Path: utzoo!utgpu!water!watmath!clyde!rutgers!sri-spam!ames!ucbcad!ucbvax!jade!eris!mwm
From: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer)
Newsgroups: comp.lang.c
Subject: Re: Autoincrement question
Message-ID: <6332@jade.BERKELEY.EDU>
Date: 18 Dec 87 23:55:11 GMT
References: <10898@brl-adm.ARPA>
Sender: usenet@jade.BERKELEY.EDU
Reply-To: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer)
Organization: Missionaria Phonibalonica
Lines: 28

In article <10898@brl-adm.ARPA> mrd@sun.mcs.clarkson.EDU (Michael R. DeCorte) writes:
<The statment that you should NEVER have an expression where a single
<variable has more than one post(pre)-increment(decrement)'s is correct.

Well, almost. The following expression is deterministic:

	a[i++] && a[i++] && a[i++]

<You should also NEVER post(pre)-increment(decrement) a variable that
<occurs on both side of the equation.

This is correct - the key words are "both sides of an equation".

I haven't been able to come up with a simple summary, but I think it's
better stated as:

	No expression should change the value of a variable more than once,
or reference a variable and make an assignment to it, unless the
assignment operator is at the top of the parse tree. Expressions
connected by operators that guarantee order of evaluation (`&&', `||'
and `,') can be treated disjointly.

	<mike
--
Take a magic carpet to the olden days			Mike Meyer
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Around in the clouds in a happy daze			ucbvax!mwm
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