occur*、subst*、insertL*、member*

どんどんいこう。

occure*

occure* はS式のリスト l の中にアトム a がいくつあるかを返す。

(use mymodule)

(define occur*
  (lambda (a l)
    (cond
      ((null? l) 0)
      ((atom? (car l))
        (cond
          ((eqan? (car l) a) (add1 (occur* a (cdr l))))
          (else (occur* a (cdr l)))))
      (else (o+ (occur* a (car l)) (occur* a (cdr l)))))))

(print (occur* 'banana
               '((banana)
               (split ((((banana ice)))
               (cream (banana))
               sherbe))
  (banana)
  (bread)
  (banana brandy))))

^o^ > gosh -I. occur_star.scm
5

subst*

subst* は、S式のリスト l の中のアトム old すべてを new に置き換える。

(use mymodule)

(define subst*
  (lambda (new old l)
    (cond
      ((null? l) (quote ()))
      ((atom? (car l))
        (cond
          ((eqan? (car l) old) (cons new (subst* new old (cdr l))))
          (else (cons (car l) (subst* new old (cdr l))))))
      (else (cons (subst* new old (car l)) (subst* new old (cdr l)))))))

(print (subst* 'orange
               'banana
               '((banana)
                 (split ((((banana ice)))
                 (ceam (banana))
                 sherbet))
  (banana)
  (bread)
  (banana brandy))))

^o^ > gosh -I. subst_star.scm
((orange) (split ((((orange ice))) (ceam (orange)) sherbet)) (orange) (bread) (o
range brandy))

insertL*

insertL* はS式のリストの中のアトム old すべての左に new を挿入する。

(use mymodule)

(define insertL*
  (lambda (new old l)
    (cond
      ((null? l) (quote ()))
      ((atom? (car l))
        (cond
          ((eqan? (car l) old) (cons new (cons old (insertL* new old (cdr l)))))
          (else (cons (car l) (insertL* new old (cdr l))))))
      (else
        (cons (insertL* new old (car l)) (insertL* new old (cdr l)))))))

(print (insertL* 'roast
                 'chuck
                 '((hew much (wood))
                 could
                 ((a (wood) chuck))
                 (((chuck)))
  (if (a)
      ((wood chuck)))
      could chuck wood)))

^o^ > gosh -I. insertL_star.scm
((hew much (wood)) could ((a (wood) roast chuck)) (((roast chuck))) (if (a) ((wo
od roast chuck))) could roast chuck wood)

member*

member* は、S式のリストの中にアトム a があれば #t を返し、そうでなければ #f を返す。

(use mymodule)

(define member*
  (lambda (a l)
    (cond
      ((null? l) #f)
      ((atom? (car l))
      (cond
        ((eqan? (car l) a) #t)
        (else (member* a (cdr l)))))
      (else (or (member* a (car l)) (member* a (cdr l)))))))

(print (member* 'chips '((potato) (chips ((with) fish) (chips)))))

^o^ > gosh -I. member_star.scm
#t