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From: simons@tetrauk.UUCP (Simon Shaw)
Newsgroups: comp.lang.c
Subject: Re: TRUE and FALSE
Message-ID: <728@tetrauk.UUCP>
Date: 7 Sep 90 11:33:09 GMT
References: <11215@alice.UUCP> <514@demott.COM> <2316@cirrusl.UUCP> <F4u9._?1@cs.psu.edu> <926@hls0.hls.oz>
Reply-To: simons@tetrauk.UUCP (Simon Shaw)
Organization: Tetra Ltd., Maidenhead, UK
Lines: 35

In article <926@hls0.hls.oz> george@hls0.hls.oz (George Turczynski) writes:
>In article <F4u9._?1@cs.psu.edu>, flee@guardian.cs.psu.edu (Felix Lee) writes:
>
>> Personally, I use this set of macros:
>> #define CNAND(a,b)	(!((a)&&(b)))
>> #define CNOT(a)		CNAND(a,a)
>> #define CXOR(a,b)	CNAND(CNAND(a,CNOT(b)),CNAND(b,CNOT(a)))
> 
>Why not try these:
> 
>#define CNOT(a)        (!(a)) 
>#define CAND(a,b)      ((a)&&(b)) 
>#define COR(a,b)       ((a)||(b)) 
>#define CNOR(a,b)      CNOT(COR(a,b)) 
>#define CXOR(a,b)      CNOR(CAND(a,b),CNOR(a,b)) 

If because the value returned by an expression of the form (a == b)
is _defined_ to be 0 or 1, we are defining TRUE as 1 and ZERO as 0
(no contention yet, I hope), then the worst of these expansions, 
XOR, should be contracted by the use of the bitwise XOR.

#define	CXOR(a,b) ((a)^(b))

with this assumption (TRUE==1, FALSE==0), are there any circumstances 
where the use of the bitwise operator would be unsafe ?

IMHO, the compounds NOR and NAND, while much more useful if constructing 
electronic circuitry, are considerably less clear in code (Not to mention
XNOR, which even now takes me a few seconds to work out).  Lets not
forget the poor sods who've got to maintain this code !

Anyone disagree ?

-- 
Simon Shaw ; simons@tetrauk.uucp