Add Const and Validated instances and derivation from SemigroupK and …

…Apply
typelevel · Sep 25, 2019 · c5084bf · c5084bf
1 parent 909a33a
commit c5084bf
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Showing 12 changed files with 99 additions and 5 deletions.
diff --git a/core/src/main/scala/cats/Align.scala b/core/src/main/scala/cats/Align.scala
@@ -45,3 +45,9 @@ import cats.data.Ior
   def padZipWith[A, B, C](fa: F[A], fb: F[B])(f: (Option[A], Option[B]) => C): F[C] =
     alignWith(fa, fb)(ior => Function.tupled(f)(ior.pad))
 }
+
+object Align {
+  def semigroup[F[_]: Align, A: Semigroup]: Semigroup[F[A]] = new Semigroup[F[A]] {
+    def combine(x: F[A], y: F[A]): F[A] = Align[F].alignCombine(x, y)
+  }
+}
diff --git a/core/src/main/scala/cats/Apply.scala b/core/src/main/scala/cats/Apply.scala
@@ -2,6 +2,7 @@ package cats
 
 import simulacrum.typeclass
 import simulacrum.noop
+import cats.data.Ior
 
 /**
  * Weaker version of Applicative[F]; has apply but not pure.
@@ -225,6 +226,11 @@ object Apply {
    */
   def semigroup[F[_], A](implicit f: Apply[F], sg: Semigroup[A]): Semigroup[F[A]] =
     new ApplySemigroup[F, A](f, sg)
+
+  def align[F[_]: Apply]: Align[F] = new Align[F] {
+    def align[A, B](fa: F[A], fb: F[B]): F[Ior[A, B]] = Apply[F].map2(fa, fb)(Ior.both)
+    def functor: Functor[F] = Apply[F]
+  }
 }
 
 private[cats] class ApplySemigroup[F[_], A](f: Apply[F], sg: Semigroup[A]) extends Semigroup[F[A]] {

diff --git a/core/src/main/scala/cats/SemigroupK.scala b/core/src/main/scala/cats/SemigroupK.scala
@@ -1,6 +1,7 @@
 package cats
 
 import simulacrum.typeclass
+import cats.data.Ior
 
 /**
  * SemigroupK is a universal semigroup which operates on kinds.
@@ -68,3 +69,11 @@ import simulacrum.typeclass
       val F = self
     }
 }
+
+object SemigroupK {
+  def align[F[_]: SemigroupK: Functor]: Align[F] = new Align[F] {
+    def align[A, B](fa: F[A], fb: F[B]): F[Ior[A, B]] =
+      SemigroupK[F].combineK(Functor[F].map(fa)(Ior.left), Functor[F].map(fb)(Ior.right))
+    def functor: Functor[F] = Functor[F]
+  }
+}
diff --git a/core/src/main/scala/cats/data/Const.scala b/core/src/main/scala/cats/data/Const.scala
@@ -74,6 +74,12 @@ sealed abstract private[data] class ConstInstances extends ConstInstances0 {
       x.compare(y)
   }
 
+  implicit def catsDataAlignForConst[A: Semigroup]: Align[Const[A, *]] = new Align[Const[A, *]] {
+    def align[B, C](fa: Const[A, B], fb: Const[A, C]): Const[A, Ior[B, C]] =
+      Const(Semigroup[A].combine(fa.getConst, fb.getConst))
+    def functor: Functor[Const[A, *]] = catsDataFunctorForConst
+  }
+
   implicit def catsDataShowForConst[A: Show, B]: Show[Const[A, B]] = new Show[Const[A, B]] {
     def show(f: Const[A, B]): String = f.show
   }

diff --git a/core/src/main/scala/cats/data/Validated.scala b/core/src/main/scala/cats/data/Validated.scala
@@ -371,6 +371,27 @@ sealed abstract private[data] class ValidatedInstances extends ValidatedInstance
       }
     }
 
