fork(2) download
copy 
  1. ; triple or add five
  2.  
  3. (define (make-queue) (list (list)))
  4.  
  5. (define (enqueue q x) (cons (car q) (cons x (cdr q))))
  6.  
  7. (define (head q)
  8.   (if (pair? (car q))
  9.       (caar q)
  10.       (if (pair? (cdr q))
  11.           (car (reverse (cdr q)))
  12.           (error 'head "empty"))))
  13.  
  14. (define (tail q)
  15.   (if (pair? (car q))
  16.       (cons (cdar q) (cdr q))
  17.       (if (pair? (cdr q))
  18.           (cons (cdr (reverse (cdr q))) (list))
  19.           (error 'tail "empty"))))
  20.  
  21. (define (empty? q) (and (null? (car q)) (null? (cdr q))))
  22.  
  23. (define (triple-or-add-five n)
  24.   (let loop ((queue (enqueue (make-queue) (list n))))
  25.     (if (empty? queue) #f
  26.       (let ((seq (head queue)) (queue (tail queue)))
  27.         (if (= (car seq) 1) seq
  28.           (if (< (car seq) 1) (loop queue)
  29.             (let ((queue (enqueue queue (cons (- (car seq) 5) seq))))
  30.               (if (zero? (modulo (car seq) 3))
  31.                   (loop (enqueue queue (cons (/ (car seq) 3) seq)))
  32.                   (loop queue)))))))))
  33.  
  34. (display (triple-or-add-five 24)) (newline)
  35. (display (triple-or-add-five 99)) (newline)
  36. (display (triple-or-add-five 15)) (newline)
Success #stdin #stdout 0.02s 8288KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
(1 3 8 24)
(1 6 11 33 99)
#f
https://ideone.com/SqaA2U
language:
Scheme (guile 2.2.4)
created:
5 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!