Xref: utzoo comp.lang.c:15792 comp.lang.c++:2481
Path: utzoo!attcan!uunet!lll-winken!ncis.llnl.gov!helios.ee.lbl.gov!pasteur!ames!pacbell!att!chinet!mcdchg!clyde!wayback!atux01!gal
From: gal@atux01.UUCP (G. Levine)
Newsgroups: comp.lang.c,comp.lang.c++
Subject: Re: Would *you* get caught by this one?
Summary: parentheses!!!
Keywords: Assignops
Message-ID: <946@atux01.UUCP>
Date: 24 Jan 89 15:43:11 GMT
References: <139@mole-end.UUCP> <1989Jan13.085902.2057@LTH.Se>
Organization: AT&T CSEd/CET, Piscataway, N.J.
Lines: 25

In article <1989Jan13.085902.2057@LTH.Se>, newsuser@LTH.Se (LTH network news server) writes:
> In article <139@mole-end.UUCP> mat@mole-end.UUCP (Mark A Terribile) writes:
> >	When is     a *= b      not the same as     a = a * b   ?
>
> For example, if you have:
>
> 	#define b x + y
>
> then:
>
> 	a *= b		<=> 	a *= (x + y)
> 	a = a * b	<=>	a = (a * x) + y

This is why its so important to use parentheses in a #define
statement.  Changing the define statement to

	#define b (x + y)

will save a lot ot headaches!

					gary

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