Merge pull request #1191 from mpilquist/topic/random

Added Stream.random and Stream.randomSeeded

core/jvm/src/test/scala/fs2/StreamSpec.scala

@@ -463,6 +463,18 @@ class StreamSpec extends Fs2Spec with Inside {
       }
     }
 
+    "random" in {
+      val x = runLog(Stream.random[IO].take(100))
+      val y = runLog(Stream.random[IO].take(100))
+      x should not be y
+    }
+
+    "randomSeeded" in {
+      val x = Stream.randomSeeded(1L).take(100).toList
+      val y = Stream.randomSeeded(1L).take(100).toList
+      x shouldBe y
+    }
+
     "regression #1089" in {
       (Stream.chunk(Chunk.bytes(Array.fill(2000)(1.toByte))) ++ Stream.eval(
         IO.async[Byte](_ => ())))

core/shared/src/main/scala/fs2/Stream.scala

@@ -2447,6 +2447,26 @@ object Stream {
   def raiseError[F[x] >: Pure[x], O](e: Throwable): Stream[F, O] =
     fromFreeC(Algebra.raiseError(e))
 
+  /**
+    * Creates a random stream of integers using a random seed.
+    */
+  def random[F[_]](implicit F: Sync[F]): Stream[F, Int] =
+    Stream.eval(F.delay(new scala.util.Random())).flatMap { r =>
+      def loop: Stream[F, Int] = Stream.emit(r.nextInt) ++ loop
+      loop
+    }
+
+  /**
+    * Creates a random stream of integers using the supplied seed.
+    * Returns a pure stream, as the psuedo random number generator is
+    * deterministic based on the supplied seed.
+    */
+  def randomSeeded[F[x] >: Pure[x]](seed: Long): Stream[F, Int] = Stream.suspend {
+    val r = new scala.util.Random(seed)
+    def loop: Stream[F, Int] = Stream.emit(r.nextInt) ++ loop
+    loop
+  }
+
   /**
     * Lazily produce the range `[start, stopExclusive)`. If you want to produce
     * the sequence in one chunk, instead of lazily, use