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2015-12-11から1日間の記事一覧

SICP 問題 3.65

(define (ln2-summands n) (cons-stream (/ 1.0 n) (stream-map - (ln2-summands (+ n 1))))) (define ln2-stream (partial-sums (ln2-summands 1))) gosh> (stream-head ln2-stream 20) 1.0 0.5 0.8333333333333333 0.5833333333333333 0.7833333333333332 …

SICP 問題 3.64

(define (sqrt-improve guess x) (average guess (/ x guess))) (define (average x y) (/ (+ x y) 2)) (define (stream-limit s tolerance) (let ((s1 (stream-car s)) (s2 (stream-car (stream-cdr s)))) (if (> tolerance (abs (- s1 s2))) s2 (stream-li…

SICP 問題 3.63

(define (sqrt-stream x) (define guesses (cons-stream 1.0 (stream-map (lambda (guess) (sqrt-improve guess x)) guesses))) guesses) (define (sqrt-stream x) (cons-stream 1.0 (stream-map (lambda (guess) (sqrt-improve guess x)) (sqrt-stream x)))…