simply scheme 第十四章 练习

14.1
Keep
(define (remove-once wd sent)
  (cond((empty? sent)'())
       ((equal? wd(first sent))
        (se (bf sent)))
       (else (se (first sent)(remove-once wd(bf sent))))))
14.2
Every
(define(up wd)
  (if(empty? wd)
     '()
     (se (up (bl wd))wd)))
14.3
(define (remdup sent)
  (cond((empty? sent)
        '())
       ((if(in? (first sent)(bf sent))
        (se (remdup(bf sent)))
        (se (first sent)(remdup (bf sent)))))))
(define (in? wd sent)
  (if(empty? sent)
     #f
     (if(equal? wd (first sent))
        #t
        (in? wd (bf sent)))))
14.4
(define (odds sent)
  (if(or(empty? sent)(=(count sent)1))
     (first sent)
     (se (first sent)(odds (bf(bf sent))))))
14.5
(define (letter-count sent)
  (if(empty? sent)
     0
     (+ (count (first sent))(letter-count(bf sent)))))
14.6
(define (member? wd sent)
  (if(empty? sent)
     #f
     (if(equal? wd (first sent))
        #t
        (member? wd (bf sent)))))
14.7
(define (differences sent)
  (if(=(count sent)2)
     (-(first(bf sent))(first sent))
     (se (-(first(bf sent))(first sent))
         (differences (bf sent)))))
14.8
(define (expand sent)
  (if(empty? sent)
     '()
     (if(number? (first sent))
        (se (repeat(-(first sent)1)(first(bf sent)))
            (expand (bf sent)))
        (se (first sent)(expand(bf sent))))))
(define (repeat num wd)
  (if(= num 0)
     '()
     (se wd (repeat (- num 1)wd))))
14.9
(define (l wd sent)
  (if(empty? sent)
     2
     (if(not(equal? wd (first sent)))
        (+ 1 (l wd (bf sent)))
        (+ 1))))
(define (location wd sent)
  (if(< (count sent)(l wd sent))
     #f
     (l wd sent)))
14.10
(define (count-adjacent-duplicates sent)
  (if(=(count sent)1)
     0
     (if(equal? (first sent)(first(bf sent)))
        (+ 1 (count-adjacent-duplicates (bf sent)))
        (+ (count-adjacent-duplicates (bf sent))))))
14.11
(define (remove-adjacent-duplicates sent)
  (if(=(count sent)1)
     (first sent)
     (if(equal? (first sent)(first(bf sent)))
        (se (remove-adjacent-duplicates (bf sent)))
        (se (first sent)(remove-adjacent-duplicates(bf sent))))))
14.12
(define (progressive-squares? sent)
  (if(=(count sent)1)
     #t
     (if(=(first(bf sent))(*(first sent)(first sent)))
        (progressive-squares? (bf sent))
        #f)))
14.13
14.14
(define (same-shape? s1 s2)
  (if(=(count s1)(count s2))
     (if(empty? s1)
        #t
        (if(=(count(first s1))(count(first s2)))
           (same-shape?(bf s1)(bf s2))
           #f))
     #f))
14.15
(define (merge s1 s2)
  (if(and(empty? s1)(empty? s2))
     '()
     (cond((empty? s1)s2)
          ((empty? s2)s1)
          ((< (first s1)(first s2))
              (se (first s1)(merge(bf s1)s2)))
          (else
              (se (first s2)(merge(bf s2)s1))))))
14.16
I have no idea about vowel