Add Order->Ordering implicit conversion to implicits, instances

typelevel · Jun 28, 2017 · ed8c873 · ed8c873
1 parent bbc97b8
commit ed8c873
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/core/src/main/scala/cats/instances/order.scala b/core/src/main/scala/cats/instances/order.scala
@@ -3,7 +3,7 @@ package instances
 
 import cats.functor.Contravariant
 
-trait OrderInstances {
+trait OrderInstances extends cats.kernel.OrderToOrderingConversion {
 
   implicit val catsFunctorContravariantForOrder: Contravariant[Order] =
     new Contravariant[Order] {
@@ -14,3 +14,4 @@ trait OrderInstances {
       def contramap[A, B](fa: Order[A])(f: B => A): Order[B] = fa.on(f)
     }
 }
+
diff --git a/kernel/src/main/scala/cats/kernel/Order.scala b/kernel/src/main/scala/cats/kernel/Order.scala
@@ -139,6 +139,15 @@ abstract class OrderFunctions[O[T] <: Order[T]] extends PartialOrderFunctions[O]
     ev.max(x, y)
 }
 
+trait OrderToOrderingConversion {
+  /**
+   * Implicitly derive a `scala.math.Ordering[A]` from a `Order[A]`
+   * instance.
+   */
+  implicit def catsKernelOrderingForOrder[A](implicit ev: Order[A]): Ordering[A] =
+    ev.toOrdering
+}
+
 object Order extends OrderFunctions[Order] {
   /**
    * Access an implicit `Order[A]`.