missing 'xor' Boolean operator

Dr. Phillip M. Feldman pfeldman at verizon.net
Sat Jul 18 03:09:37 CEST 2009


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


MRAB-2 wrote:
> 
> 
> <snip>
> 
> What values should 'xor' return? IMHO, if only one of the values is true
> then it should return that value, otherwise it should return False.
> 
>      1 xor 0 => 1
>      0 xor 2 => 2
>      1 xor 2 => False
>      0 xor 0 => False
> 
> This is because it's a Boolean operator, so it should fall back to
> Boolean values when necessary, like 'not':
> 
>      not 0 => True
>      not 1 => False
> 
> Also:
> 
>      x and y and z => (x and y) and z
>      x or y or z => (x or y) or z
> 
> therefore:
> 
>      x xor y xor z => (x xor y) xor z
> -- 
> http://mail.python.org/mailman/listinfo/python-list
> 
> 

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