Portable XOR

[Joseph Beckenbach {Adapter Software Release Engr}]

	Following up my own article here, and apologies for missed names:

>	In <157 at revcan.UUCP> darren at revcan.UUCP (Darren Morbey) writes,
>asking for a macro returning XOR of its arguments, evaluating once and
>only once.  I've not worked out a more elegant solution for my toolbag,

	... but I've had a light flurry of mail with comments, including
one from the Netherlands pointing out that XOR(a,XOR(b,c)) would fail using
my implementation.  Serves me right for reusing old code without doing a
double-check of other things! :-)

	Another sent me the macro
#define XOR(o,_) ((o)?!(_):(_))
which "does the right thing".  Another macro for toolbox.h :-)

		Joseph Beckenbach
		journeyman programmer
		(still working towards craftsman status)
-- 
Joseph Beckenbach	jerbil at ultra.com		VEGGIES FOREVER!
	work 408-922-0100 x246