Add IndexedState alias (typelevel#2686)

valydia · Jan 10, 2019 · ebacd83 · ebacd83
1 parent d88b3c4
commit ebacd83
Show file tree

Hide file tree

Showing 2 changed files with 9 additions and 0 deletions.
diff --git a/core/src/main/scala/cats/data/IndexedStateT.scala b/core/src/main/scala/cats/data/IndexedStateT.scala
@@ -319,6 +319,12 @@ sealed abstract private[data] class IndexedStateTInstances4 {
     new IndexedStateTStrong[F, V] { implicit def F = F0 }
 }
 
+abstract private[data] class IndexedStateFunctions {
+
+  def apply[S1, S2, A](f: S1 => (S2, A)): IndexedState[S1, S2, A] =
+    IndexedStateT.applyF(Now((s: S1) => Now(f(s))))
+}
+
 // To workaround SI-7139 `object State` needs to be defined inside the package object
 // together with the type alias.
 abstract private[data] class StateFunctions {

diff --git a/core/src/main/scala/cats/data/package.scala b/core/src/main/scala/cats/data/package.scala
@@ -43,6 +43,9 @@ package object data {
     def tell[L](l: L): Writer[L, Unit] = WriterT.tell(l)
   }
 
+  type IndexedState[S1, S2, A] = IndexedStateT[Eval, S1, S2, A]
+  object IndexedState extends IndexedStateFunctions
+
   /**
    * `StateT[F, S, A]` is similar to `Kleisli[F, S, A]` in that it takes an `S`
    * argument and produces an `A` value wrapped in `F`. However, it also produces