Re: 7 logical-xor implementations in source tree

[Paul Eggert]

Mattias Engdegård wrote:

> I would probably use the negation, boolean equivalence, more often than xor 
> myself.

Me too. This was also Dijkstra's opinion (I attended an infamous lecture by him 
on the subject).

> define-inline in particular will produce decent code.

I don't think performance is much of a concern here, and would favor defining 
them as functions instead; that's simpler and allows them to be used in more 
contexts when code is written using a functional style.

> +(defmacro equiv (&rest args)
> +  "Boolean equivalence: t if arguments are all non-nil or all nil."

When equiv has one or more arguments and they are all non-nil, it might be more 
useful for equiv to return its last argument instead of returning t. Of course 
I'm bike-shedding here....