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Implementation of MAP, SOME, EVERY, etc...

Moon claims:

    The Common Lisp LENGTH function returns NIL when given a circular list.

I disagree.  On page 265 of the aluminum edition, we find the following

"LIST-LENGTH differs from LENGTH when the list is circular; LENGTH may
 fail to return, whereas LIST-LENGTH will return NIL."

The feeling was that LENGTH was used often, and we didn't want to
require that it run more slowly on all lists just to accommodate the
rare case of a circular list.

-- Scott