polite to post things outside of
the topic in a newsgroup, especially a technical one.

> If this question arises it is because people need that isn't it?

I've never needed it, and if I did I'd probably change languages.
(Although the idea of a variadic with the first argument declaring
type is neat...) But needs aren't really here or there when it comes
to topicality on this newsgroup. The topic is Standard C and/or
pre-Standard K&R C, and neither languages has any concept of function
overloading or polymorphism or inheritance or anything else of the
sort.

And, good job with curing yourself of top-posting! It's appreciated,
and makes people more likely to regard you as clueful.