Kimura Fuyuki
fuyuk****@hadal*****
2003年 1月 27日 (月) 08:46:32 JST
対案…
- keys が与えられた場合、常にそのキーについて繰り返す。存在しないキー
があっても重複があってもかまわない。
- (cursor 'exists?) を追加。
- update! と insert! は put! にまとめる。キーが存在するかどうかで処理
を分ける。
とすると、こんなふうになります。
(define-method call-with-iterator ((self <hash-table>) iteratee seed . keys)
(let* ((inserted '())
(r (let loop ((keys (if (null? keys) (hash-table-keys self) keys))
(seed seed))
(if (null? keys)
seed
(let* ((key (car keys))
(exists? (hash-table-exists? self key)))
(define (cursor method . args)
(define (next seed)
(loop (cdr keys) seed))
(define (get)
(unless exists? (error "i don't exist"))
(values key (hash-table-get self key)))
(define (put! val)
(cond (exists? (hash-table-put! self key val))
(else (push! inserted (cons key val)))))
(define (delete!)
(unless exists? (error "i don't exist"))
(hash-table-delete! self key)
(set! exists? #f))
(case method
((next) (apply next args))
((get) (get))
((put!) (apply put! args))
((exists?) exists?)
((delete!) (delete!))
(else (error "speak english"))))
(iteratee cursor seed))))))
(dolist (kv inserted)
(hash-table-put! self (car kv) (cdr kv)))
r))
;; demos
(define h (make-hash-table))
(define-method put! ((self <hash-table>) key val)
(define (iteratee cursor seed)
(cursor 'put! val))
(call-with-iterator self iteratee 0 key))
(define-method get ((self <hash-table>) key)
(define (iteratee cursor seed)
(cond ((cursor 'exists?) (receive (key val) (cursor 'get) val))
(else (error "dictionary doesn't have an entry for key" key))))
(call-with-iterator self iteratee 0 key))
(define-method get ((self <hash-table>) key default)
(define (iteratee cursor seed)
(cond ((cursor 'exists?) (receive (key val) (cursor 'get) val))
(else default)))
(call-with-iterator self iteratee 0 key))
(put! h 'a 1)
(put! h 'a 2)
(print (get h 'a))
(print (get h 'b #f))
--
木村 冬樹