Add valueOrF to EitherT (#2192)

typelevel · Mar 14, 2018 · f644982 · f644982
1 parent 5b85396
commit f644982
Show file tree

Hide file tree

Showing 2 changed files with 13 additions and 0 deletions.
diff --git a/core/src/main/scala/cats/data/EitherT.scala b/core/src/main/scala/cats/data/EitherT.scala
@@ -48,6 +48,13 @@ final case class EitherT[F[_], A, B](value: F[Either[A, B]]) {
 
   def valueOr[BB >: B](f: A => BB)(implicit F: Functor[F]): F[BB] = fold(f, identity)
 
+  def valueOrF[BB >: B](f: A => F[BB])(implicit F: Monad[F]): F[BB] = {
+      F.flatMap(value){
+        case Left(a) => f(a)
+        case Right(b) => F.pure(b)
+      }
+  }
+
   def forall(f: B => Boolean)(implicit F: Functor[F]): F[Boolean] = F.map(value)(_.forall(f))
 
   def exists(f: B => Boolean)(implicit F: Functor[F]): F[Boolean] = F.map(value)(_.exists(f))

diff --git a/tests/src/test/scala/cats/tests/EitherTSuite.scala b/tests/src/test/scala/cats/tests/EitherTSuite.scala
@@ -282,6 +282,12 @@ class EitherTSuite extends CatsSuite {
     }
   }
 
+  test("valueOrF with Id consistent with Either valueOr") {
+    forAll{ (eithert: EitherT[Id, String, Int], f: String => Int) =>
+      eithert.valueOrF(f) should === (eithert.value.valueOr(f))
+    }
+  }
+
   test("getOrElse with Id consistent with Either getOrElse") {
     forAll { (eithert: EitherT[Id, String, Int], i: Int) =>
       eithert.getOrElse(i) should === (eithert.value.getOrElse(i))