Merge pull request #497 from drostron/set-monoid-instance

add setMonoid
typelevel · Sep 11, 2015 · 2d5c6e1 · 2d5c6e1
2 parents 82da887 + 345df6c
commit 2d5c6e1
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diff --git a/core/src/main/scala/cats/std/set.scala b/core/src/main/scala/cats/std/set.scala
@@ -23,4 +23,6 @@ trait SetInstances extends algebra.std.SetInstances {
 
       override def isEmpty[A](fa: Set[A]): Boolean = fa.isEmpty
     }
+
+    implicit def setMonoid[A]: Monoid[Set[A]] = MonoidK[Set].algebra[A]
 }
diff --git a/tests/shared/src/test/scala/cats/tests/SetTests.scala b/tests/shared/src/test/scala/cats/tests/SetTests.scala
@@ -4,6 +4,8 @@ package tests
 import cats.laws.discipline.{FoldableTests, MonoidKTests, SerializableTests}
 
 class SetTests extends CatsSuite {
+  checkAll("Set[Int]", algebra.laws.GroupLaws[Set[Int]].monoid)
+
   checkAll("Set[Int]", MonoidKTests[Set].monoidK[Int])
   checkAll("MonoidK[Set]", SerializableTests.serializable(MonoidK[Set]))