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Add Foldable
, Traverse
and Comonad
instances to WriterT
#2182
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Original file line number | Diff line number | Diff line change |
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@@ -1,8 +1,8 @@ | ||
package cats | ||
package data | ||
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import cats.Foldable | ||
import cats.kernel.instances.tuple._ | ||
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import cats.kernel.CommutativeMonoid | ||
import cats.syntax.semigroup._ | ||
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@@ -63,6 +63,17 @@ final case class WriterT[F[_], L, V](run: F[(L, V)]) { | |
mapWritten(_ => monoidL.empty) | ||
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def show(implicit F: Show[F[(L, V)]]): String = F.show(run) | ||
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def foldLeft[C](c: C)(f: (C, V) => C)(implicit F: Foldable[F]): C = | ||
F.foldLeft(run, c)((z, lv) => f(z, lv._2)) | ||
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def foldRight[C](lc: Eval[C])(f: (V, Eval[C]) => Eval[C])(implicit F: Foldable[F]): Eval[C] = | ||
F.foldRight(run, lc)((lv, z) => f(lv._2, z)) | ||
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def traverse[G[_], V1](f: V => G[V1])(implicit F: Traverse[F], G: Applicative[G]): G[WriterT[F, L, V1]] = | ||
G.map( | ||
F.traverse(run)(lv => G.product(G.pure(lv._1), f(lv._2))) | ||
)(WriterT.apply) | ||
} | ||
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object WriterT extends WriterTInstances with WriterTFunctions { | ||
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@@ -95,9 +106,23 @@ private[data] sealed abstract class WriterTInstances extends WriterTInstances0 { | |
implicit val F0: Monad[F] = F | ||
implicit val L0: Monoid[L] = L | ||
} | ||
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implicit def catsDataTraverseForWriterTId[L](implicit F: Traverse[Id]): Traverse[WriterT[Id, L, ?]] = | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. @barambani you can't have any instance that potentially conflicts in the same trait level. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. to be clear I didn't see the actually error message on travis. But I think separating them out might solve the problem. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Sorry for the confusion, my bad for the lack of clarity. This prioritisation should work (let's see when the CI completes). My question was more in general about the reason why we needed to create instances for There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. @barambani I don't know the underlying reason that There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. @ceedubs thanks a lot, I didn't want for you to waste time on this. I was just taking advantage of this discussion in case you knew it out of your head 😃 👍 |
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catsDataTraverseForWriterT[Id, L](F) | ||
} | ||
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private[data] sealed abstract class WriterTInstances0 extends WriterTInstances1 { | ||
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implicit def catsDataTraverseForWriterT[F[_], L](implicit F: Traverse[F]): Traverse[WriterT[F, L, ?]] = | ||
new WriterTTraverse[F, L] { | ||
val F0: Traverse[F] = F | ||
} | ||
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implicit def catsDataFoldableForWriterTId[L](implicit F: Foldable[Id]): Foldable[WriterT[Id, L, ?]] = | ||
catsDataFoldableForWriterT[Id, L](F) | ||
} | ||
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private[data] sealed abstract class WriterTInstances1 extends WriterTInstances2 { | ||
implicit def catsDataMonadErrorForWriterT[F[_], L, E](implicit F: MonadError[F, E], L: Monoid[L]): MonadError[WriterT[F, L, ?], E] = | ||
new WriterTMonadError[F, L, E] { | ||
implicit val F0: MonadError[F, E] = F | ||
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@@ -134,9 +159,14 @@ private[data] sealed abstract class WriterTInstances0 extends WriterTInstances1 | |
