Lisp's eval function

eval.lisp

(label eval (lambda (e a)
  (cond
    ((atom e) (assoc e a)
    ((atom (car e))
     (cond
       ((eq (car e) quote) (cadr e))
       ((eq (car e) atom)  (atom (eval (cadr e) a)))
       ((eq (car e) eq)    (eq   (eval (card e a)
                                 (eval (caddr e) a)))
       ((eq (car e) car)   (car  (eval (cadr e) a)))
       ((eq (car e) cdr)   (cdr  (eval (cadr e) a)))
       ((eq (car e) cons)  (cons (eval (cadr e) a)
                                 (eval (caddr e) a)))
       ((eq (car e) cond)  (evcon (cdr e) a))
       (t (eval (cons (assoc (car e) a)
                      (cdr e))
                 a))))
    ((eq (caar e) label)
     (eval (cons (caddar e) (cdr e))
           (cons (list (cadar e) (car e)) a)))
    ((eq (caar e) lambda)
     (eval (caddar e)
           (append (pair (pair (cadar e) (evlis (cdr e) a))
                         a))))))
(defun evcon (c a)
  (cond ((eval (caar c) a)
         (eval (cadar c) a))
        (t (evcon (cdr c) a))))
(defun evlis (m a)
  (cond ((null m) f)
        (t (cons (eval  (car m) a)
                 (evlis (car m) a)))))