問題 3-70 - 72

3-70 を解こうと思いましたが，下記のが gosh で暴走してしまって (たぶん無限ループしてる)，にっちもさっちもいかない! 飛ばす!!

(define (merge-weighted s1 s2 weight)
  (cond ((stream-null? s1) s2)
        ((stream-null? s2) s1)
        (else
         (let ((s1car (stream-car s1))
               (s2car (stream-car s2)))
           (if (< (weight s1car) (weight s2car))
               (cons-stream s1car (merge-weighted (stream-cdr s1) s2 weight))
               (cons-stream s2car (merge-weighted s1 (stream-cdr s2) weight)))))))

(define (weighted-pairs s t weight)
  (cons-stream
   (list (stream-car s) (stream-car t))
   (merge-weighted
    (stream-map (lambda (x) (list (stream-car s) x))
                (stream-cdr t))
    (weighted-pairs (stream-cdr s) (stream-cdr t) weight)
    weight)))

(define ansA
  (weighted-pairs integers integers (lambda (x) (+ (car pair) (cadr pair)))))

(stream-ref ansA 1)