SICPゼミ第12回

ほげぴよ〜

練習問題2.71

こんな感じだから最も頻度が高い文字が1bitで最も頻度が低いものがn-1bit

SICPゼミ第11回

練習問題2.59

(define (union-set set1 set2)
	(cond
		((null? set1) set2)
		(else (adjoin-set (car set1) (union-set (cdr set1) set2)))
		)
	)

by dolicas

練習問題2.60

union-set、adjoin-setは実装が楽で計算も軽い。intersectionの効率が悪い。これ役に立つシチュエーションってあるの？

SICPゼミ第10回

練習問題2.53

gosh> (list 'a 'b 'c)
(a b c)
gosh> (list (list 'george ))
((george))
gosh> (cdr '((x1 x2) (y1 y2)))
((y1 y2))
gosh> (cadr '((x1 x2) (y1 y2)))
(y1 y2)
gosh> (pair? (car '(a short list )))
#f
gosh> (memq 'red '((red shoes) (blue socks )))
#f
gosh> (memq 'red '(red shoes blue socks ))
(red shoes blue socks)

by pine

SICPゼミ第9回

練習問題2.43

(queen-cols (- k 1)) をk回呼び出しているのでごみ。

注意

これから先の範囲は図形言語を前提としているので、tube は Racket で、ほか三人は Gauche でがんばって図形言語を入れました。

SICPゼミ第8回

練習問題2.33

(define nil '())

(define (accumulate op initial sequence)
  (if (null? sequence)
      initial
      (op (car sequence)
          (accumulate op initial (cdr sequence )))))

(define (map p sequence)
  (accumulate (lambda (x y) (cons (p x) y)) nil sequence ))

(define (append seq1 seq2)
  (accumulate cons seq2 seq1))

(define (length sequence)
  (accumulate (lambda (x y) (+ y 1)) 0 sequence ))

by pine

(define (map p sequence)
  (accumulate (lambda (x y) (cons (p (car sequence)) (map p (cdr sequence)) )) nil sequence))

SICPゼミ第7回

練習問題2.24

練習問題2.25

(car (cdr (car (cdr (cdr (list 1 3 (list 5 7) 9))))))
(car (car (list (list 7))))
(car (cdr (car (cdr (car (cdr (car (cdr (car (cdr (car (cdr (list 1 (list 2 (list 3 (list 4 (list 5 (list 6 7))))))))))))))))))

by pine

(define x (list 1 3 (cons 5 7) 9))
(cdaddr x)

(define x (list (list 7)))
(caar x)

(define x (cons 1 (cons 2 (cons 3 (cons 4 (cons 5 (cons 6 7)))))))
(cddr (cddddr x))

by tube

どうもcaaaarとか調子乗ると死ぬっぽい

(cadr (caddr (list 1 3 (list 5 7) 9)))

は動くけど，

(cadaddr (list 1 3 (list 5 7) 9))

は死ぬ

SCIPゼミ第6回

練習問題2.12

(define (make-center-percent c p) 
	(define w (* c (/ p 100)))
	(make-interval (- c w) (+ c w)))

by どりきゃす