鑑於LISP評估函數的以下definition - 添加defmacro
函數需要什麼? (甚至只是評估宏)鑑於以下LISP評估函數 - 添加defmacro需要什麼?
(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)))))
(eval '(car '(a a)))
這是另一種[宏觀實現方法] [1]。 [1]:http://stackoverflow.com/questions/3465868/how-to-implement-a-lisp-macro-system/10363040#10363040 – hawkeye 2012-04-28 11:26:49