Re: set-difference

[kab (Kim Barrett)]

> (eval-when (eval compile load)
>   (defpackage new-package (:shadowing-import-from "COMMON-LISP" set-difference))
>   (in-package :new-package))

Your problem is here.  You want (:shadow set-difference) rather than the 
:shadowing-import-from clause.

On the other hand, you might want to write your own set-difference function that 
guarantees the order, rather than relying on a particular implementation returning 
a particular order that might have changed the next time you upgrade.