+  implicit def catsDataAlignForValidated[E: Semigroup]: Align[Validated[E, *]] =
+    new Align[Validated[E, *]] {
+      def functor: Functor[Validated[E, *]] = catsDataTraverseFunctorForValidated
+      def align[A, B](fa: Validated[E, A], fb: Validated[E, B]): Validated[E, Ior[A, B]] =
+        alignWith(fa, fb)(identity)
+
+      override def alignWith[A, B, C](fa: Validated[E, A], fb: Validated[E, B])(f: Ior[A, B] => C): Validated[E, C] =
+        fa match {
+          case Invalid(e) =>
+            fb match {
+              case Invalid(e2) => Invalid(Semigroup[E].combine(e, e2))
+              case Valid(b)    => Valid(f(Ior.right(b)))
+            }
+          case Valid(a) =>
+            fb match {
+              case Invalid(e) => Valid(f(Ior.left(a)))
+              case Valid(b)   => Valid(f(Ior.both(a, b)))
+            }
+        }
+    }
+
   implicit def catsDataMonoidForValidated[A, B](implicit A: Semigroup[A], B: Monoid[B]): Monoid[Validated[A, B]] =
     new Monoid[Validated[A, B]] {
       def empty: Validated[A, B] = Valid(B.empty)

diff --git a/laws/src/main/scala/cats/laws/AlignLaws.scala b/laws/src/main/scala/cats/laws/AlignLaws.scala
@@ -18,10 +18,7 @@ trait AlignLaws[F[_]] {
   def alignAssociativity[A, B, C](fa: F[A], fb: F[B], fc: F[C]): IsEq[F[Ior[Ior[A, B], C]]] =
     fa.align(fb).align(fc) <-> fa.align(fb.align(fc)).map(assoc)
 
-  def alignSelfBoth[A](fa: F[A]): IsEq[F[A Ior A]] =
-    fa.align(fa) <-> fa.map(a => Ior.both(a, a))
-
-  def alignHomomorphism[A, B, C, D](fa: F[A], fb: F[B], f: A => C, g: B => D): IsEq[F[C Ior D]] =
+  def alignHomomorphism[A, B, C, D](fa: F[A], fb: F[B], f: A => C, g: B => D): IsEq[F[Ior[C, D]]] =
     fa.map(f).align(fb.map(g)) <-> fa.align(fb).map(_.bimap(f, g))
 
   def alignWithConsistent[A, B, C](fa: F[A], fb: F[B], f: A Ior B => C): IsEq[F[C]] =

diff --git a/laws/src/main/scala/cats/laws/discipline/AlignTests.scala b/laws/src/main/scala/cats/laws/discipline/AlignTests.scala
@@ -32,7 +32,6 @@ trait AlignTests[F[_]] extends Laws {
     new DefaultRuleSet(name = "align",
                        parent = None,
                        "align associativity" -> forAll(laws.alignAssociativity[A, B, C] _),
-                       "align self both" -> forAll(laws.alignSelfBoth[A] _),
                        "align homomorphism" -> forAll { (fa: F[A], fb: F[B], f: A => C, g: B => D) =>
                          laws.alignHomomorphism[A, B, C, D](fa, fb, f, g)
                        },

diff --git a/tests/src/test/scala/cats/tests/AlignSuite.scala b/tests/src/test/scala/cats/tests/AlignSuite.scala
@@ -0,0 +1,14 @@
+package cats.tests
+
+import cats.Align
+import cats.kernel.laws.discipline.SemigroupTests
+
+class AlignSuite extends CatsSuite {
+  {
+    val optionSemigroup = Align.semigroup[Option, Int]
+    checkAll("Align[Option].semigroup", SemigroupTests[Option[Int]](optionSemigroup).semigroup)
+
+    val listSemigroup = Align.semigroup[List, String]
+    checkAll("Align[List].semigroup", SemigroupTests[List[String]](listSemigroup).semigroup)
+  }
+}
diff --git a/tests/src/test/scala/cats/tests/ApplicativeSuite.scala b/tests/src/test/scala/cats/tests/ApplicativeSuite.scala
@@ -6,6 +6,7 @@ import cats.kernel.laws.discipline.{MonoidTests, SemigroupTests}
 import cats.data.{Const, Validated}
 import cats.laws.discipline.arbitrary._
 import cats.laws.discipline.CoflatMapTests
+import cats.laws.discipline.AlignTests
 
