On Wed, Jul 15, 2009 at 3:57 PM, Wayne Brehaut<wbreh...@mcsnet.ca> wrote: > On 15 Jul 2009 09:11:44 GMT, Steven D'Aprano > <ste...@remove.this.cybersource.com.au> wrote: > >>On Tue, 14 Jul 2009 11:25:08 -0700, Dr. Phillip M. Feldman wrote: >> >>> Current Boolean operators are 'and', 'or', and 'not'. It would be nice >>> to have an 'xor' operator as well. >> >>I've often wished there was too, for the sake of completeness and >>aesthetics, I'd love to be able to write: >> >>a xor b >> >>instead of defining a function xor(a, b). >> >>Unfortunately, outside of boolean algebra and simulating electrical >>circuits, I can't think of any use-cases for an xor operator. Do you have >>any? > > Since xor in set theory is the symmetric difference, perhaps we'd > like to know all items in exactly one of two word lists or > dictionaries, or anything else we could easily set-ize: > >>>> cheese = set(['cheddar', 'limburger', 'stilton']) >>>> stinky = set(['skunk', 'limburger', 'stilton', 'polecat', 'doggy-doo', >>>> 'civet']) >>>> nasty = set(['doggy-doo', 'polecat', 'limburger', 'Perl']) >>>> cheese & stinky # stinky cheese > set(['limburger', 'stilton']) >>>> cheese ^ stinky # either cheese or stinky but not both > set(['doggy-doo', 'civet', 'polecat', 'skunk', 'cheddar']) >>>> cheese ^ stinky ^ nasty # in an odd number of these sets (1 or 3) > set(['civet', 'cheddar', 'Perl', 'limburger', 'skunk']) > > Who hasn't needed that occasionally?
This discussion is about adding a *logical* operator for use in boolean expressions. We obviously already have ^ for non-boolean use. Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
