Why can't I xor strings?

dimitri pater dimitri.pater at gmail.com
Fri Oct 8 23:02:22 CEST 2004


On Fri, 8 Oct 2004 16:59:02 -0400, Phil Frost <indigo at bitglue.com> wrote:
> On Fri, Oct 08, 2004 at 04:53:02PM -0400, dataangel wrote:
> > Phil Frost wrote:
> >
> > >^ is the bitwise xor operator. Performing bitwise operations on strings
> > >doesn't make much sense, so it's invalid. You can define a logical xor
> > >function like so:
> > >
> > >xor = lambda p, q: (p and not q) or (not p and q)
> > >
> > >or equivalently:
> > >
> > >xor = lambda p, q: bool(p) != bool(q)
> > >
> > >On Fri, Oct 08, 2004 at 04:19:22PM -0400, dataangel wrote:
> > >
> > >
> > >> ...
> > >>Regardless of whether this is the best implementation for detecting if
> > >>two strings are similar, I don't see why xor for strings shouldn't be
> > >>supported. Am I missing something? Inparticular, I think it'd be cool to
> > >>have "xor" as opposed to "^". The carrot would return the resulting
> > >>value, while "xor" would act like and/or do and return the one that was
> > >>true (if any).
> > >
> > >
> > Nice =D
> >
> > But why no xor builtin? :P
> 
> I think it would be nice, but one argument is that it's not possible to
> short-circut xor, both sides must be evaluated to determine the result.
> Contrast this with 'and' and 'or', which know after evaluating the first
> expression if it's required to evaluate the latter. For example:
> 
> 0 and 123       -> 0
> False and 123   -> False
> 123 or False    -> 123
> 
> But since both sides of xor must be evaluated, there is no reason to
> return one expression over the other. I would argue it should always
> return True or False.
> 
> 
> --
> http://mail.python.org/mailman/listinfo/python-list
> 


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