sequenceK semigroup combine fix

arrow-kt · Jul 3, 2018 · 48c8d88 · 48c8d88
1 parent 35ebe3f
commit 48c8d88
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Showing 2 changed files with 12 additions and 3 deletions.
diff --git a/modules/core/arrow-data/src/test/kotlin/arrow/data/SequenceKTest.kt b/modules/core/arrow-data/src/test/kotlin/arrow/data/SequenceKTest.kt
@@ -9,6 +9,8 @@ import arrow.test.laws.*
 import arrow.typeclasses.Eq
 import arrow.typeclasses.Show
 import io.kotlintest.KTestJUnitRunner
+import io.kotlintest.properties.Gen
+import io.kotlintest.properties.map
 import org.junit.runner.RunWith
 
 @RunWith(KTestJUnitRunner::class)
@@ -32,7 +34,14 @@ class SequenceKTest : UnitSpec() {
         ShowLaws.laws(show, eq) { sequenceOf(it).k() },
         MonadLaws.laws(this, eq),
         MonoidKLaws.laws(this, this, eq),
-        TraverseLaws.laws(this, this, { n: Int -> SequenceK(sequenceOf(n)) }, eq)
+        TraverseLaws.laws(this, this, { n: Int -> SequenceK(sequenceOf(n)) }, eq),
+        SemigroupKLaws.laws(this, this, eq),
+        MonoidLaws.laws(SequenceK.monoid(), Gen.list(Gen.int()).map{it.asSequence()}.generate().k(), eq),
+        SemigroupLaws.laws(SequenceK.semigroup(),
+          Gen.list(Gen.int()).map{it.asSequence()}.generate().k(),
+          Gen.list(Gen.int()).map{it.asSequence()}.generate().k(),
+          Gen.list(Gen.int()).map{it.asSequence()}.generate().k(),
+          eq)
       )
     }
   }

diff --git a/modules/core/arrow-instances-data/src/main/kotlin/arrow/instances/sequence.kt b/modules/core/arrow-instances-data/src/main/kotlin/arrow/instances/sequence.kt
@@ -11,12 +11,12 @@ import arrow.data.combineK as sequenceCombineK
 
 @instance(SequenceK::class)
 interface SequenceKSemigroupInstance<A> : Semigroup<SequenceK<A>> {
-  override fun SequenceK<A>.combine(b: SequenceK<A>): SequenceK<A> = (this + b).k()
+  override fun SequenceK<A>.combine(b: SequenceK<A>): SequenceK<A> = (this.sequence + b.sequence).k()
 }
 
 @instance(SequenceK::class)
 interface SequenceKMonoidInstance<A> : Monoid<SequenceK<A>> {
-  override fun SequenceK<A>.combine(b: SequenceK<A>): SequenceK<A> = (this + b).k()
+  override fun SequenceK<A>.combine(b: SequenceK<A>): SequenceK<A> = (this.sequence + b.sequence).k()
 
   override fun empty(): SequenceK<A> = emptySequence<A>().k()
 }