Re: Exclusive-or

[Hans Boldt <boldt@xxxxxxxxxx>]

Mark:  I'll see what I can do.  I agree that XOR is logically a different
operation from <>.  For one thing, it belongs in a different place in the
precedence hierarchy.

Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com




owner-midrange-l@midrange.com on 98-03-29 01:04:15
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Subject: Exclusive-or


Hans,

At 08:40 AM 3/26/98 -0500, you wrote:
>>Hi Mark!  How to check if exactly 1 out of n conditions is true?

>I can't think of any easy way to do that.  With a bit of analysis, it's
clear that
>A XOR B XOR C works for all cases except where all three operands
>are true.  Generalizing to more conditions, it appears that stringing
>together conditions using XOR gives TRUE if the number of TRUE
>conditions is odd, FALSE if an even number.  So it looks like some
>other technique is needed.

 I was thinking the same thing.  I was thinking through the logic and came
to the same conlusion as you did.

>Will XOR be added to RPG IV?  About half a year ago, I suggested
>that it might be.  However, when I raised the idea in my group, the
>response was why bother, since <> provides equivalent function.
>So, one way to answer the question is that the language already
>has XOR!

 Except that from a program maintenance (readability) aspect, "<>"
definitely not as clear as XOR.  Logically, it is a lot more similar to AND
and OR than it is to conditioning operands. Technically, it works.  Can you
reinstate the vote?  Thanks.

>But if an explicit XOR is added, it still wouldn't help for
>your specific situation.

 Agreed.

 -mark

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