member and defparameter

Question

In the following Lisp REPL interaction:

CL-USER> (defparameter *unison* 0)
*UNISON*
CL-USER> (member *unison* '(*unison*))
NIL

why is nil returned?

Answer 1

Because the *unison* variable is bound to 0, and the list has only a *unison* symbol since it's quoted. Try this in comparison:

(member *unison* (list *unison*))

This will actually evaluate the second *unison* which returns 0, resulting in a (0) list.