For completeness, we repeat here the necessary constants and low-level functions from ELIZA:

(defconstant f a i l n i l "Indicates pat-match f a i l u r e ")

(defconstant no-bindings '((t . t))

"Indicates pat-match success, with no v a r i a b l e s .")

(defun variable-p (x)

" Is x a variable (a symbol beginning with '?'I?"