Add MaybeK wrapper for RxJava Maybe

infographic/arrow-infographic.txt

@@ -46,17 +46,7 @@
 [<typeclasses>Each]<-[<instances>Each Instances|ListKEachInstance|OptionEachInstance|EitherEachInstance|TryEachInstance|SequenceKEachInstance|NonEmptyListEachInstance|MapKEachInstance]
 [<typeclasses>Monoid]<-[<instances>Monoid Instances|OptionMonoidInstance|ConstMonoidInstance|Tuple2MonoidInstance|ListKMonoidInstance|SequenceKMonoidInstance|MapKMonoidInstance|SetKMonoidInstance|SortedMapKMonoidInstance|IOMonoidInstance]
 [<typeclasses>Semigroup]<-[<instances>Semigroup Instances|ConstSemigroupInstance|OptionSemigroupInstance|SetKSemigroupInstance|NonEmptyListSemigroupInstance|SequenceKSemigroupInstance|ListKSemigroupInstance|MapKSemigroupInstance|SortedMapKSemigroupInstance|IOMonoidInstance|IOSemigroupInstance]
-[<typeclasses>Traverse]<-[<instances>Traverse Instances|OptionTraverseInstance|ConstTraverseInstance|TryTraverseInstance|IdTraverseInstance|Tuple2TraverseInstance|EitherTraverseInstance|ListKTraverseInstance|ValidatedTraverseInstance|OptionTTraverseInstance|MapKTraverseInstance|NonEmptyListTraverseInstance|CoproductTraverseInstance|SequenceKTraverseInstance|SortedMapKTraverseInstance|IorTraverseInstance|FlowableKTraverseInstance|ObservableKTraverseInstance]
-[<typeclasses>Foldable]<-[<instances>Foldable Instances|IdFoldableInstance|EitherFoldableInstance|Tuple2FoldableInstance|OptionFoldableInstance|TryFoldableInstance|ConstFoldableInstance|SortedMapKFoldableInstance|SequenceKFoldableInstance|NonEmptyListFoldableInstance|CoproductFoldableInstance|IorFoldableInstance|SetKFoldableInstance|OptionTFoldableInstance|ListKFoldableInstance|ValidatedFoldableInstance|MapKFoldableInstance|ObservableKFoldableInstance|FlowableKFoldableInstance]
-[<typeclasses>MonadDefer]<-[<instances>MonadDefer Instances|IOMonadDeferInstance|DeferredKMonadDeferInstance|SingleKMonadDeferInstance|FlowableKMonadDeferInstance|ObservableKMonadDeferInstance]
-[<typeclasses>Async]<-[<instances>Async Instances|IOAsyncInstance|DeferredKAsyncInstance|FlowableKAsyncInstance|ObservableKAsyncInstance|SingleKAsyncInstance]
-[<typeclasses>Effect]<-[<instances>Effect Instances|IOEffectInstance|DeferredKEffectInstance|ObservableKEffectInstance|FlowableKEffectInstance|SingleKEffectInstance]
-[<typeclasses>ApplicativeError]<-[<instances>ApplicativeError Instances|EitherApplicativeErrorInstance|TryApplicativeErrorInstance|OptionApplicativeErrorInstance|ValidatedApplicativeErrorInstance|StateTApplicativeErrorInstance|KleisliApplicativeErrorInstance|IOApplicativeErrorInstance|DeferredKApplicativeErrorInstance|ObservableKApplicativeErrorInstance|SingleKApplicativeErrorInstance|FlowableKApplicativeErrorInstance]
-[<typeclasses>MonadError]<-[<instances>MonadError Instances|EitherMonadErrorInstance|TryMonadErrorInstance|OptionMonadErrorInstance|KleisliMonadErrorInstance|StateTMonadErrorInstance|IOMonadErrorInstance|DeferredKMonadErrorInstance|SingleKMonadErrorInstance|FlowableKMonadErrorInstance|ObservableKMonadErrorInstance]
