missing 'xor' Boolean operator
Mark Dickinson
dickinsm at gmail.com
Tue Jul 21 04:51:50 EDT 2009
On Jul 20, 11:34 pm, Ethan Furman <et... at stoneleaf.us> wrote:
> Dr. Phillip M. Feldman wrote:
> > Suppose that 'xor' returns the value that is true when only one value is
> > true, and False otherwise. This definition of xor doesn't have the
> standard
> > associative property, that is,
> >
> > (a xor b) xor c
> >
> > will not necessarily equal
> >
> > a xor (b xor c)
> >
> > To see that this is the case, let a= 1, b= 2, and c= 3.
> >
> > (a xor b) xor c
> >
> > yields 3, while
> >
> > a xor (b xor c)
> >
> > yields 1. So, I'd prefer an xor operator that simply returns True or
> False.
> >
> > Phillip
> >
>
> You are, of course, free to write your version however it makes sense to
> you and your team. :)
>
> Since the 'and' and 'or' already return objects (and objects evaluate to
> true or false), then 'xor' should behave likewise, IMO. I expect that
> would be the case if it were ever added to the language.
I'm not so sure. Did you ever wonder why the any() and all()
functions introduced in 2.5 return a boolean rather than returning
one of their arguments? (I did, and I'm still not sure what the
answer is.)
Mark
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