Path: utzoo!utgpu!attcan!uunet!mtxinu!ed
From: ed@mtxinu.UUCP (Ed Gould)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Arrays of functions in THINK C
Keywords: Why does this not work?
Message-ID: <633@mtxinu.UUCP>
Date: 8 Aug 88 23:27:10 GMT
References: <2884@mit-amt.MEDIA.MIT.EDU> <9651@dartvax.Dartmouth.EDU> <1131@aimt.UUCP>
Reply-To: ed@mtxinu.UUCP (Ed Gould)
Organization: mt Xinu, Berkeley
Lines: 62

>Actually, K&R does say something about it.  On page 182  (section 7.1
>of appendix A)  it says:

>	A function call is a primary expression followed by parentheses
>	containing a possibly empty, comma-separated list of expressions
>	which constitute the actual arguments to the function.  The
>	primary expression must be of type "function returning ...", and
>	the result of the function call is of type "...".

>At least I take this to mean that the primary expression shouldn't be
>of type "pointer to function returning ...".  Funny, it's the unix
>compilers that are broken in this case.  Of course my "analysis" may
>be flawed.

Your analysis is slightly flawed.  "function returning ..." can
mean, for example, function returning pointer to ...  A primary
expression that is a function call is not a pointer; it is a
reference to a pointer.  Consider

	char	*f();
	char	*(*g)();

	main() {
		g = f;
		f();
		g();
		(*g)();
	}

The declarations are for "f", a function returning pointer to char, and
"g", a pointer to a function returning pointer to char.  There are
three function calls in this program.  The first, "f()", is the usual
sort of call:  "f" is the name of a function.  The second, "g()" is a
misleading form:  It looks like "g" is the name of a function, but
really it's an implicit dereference (this form may not be alliwed by
ANSI - I'm not sure).  The third is an explicit dereference of a
pointer to a function.

To get back to the original question about arrays of functions, they
are not allowed so far as I know.  Arrays of pointers to functions
are.  Consider:  What would be the definition of an array of functions,
anyway?  Would

	f[2]()
	{
		printf("this if f[0]\n");
	}
	{
		printf("this is f[1]]\n");
	}

be one?  This isn't legal syntax, nor is there any.  An array of
pointers to functions (all returning the same type - pointer to
char in this example) may be declared

	char	*(*h)[];

-- 
Ed Gould                    mt Xinu, 2560 Ninth St., Berkeley, CA  94710  USA
{ucbvax,uunet}!mtxinu!ed    +1 415 644 0146

"I'll fight them as a woman, not a lady.  I'll fight them as an engineer."