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Use Compose/Category.algebraK for endomorphic SemigroupK/MonoidK #1496

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Dec 22, 2016
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Use Compose/Category.algebraK for endomorphic SemigroupK/MonoidK #1496

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18 changes: 3 additions & 15 deletions core/src/main/scala/cats/data/Cokleisli.scala
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
package cats
package data

import cats.arrow.{Arrow, Split}
import cats.arrow.{Arrow, Category, Compose, Split}
import cats.functor.{Contravariant, Profunctor}
import cats.{CoflatMap, Comonad, Functor, Monad}
import scala.annotation.tailrec
Expand Down Expand Up @@ -70,7 +70,7 @@ private[data] sealed abstract class CokleisliInstances extends CokleisliInstance
}

implicit def catsDataMonoidKForCokleisli[F[_]](implicit ev: Comonad[F]): MonoidK[λ[α => Cokleisli[F, α, α]]] =
new CokleisliMonoidK[F] { def F: Comonad[F] = ev }
Category[Cokleisli[F, ?, ?]].algebraK
}

private[data] sealed abstract class CokleisliInstances0 {
Expand All @@ -81,7 +81,7 @@ private[data] sealed abstract class CokleisliInstances0 {
new CokleisliProfunctor[F] { def F: Functor[F] = ev }

implicit def catsDataSemigroupKForCokleisli[F[_]](implicit ev: CoflatMap[F]): SemigroupK[λ[α => Cokleisli[F, α, α]]] =
new CokleisliSemigroupK[F] { def F: CoflatMap[F] = ev }
Compose[Cokleisli[F, ?, ?]].algebraK

implicit def catsDataContravariantForCokleisli[F[_]: Functor, A]: Contravariant[Cokleisli[F, ?, A]] =
new Contravariant[Cokleisli[F, ?, A]] {
Expand Down Expand Up @@ -133,15 +133,3 @@ private trait CokleisliProfunctor[F[_]] extends Profunctor[Cokleisli[F, ?, ?]] {
override def rmap[A, B, C](fab: Cokleisli[F, A, B])(f: B => C): Cokleisli[F, A, C] =
fab.map(f)
}

private trait CokleisliSemigroupK[F[_]] extends SemigroupK[λ[α => Cokleisli[F, α, α]]] {
implicit def F: CoflatMap[F]

def combineK[A](a: Cokleisli[F, A, A], b: Cokleisli[F, A, A]): Cokleisli[F, A, A] = a compose b
}

private trait CokleisliMonoidK[F[_]] extends MonoidK[λ[α => Cokleisli[F, α, α]]] with CokleisliSemigroupK[F] {
implicit def F: Comonad[F]

def empty[A]: Cokleisli[F, A, A] = Cokleisli(F.extract[A])
}
49 changes: 17 additions & 32 deletions core/src/main/scala/cats/data/Kleisli.scala
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
package cats
package data

import cats.arrow.{Arrow, Choice, Split, FunctionK}
import cats.arrow.{Arrow, Category, Choice, Compose, Split, FunctionK}
import cats.functor.{Contravariant, Strong}

/**
Expand Down Expand Up @@ -86,7 +86,7 @@ private[data] sealed abstract class KleisliInstances extends KleisliInstances0 {
new KleisliMonoid[F, A, B] { def FB: Monoid[F[B]] = M }

implicit def catsDataMonoidKForKleisli[F[_]](implicit M: Monad[F]): MonoidK[λ[α => Kleisli[F, α, α]]] =
new KleisliMonoidK[F] { def F: Monad[F] = M }
Category[Kleisli[F, ?, ?]].algebraK

implicit val catsDataMonoidKForKleisliId: MonoidK[λ[α => Kleisli[Id, α, α]]] =
catsDataMonoidKForKleisli[Id]
Expand All @@ -97,20 +97,6 @@ private[data] sealed abstract class KleisliInstances extends KleisliInstances0 {
implicit val catsDataArrowForKleisliId: Arrow[Kleisli[Id, ?, ?]] =
catsDataArrowForKleisli[Id]

implicit def catsDataChoiceForKleisli[F[_]](implicit ev: Monad[F]): Choice[Kleisli[F, ?, ?]] =
new Choice[Kleisli[F, ?, ?]] {
def id[A]: Kleisli[F, A, A] = Kleisli(ev.pure)

def choice[A, B, C](f: Kleisli[F, A, C], g: Kleisli[F, B, C]): Kleisli[F, Either[A, B], C] =
Kleisli(_.fold(f.run, g.run))

def compose[A, B, C](f: Kleisli[F, B, C], g: Kleisli[F, A, B]): Kleisli[F, A, C] =
f.compose(g)
}

implicit val catsDataChoiceForKleisliId: Choice[Kleisli[Id, ?, ?]] =
catsDataChoiceForKleisli[Id]

implicit def catsDataMonadReaderForKleisliId[A]: MonadReader[Kleisli[Id, A, ?], A] =
catsDataMonadReaderForKleisli[Id, A]

