Arrow Collectors #3280
Arrow Collectors #3280
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arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Collectors.kt
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arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Collectors.kt
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Great. Arrow will be more popular 😂. |
arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Collectors.kt
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arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Collectors.kt
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arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Flow.kt
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| * so it's potential faster than [Collectors.map]. | ||
| */ | ||
| @Suppress("UnusedReceiverParameter") | ||
| public fun <K, V> Collectors.concurrentMap(): Collector<Pair<K, V>, ConcurrentMap<K, V>> = |
| public fun <T, R> java.util.stream.Collector<T, *, R>.asCollector(): Collector<T, R> = | ||
| Collectors.jvm(this) |
arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Collect.kt
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…lectors/Collect.kt Co-authored-by: Petrus Nguyễn Thái Học <hoc081098@gmail.com>
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Ready for review! If this gets merged, I’ll happily write docs for the Arrow Website. And even some sort of blog post, if you want! |
arrow-libs/fx/arrow-collectors/src/commonMain/kotlin/arrow/collectors/Collector.kt
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| nodejs { | ||
| testTask { | ||
| useMocha { | ||
| timeout = "60s" | ||
| } | ||
| } | ||
| } | ||
| browser { | ||
| testTask { | ||
| useKarma { | ||
| useChromeHeadless() | ||
| timeout.set(Duration.ofMinutes(1)) | ||
| } | ||
| } | ||
| } |
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Off-topic: I think would be good if we can put this in some common configuration at some point. Still not sure what's the best way to do that in Gradle 🙃
| * Java's [`Collector`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collector.html) | ||
| * and Haskell's [`foldl` library](https://hackage.haskell.org/package/foldl/docs/Control-Foldl.html). | ||
| */ | ||
| public interface CollectorI<InternalAccumulator, in Value, out Result> { |
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Nit: Not a huge fan of CollectorI but not sure if something else makes sense.. I guess InternalAccumulator is State? What about StateCollector<State, in Value, out Result>, or StatefulCollector? Not sure if this makes sense though, since all Collector have State. We had a similar issue with Schedule when we originally designed it, but don't think we can take the same/similar approach to solve this issue.
This is just a nit, feel free to ignore. For me it's also fine without any changes, just wanted to leave some thoughts.
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Going to merge. Feel free to discuss further on my nit remark, or to ignore completely |
Documentation for arrow-kt/arrow#3280
This is an idea for a new library heavily influenced by Java's
Collectorand Haskell'sfoldllibrary. The goal is to build complex computations over sequences of values, guaranteeing that those values are consumed only once.For example, if you want to compute the average of a sequence in one go, you can write:
The "trick" is that collectors have a nice interface based on
map/contramap/zip(they are applicative functors and profunctors, if we were to use fancy words). Combined with Kotlin's coldFlows, they provide a nice combination.Since this is a pattern coming from functional programming, I thought that it may be a good fit for Arrow.