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From: keesan@bbn.com (Morris M. Keesan)
Newsgroups: comp.lang.c
Subject: Re: Type-independent ABS
Keywords: abs labs
Message-ID: <46916@bbn.COM>
Date: 13 Oct 89 20:59:48 GMT
References: <1392@cipc1.Dayton.NCR.COM>
Sender: news@bbn.COM
Reply-To: keesan@bbn.com (Morris M. Keesan)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 16

In article <1392@cipc1.Dayton.NCR.COM> gmaranca@cipc1.Dayton.NCR.COM (Gabriel Maranca) writes:
>#define ABS(x) (((x) < 0) ? (-(x)) : (x))
. . .
>bill davidsen (davidsen@crdos1.crd.GE.COM) writes:
>>	1. instead of -(x) use (-(x)).
>Good point. I had overlooked this potential trap in my original macro.

I don't see why the extra parentheses are necessary, or their absence a trap.
#define ABS(x) ((x) < 0 ? -(x) : (x))
should work fine, because both < and - have higher precedence than ?:, and the
whole expansion is protected by the outermost parentheses.  It's not as if
-(x) were the full expansion of the macro.
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