Expand All @@ -132,6 +118,20 @@ private[data] sealed abstract class KleisliInstances extends KleisliInstances0 {
}

private[data] sealed abstract class KleisliInstances0 extends KleisliInstances1 {
implicit def catsDataChoiceForKleisli[F[_]](implicit ev: Monad[F]): Choice[Kleisli[F, ?, ?]] =
new Choice[Kleisli[F, ?, ?]] {
def id[A]: Kleisli[F, A, A] = Kleisli(ev.pure)

def choice[A, B, C](f: Kleisli[F, A, C], g: Kleisli[F, B, C]): Kleisli[F, Either[A, B], C] =
Kleisli(_.fold(f.run, g.run))

def compose[A, B, C](f: Kleisli[F, B, C], g: Kleisli[F, A, B]): Kleisli[F, A, C] =
f.compose(g)
}

implicit val catsDataChoiceForKleisliId: Choice[Kleisli[Id, ?, ?]] =
catsDataChoiceForKleisli[Id]

implicit def catsDataSplitForKleisli[F[_]](implicit ev: FlatMap[F]): Split[Kleisli[F, ?, ?]] =
new KleisliSplit[F] { def F: FlatMap[F] = ev }

Expand All @@ -153,8 +153,7 @@ private[data] sealed abstract class KleisliInstances0 extends KleisliInstances1
new KleisliSemigroup[F, A, B] { def FB: Semigroup[F[B]] = M }

implicit def catsDataSemigroupKForKleisli[F[_]](implicit ev: FlatMap[F]): SemigroupK[λ[α => Kleisli[F, α, α]]] =
new KleisliSemigroupK[F] { def F: FlatMap[F] = ev }

Compose[Kleisli[F, ?, ?]].algebraK
}

private[data] sealed abstract class KleisliInstances1 extends KleisliInstances2 {
Expand Down Expand Up @@ -261,19 +260,6 @@ private trait KleisliMonoid[F[_], A, B] extends Monoid[Kleisli[F, A, B]] with Kl
override def empty: Kleisli[F, A, B] = Kleisli[F, A, B](a => FB.empty)
}

private trait KleisliSemigroupK[F[_]] extends SemigroupK[λ[α => Kleisli[F, α, α]]] {
implicit def F: FlatMap[F]

override def combineK[A](a: Kleisli[F, A, A], b: Kleisli[F, A, A]): Kleisli[F, A, A] = a compose b
}

private trait KleisliMonoidK[F[_]] extends MonoidK[λ[α => Kleisli[F, α, α]]] with KleisliSemigroupK[F] {
implicit def F: Monad[F]

override def empty[A]: Kleisli[F, A, A] = Kleisli(F.pure[A])
}


private trait KleisliApplicativeError[F[_], A, E] extends KleisliApplicative[F, A] with ApplicativeError[Kleisli[F, A, ?], E] {
type K[T] = Kleisli[F, A, T]

Expand All @@ -289,7 +275,6 @@ private trait KleisliApplicativeError[F[_], A, E] extends KleisliApplicative[F,

}


private trait KleisliApplicative[F[_], A] extends Applicative[Kleisli[F, A, ?]] {
implicit def F: Applicative[F]

Expand Down
7 changes: 2 additions & 5 deletions core/src/main/scala/cats/instances/function.scala
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
package cats
package instances

import cats.arrow.{Arrow, Choice}
import cats.arrow.{Arrow, Category, Choice}
import cats.functor.Contravariant
import annotation.tailrec

Expand Down Expand Up @@ -90,8 +90,5 @@ private[instances] sealed trait Function1Instances {
}

implicit val catsStdMonoidKForFunction1: MonoidK[λ[α => Function1[α, α]]] =
new MonoidK[λ[α => Function1[α, α]]] {
def empty[A]: A => A = identity[A]
def combineK[A](x: A => A, y: A => A): A => A = x compose y
}
Category[Function1].algebraK
}