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Path: utzoo!mnetor!seismo!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.sys.ibm.pc,comp.lang.c
Subject: Re: Assigning to Pointers
Message-ID: <6611@mimsy.UUCP>
Date: Sun, 10-May-87 10:57:36 EDT
Article-I.D.: mimsy.6611
Posted: Sun May 10 10:57:36 1987
Date-Received: Mon, 11-May-87 02:46:23 EDT
References: <3537@vrdxhq.UUCP> <857@killer.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 52
Xref: mnetor comp.sys.ibm.pc:3929 comp.lang.c:2130

In article <857@killer.UUCP> jfh@killer.UUCP (John Haugh) writes:
>The parenthesis come in real handy at times, for example (small lesson in
>C to follow :-) when you can't figure out how to declare a 'something' with
>a weird shape.  My weakness is pointers to functions -
>	int	foo ();		/* this is a function */

Right;

>	int	*foo ();	/* this is a function RETURNING a pointer */

right; and

>	int	*(foo ());	/* pointer to first function */

wrong: this last is `function returning pointer to int'.

>I won't even bother with POINTER to FUNCTION returning POINTER to FUNCTION
>returning an integer (the return value of signal() is one of these).

Actually, the return value from signal is not representable,
as it is `pointer to function returning pointer to function
returning pointer to function returning ...', with no final
type.  Instead, we all cheat and use `pointer to function
returning int' (or, in some cases, `returning void').

The program `cdecl' is handy for this sort of thing.  It has been
posted several times, so your neighbor probably has a copy, and it
is available via anonymous FTP from host mimsy.umd.edu on the
ARPAnet.

	% cdecl
	declare foo as pointer to function returning pointer to \
	function returning int
	int (*(*foo)())()

(cdecl does not handle `\' continuation lines; this is purely a
mailer-bug-avoidance device)

	explain int (*(*foo)())()
	declare foo as pointer to function returning pointer to \
	function returning int

You can create horrendous things that no one ever would use:

	declare a as array 5 of pointer to function returning pointer to \
	pointer to function returning pointer to array 3 of pointer to char
	char *(*(**(*a[5])())())[3]

Amaze your friends by getting types like this right the first time!
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris