(defun equal (pat inp)
  (if (consp pat)          ; interior node?
      (and (consp inp)
           (equal (first pat) (first inp))
           (equal (rest pat) (rest inp)))
      (eql pat inp) ) )    ; leaf node

(defun match (pat inp) (matchb pat inp '((t t))))
(defun matchb (pat inp bindings)
  (and bindings
    (if (consp pat)           ; interior node?
        (and (consp inp)
             (matchb (rest pat) 
                     (rest inp)
                     (matchb (first pat)
                             (first inp) bindings)))
        (if (varp pat)        ; leaf: variable?
            (let ((binding (assoc pat bindings)))
              (if binding
                  (and (equal inp (second binding))
                       bindings)
                  (cons (list pat inp) bindings)))
            (and (eql pat inp) bindings)) ) ) )

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