parser.lisp (defun is-whitespace (c) (or (eq c #\Space) (eq c #\Tab) (eq c #\Return))) (defun is-comment-char (c) (or (eq c #\;) (eq c #\#))) eq should be changed into char=, since "Common Lisp makes no guarantee that eq is true even when both its arguments are ``the same thing'' if that thing is a character or number." Best regards, S. Kondratyev.