enum-coprimes.sps

#!r6rs

(import (rnrs))

(define (print . args)
  (for-each display args)
  (newline))

(define (enum-coprimes/stern-brocot-tree N)
  (let recur ([a 0] [b 1] [x 1] [y 1])
    (let ([n (+ a x)]
          [d (+ b y)])
      (when (<= d N)
        (print n ", " d)
        (recur a b n d)
        (recur n d x y)))))

(define (enum-coprimes/reverse-euclid N)
  (let recur ([a 1] [b 1])
    (let loop ([d (+ a b)])
      (when (<= d N)
        (print b ", " d)
        (recur b d)
        (loop (+ d b))))))


(enum-coprimes/stern-brocot-tree 6)
(print "--------------------")
(enum-coprimes/reverse-euclid 6)