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Refactor - #2812 iterable separate performance #2815

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merged 5 commits into from Sep 12, 2022
Merged

Refactor - #2812 iterable separate performance #2815

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20a8967
Refactor: Use fold to separate Iterable of Either
Khepu Sep 2, 2022
f9b32aa
Refactor: Use fold to separate Iterable of Validated
Khepu Sep 2, 2022
de16de1
Merge branch 'main' into refactor/2812-iterable-separate-performance
Khepu Sep 2, 2022
a7d8283
Merge branch 'main' into refactor/2812-iterable-separate-performance
nomisRev Sep 5, 2022
3690520
Refactor: Implementation closer to STD
Khepu Sep 6, 2022
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24 changes: 14 additions & 10 deletions arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/Iterable.kt
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Expand Up @@ -997,23 +997,27 @@ public fun <A, B> Iterable<Validated<A, B>>.uniteValidated(): List<B> =
* @receiver Iterable of Validated
* @return a tuple containing List with [Either.Left] and another List with its [Either.Right] values.
*/
public fun <A, B> Iterable<Either<A, B>>.separateEither(): Pair<List<A>, List<B>> {
val asep = flatMap { gab -> gab.fold({ listOf(it) }, { emptyList() }) }
val bsep = flatMap { gab -> gab.fold({ emptyList() }, { listOf(it) }) }
return asep to bsep
}
public fun <A, B> Iterable<Either<A, B>>.separateEither(): Pair<List<A>, List<B>> =
fold(listOf<A>() to listOf<B>()) { (lefts, rights), either ->
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Should we use mutableListOf here and use add inside of the fold body? That would avoid having to recreate Pair on every element of the List. The returned type can still be read-only List.

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It can also be rewritten to while if we'd pattern similar to Kotlin Std implementations.

val left = ArrayList<A>(collectionSizeOrDefault(10))
val right = ArrayList<B>(collectionSizeOrDefault(10))
forEach { either ->
  when(either) {
     is Left -> left.add(either.value)
     is Right -> right.add(either.value)
   }
}
Pair(left, right)

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This eliminates List.size allocations.

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@Khepu Khepu Sep 5, 2022 •
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I think mimicking the Kotlin stdlib is a good way to go. Looking at the implementation it's gonna be a lot like this (based on map):

public fun <A, B> Iterable<Either<A, B>>.separateEither(): Pair<List<A>, List<B>> {
  val left = ArrayList<A>(collectionSizeOrDefault(10))
  val right = ArrayList<B>(collectionSizeOrDefault(10))

  for (either in this)
    when(either) {
      is Left -> left.add(either.value)
      is Right -> right.add(either.value)
    }

  return Pair(left, right)
}

If that is something we are happy with, let me know!

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Yes, that looks perfect to me @Khepu!

when (either) {
is Left -> lefts + either.value to rights
is Right -> lefts to rights + either.value
}
}

/**
* Separate the inner [Validated] values into the [Validated.Invalid] and [Validated.Valid].
*
* @receiver Iterable of Validated
* @return a tuple containing List with [Validated.Invalid] and another List with its [Validated.Valid] values.
*/
public fun <A, B> Iterable<Validated<A, B>>.separateValidated(): Pair<List<A>, List<B>> {
val asep = flatMap { gab -> gab.fold({ listOf(it) }, { emptyList() }) }
val bsep = flatMap { gab -> gab.fold({ emptyList() }, { listOf(it) }) }
return asep to bsep
}
public fun <A, B> Iterable<Validated<A, B>>.separateValidated(): Pair<List<A>, List<B>> =
fold(listOf<A>() to listOf<B>()) { (invalids, valids), validated ->
when (validated) {
is Valid -> invalids to valids + validated.value
is Invalid -> invalids + validated.value to valids
}
}

public fun <A> Iterable<Iterable<A>>.flatten(): List<A> =
flatMap(::identity)
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