vallog: [scheme]stack（大域変数＋副作用）

2009/05/12

[scheme]stack（大域変数＋副作用）

思い切ったstack。

(define *stack*i
'())

(define push
(lambda (data)
    (cond
     ((null? *stack*)
      (set! *stack* (list data)))
     (else (set! *stack* (cons data *stack*))))
    *stack*))

(define pop
(lambda ()
    (cond
     ((null? *stack*) 'empty)
     (else ((lambda (x)
              (set! x (car *stack*))
              (set! *stack* (cdr *stack*))
              x)
            '())))))

(push 'one)
(push 'two)
(pop)
(pop)
(pop)

;;処理結果

gosh> *stack*
gosh> push
gosh> pop
gosh> (one)
gosh> (two one)
gosh> two
gosh> one
gosh> empty
gosh>