*Warning this message contains mutable state and may hurt functional
sensibilities.*
Ugly hack:
(defn my-split-with [pred coll]
(let [s (atom coll)
p #(when-let [r (pred %)] (swap! s rest) r)]
[(take-while p coll) (drop-while pred (lazy-seq @s))]))
Now it works ;-)
Laurent PETIT a écrit :
> This is a general problem with function (split-with) (and derivatives
> such as partition-by ...),
>
> This should certainly deserve a mention in their respective
> docstrings, I think. Because the docstring speak about lazyness, but
> not the kind of lazyness that can avoid Out of Memory in corner cases.
>
> Rich, if you agree with that, would you me to issue a patch on google group ?
>
> 2009/4/23 Christophe Grand <[email protected]>:
>
>> Laurent PETIT a écrit :
>>
>>> Hi Meikel,
>>>
>>> It seems to me that your version is the only safe one so far, that
>>> would succesfully indefinitely return values with this test:
>>>
>>> (dorun (mystery-function true? :foo (repeat true)))
>>>
>>> Mine, a new version of mine I'll never bother to publish, and
>>> Christophe's all retain head.
>>> To explain on Christophe's one for example:
>>>
>>> It uses (split-with) which, in case pred always match coll elements,
>>> will retain the head of coll in etc, while eating more and more
>>> elements of coll via running on run :
>>> 1:21 user=> (defn mystery-function [pred coll]
>>> (lazy-seq
>>> (when (seq coll)
>>> (let [[run etc] (split-with pred coll)]
>>> (if (seq run)
>>> (concat run (cons :foo (mystery-function pred etc)))
>>> (cons (first coll) (mystery-function pred (rest coll))))))))
>>> 1:22 user=> (dorun (mystery-function true? (repeat true)))
>>> java.lang.OutOfMemoryError: GC overhead limit exceeded (repl-1:22)
>>>
>>>
>> Nice catch!
>>
>>
>> --
>> Professional: http://cgrand.net/ (fr)
>> On Clojure: http://clj-me.blogspot.com/ (en)
>>
>>
>>
>>
>
> >
>
>
--
Professional: http://cgrand.net/ (fr)
On Clojure: http://clj-me.blogspot.com/ (en)
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