test_streams.scm

;:
;: The stream can be implemented by lazy evaluator.
;: Please run (load "test_streams.scm") in lazy-evaluator's REPL.


(define (cons x y)
    (lambda (m) (m x y)))

(define (car z)
    (z (lambda (p q) p)))

(define (cdr z)
    (z (lambda (p q) q)))


(define (list-ref items n)
    (if (= n 0)
        (car items)
        (list-ref (cdr items) (- n 1))))

(define (map proc items)
    (if (null? items)
        '()
        (cons (proc (car items))
              (map proc (cdr items)))))


(define (scale-list items factor)
    (map (lambda (x) (* x factor))
         items))

(define (add-lists list1 list2)
    (cond ((null? list1) list2)
          ((null? list2) list2)
          (else (cons (+ (car list1) (car list2))
                      (add-lists (cdr list1) (cdr list2))))))

(define ones (cons 1 ones))

(define integers (cons 1 (add-lists ones integers)))