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Reverse argument order for Kleisli ap method #3462

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merged 8 commits into from
Jun 10, 2020
Merged

Reverse argument order for Kleisli ap method #3462

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8340303
Correct some mistakes in Comonad documentatoin
justinhj Sep 22, 2019
b872595
Fix link in traverse doc
Apr 2, 2020
cafd639
Merge branch 'master' of github.com:justinhj/cats
Apr 2, 2020
c4593e3
Merge branch 'master' of github.com:typelevel/cats
Jun 2, 2020
dccf39b
Merge branch 'master' of github.com:typelevel/cats into reverse-kleis…
justinhj Jun 9, 2020
26b2a11
Compiles
justinhj Jun 9, 2020
a560f89
Use coerce instead of instanceOf. Add overload of previous ap for bin…
justinhj Jun 10, 2020
d670d0d
update formatting
justinhj Jun 10, 2020
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13 changes: 11 additions & 2 deletions core/src/main/scala/cats/data/Kleisli.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -3,15 +3,24 @@ package data

import cats.{Contravariant, Id}
import cats.arrow._
import cats.evidence.As

/**
* Represents a function `A => F[B]`.
*/
final case class Kleisli[F[_], -A, B](run: A => F[B]) { self =>

def ap[C, AA <: A](f: Kleisli[F, AA, B => C])(implicit F: Apply[F]): Kleisli[F, AA, C] =
private[data] def ap[C, AA <: A](f: Kleisli[F, AA, B => C])(implicit F: Apply[F]): Kleisli[F, AA, C] =
Kleisli(a => F.ap(f.run(a))(run(a)))

def ap[C, D, AA <: A](f: Kleisli[F, AA, C])(implicit F: Apply[F], ev: B As (C => D)): Kleisli[F, AA, D] = {
Kleisli { a =>
val fb: F[C => D] = F.map(run(a))(ev.coerce)
val fc: F[C] = f.run(a)
F.ap(fb)(fc)
}
}

/**
* Performs [[local]] and [[map]] simultaneously.
*/
Expand Down Expand Up @@ -620,7 +629,7 @@ private[data] trait KleisliApply[F[_], A] extends Apply[Kleisli[F, A, *]] with K
implicit def F: Apply[F]

override def ap[B, C](f: Kleisli[F, A, B => C])(fa: Kleisli[F, A, B]): Kleisli[F, A, C] =
fa.ap(f)
f.ap(fa)

override def product[B, C](fb: Kleisli[F, A, B], fc: Kleisli[F, A, C]): Kleisli[F, A, (B, C)] =
Kleisli(a => F.product(fb.run(a), fc.run(a)))
Expand Down