Add ApplicativeError.redeem and ApplicativeError.redeemWith

typelevel · Oct 15, 2018 · c7c2f7a · c7c2f7a
1 parent 191fae4
commit c7c2f7a
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diff --git a/core/src/main/scala/cats/ApplicativeError.scala b/core/src/main/scala/cats/ApplicativeError.scala
@@ -72,6 +72,16 @@ trait ApplicativeError[F[_], E] extends Applicative[F] {
    */
   def attemptT[A](fa: F[A]): EitherT[F, E, A] = EitherT(attempt(fa))
 
+  /**
+    * Returns a new value that transforms the result of the source,
+    * given the `recover` or `map` functions, which get executed depending
+    * on whether the result is successful or if it ends in error.
+    *
+    * This is an optimization on usage of [[attempt]] and [[map]].
+    */
+  def redeem[A, B](fa: F[A])(recover: E => B, mapper: A => B): F[B] =
+    map(attempt(fa))(_.fold(recover, mapper))
+
   /**
    * Recover from certain errors by mapping them to an `A` value.
    *

diff --git a/core/src/main/scala/cats/MonadError.scala b/core/src/main/scala/cats/MonadError.scala
@@ -42,6 +42,16 @@ trait MonadError[F[_], E] extends ApplicativeError[F, E] with Monad[F] {
   def adaptError[A](fa: F[A])(pf: PartialFunction[E, E]): F[A] =
     flatMap(attempt(fa))(_.fold(e => raiseError(pf.applyOrElse[E, E](e, _ => e)), pure))
 
+  /**
+    * Returns a new value that transforms the result of the source,
+    * given the `recover` or `bind` functions, which get executed depending
+    * on whether the result is successful or if it ends in error.
+    *
+    * This is an optimization on usage of [[attempt]] and [[flatMap]].
+    */
+  def redeemWith[A, B](fa: F[A])(recover: E => F[B], bind: A => F[B]): F[B] =
+    flatMap(attempt(fa))(_.fold(recover, bind))
+
   /**
    * Inverse of `attempt`
    *

diff --git a/core/src/main/scala/cats/syntax/applicativeError.scala b/core/src/main/scala/cats/syntax/applicativeError.scala
@@ -84,6 +84,9 @@ final class ApplicativeErrorOps[F[_], E, A](val fa: F[A]) extends AnyVal {
   def attemptT(implicit F: ApplicativeError[F, E]): EitherT[F, E, A] =
     F.attemptT(fa)
 
+  def redeem[B](recover: E => B, map: A => B)(implicit F: ApplicativeError[F, E]): F[B] =
+    F.redeem(fa)(recover, map)
+
   def recover(pf: PartialFunction[E, A])(implicit F: ApplicativeError[F, E]): F[A] =
     F.recover(fa)(pf)
 

diff --git a/core/src/main/scala/cats/syntax/monadError.scala b/core/src/main/scala/cats/syntax/monadError.scala
@@ -23,6 +23,9 @@ final class MonadErrorOps[F[_], E, A](val fa: F[A]) extends AnyVal {
 
   def adaptError(pf: PartialFunction[E, E])(implicit F: MonadError[F, E]): F[A] =
     F.adaptError(fa)(pf)
+
+  def redeemWith[B](recover: E => F[B], bind: A => F[B])(implicit F: MonadError[F, E]): F[B] =
+    F.redeemWith(fa)(recover, bind)
 }
 
 final class MonadErrorRethrowOps[F[_], E, A](val fea: F[Either[E, A]]) extends AnyVal {