ref: 63274538954ad3aa062290f7a349ff461adca2b4
dir: /attic/system-old.lsp/
(define (equal a b)
(if (and (consp a) (consp b))
(and (equal (car a) (car b))
(equal (cdr a) (cdr b)))
(eq a b)))
; compare imposes an ordering on all values. yields -1 for a<b,
; 0 for a==b, and 1 for a>b. lists are compared up to the first
; point of difference.
(defun compare (a b)
(cond ((eq a b) 0)
((or (atom a) (atom b)) (if (< a b) -1 1))
(T (let ((c (compare (car a) (car b))))
(if (not (eq c 0))
c
(compare (cdr a) (cdr b)))))))
(defun length (l)
(if (null l) 0
(+ 1 (length (cdr l)))))
(define (assoc item lst)
(cond ((atom lst) ())
((eq (caar lst) item) (car lst))
(T (assoc item (cdr lst)))))