exercise 3.64, 65

まずい、今日は進みが遅い・・・。
それ以上に生活リズムが…

ex3.64

(define (stream-limit stream tolerance)
  (if (< (abs (- (stream-car stream) (stream-car (stream-cdr stream))))
         tolerance)
      (stream-car (stream-cdr stream))
      (stream-limit (stream-cdr stream) tolerance)))

(define (sqrt x tolerance)
  (stream-limit (sqrt-stream x) tolerance))

ex3.65

(define (ln2-summands n)
  (cons-stream (/ 1.0 n)
               (stream-map - (ln2-summands (+ n 1)))))

(define ln2-stream
  (partial-sums (ln2-summands 1.0)))