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From: tim@amdcad.AMD.COM (Tim Olson)
Newsgroups: comp.unix.questions
Subject: Re: Wierd Compilers
Message-ID: <18998@amdcad.AMD.COM>
Date: Wed, 4-Nov-87 11:59:51 EST
Article-I.D.: amdcad.18998
Posted: Wed Nov  4 11:59:51 1987
Date-Received: Sat, 7-Nov-87 10:17:19 EST
References: <367@white.gcm> <18964@amdcad.AMD.COM> <44177@beno.seismo.CSS.GOV>
Reply-To: tim@amdcad.UUCP (Tim Olson)
Organization: Advanced Micro Devices
Lines: 25
Keywords: Sun

In article <44177@beno.seismo.CSS.GOV> rick@seismo.CSS.GOV (Rick Adams) writes:
| Even a mediocre compiler should be able to recognize that
| 	a++;
| is equivalent to
| 	++a;
| if there is no assignment, etc.
| 
| There is really no excuse for not making this trivial optimization. You should
| not have to depend on the user doing it.

If a compiler made this "optimization" in the original programs to which
this discussion is referring, it would be wrong.  The return value of
the decrement operators *is* used, by the while statement.

#1:
	count = 5000;
	while (--count);	/* executes 4999 loops */
	
#2:
	count = 5000;
	while (count--);	/* executes 5000 loops */
	
	-- Tim Olson
	Advanced Micro Devices
	(tim@amdcad.amd.com)