missing 'xor' Boolean operator

[pdpi]

On Jul 15, 12:37 pm, Christian Heimes <li... at cheimes.de> wrote:
> pdpi wrote:
> > On Jul 15, 12:08 am, Christian Heimes <li... at cheimes.de> wrote:
> >> Chris Rebert wrote:
> >>> Using the xor bitwise operator is also an option:
> >>> bool(x) ^ bool(y)
> >> I prefer something like:
>
> >>     bool(a) + bool(b) == 1
>
> >> It works even for multiple tests (super xor):
>
> >>   if bool(a) + bool(b) + bool(c) + bool(d) != 1:
> >>       raise ValueError("Exactly one of a, b, c and d must be true")
>
> >> Christian
>
> > "if bool(a) + bool(b) + bool(c) + bool(d) != 1:" is not equivalent to
> > xor. 1 xor 1 xor 1 = 1 xor (1 xor 1) = 1 xor 0 = 1 (or = (1 xor 1) xor
> > 1 = 0 xor 1 = 1 if you assicate to the left)
>
> I'm well aware of the fact that I've described something differently.
> 'xor' can be explained as 'check if exactly one element of two elements
> is true'. My algorithms describes a super xor, aka 'check if exactly one
> element of n elements is true'.
>
> Christian

Well, I just wouldn't call it a "super xor" then, when "unicity test"
works much better -- especially as an alternative to an actual xor
without any specification to the actual intended functionality except
the exception text.