Keith Hodges wrote:
> true xor: [ true ]  => true

I don't think it's a bug. Unless you want to sprinkle lots of code with 
type tests, the result is whatever the implementation says, in this case:

xor: aBoolean
	"Exclusive OR. Answer true if the receiver is not equivalent to aBoolean."

	^(self == aBoolean) not

You could equally complain about

	true & "anything"

answering the argument instead of raising an error.

Cheers,
   - Andreas