Merge pull request #3630 from bplommer/functionk-widen-narrow

typelevel · Oct 10, 2020 · fb0678d · fb0678d
2 parents c28b4de + 57c5571
commit fb0678d
Showing 1 changed file with 10 additions and 0 deletions.
diff --git a/core/src/main/scala/cats/arrow/FunctionK.scala b/core/src/main/scala/cats/arrow/FunctionK.scala
@@ -59,6 +59,16 @@ trait FunctionK[F[_], G[_]] extends Serializable { self =>
    */
   def and[H[_]](h: FunctionK[F, H]): FunctionK[F, Tuple2K[G, H, *]] =
     new FunctionK[F, Tuple2K[G, H, *]] { def apply[A](fa: F[A]): Tuple2K[G, H, A] = Tuple2K(self(fa), h(fa)) }
+
+  /**
+   * Widens the output type of this `FunctionK` from `G` to `G0`
+   */
+  def widen[G0[x] >: G[x]]: FunctionK[F, G0] = this.asInstanceOf[FunctionK[F, G0]]
+
+  /**
+   * Narrows the input type of this `FunctionK` from `F` to `F0`
+   */
+  def narrow[F0[x] <: F[x]]: FunctionK[F0, G] = this.asInstanceOf[FunctionK[F0, G]]
 }
 
 object FunctionK extends FunctionKMacroMethods {