Re: What?

[Gabor Greif <address@hidden>]

Am Sonntag den, 11. August 2002, um 14:30, schrieb Rainer Joswig:

>>
>> Something like this would be interesting:
>>
>> define method read-lines ( stream )
>>    choose-until(identity, lazy-sequence(curry(read-line, stream,
>> on-end-of-stream: #f )))
>> end;
>>
>> With appropriate definitions of choose-until and lazy-sequence.
>
> Using the series package from Richard Waters it would be something
> like this (just a raw version):
>
> (defun sum-stream (stream)
>   (series:collect-sum
>    (series:map-fn 'string
>                   #'parse-integer
>                   (series:scan-fn t
>                                   (lambda ()
>                                     (read-line stream nil nil))
>                                   (lambda (ignore)
>                                     (read-line stream nil nil))
>                                   #'null))))
>

In Dylan you would do it using forward-iteration-protocol on 
<lazy-sequence>:

      forward-iteration-protocol collection
         => initial-state limit next-state finished-state? current-key 
current-element current-element-setter copy-state

The next-state function would call the read-line,
finished-state? related information could be supplied by
    lazy-sequence(curry(read-line, stream, on-end-of-stream: #f ), 
finished?: identity)

this would also eliminate the \choose-until.


Time to write this down into the Wiki.

	Gabor