Internal and External truncation conditions (original) (raw)

Remi Forax forax at univ-mlv.fr
Sun Feb 10 05:46:08 PST 2013

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

Rémi

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