1) NIL is a symbol. Like all symbols, it has a plist (see CLtL p.4 for an
example).
2) NIL is a list.
Therefore, does (SETQ z NIL)
(SETF (GETF z :a) :b)
z
return NIL or (:a :b)? (That is, does the property go on NIL's plist or
directly into the list referenced by z?)
Golden Common LISP (ver. 2.2LM) resolves this by having no plist on NIL. I
consider this a bug, however.
David Loewenstern
<dml@nadc>