 [<typeclasses>Comonad]<-[<instances>Comonad Instances|Tuple2ComonadInstance|Function0ComonadInstance|IdComonadInstance|EvalComonadInstance|NonEmptyListComonadInstance|CoproductComonadInstance|CofreeComonadInstance]
-[<typeclasses>Functor]<-[<instances>Functor Instances|Function1FunctorInstance|Tuple2FunctorInstance|ConstFunctorInstance|Function0FunctorInstance|EitherFunctorInstance|IdFunctorInstance|OptionFunctorInstance|EvalFunctorInstance|TryFunctorInstance|NonEmptyListFunctorInstance|IorFunctorInstance|CoproductFunctorInstance|KleisliFunctorInstance|SequenceKFunctorInstance|MapKFunctorInstance|StateTFunctorInstance|SortedMapKFunctorInstance|WriterTFunctorInstance|ListKFunctorInstance|OptionTFunctorInstance|ValidatedFunctorInstance|IOFunctorInstance|CofreeFunctorInstance|FreeApplicativeFunctorInstance|CoyonedaFunctorInstance|FreeFunctorInstance|YonedaFunctorInstance|DeferredKFunctorInstance|SingleKFunctorInstance|FlowableKFunctorInstance|ObservableKFunctorInstance]
-[<typeclasses>Applicative]<-[<instances>Applicative Instances|Tuple2ApplicativeInstance|Function1ApplicativeInstance|EvalApplicativeInstance|EitherApplicativeInstance|OptionApplicativeInstance|IdApplicativeInstance|TryApplicativeInstance|ConstApplicativeInstance|Function0ApplicativeInstance|IorApplicativeInstance|StateTApplicativeInstance|OptionTApplicativeInstance|ListKApplicativeInstance|WriterTApplicativeInstance|SequenceKApplicativeInstance|NonEmptyListApplicativeInstance|ValidatedApplicativeInstance|KleisliApplicativeInstance|IOApplicativeInstance|FreeApplicativeInstance|FreeApplicativeApplicativeInstance|DeferredKApplicativeInstance|SingleKApplicativeInstance|FlowableKApplicativeInstance|ObservableKApplicativeInstance]
-[<typeclasses>Monad]<-[<instances>Monad Instances|TryMonadInstance|IdMonadInstance|OptionMonadInstance|EvalMonadInstance|EitherMonadInstance|Tuple2MonadInstance|Function0MonadInstance|Function1MonadInstance|KleisliMonadInstance|OptionTMonadInstance|WriterTMonadInstance|ListKMonadInstance|StateTMonadInstance|IorMonadInstance|NonEmptyListMonadInstance|SequenceKMonadInstance|IOMonadInstance|FreeMonadInstance|DeferredKMonadInstance|ObservableKMonadInstance|FlowableKMonadInstance|SingleKMonadInstance]
 [<typeclasses>MonadState]<-[<instances>MonadState Instances|StateTMonadStateInstance]
 [<typeclasses>MonadReader]<-[<instances>MonadReader Instances|KleisliMonadReaderInstance|Function1MonadReaderInstance]
 [<typeclasses>MonadCombine]<-[<instances>MonadCombine Instances|StateTMonadCombineInstance|ListKMonadCombineInstance]
@@ -66,4 +56,14 @@
 [<typeclasses>MonadWriter]<-[<instances>MonadWriter Instances|WriterTMonadWriterInstance]
 [<typeclasses>Recursive]<-[<instances>Recursive Instances|MuRecursiveInstance|NuRecursiveInstance|FixRecursiveInstance]
