extended euclid iter2

;extended euclid algorithm

(define (solve-ax+by=1 a b)
  (euclid1 a b (floor (/ a b)) (modulo a b) 1 0 0 1))
(define (euclid1 dividend divisor quot rem x y x1 y1)
  ;; What is the invalid case?
  (cond ((not (= (gcd dividend divisor) 1)) (display "no solution orz"))
        ((= rem 0) (cons x1 y1))
        (else (euclid1 divisor rem (floor (/ divisor rem)) (modulo divisor rem) x1 y1 (- x (* quot x1)) (- y (* quot y1))))))