;;; -*- Scheme -*-
;;;
;;; list.xhl
;;;
;;; Simple list implementation using lambda expressions
;;;
;;; Created 980317
;;;
;;; Authors: Magnus Ljung and Stefan Hellkvist


;; Cons
;;
;; Each node in the list is a lambda expression

(define cons
  (lambda (f s)
    (lambda (w)
      (if (equal? w 1)
	  f
	  s))))

(define car
  (lambda (p)
    (p 1)))

(define cdr
  (lambda (p)
    (p 2)))

(define null? (lambda (o) (equal? o nil)))


(define print-list
  (lambda (l)
    (define inside
      (lambda (l)
	(if (null? l)
	    nil
	    ((lambda ()
	       (insert (car l) (if (null? (cdr l)) "" " "))
	       (inside (cdr l)))))))
    (insert "(")
    (inside l)
    (insert ")")))

(define map
  (lambda (func l)
    (if (null? l)
	nil
	(cons (func (car l)) (map func (cdr l))))))

(define for-each
  (lambda (func l)
    (if (null? l)
	nil
	((lambda ()
	   (func (car l))
	   (for-each func (cdr l)))))))

(define list-ref
  (lambda (ls n)
    (if (null? ls)
	nil
	(if (equal? 0 n)
	    (car ls)
	    (list-ref (cdr ls) (- n 1))))))