Programmation déclarative - Q1AB - 06/2012

(define (number->list n)
  (letrec
      ((convert (lambda (x l)
                 (if (= x 0)
                     l
                     (convert (truncate (/ x 10)) (cons (inexact->exact (modulo x 10)) l))
                     )
                  )
               ))
    (convert (exact->inexact n) '())
    )
  )

(define (fold f null l)
  (if (eq? l '())
      null
      (fold f (f (car l) null) (cdr l))))

(define (multiple-de-3 n)
  (if (or (= n 3) (= n 6) (= n 9))
      #t
      (if (< n 9)
          #f
          (multiple-de-3 (fold + 0 (number->list n)))
          )
      )
  )