learning-sicp

My embarrassing half assed SICP run.
git clone https://kaka.farm/~git/learning-sicp
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exercise-15.scm (1094B)

      1 (define-library (sicp solutions chapter-1 exercise-15)
      2   (import (scheme base)
      3           (scheme write))
      4   (export sine
      5           sine-times)
      6 
      7   (begin
      8     (define (cube x) (* x x x))
      9 
     10     (define (p x) (- (* 3 x) (* 4 (cube x))))
     11 
     12     (define (sine angle)
     13       (if (not (> (abs angle) 0.1))
     14           angle
     15           (p (sine (/ angle 3.0)))))
     16 
     17     (define (sine-times angle)
     18       (let loop ((angle angle)
     19                  (times 1))
     20         (display (string-append "angle: "
     21                                 (number->string angle)
     22                                 "; times: "
     23                                 (number->string times)))
     24         (newline)
     25         (if (not (> (abs angle) 0.0001))
     26             (cons angle
     27                   times)
     28             (let* ((result (loop (/ angle 3.0)
     29                                  (+ times 1)))
     30                    (approx (p (car result))))
     31               (display (string-append "approximation: "
     32                                       (number->string approx)))
     33               (newline)
     34               (cons approx
     35                     (cdr result))))))))