Order for Ior (#3554)

* Order for Ior * Move compare definition onto Ior itself * Fix typo * Reduce allocations in compare * Make Both > Right
typelevel · Aug 10, 2020 · ed75d10 · ed75d10
1 parent cc20fbc
commit ed75d10
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Showing 2 changed files with 27 additions and 4 deletions.
diff --git a/core/src/main/scala/cats/data/Ior.scala b/core/src/main/scala/cats/data/Ior.scala
@@ -708,6 +708,20 @@ sealed abstract class Ior[+A, +B] extends Product with Serializable {
       (a, b) => that.fold(a2 => false, b2 => false, (a2, b2) => AA.eqv(a, a2) && BB.eqv(b, b2))
     )
 
+  final def compare[AA >: A, BB >: B](that: AA Ior BB)(implicit AA: Order[AA], BB: Order[BB]): Int =
+    (this, that) match {
+      case (Ior.Left(a1), Ior.Left(a2))   => AA.compare(a1, a2)
+      case (Ior.Left(_), _)               => -1
+      case (Ior.Right(b1), Ior.Right(b2)) => BB.compare(b1, b2)
+      case (Ior.Right(_), Ior.Left(_))    => 1
+      case (Ior.Right(_), Ior.Both(_, _)) => -1
+      case (Ior.Both(a1, b1), Ior.Both(a2, b2)) => {
+        val r = AA.compare(a1, a2)
+        if (r == 0) BB.compare(b1, b2) else r
+      }
+      case (Ior.Both(_, _), _) => 1
+    }
+
   final def show[AA >: A, BB >: B](implicit AA: Show[AA], BB: Show[BB]): String =
     fold(
       a => s"Ior.Left(${AA.show(a)})",
@@ -752,9 +766,10 @@ sealed abstract private[data] class IorInstances extends IorInstances0 {
       }
   }
 
-  implicit def catsDataEqForIor[A: Eq, B: Eq]: Eq[A Ior B] =
-    new Eq[A Ior B] {
-      def eqv(x: A Ior B, y: A Ior B): Boolean = x === y
+  implicit def catsDataOrderForIor[A: Order, B: Order]: Order[A Ior B] =
+    new Order[A Ior B] {
+
+      def compare(x: Ior[A, B], y: Ior[A, B]): Int = x.compare(y)
     }
 
   implicit def catsDataShowForIor[A: Show, B: Show]: Show[A Ior B] =
@@ -879,6 +894,12 @@ sealed abstract private[data] class IorInstances0 {
       override def map[B, C](fa: A Ior B)(f: B => C): A Ior C =
         fa.map(f)
     }
+
+  implicit def catsDataEqForIor[A: Eq, B: Eq]: Eq[A Ior B] =
+    new Eq[A Ior B] {
+
+      def eqv(x: A Ior B, y: A Ior B): Boolean = x === y
+    }
 }
 
 sealed private[data] trait IorFunctions {

diff --git a/tests/src/test/scala/cats/tests/IorSuite.scala b/tests/src/test/scala/cats/tests/IorSuite.scala
@@ -3,7 +3,7 @@ package cats.tests
 import cats.{Bitraverse, MonadError, Semigroupal, Show, Traverse}
 import cats.data.{EitherT, Ior, NonEmptyChain, NonEmptyList, NonEmptySet}
 import cats.kernel.{Eq, Semigroup}
-import cats.kernel.laws.discipline.SemigroupTests
+import cats.kernel.laws.discipline.{OrderTests, SemigroupTests}
 import cats.laws.discipline.{
   BifunctorTests,
   BitraverseTests,
@@ -37,6 +37,8 @@ class IorSuite extends CatsSuite {
   checkAll("BitraverseTests Ior[*, *]", BitraverseTests[Ior].bitraverse[Option, Int, Int, Int, String, String, String])
   checkAll("Bitraverse[Ior]", SerializableTests.serializable(Bitraverse[Ior]))
 
+  checkAll("Order[Ior[A: Order, B: Order]]", OrderTests[Ior[Int, Int]].order)
+
   checkAll("Semigroup[Ior[A: Semigroup, B: Semigroup]]", SemigroupTests[Ior[List[Int], List[Int]]].semigroup)
   checkAll("SerializableTest Semigroup[Ior[A: Semigroup, B: Semigroup]]",
            SerializableTests.serializable(Semigroup[Ior[List[Int], List[Int]]])