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implicit def catsDataMonoidForWriterTId[L:Monoid, V:Monoid]: Monoid[WriterT[Id, L, V]] = | ||
catsDataMonoidForWriterT[Id, L, V] | ||
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implicit def catsDataFoldableForWriterT[F[_], L](implicit F: Foldable[F]): Foldable[WriterT[F, L, ?]] = | ||
new WriterTFoldable[F, L]{ | ||
val F0: Foldable[F] = F | ||
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances1 extends WriterTInstances2 { | ||
private[data] sealed abstract class WriterTInstances2 extends WriterTInstances3 { | ||
implicit def catsDataMonadForWriterTId[L:Monoid]: Monad[WriterT[Id, L, ?]] = | ||
catsDataMonadForWriterT[Id, L] | ||
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@@ -145,9 +175,12 @@ private[data] sealed abstract class WriterTInstances1 extends WriterTInstances2 | |
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implicit def catsDataSemigroupForWriterTId[L:Semigroup, V:Semigroup]: Semigroup[WriterT[Id, L, V]] = | ||
catsDataSemigroupForWriterT[Id, L, V] | ||
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implicit def catsDataComonadForWriterTId[L](implicit F: Comonad[Id]): Comonad[WriterT[Id, L, ?]] = | ||
catsDataComonadForWriterT[Id, L](F) | ||
} | ||
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private[data] sealed abstract class WriterTInstances2 extends WriterTInstances3 { | ||
private[data] sealed abstract class WriterTInstances3 extends WriterTInstances4 { | ||
implicit def catsDataMonadForWriterT[F[_], L](implicit F: Monad[F], L: Monoid[L]): Monad[WriterT[F, L, ?]] = | ||
new WriterTMonad[F, L] { | ||
implicit val F0: Monad[F] = F | ||
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@@ -163,12 +196,12 @@ private[data] sealed abstract class WriterTInstances2 extends WriterTInstances3 | |
catsDataCoflatMapForWriterT[Id, L] | ||
} | ||
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private[data] sealed abstract class WriterTInstances3 extends WriterTInstances4 { | ||
private[data] sealed abstract class WriterTInstances4 extends WriterTInstances5 { | ||
implicit def catsDataFlatMapForWriterTId[L:Semigroup]: FlatMap[WriterT[Id, L, ?]] = | ||
catsDataFlatMapForWriterT2[Id, L] | ||
} | ||
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private[data] sealed abstract class WriterTInstances4 extends WriterTInstances5 { | ||
private[data] sealed abstract class WriterTInstances5 extends WriterTInstances6 { | ||
implicit def catsDataFlatMapForWriterT1[F[_], L](implicit F: FlatMap[F], L: Monoid[L]): FlatMap[WriterT[F, L, ?]] = | ||
new WriterTFlatMap1[F, L] { | ||
implicit val F0: FlatMap[F] = F | ||
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@@ -181,15 +214,15 @@ private[data] sealed abstract class WriterTInstances4 extends WriterTInstances5 | |
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances5 extends WriterTInstances6 { | ||
private[data] sealed abstract class WriterTInstances6 extends WriterTInstances7 { | ||
implicit def catsDataApplicativeErrorForWriterT[F[_], L, E](implicit F: ApplicativeError[F, E], L: Monoid[L]): ApplicativeError[WriterT[F, L, ?], E] = | ||
new WriterTApplicativeError[F, L, E] { | ||
implicit val F0: ApplicativeError[F, E] = F | ||
implicit val L0: Monoid[L] = L | ||
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances6 extends WriterTInstances7 { | ||
private[data] sealed abstract class WriterTInstances7 extends WriterTInstances8 { | ||
implicit def catsDataAlternativeForWriterT[F[_], L](implicit F: Alternative[F], L: Monoid[L]): Alternative[WriterT[F, L, ?]] = | ||
new WriterTAlternative[F, L] { | ||
implicit val F0: Alternative[F] = F | ||
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@@ -202,7 +235,7 @@ private[data] sealed abstract class WriterTInstances6 extends WriterTInstances7 | |
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances7 extends WriterTInstances8 { | ||
private[data] sealed abstract class WriterTInstances8 extends WriterTInstances9 { | ||
implicit def catsDataMonoidKForWriterT[F[_], L](implicit F: MonoidK[F]): MonoidK[WriterT[F, L, ?]] = | ||
new WriterTMonoidK[F, L] { | ||
