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From: mouse@mcgill-vision.UUCP
Newsgroups: net.lang.c
Subject: Re: SWAP macro
Message-ID: <454@mcgill-vision.UUCP>
Date: Sat, 12-Jul-86 03:10:01 EDT
Article-I.D.: mcgill-v.454
Posted: Sat Jul 12 03:10:01 1986
Date-Received: Sun, 13-Jul-86 07:00:46 EDT
References: <857@bu-cs.UUCP>
Organization: McGill University, Montreal
Lines: 39

In article <857@bu-cs.UUCP>, bzs@bu-cs.UUCP (Barry Shein) writes:
> And then again, there's always [...]
> 
> #define swap(x,y,t) { \
> 			t *p1 = &(x), *p2 = &(y), tmp; \
>  \
[...swap code...]
> Also, pointer types would have to be typedef'd to be useful as
> swap(x,y,char *) would not quite work (but w/ a typedef it works
> fine.)

     Because you wrote the declaration carelessly.  Should  work fine if
you write it as
	{ \
	 t *p1 = &(x);
	 t *p2 = &(y);
	 t tmp;
(assuming there are no side-effects in the type argument :-).   See, now
*I* always write declarations one declaration per variable, even writing
	int i;
	int j;
instead of
	int i,j;
This sort of thing is where the habit pays off (preen preen :-).

Now  you *still*  need  a  typedef  when  the  type involves  arrays  or
functions (such as a pointer to function, a  reasonable thing to want to
exchange).  I  suspect  there  is no  way  around  this, anyone  care to
produce a counterexample?
-- 
					der Mouse

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