typelevel#3141 [WIP] Implemented .reduceA

EpamLifeSciencesTeam · Nov 14, 2019 · ac9efdc · ac9efdc
1 parent 2ce81ea
commit ac9efdc
Showing 1 changed file with 9 additions and 0 deletions.
diff --git a/core/src/main/scala/cats/Reducible.scala b/core/src/main/scala/cats/Reducible.scala
@@ -66,6 +66,15 @@ import simulacrum.typeclass
   def reduceLeftM[G[_], A, B](fa: F[A])(f: A => G[B])(g: (B, A) => G[B])(implicit G: FlatMap[G]): G[B] =
     reduceLeftTo(fa)(f)((gb, a) => G.flatMap(gb)(g(_, a)))
 
+  /**
+    * Reduce a `F[G[A]]` value using `Applicative[G]` and `Semigroup[A]`, a universal
+    * semigroup for `G[_]`.
+    *
+    * This method is a generalization of `reduce`.
+    */
+  def reduceA[G[_], A](fga: F[G[A]])(implicit G: Applicative[G], A: Semigroup[A]): G[A] =
+    reduceLeft(fga)((ga1, ga2) => G.map2(ga1, ga2)(A.combine))
+
   /**
    * Monadic reducing by mapping the `A` values to `G[B]`. combining
    * the `B` values using the given `Semigroup[B]` instance.