 [<typeclasses>Birecursive]<-[<instances>Birecursive Instances|FixBirecursiveInstance|NuBirecursiveInstance|MuBirecursiveInstance]
-[<typeclasses>Corecursive]<-[<instances>Corecursive Instances|FixCorecursiveInstance|NuCorecursiveInstance|MuCorecursiveInstance]
+[<typeclasses>Corecursive]<-[<instances>Corecursive Instances|FixCorecursiveInstance|NuCorecursiveInstance|MuCorecursiveInstance]
+[<typeclasses>Traverse]<-[<instances>Traverse Instances|OptionTraverseInstance|ConstTraverseInstance|TryTraverseInstance|IdTraverseInstance|Tuple2TraverseInstance|EitherTraverseInstance|ListKTraverseInstance|ValidatedTraverseInstance|OptionTTraverseInstance|MapKTraverseInstance|NonEmptyListTraverseInstance|CoproductTraverseInstance|SequenceKTraverseInstance|SortedMapKTraverseInstance|IorTraverseInstance|FlowableKTraverseInstance|ObservableKTraverseInstance]
+[<typeclasses>Foldable]<-[<instances>Foldable Instances|IdFoldableInstance|EitherFoldableInstance|Tuple2FoldableInstance|OptionFoldableInstance|TryFoldableInstance|ConstFoldableInstance|SortedMapKFoldableInstance|SequenceKFoldableInstance|NonEmptyListFoldableInstance|CoproductFoldableInstance|IorFoldableInstance|SetKFoldableInstance|OptionTFoldableInstance|ListKFoldableInstance|ValidatedFoldableInstance|MapKFoldableInstance|ObservableKFoldableInstance|FlowableKFoldableInstance|MaybeKFoldableInstance]
+[<typeclasses>MonadDefer]<-[<instances>MonadDefer Instances|IOMonadDeferInstance|DeferredKMonadDeferInstance|SingleKMonadDeferInstance|FlowableKMonadDeferInstance|ObservableKMonadDeferInstance|MaybeKMonadDeferInstance]
+[<typeclasses>Async]<-[<instances>Async Instances|IOAsyncInstance|DeferredKAsyncInstance|FlowableKAsyncInstance|ObservableKAsyncInstance|SingleKAsyncInstance|MaybeKAsyncInstance]
+[<typeclasses>Effect]<-[<instances>Effect Instances|IOEffectInstance|DeferredKEffectInstance|ObservableKEffectInstance|FlowableKEffectInstance|SingleKEffectInstance|MaybeKEffectInstance]
+[<typeclasses>ApplicativeError]<-[<instances>ApplicativeError Instances|EitherApplicativeErrorInstance|TryApplicativeErrorInstance|OptionApplicativeErrorInstance|ValidatedApplicativeErrorInstance|StateTApplicativeErrorInstance|KleisliApplicativeErrorInstance|IOApplicativeErrorInstance|DeferredKApplicativeErrorInstance|ObservableKApplicativeErrorInstance|SingleKApplicativeErrorInstance|FlowableKApplicativeErrorInstance|MaybeKApplicativeErrorInstance]
+[<typeclasses>MonadError]<-[<instances>MonadError Instances|EitherMonadErrorInstance|TryMonadErrorInstance|OptionMonadErrorInstance|KleisliMonadErrorInstance|StateTMonadErrorInstance|IOMonadErrorInstance|DeferredKMonadErrorInstance|SingleKMonadErrorInstance|FlowableKMonadErrorInstance|ObservableKMonadErrorInstance|MaybeKMonadErrorInstance]
