Question about C Functions

[jobo]

If I have the function:

int f(int (*h)(int)) {
return (*h)(13);
}

What exactly does (int (*h)(int)) do? So it's taking a pointer but
what's with the two ints? Thanks.

[Default User]

Richard Heathfield wrote:

Default User said:

<snip>

Mr. Heathfield took people to task for what he deemed a worsening
the signal to noise ratio of the group when complaining solely about
top-posting.

Yes, since it was becoming a significant proportion of the traffic.

No, it wasn't. Especially not compared to some of your interminable
arguments with people.

I think what he's doing is every bit as bad

That's your privilege, but (a) the volume isn't actually all that
high, and (b) it has declined rapidly, as I have effectively given up
on the guy ever gaining a clue.

Fine.

(as are his
interminable arguments with Mr. Navia).

I can't help it if the guy is almost always wrong. But in any case,
other people seem to have noticed that he's almost always wrong, so I
don't need to point out his errors quite so often - the load is
distributed more evenly nowadays.

Correcting him on factual matters is a good thing - once. Protracted
arguments aren't. There have been a number of times where I looked at a
newsgroup thread and saw 20 or more posts, the vast majority coming
from two people: Richard Heathfield and Jacob Navia. You can't convince
of anything.

Brian

[Dik T. Winter]

In article <KV************ *******@news.in digo.ieFrederic k Gotham <fg*******@SPAM .comwrites:

Dik T. Winter:

The following is a bit complicated:
void (*(*f)(int (*)(int)))(int (*)());
cdecl has no problems with it.

....
Now all those f's below are a bit confusing:

(1) f is a pointer.
(2) f is a function whose sole parameter is a pointer to an int-returning-
function whose sole parameter is an int.
(3) f is a pointer.
(4) f is a void-returning-function whose sole parameter is a pointer to an
int-returning-function whose parameter list is void.

(1) and (2) are correct, but this description makes not clear what the
original f does return.
....

It shouldn't be too hard to work with the type now. I'd post example code,
but I can't think of any contrived usage which wouldn't come across as
utterly facetious (given the obscure nature of the type in question).

Obscure? From signal.h under Solaris:
int (*sigset(int, int (*)(int)))(int) ;
I think that declaration has been in there since BSD times. If f were
declared as:
int (*(*(*f)(int (*)(int)))(int, int (*)(int)))(int) ;
it might have been a function that took as parametera sighandler and
returned something of the type of sigset.

cdecl is quite handy at times. For the one I gave above:
cdeclexplain void (*(*f)(int (*)(int)))(int (*)());
declare f as pointer to function (pointer to function (int) returning int)
returning pointer to function (pointer to function returning int)
returning void
cdecl>
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, [phone]
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Al Balmer]

On 4 Nov 2006 00:27:02 GMT, "Default User" <de***********@ yahoo.com>
wrote:

>No, it wasn't. Especially not compared to some of your interminable
arguments with people.

Speaking of interminable arguments, let's stop this one.

--
Al Balmer
Sun City, AZ

[Frederick Gotham]

Dik T. Winter:

Now all those f's below are a bit confusing:

(1) f is a pointer.
(2) f is a function whose sole parameter is a pointer to an
int-returning- function whose sole parameter is an int.
(3) f is a pointer.
(4) f is a void-returning-function whose sole parameter is a pointer
to an int-returning-function whose parameter list is void.

(1) and (2) are correct, but this description makes not clear what the
original f does return.

That's because the return value is dependant upon the rest of the
breakdown.

It shouldn't be too hard to work with the type now. I'd post example
code, but I can't think of any contrived usage which wouldn't come
across as utterly facetious (given the obscure nature of the type in
question).

Obscure? From signal.h under Solaris:
int (*sigset(int, int (*)(int)))(int) ;

This is far less obscure. It's simply a function which takes a function
pointer and returns one:

typedef int (*FuncPtr)(int) ;

FuncPtr sigset(int,Func Ptr);

--

Frederick Gotham