Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!mordor!sri-spam!ames!ptsfa!dmt
From: dmt@ptsfa.UUCP (Dave Turner)
Newsgroups: comp.lang.c
Subject: Re: Associativity -- what is it?
Message-ID: <4140@ptsfa.UUCP>
Date: 25 Feb 88 01:45:09 GMT
References: <226@mccc.UUCP> <224@sdrc.UUCP> <234@mccc.UUCP> <3466@killer.UUCP>
Reply-To: dmt@ptsfa.UUCP (Dave Turner)
Organization: Pacific * Bell, San Ramon, CA
Lines: 34

In article <3466@killer.UUCP> jfh@killer.UUCP (The Beach Bum) writes:
>In article <234@mccc.UUCP> pjh@mccc.UUCP (Peter J. Holsberg) writes:
>
>
>pre-fix:	++ X	->	(X = X + 1)
>post-fix:	X ++	->	((X = X + 1), X - 1)
>
>Try this:
>		x = 5;
>		printf ("3 * x ++ = %d\n", 3 * x ++);
>		printf ("now x = %d\n", x);
>
>You should get 15 and 4.  I suspect you expected 18 or 16 or something
>like that.
>


I expected to get 15 and 6 (not 4) which is exactly what I got when I tried it.

I've always found it to be useful to look at ++x and x++ and say:

	++x	increment x before using it in another expression in the
		same statement

and

	x++	use the present value of x in any other expressions in this
		statement before incrementing x.
		X in the next statement will have the new value.

There's more to be said but the above has been satisfactory for over 11 years.


-- 
Dave Turner	415/542-1299	{ihnp4,lll-crg,qantel,pyramid}!ptsfa!dmt