Charpter11.bak

#|【Scheme Basic Functions by Kevin&poi~】|#



;function: ture if input is a vowel, false if not.

;argument: 1 character

(define (vowel? char)

  (member? char '(a e i o u)))

;square the number

;argument: 1 number

(define (square num)

  (* num num))

;cube the number

;argument: 1 number

(define (cube num)

  (* num num num))

;find the second word/character in a string/word

;argument: word/string

(define (second x)

  (first (bf x)))

;reverse the order of the word

;argument:word

(define (reverse_order wd)

  (accumulate (lambda (x y)(word y x))wd))

(define (downup2 wd)
  (se  wd (word (first wd) (second wd))(first wd)))
(define (downup wd)
  (if (= (count wd) 1)
      (se wd)
      (se wd (downup (bl wd))wd)))
(define (explode wd)
  (if ( = (count wd) 0)
      ()
       (se (first wd)(explode (bf wd)))))
 (define (pairs wd)
   (if (<= (count wd) 1)
       ()
       (se (word(first wd)(second wd))(pairs (bf wd)))))