implicit val F0: MonoidK[F] = F | ||
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@@ -219,7 +252,7 @@ private[data] sealed abstract class WriterTInstances7 extends WriterTInstances8 | |
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances8 extends WriterTInstances9 { | ||
private[data] sealed abstract class WriterTInstances9 extends WriterTInstances10 { | ||
implicit def catsDataSemigroupKForWriterT[F[_], L](implicit F: SemigroupK[F]): SemigroupK[WriterT[F, L, ?]] = | ||
new WriterTSemigroupK[F, L] { | ||
implicit val F0: SemigroupK[F] = F | ||
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@@ -230,18 +263,24 @@ private[data] sealed abstract class WriterTInstances8 extends WriterTInstances9 | |
implicit val F0: Applicative[F] = F | ||
implicit val L0: Monoid[L] = L | ||
} | ||
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} | ||
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private[data] sealed abstract class WriterTInstances9 extends WriterTInstances10 { | ||
private[data] sealed abstract class WriterTInstances10 extends WriterTInstances11 { | ||
implicit def catsDataApplyForWriterT[F[_], L](implicit F: Apply[F], L: Semigroup[L]): Apply[WriterT[F, L, ?]] = | ||
new WriterTApply[F, L] { | ||
implicit val F0: Apply[F] = F | ||
implicit val L0: Semigroup[L] = L | ||
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances10 { | ||
private[data] sealed abstract class WriterTInstances11 extends WriterTInstances12 { | ||
implicit def catsDataComonadForWriterT[F[_], L](implicit F: Comonad[F]): Comonad[WriterT[F, L, ?]] = | ||
new WriterTComonad[F, L] { | ||
implicit val F0: Comonad[F] = F | ||
} | ||
} | ||
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private[data] sealed abstract class WriterTInstances12 { | ||
implicit def catsDataCoflatMapForWriterT[F[_], L](implicit F: Functor[F]): CoflatMap[WriterT[F, L, ?]] = | ||
new WriterTCoflatMap[F, L] { | ||
implicit val F0: Functor[F] = F | ||
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@@ -410,6 +449,27 @@ private[data] sealed trait WriterTCoflatMap[F[_], L] extends CoflatMap[WriterT[F | |
def coflatMap[A, B](fa: WriterT[F, L, A])(f: WriterT[F, L, A] => B): WriterT[F, L, B] = fa.map(_ => f(fa)) | ||
} | ||
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private[data] sealed trait WriterTFoldable[F[_], L] extends Foldable[WriterT[F, L, ?]] { | ||
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implicit def F0: Foldable[F] | ||
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def foldLeft[A, B](fa: WriterT[F, L, A], b: B)(f: (B, A) => B): B = fa.foldLeft(b)(f) | ||
def foldRight[A, B](fa: WriterT[F, L, A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] = fa.foldRight(lb)(f) | ||
} | ||
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private[data] sealed trait WriterTTraverse[F[_], L] extends Traverse[WriterT[F, L, ?]] with WriterTFoldable[F, L] { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. If you extends There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I will change it thanks 👍 |
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override implicit def F0: Traverse[F] | ||
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def traverse[G[_]: Applicative, A, B](fa: WriterT[F, L, A])(f: A => G[B]): G[WriterT[F, L, B]] = fa.traverse(f) | ||
} | ||
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private[data] sealed trait WriterTComonad[F[_], L] extends Comonad[WriterT[F, L, ?]] with WriterTCoflatMap[F, L] { | ||
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override implicit def F0: Comonad[F] | ||
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def extract[A](fa: WriterT[F, L, A]): A = F0.extract(F0.map(fa.run)(_._2)) | ||
} | ||
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private[data] trait WriterTFunctions { | ||
def putT[F[_], L, V](vf: F[V])(l: L)(implicit functorF: Functor[F]): WriterT[F, L, V] = | ||
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Can this be
G.tupleLeft(f(lv._2), lv._1)
instead ofG.product(G.pure(lv._1), f(lv._2))
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sure changing it 👍