+[<typeclasses>Functor]<-[<instances>Functor Instances|Function1FunctorInstance|Tuple2FunctorInstance|ConstFunctorInstance|Function0FunctorInstance|EitherFunctorInstance|IdFunctorInstance|OptionFunctorInstance|EvalFunctorInstance|TryFunctorInstance|NonEmptyListFunctorInstance|IorFunctorInstance|CoproductFunctorInstance|KleisliFunctorInstance|SequenceKFunctorInstance|MapKFunctorInstance|StateTFunctorInstance|SortedMapKFunctorInstance|WriterTFunctorInstance|ListKFunctorInstance|OptionTFunctorInstance|ValidatedFunctorInstance|IOFunctorInstance|CofreeFunctorInstance|FreeApplicativeFunctorInstance|CoyonedaFunctorInstance|FreeFunctorInstance|YonedaFunctorInstance|DeferredKFunctorInstance|SingleKFunctorInstance|FlowableKFunctorInstance|ObservableKFunctorInstance|MaybeKFunctorInstance]
+[<typeclasses>Applicative]<-[<instances>Applicative Instances|Tuple2ApplicativeInstance|Function1ApplicativeInstance|EvalApplicativeInstance|EitherApplicativeInstance|OptionApplicativeInstance|IdApplicativeInstance|TryApplicativeInstance|ConstApplicativeInstance|Function0ApplicativeInstance|IorApplicativeInstance|StateTApplicativeInstance|OptionTApplicativeInstance|ListKApplicativeInstance|WriterTApplicativeInstance|SequenceKApplicativeInstance|NonEmptyListApplicativeInstance|ValidatedApplicativeInstance|KleisliApplicativeInstance|IOApplicativeInstance|FreeApplicativeInstance|FreeApplicativeApplicativeInstance|DeferredKApplicativeInstance|SingleKApplicativeInstance|FlowableKApplicativeInstance|ObservableKApplicativeInstance|MaybeKApplicativeInstance]
+[<typeclasses>Monad]<-[<instances>Monad Instances|TryMonadInstance|IdMonadInstance|OptionMonadInstance|EvalMonadInstance|EitherMonadInstance|Tuple2MonadInstance|Function0MonadInstance|Function1MonadInstance|KleisliMonadInstance|OptionTMonadInstance|WriterTMonadInstance|ListKMonadInstance|StateTMonadInstance|IorMonadInstance|NonEmptyListMonadInstance|SequenceKMonadInstance|IOMonadInstance|FreeMonadInstance|DeferredKMonadInstance|ObservableKMonadInstance|FlowableKMonadInstance|SingleKMonadInstance|MaybeKMonadInstance]

modules/docs/arrow-docs/docs/docs/integrations/rx2/README.md

@@ -48,6 +48,11 @@ val single = Single.fromCallable { 1 }.k()
 single
 ```
 
+```kotlin:ank
+val maybe = Maybe.fromCallable { 1 }.k()
+maybe
+```
+
 ```kotlin:ank
 val subject = PublishSubject.create<Int>().k()
 subject
@@ -67,6 +72,10 @@ flow.value()
 single.value()
 ```
 
+```kotlin:ank
+maybe.value()
+```
+
 ```kotlin:ank
 subject.value()
 ```
@@ -84,6 +93,7 @@ fun <F> getSongUrlAsync(MS: MonadDefer<F>) =
 val songObservable: ObservableKOf<Url> = getSongUrlAsync(ObservableK.monadDefer())
 val songFlowable: FlowableKOf<Url> = getSongUrlAsync(FlowableK.monadDefer())
 val songSingle: SingleKOf<Url> = getSongUrlAsync(SingleK.monadDefer())
+val songMaybe: SingleKOf<Url> = getSongUrlAsync(MaybeK.monadDefer())
 ```
 
 [`MonadError`]({{ '/docs/typeclasses/monaderror' | relative_url }}) can be used to start a [Monad Comprehension]({{ '/docs/patterns/monad_comprehensions' | relative_url }}) using the method `bindingCatch`, with all its benefits.