 class ApplicativeSuite extends CatsSuite {
 
@@ -59,6 +60,15 @@ class ApplicativeSuite extends CatsSuite {
 
     implicit val constCoflatMap = Applicative.coflatMap[Const[String, *]]
     checkAll("Applicative[Const].coflatMap", CoflatMapTests[Const[String, *]].coflatMap[String, String, String])
+
+    implicit val listwrapperAlign = Apply.align[ListWrapper]
+    checkAll("Apply[ListWrapper].align", AlignTests[ListWrapper].align[Int, Int, Int, Int])
+
+    implicit val validatedAlign = Apply.align[Validated[String, *]]
+    checkAll("Apply[Validated].align", AlignTests[Validated[String, *]].align[Int, Int, Int, Int])
+
+    implicit val constAlign = Apply.align[Const[String, *]]
+    checkAll("Apply[Const].align", AlignTests[Const[String, *]].align[Int, Int, Int, Int])
   }
 
 }
diff --git a/tests/src/test/scala/cats/tests/ConstSuite.scala b/tests/src/test/scala/cats/tests/ConstSuite.scala
@@ -32,6 +32,9 @@ class ConstSuite extends CatsSuite {
   checkAll("Const[String, Int]", TraverseFilterTests[Const[String, *]].traverseFilter[Int, Int, Int])
   checkAll("TraverseFilter[Const[String, *]]", SerializableTests.serializable(TraverseFilter[Const[String, *]]))
 
+  checkAll("Const[String, Int]", AlignTests[Const[String, *]].align[Int, Int, Int, Int])
+  checkAll("Align[Const[String, *]]", SerializableTests.serializable(Align[Const[String, *]]))
+
   // Get Apply[Const[C : Semigroup, *]], not Applicative[Const[C : Monoid, *]]
   {
     implicit def nonEmptyListSemigroup[A]: Semigroup[NonEmptyList[A]] = SemigroupK[NonEmptyList].algebra

diff --git a/tests/src/test/scala/cats/tests/SemigroupKSuite.scala b/tests/src/test/scala/cats/tests/SemigroupKSuite.scala
@@ -0,0 +1,20 @@
+package cats.tests
+
+import cats.SemigroupK
+import cats.data.{Chain, Validated}
+import cats.laws.discipline.AlignTests
+import cats.laws.discipline.arbitrary._
+
+class SemigroupKSuite extends CatsSuite {
+  {
+    implicit val listwrapperSemigroupK = ListWrapper.alternative
+    implicit val listwrapperAlign = SemigroupK.align[ListWrapper]
+    checkAll("SemigroupK[ListWrapper].align", AlignTests[ListWrapper].align[Int, Int, Int, Int])
+
+    implicit val validatedAlign = SemigroupK.align[Validated[String, *]]
+    checkAll("SemigroupK[Validated].align", AlignTests[Validated[String, *]].align[Int, Int, Int, Int])
+
+    implicit val chainAlign = SemigroupK.align[Chain]
+    checkAll("SemigroupK[Chain].align", AlignTests[Chain].align[Int, Int, Int, Int])
+  }
+}
diff --git a/tests/src/test/scala/cats/tests/ValidatedSuite.scala b/tests/src/test/scala/cats/tests/ValidatedSuite.scala
@@ -41,6 +41,9 @@ class ValidatedSuite extends CatsSuite {
   checkAll("CommutativeApplicative[Validated[Int, *]]",
            SerializableTests.serializable(CommutativeApplicative[Validated[Int, *]]))
 
+  checkAll("Validated[Int, Int]", AlignTests[Validated[Int, *]].align[Int, Int, Int, Int])
+  checkAll("Align[Validated[Int, *]]", SerializableTests.serializable(Align[Validated[Int, *]]))
+
   {
     implicit val L = ListWrapper.semigroup[String]
     checkAll("Validated[ListWrapper[String], *]", SemigroupKTests[Validated[ListWrapper[String], *]].semigroupK[Int])