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; The Lisp defined in McCarthy's 1960 paper, translated into CL. | |
; Assumes only quote, atom, eq, cons, car, cdr, cond. | |
; Bug reports to lispcode@paulgraham.com. | |
(defun null. (x) | |
(eq x '())) | |
(defun and. (x y) | |
(cond (x (cond (y 't) ('t '()))) | |
('t '()))) | |
(defun not. (x) | |
(cond (x '()) | |
('t 't))) | |
(defun append. (x y) | |
(cond ((null. x) y) | |
('t (cons (car x) (append. (cdr x) y))))) | |
(defun list. (x y) | |
(cons x (cons y '()))) | |
(defun pair. (x y) | |
(cond ((and. (null. x) (null. y)) '()) | |
((and. (not. (atom x)) (not. (atom y))) | |
(cons (list. (car x) (car y)) | |
(pair. (cdr x) (cdr y)))))) | |
(defun assoc. (x y) | |
(cond ((eq (caar y) x) (cadar y)) | |
('t (assoc. x (cdr y))))) | |
(defun eval. (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. (cadr 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. (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) '()) | |
('t (cons (eval. (car m) a) | |
(evlis. (cdr m) a))))) |
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