Optimize foldMap implementations with combineAll

Author: carymrobbins

alleycats-core/src/main/scala/alleycats/std/iterable.scala

@@ -1,7 +1,7 @@
 package alleycats
 package std
 
-import cats.{Eval, Foldable}
+import cats.{Eval, Foldable, Monoid}
 import export._
 
 @reexports(IterableInstances)
@@ -16,6 +16,9 @@ object IterableInstances {
 
       override def foldRight[A, B](fa: Iterable[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
         Foldable.iterateRight(fa, lb)(f)
+
+      override def foldMap[A, B](fa: Iterable[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.iterator.map(f))
     }
 
 }

alleycats-core/src/main/scala/alleycats/std/set.scala

@@ -68,6 +68,9 @@ object SetInstances {
       def foldRight[A, B](fa: Set[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
         Foldable.iterateRight(fa, lb)(f)
 
+      override def foldMap[A, B](fa: Set[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.map(f))
+
       def traverse[G[_]: Applicative, A, B](sa: Set[A])(f: A => G[B]): G[Set[B]] = {
         val G = Applicative[G]
         sa.foldLeft(G.pure(Set.empty[B])) { (buf, a) =>

core/src/main/scala/cats/data/NonEmptyList.scala

@@ -472,6 +472,9 @@ private[data] sealed abstract class NonEmptyListInstances extends NonEmptyListIn
       override def foldRight[A, B](fa: NonEmptyList[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
         fa.foldRight(lb)(f)
 
+      override def foldMap[A, B](fa: NonEmptyList[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.toList.iterator.map(f))
+
       def tailRecM[A, B](a: A)(f: A => NonEmptyList[Either[A, B]]): NonEmptyList[B] = {
         val buf = new ListBuffer[B]
         @tailrec def go(v: NonEmptyList[Either[A, B]]): Unit = v.head match {

core/src/main/scala/cats/data/NonEmptyVector.scala

@@ -290,6 +290,9 @@ private[data] sealed abstract class NonEmptyVectorInstances {
       override def foldRight[A, B](fa: NonEmptyVector[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
         fa.foldRight(lb)(f)
 
+      override def foldMap[A, B](fa: NonEmptyVector[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.toVector.iterator.map(f))
+
       override def nonEmptyPartition[A, B, C](fa: NonEmptyVector[A])(f: (A) => Either[B, C]): Ior[NonEmptyList[B], NonEmptyList[C]] = {
         import cats.syntax.either._
         import cats.syntax.reducible._

core/src/main/scala/cats/instances/list.scala

@@ -65,6 +65,9 @@ trait ListInstances extends cats.kernel.instances.ListInstances {
         Eval.defer(loop(fa))
       }
 
+      override def foldMap[A, B](fa: List[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.iterator.map(f))
+
       def traverse[G[_], A, B](fa: List[A])(f: A => G[B])(implicit G: Applicative[G]): G[List[B]] =
         foldRight[A, G[List[B]]](fa, Always(G.pure(List.empty))){ (a, lglb) =>
           G.map2Eval(f(a), lglb)(_ :: _)

core/src/main/scala/cats/instances/queue.scala

@@ -2,7 +2,6 @@ package cats
 package instances
 
 import cats.syntax.show._
-
 import scala.annotation.tailrec
 import scala.collection.immutable.Queue
 import scala.util.Try
@@ -75,6 +74,9 @@ trait QueueInstances extends cats.kernel.instances.QueueInstances {
         Eval.defer(loop(fa))
       }
 
+      override def foldMap[A, B](fa: Queue[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.iterator.map(f))
+
       def traverse[G[_], A, B](fa: Queue[A])(f: A => G[B])(implicit G: Applicative[G]): G[Queue[B]] =
         foldRight[A, G[Queue[B]]](fa, Always(G.pure(Queue.empty))){ (a, lglb) =>
           G.map2Eval(f(a), lglb)(_ +: _)

core/src/main/scala/cats/instances/sortedSet.scala

@@ -19,6 +19,9 @@ trait SortedSetInstances extends SortedSetInstances1 {
       def foldRight[A, B](fa: SortedSet[A], lb: Eval[B])(f: (A, Eval[B]) => Eval[B]): Eval[B] =
         Foldable.iterateRight(fa, lb)(f)
 
+      override def foldMap[A, B](fa: SortedSet[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.iterator.map(f))
+
       override def get[A](fa: SortedSet[A])(idx: Long): Option[A] = {
         @tailrec
         def go(idx: Int, it: Iterator[A]): Option[A] = {

core/src/main/scala/cats/instances/stream.scala

@@ -42,6 +42,9 @@ trait StreamInstances extends cats.kernel.instances.StreamInstances {
           if (s.isEmpty) lb else f(s.head, Eval.defer(foldRight(s.tail, lb)(f)))
         }
 
+      override def foldMap[A, B](fa: Stream[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.iterator.map(f))
+
       def traverse[G[_], A, B](fa: Stream[A])(f: A => G[B])(implicit G: Applicative[G]): G[Stream[B]] = {
         // We use foldRight to avoid possible stack overflows. Since
         // we don't want to return a Eval[_] instance, we call .value

core/src/main/scala/cats/instances/vector.scala

@@ -41,6 +41,9 @@ trait VectorInstances extends cats.kernel.instances.VectorInstances {
         Eval.defer(loop(0))
       }
 
+      override def foldMap[A, B](fa: Vector[A])(f: A => B)(implicit B: Monoid[B]): B =
+        B.combineAll(fa.iterator.map(f))
+
       def tailRecM[A, B](a: A)(fn: A => Vector[Either[A, B]]): Vector[B] = {
         val buf = Vector.newBuilder[B]
         var state = List(fn(a).iterator)