Path: utzoo!mnetor!uunet!husc6!ukma!rutgers!mtune!codas!killer!richardh
From: richardh@killer.UUCP (Richard Hargrove)
Newsgroups: comp.lang.c
Subject: Re: "logical" xor
Message-ID: <2800@killer.UUCP>
Date: 12 Jan 88 03:28:49 GMT
References: <2946@zeus.TEK.COM> <195@fxgrp.UUCP>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 29
Summary: need logical xor? try !=

In article <195@fxgrp.UUCP>, ljz@fxgrp.UUCP (Lloyd Zusman, Master Byte Software) writes:
> In article <2946@zeus.TEK.COM> dant@tekla.UUCP (Dan Tilque) writes:
> > ...
> >Tell me, what is the ^^ supposed to add that is not already done by ^ ?
> >The answer is nothing.  The "bitwise" xor does exactly what you would want
> >a "logical" xor to do.  In fact, the terms "bitwise" and "logical" are
> 
> I'm sorry, but I disagree.  Try running this program:

 { code and text deleted...}

> bit testing, etc.  The 'logical' versions are guaranteed to result in
> 1 or 0.

This topic came up about a year ago. I had found a need for a logical xor
operator a couple of times and added my _naive_ voice to the clamor to add 
it to C. A number of folks graciously pointed out that logical xor operator
(and its complement, logical equivalence) already exist in C: they are != 
and == used with pure "boolean" operands (canonical TRUE and FALSE, 1 and 0) 
and that any numeric operand can be converted to canonical "boolean" form 
with the != operator. Therefore 

	((x != 0) != (y != 0))

is the logical xor of x and y.

richard hargrove
...!killer!richardh
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