From: Tom Kramer
Subject: Re: puzzle
Date: Wed, 17 Feb 1993 15:06:14 +0000
Message-ID: <20959@cosmos.cme.nist.gov>

The question was:
> What is the shortest non-atomic expression (fails atomp) that
> returns itself?

In the LISP I am running, Allegro Common LISP, (atom -) returns nil,
and the single character expression consisting of nothing but a 
minus sign "-" (without the quotes) returns itself. Can't get shorter
than that.