XOR

[David C. Plummer <DCP@SCRC-QUABBIN.ARPA>]

    Date: Mon, 16 Dec 85 13:05 EST
    From: Guy Steele <gls@THINK-AQUINAS.ARPA>

	Date: Sun, 15 Dec 85 16:35 EST
	From: David A. Moon <Moon@SCRC-STONY-BROOK.ARPA>

	The XOR function in your list of suggested language improvements
	handed out last week was intended to be a joke, wasn't it?  I assumed
	it was, but other people on the mailing list are taking it seriously,
	so I'm asking for clarification.

    Of all the functions not in Common Lisp that I use day-to-day on my
    3600, this is the one I use most frequently.  I admit that I have been,
    among other things, constructing logic models of various kinds.
    However, I also find it useful in random COND clauses.  Maybe the rest
    of you will decide it is not useful, but in any case it is not a joke.

One argument I have heard against XOR is that, unlike AND and OR, it
must evaluate all of its forms.

Of course, MLB once sent an amusing thing describing an XOR that returns
the right answer but somehow knows what the forms evaluate to so it can
stop early after the things it doesn't know a priori !-}