modules/effects/arrow-effects-rx2/src/main/kotlin/arrow/effects/MaybeK.kt

@@ -0,0 +1,82 @@
+package arrow.effects
+
+import arrow.core.*
+import arrow.effects.typeclasses.Proc
+import arrow.higherkind
+import io.reactivex.Maybe
+import io.reactivex.MaybeEmitter
+
+fun <A> Maybe<A>.k(): MaybeK<A> = MaybeK(this)
+
+fun <A> MaybeKOf<A>.value(): Maybe<A> = this.fix().maybe
+
+@higherkind
+data class MaybeK<A>(val maybe: Maybe<A>) : MaybeKOf<A>, MaybeKKindedJ<A> {
+
+  fun <B> map(f: (A) -> B): MaybeK<B> =
+    maybe.map(f).k()
+
+  fun <B> ap(fa: MaybeKOf<(A) -> B>): MaybeK<B> =
+    flatMap { a -> fa.fix().map { ff -> ff(a) } }
+
+  fun <B> flatMap(f: (A) -> MaybeKOf<B>): MaybeK<B> =
+    maybe.flatMap { f(it).fix().maybe }.k()
+
+  fun <B> fold(ifEmpty: () -> B, ifSome: (A) -> B): B = maybe.blockingGet().let {
+    if (it == null) ifEmpty() else ifSome(it)
+  }
+
+  fun <B> foldLeft(b: B, f: (B, A) -> B): B =
+    fold({ b }, { a -> f(b, a) })
+
+  fun <B> foldRight(lb: Eval<B>, f: (A, Eval<B>) -> Eval<B>): Eval<B> =
+    Eval.defer { fold({ lb }, { a -> f(a, lb) }) }
+
+  fun isEmpty(): Boolean = maybe.isEmpty.blockingGet()
+
+  fun nonEmpty(): Boolean = !isEmpty()
+
+  fun exists(predicate: Predicate<A>): Boolean = fold({ false }, { a -> predicate(a) })
+
+  fun forall(p: Predicate<A>): Boolean = fold({ true }, p)
+
+  fun handleErrorWith(function: (Throwable) -> MaybeK<A>): MaybeK<A> =
+    maybe.onErrorResumeNext { t: Throwable -> function(t).maybe }.k()
+
+  fun runAsync(cb: (Either<Throwable, A>) -> MaybeKOf<Unit>): MaybeK<Unit> =
+    maybe.flatMap { cb(Right(it)).value() }.onErrorResumeNext(io.reactivex.functions.Function { cb(Left(it)).value() }).k()
+
+  companion object {
+    fun <A> just(a: A): MaybeK<A> =
+      Maybe.just(a).k()
+
+    fun <A> raiseError(t: Throwable): MaybeK<A> =
+      Maybe.error<A>(t).k()
+
+    operator fun <A> invoke(fa: () -> A): MaybeK<A> =
+      defer { just(fa()) }
+
+    fun <A> defer(fa: () -> MaybeKOf<A>): MaybeK<A> =
+      Maybe.defer { fa().value() }.k()
+
+    fun <A> async(fa: Proc<A>): MaybeK<A> =
+      Maybe.create({ emitter: MaybeEmitter<A> ->
+        fa { either: Either<Throwable, A> ->
+          either.fold({
+            emitter.onError(it)
+          }, {
+            emitter.onSuccess(it)
+          })
+
+        }
+      }).k()
+
+    tailrec fun <A, B> tailRecM(a: A, f: (A) -> MaybeKOf<Either<A, B>>): MaybeK<B> {
+      val either = f(a).fix().value().blockingGet()
+      return when (either) {
+        is Either.Left -> tailRecM(either.a, f)
+        is Either.Right -> Maybe.just(either.b).k()
+      }
+    }
+  }
+}

modules/effects/arrow-effects-rx2/src/main/kotlin/arrow/effects/MaybeKInstances.kt

@@ -0,0 +1,115 @@
+package arrow.effects
+
+import arrow.Kind
+import arrow.core.Either
+import arrow.core.Eval
+import arrow.effects.typeclasses.Async
+import arrow.effects.typeclasses.Effect
+import arrow.effects.typeclasses.MonadDefer
+import arrow.effects.typeclasses.Proc
+import arrow.instance
+import arrow.typeclasses.*
+
+@instance(MaybeK::class)
