Programmation déclarative - Q4A - 08/2012

(define (sub-stream s)
  (letrec
      ((elements-to-jump (lambda ()
                           (truncate (* (random) 100))
                           )
                         )
       (jump-elements (lambda (s n)
                        (if (= n 0)
                            s
                            (jump-elements (tail s) (- n 1))
                            )
                        )
                      )
       )
    (let
        ((jumped (jump-elements s (elements-to-jump))))
      (cons-stream (head jumped) (sub-stream (tail jumped)))
      )
    )
  )