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From: jai@im4u.UUCP (Jai Srinivasan)
Newsgroups: comp.sys.ibm.pc,comp.lang.c
Subject: Re: Assigning to Pointers
Message-ID: <1823@im4u.UUCP>
Date: Sun, 10-May-87 14:55:38 EDT
Article-I.D.: im4u.1823
Posted: Sun May 10 14:55:38 1987
Date-Received: Mon, 11-May-87 03:07:26 EDT
References: <3537@vrdxhq.UUCP> <857@killer.UUCP>
Reply-To: jai@im4u.UUCP (Jai Srinivasan)
Organization: U. Texas CS Dept., Austin, Texas
Lines: 41
Xref: mnetor comp.sys.ibm.pc:3931 comp.lang.c:2131



In article <857@killer.UUCP>, John Haugh (jfh@killer.UUCP) 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 */
> 	int     *foo ();        /* this is a function RETURNING a pointer */
> 	int     *(foo ());      /* pointer to first function */

int *foo(); and int *(foo()); are equivalent because the () has a higher 
precedence than the * in the declaration.  To make foo a pointer to a
function which returns an integer, the declaration ought to be int (*foo)();.
I guess the same holds with the array declarations stated earlier in that
article because [] (like ()) has a higher precedence than the *.

Reading these declarations is not all that hard: just use the precedence
rules.  The parentheses around the * in int (*foo)(); indicates that the
* should be interpreted before the (), and reading "*" as "pointer to"
and "()" as "function that returns", one reads

int *foo();	as "foo is a function that returns a pointer to an integer",

and

int (*foo)();   as "foo is a pointer to a function that returns an integer".

Similarly,

int (*signal())(); is read as "signal is a function that returns a pointer
			       to a function which returns an integer".

I don't know if K&R ever explicitly state that the precedence rules hold
in the declaraions as well, but I assume they do.


Jai.
-----------------
Jai Srinivasan, UUCP: {gatech,harvard,ihnp4,pyramid,seismo}!ut-sally!im4u!jai
ARPA:  		      jai@im4u.UTEXAS.EDU, jai@sally.UTEXAS.EDU