Exercises 2.2.2 - S.O.W - SICPお勉強Wiki

Chapter 2.2.2

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Exercise 2.24

(define ans (cons 1 (cons (cons 2 (cons (cons 3 (cons 4 '())) '())) '())))
 

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Exercise 2.25

(define (pick x ls)
  (define (sub x ls)
    (if (null? ls) false
        (if (pair? ls) (pick x ls) (if (= x ls) true false))))
  (if (not (sub x (car ls))) (sub x (cdr ls)) true))
 

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Exercise 2.26

> (define x (list 1 2 3))
> (define y (list 4 5 6))
> (append x y)
(1 2 3 4 5 6)
> (cons x y)
((1 2 3) 4 5 6)
> (list x y)
((1 2 3) (4 5 6))
 

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Exercise 2.27

(define (rev ls)
  (define (it ls re)
    (if (null? ls) re (it (cdr ls) (cons (car ls) re))))
  (it ls '()))
(define (d-rev ls)
  (define (it ls re)
    (if (null? ls) re
        (if (pair? (car ls))
            (it (cdr ls) (cons (d-rev (car ls)) re))
            (it (cdr ls) (cons (car ls) re)))))
  (it ls '()))
 

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Exercise 2.28

(define (fringe ls)
  (if (null? ls)
      '()
      (if (pair? (car ls))
          (fringe (append (car ls) (fringe (cdr ls))))
          (cons (car ls) (fringe (cdr ls))))))
 

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Exercise 2.29

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Exercise 2.30

(define (square-tree tree)
  (define (square x) (* x x))
  (map (lambda (sub)
         (if (pair? sub)
             (square-tree sub)
             (square sub)))
       tree))
 

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Exercise 2.31

(define (tree-map f tree)
  (map (lambda (x)
         (if (pair? x)
             (tree-map f x)
             (f x)))
       tree))
 

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Exercise 2.32

(define (subsets s)
  (define (g x) (cons (car s) x))
  (if (null? s)
      (list '())
      (let ((rest (subsets (cdr s))))
        (append rest (map g rest)))))