Internal and External truncation conditions

[Remi Forax]

On 02/10/2013 02:12 PM, Doug Lea wrote:
> On 02/09/13 18:24, Remi Forax wrote:
>> if forEachUntil takes a function that return a boolean, it's easy.
>>
>> try (BufferedReader r = Files.newBufferedReader(path, 
>> Charset.defaultCharset())) {
>>    return r.lines().parallel().forEachWhile(element -> {
>>       if (regex.matcher(line).matches()) {
>>         return false;
>>       }
>>       ...process the line
>>       return true;
>>     }
>> }
>>
>
> Which then becomes a variant of what I do in ConcurrentHashMap
> search{InParallel,Sequentially}, that applies to not only this
> but several other usage contexts:
>
>     /**
>      * Returns a non-null result from applying the given search
>      * function on each (key, value), or null if none.  Upon
>      * success, further element processing is suppressed and the
>      * results of any other parallel invocations of the search
>      * function are ignored.
>      *
>      * @param searchFunction a function returning a non-null
>      * result on success, else null
>      * @return a non-null result from applying the given search
>      * function on each (key, value), or null if none
>      */
>
> You'd use this here with a function that processed if
> a match (returning null) else returning the first non-match.
> Or rework in any of a couple of ways to similar effect.
>
> This works well in CHM because of its nullness policy.
> Which allows only this single method to serve as the basis
> for all possible short-circuit/cancel applications.
> It is so handy when nulls cannot be actual elements
> that it might be worth supporting instead of forEachUntil?
> People using it  would need to ensure non-null elements.
> Just a thought.

yes, findFirst and forEachWhile/forEachUntil are the same operation from 
the implementation point of view if you have a value (not necessarily 
null) that says NO_VALUE.
Now, I think it's an implementation detail and that from the user point 
of view we should provide them both.

>
> -Doug
>
>

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