Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!ptsfa!ames!nrl-cmf!ukma!gatech!udel!rochester!rutgers!im4u!ut-sally!utah-cs!utah-gr!uplherc!esunix!rushfort
From: rushfort@esunix.UUCP (Kevin Rushforth)
Newsgroups: comp.lang.c
Subject: Re: Autoincrement question
Message-ID: <618X@esunix.UUCP>
Date: 21 Jan 88 00:00:00 GMT
References: <548@tuvie>
Organization: Evans & Sutherland, Salt Lake City, Utah
Lines: 31

in article <548@tuvie>, rcvie@tuvie (ELIN Forsch.z.) says:
> If there is any necessity to have the whole semantic in one *expression*, use
> the comma operator, as
> 
> bar->tmp = bar, bar++;
> 
> This operator *guarantees* the sequential evaluation of its operands from
> left to right.

Not quite.  While it is true that bar will be evaluated before bar++,
it is bar++, not bar, that will be assigned to bar->tmp.  There is no
guarantee as to whether bar++ or *bar (as used in bar->tmp) will be
evaluated first.  In fact, this expression is identical to:

	bar->tmp = bar++;

which was the original expression that caused the problem.  Better stick to
the two statement version:

bar->tmp = bar;
bar++;

Or the following one statement version:

bar->tmp = bar + 1;
-- 
                Kevin C. Rushforth
                Evans & Sutherland Computer Corporation

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