RE: 7 logical-xor implementations in source tree

[Drew Adams]

> Is it hard to understand (eq (not a) (not b))?

Well, someone off list pointed out that that is
(not (xor a b)); it is not (xor a b).  Yes, of
course.

I thought it'd be enough to speak to the general
thing under discussion, for which opposite-value
names such as "equiv", "iff", and `<=>' were
proposed.

But to be more pedantic/correct, is it hard to 
understand (not (eq (not a) (not b)))?
Or if you prefer, (eq (not a) (not (not b)))?

Is lack of an `xor' (or an `equiv') operator
a problem in practice?  How often have you felt
the need for it, really?

Why do you think Emacs Lisp, which was by design 
smaller than Common Lisp, needs such a function,
but Common Lisp does not?  What's the special
need we have for this?