SchemeJS

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Archivierte Version vom 2016-05-06T16:17:31+00:00. Aktuelle Version

(define stream-car car)

(define stream-cdr
  (lambda (stm)
    (force (cdr stm))))

(define-syntax stream-cons
  (syntax-rules ()
    ((_ head tail) (cons head (delay tail)))))

(define make-stream 
  (lambda (seed proc)
    (letrec 
      ((stream-builder
         (lambda (n)
           (stream-cons n (stream-builder (proc n))))))
      (stream-builder seed))))
  
(define stream-item
  (lambda (str k)
    (if (= k 0)
      (stream-car str)
      (stream-item (stream-cdr str) (- k 1)))))

(define stream-map
  (lambda (f str)
    (stream-cons
     (f (stream-car str))
     (stream-map f (stream-cdr str)))))

(define print-stream
  (lambda (stm n)
    (cond
      ((<= n 0) (display "...")(newline))
      (else
       (display (stream-car stm))
       (display ", ")
       (print-stream (stream-cdr stm) (- n 1))))))

(define nat_zahlen (make-stream 0 (lambda (n) (+ n 1))))
(print-stream nat_zahlen 11)

SchemeJS

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