Replace toList with to[Col]

Author: danslapman

src/main/scala/asyncstreams/AsyncStream.scala

@@ -1,6 +1,9 @@
 package asyncstreams
 
+import scala.collection.generic.CanBuildFrom
+import scala.annotation.unchecked.{ uncheckedVariance => uV }
 import scala.concurrent.{ExecutionContext, Future}
+import scala.language.higherKinds
 import scalaz.std.scalaFuture._
 import scalaz.syntax.std.option._
 import scalaz.syntax.monad._
@@ -16,8 +19,8 @@ case class AsyncStream[A](data: Future[Chunk[A, AsyncStream[A]]]) {
     impl(data, Future(start))
   }
 
-  def toList(implicit executor: ExecutionContext): Future[List[A]] =
-    foldLeft[List[A]](Nil)((list, el) => el :: list) map (_.reverse)
+  def to[Col[_]](implicit executor: ExecutionContext, cbf: CanBuildFrom[Nothing, A, Col[A @uV]]): Future[Col[A]] =
+    foldLeft(cbf())((col, el) => col += el).map(_.result())
 
   def takeWhile(p: A => Boolean)(implicit executor: ExecutionContext): AsyncStream[A] =
     new AsyncStream[A](data map {

src/test/scala/asyncstreams/AsyncStreamTests.scala

@@ -28,7 +28,7 @@ class AsyncStreamTests extends BaseSuite {
     val s1 = makeStream(0 :: 1 :: Nil)
     val s2 = makeStream(2 :: 3 :: Nil)
     val f = concat(s1, s2)
-    wait(f.toList) shouldBe List(0, 1, 2, 3)
+    wait(f.to[List]) shouldBe List(0, 1, 2, 3)
   }
 
   test("working as monad") {
@@ -40,21 +40,21 @@ class AsyncStreamTests extends BaseSuite {
       v2 <- s2
     } yield v1 * v2
 
-    wait(res.toList) shouldBe List(0, 0, 2, 3)
+    wait(res.to[List]) shouldBe List(0, 0, 2, 3)
   }
 
   test("takeWhile") {
     val r = makeInfStream.takeWhile(_ < 4)
-    wait(r.toList) shouldBe List(0, 1, 2, 3)
+    wait(r.to[List]) shouldBe List(0, 1, 2, 3)
   }
 
   test("take") {
     val r = makeInfStream.take(3)
-    wait(r.toList) shouldBe List(0, 1, 2)
+    wait(r.to[List]) shouldBe List(0, 1, 2)
   }
 
   test("folding large stream should not crash") {
     val r = makeInfStream.takeWhile(_ < 1000000)
-    wait(r.toList) shouldBe (0 to 999999)
+    wait(r.to[List]) shouldBe (0 to 999999)
   }
 }