+interface MaybeKFunctorInstance : Functor<ForMaybeK> {
+  override fun <A, B> Kind<ForMaybeK, A>.map(f: (A) -> B): MaybeK<B> =
+    fix().map(f)
+}
+
+@instance(MaybeK::class)
+interface MaybeKApplicativeInstance : Applicative<ForMaybeK> {
+  override fun <A, B> MaybeKOf<A>.ap(ff: MaybeKOf<(A) -> B>): MaybeK<B> =
+    fix().ap(ff)
+
+  override fun <A, B> Kind<ForMaybeK, A>.map(f: (A) -> B): MaybeK<B> =
+    fix().map(f)
+
+  override fun <A> just(a: A): MaybeK<A> =
+    MaybeK.just(a)
+}
+
+@instance(MaybeK::class)
+interface MaybeKMonadInstance : Monad<ForMaybeK> {
+  override fun <A, B> MaybeKOf<A>.ap(ff: MaybeKOf<(A) -> B>): MaybeK<B> =
+    fix().ap(ff)
+
+  override fun <A, B> MaybeKOf<A>.flatMap(f: (A) -> Kind<ForMaybeK, B>): MaybeK<B> =
+    fix().flatMap(f)
+
+  override fun <A, B> MaybeKOf<A>.map(f: (A) -> B): MaybeK<B> =
+    fix().map(f)
+
+  override fun <A, B> tailRecM(a: A, f: kotlin.Function1<A, MaybeKOf<arrow.core.Either<A, B>>>): MaybeK<B> =
+    MaybeK.tailRecM(a, f)
+
+  override fun <A> just(a: A): MaybeK<A> =
+    MaybeK.just(a)
+}
+
+@instance(MaybeK::class)
+interface MaybeKFoldableInstance : Foldable<ForMaybeK> {
+
+  override fun <A, B> Kind<ForMaybeK, A>.foldLeft(b: B, f: (B, A) -> B): B =
+    fix().foldLeft(b, f)
+
+  override fun <A, B> Kind<ForMaybeK, A>.foldRight(lb: Eval<B>, f: (A, Eval<B>) -> Eval<B>): Eval<B> =
+    fix().foldRight(lb, f)
+
+  override fun <A> Kind<ForMaybeK, A>.isEmpty(): Boolean =
+    fix().isEmpty()
+
+  override fun <A> Kind<ForMaybeK, A>.exists(p: (A) -> Boolean): Boolean =
+    fix().exists(p)
+
+  override fun <A> MaybeKOf<A>.forAll(p: (A) -> Boolean): Boolean =
+    fix().forall(p)
+
+  override fun <A> Kind<ForMaybeK, A>.nonEmpty(): Boolean =
+    fix().nonEmpty()
+}
+
+@instance(MaybeK::class)
+interface MaybeKApplicativeErrorInstance :
+  MaybeKApplicativeInstance,
+  ApplicativeError<ForMaybeK, Throwable> {
+  override fun <A> raiseError(e: Throwable): MaybeK<A> =
+    MaybeK.raiseError(e)
+
+  override fun <A> MaybeKOf<A>.handleErrorWith(f: (Throwable) -> MaybeKOf<A>): MaybeK<A> =
+    fix().handleErrorWith { f(it).fix() }
+}
+
+@instance(MaybeK::class)
+interface MaybeKMonadErrorInstance :
+  MaybeKMonadInstance,
+  MonadError<ForMaybeK, Throwable> {
+  override fun <A> raiseError(e: Throwable): MaybeK<A> =
+    MaybeK.raiseError(e)
+
+  override fun <A> MaybeKOf<A>.handleErrorWith(f: (Throwable) -> MaybeKOf<A>): MaybeK<A> =
+    fix().handleErrorWith { f(it).fix() }
+}
+
+@instance(MaybeK::class)
+interface MaybeKMonadDeferInstance :
+  MaybeKMonadErrorInstance,
+  MonadDefer<ForMaybeK> {
+  override fun <A> defer(fa: () -> MaybeKOf<A>): MaybeK<A> =
+    MaybeK.defer(fa)
+}
+
+@instance(MaybeK::class)
+interface MaybeKAsyncInstance :
+  MaybeKMonadDeferInstance,
+  Async<ForMaybeK> {
+  override fun <A> async(fa: Proc<A>): MaybeK<A> =
+    MaybeK.async(fa)
+}
+
+@instance(MaybeK::class)
+interface MaybeKEffectInstance :
+  MaybeKAsyncInstance,
+  Effect<ForMaybeK> {
+  override fun <A> MaybeKOf<A>.runAsync(cb: (Either<Throwable, A>) -> MaybeKOf<Unit>): MaybeK<Unit> =
+    fix().runAsync(cb)
+}