Merge pull request #644 from ceedubs/xort-traverse

Add Traverse and Foldable instances for XorT
typelevel · Nov 15, 2015 · b2b967b · b2b967b
2 parents 2f853d5 + aa91f29
commit b2b967b
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Showing 2 changed files with 47 additions and 3 deletions.
diff --git a/core/src/main/scala/cats/data/XorT.scala b/core/src/main/scala/cats/data/XorT.scala
@@ -171,6 +171,10 @@ private[data] abstract class XorTInstances extends XorTInstances1 {
     }
   }
 
+  implicit def xorTTraverse[F[_], L](implicit F: Traverse[F]): Traverse[XorT[F, L, ?]] =
+    new XorTTraverse[F, L] {
+      val F0: Traverse[F] = F
+    }
 }
 
 private[data] abstract class XorTInstances1 extends XorTInstances2 {
@@ -191,6 +195,11 @@ private[data] abstract class XorTInstances1 extends XorTInstances2 {
       def empty[A]: XorT[F, L, A] = XorT.left(F.pure(L.empty))(F)
     }
   }
+
+  implicit def xorTFoldable[F[_], L](implicit F: Foldable[F]): Foldable[XorT[F, L, ?]] =
+    new XorTFoldable[F, L] {
+      val F0: Foldable[F] = F
+    }
 }
 
 private[data] abstract class XorTInstances2 extends XorTInstances3 {
@@ -264,4 +273,19 @@ private[data] trait XorTMonadCombine[F[_], L] extends MonadCombine[XorT[F, L, ?]
   implicit val L: Monoid[L]
 }
 
+private[data] sealed trait XorTFoldable[F[_], L] extends Foldable[XorT[F, L, ?]] {
+  implicit def F0: Foldable[F]
+
+  def foldLeft[A, B](fa: XorT[F, L, A], b: B)(f: (B, A) => B): B =
+    fa.foldLeft(b)(f)
+
+  def foldRight[A, B](fa: XorT[F, L, A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
+    fa.foldRight(lb)(f)
+}
+
+private[data] sealed trait XorTTraverse[F[_], L] extends Traverse[XorT[F, L, ?]] with XorTFoldable[F, L] {
+  override implicit def F0: Traverse[F]
 
+  override def traverse[G[_]: Applicative, A, B](fa: XorT[F, L, A])(f: A => G[B]): G[XorT[F, L, B]] =
+    fa traverse f
+}
diff --git a/tests/src/test/scala/cats/tests/XorTTests.scala b/tests/src/test/scala/cats/tests/XorTTests.scala
@@ -1,18 +1,38 @@
 package cats
 package tests
 
+import cats.functor.Bifunctor
 import cats.data.{Xor, XorT}
-import cats.laws.discipline.{BifunctorTests, MonadErrorTests, MonoidKTests, SerializableTests}
+import cats.laws.discipline.{BifunctorTests, FoldableTests, FunctorTests, MonadErrorTests, MonoidKTests, SerializableTests, TraverseTests}
 import cats.laws.discipline.arbitrary._
 
-
 class XorTTests extends CatsSuite {
   implicit val eq0 = XorT.xorTEq[List, String, String Xor Int]
   implicit val eq1 = XorT.xorTEq[XorT[List, String, ?], String, Int](eq0)
   checkAll("XorT[List, String, Int]", MonadErrorTests[XorT[List, String, ?], String].monadError[Int, Int, Int])
-  checkAll("XorT[List, String, Int]", MonoidKTests[XorT[List, String, ?]].monoidK[Int])
   checkAll("MonadError[XorT[List, ?, ?]]", SerializableTests.serializable(MonadError[XorT[List, String, ?], String]))
+  checkAll("XorT[List, String, Int]", MonoidKTests[XorT[List, String, ?]].monoidK[Int])
+  checkAll("MonoidK[XorT[List, String, ?]]", SerializableTests.serializable(MonoidK[XorT[List, String, ?]]))
   checkAll("XorT[List, ?, ?]", BifunctorTests[XorT[List, ?, ?]].bifunctor[Int, Int, Int, String, String, String])
+  checkAll("Bifunctor[XorT[List, ?, ?]]", SerializableTests.serializable(Bifunctor[XorT[List, ?, ?]]))
+  checkAll("XorT[List, Int, ?]", TraverseTests[XorT[List, Int, ?]].foldable[Int, Int])
+  checkAll("Traverse[XorT[List, Int, ?]]", SerializableTests.serializable(Traverse[XorT[List, Int, ?]]))
+
+  {
+    implicit val F = ListWrapper.foldable
+    checkAll("XorT[ListWrapper, Int, ?]", FoldableTests[XorT[ListWrapper, Int, ?]].foldable[Int, Int])
+    checkAll("Foldable[XorT[ListWrapper, Int, ?]]", SerializableTests.serializable(Foldable[XorT[ListWrapper, Int, ?]]))
+  }
+
+  {
+    implicit val F = ListWrapper.functor
+    checkAll("XorT[ListWrapper, Int, ?]", FunctorTests[XorT[ListWrapper, Int, ?]].functor[Int, Int, Int])
+    checkAll("Functor[XorT[ListWrapper, Int, ?]]", SerializableTests.serializable(Functor[XorT[ListWrapper, Int, ?]]))
+  }
+
+  // make sure that the Monad and Traverse instances don't result in ambiguous
+  // Functor instances
+  Functor[XorT[List, Int, ?]]
 
   test("toValidated") {
     forAll { (xort: XorT[List, String, Int]) =>