fixed problem with Stream.flatMap, changed text...

fixed problem with Stream.flatMap, changed text of error message for
assume failure in Predef.

2 files changed, 4 insertions, 11 deletions

diff --git a/src/library/scala/Predef.scala b/src/library/scala/Predef.scala
index d099fbe8b0..2ecc8fa119 100644
--- a/src/library/scala/Predef.scala
+++ b/src/library/scala/Predef.scala
@@ -103,7 +103,7 @@ object Predef {
 
   def assume(assumption: Boolean, message: Any) {
     if (!assumption)
-      throw new IllegalArgumentException("assumption failed: " + message)
+      throw new IllegalArgumentException(message.toString)
   }
 
   // tupling ------------------------------------------------------------
diff --git a/src/library/scala/Stream.scala b/src/library/scala/Stream.scala
index fb8f5e92bd..a771e1d217 100644
--- a/src/library/scala/Stream.scala
+++ b/src/library/scala/Stream.scala
@@ -431,16 +431,9 @@ trait Stream[+A] extends Seq.Projection[A] {
    *  @return  <code>f(a<sub>0</sub>) ::: ... ::: f(a<sub>n</sub>)</code> if
    *           this stream is <code>[a<sub>0</sub>, ..., a<sub>n</sub>]</code>.
    */
-  override def flatMap[B](f: A => Iterable[B]): Stream[B] = {
-    var acc: Stream[B] = Stream.empty
-    var these = this
-    while (!these.isEmpty) {
-      val those = f(these.head)
-      if (!those.isEmpty) acc = acc append those.toStream
-      these = these.tail
-    }
-    acc
-  }
+  override def flatMap[B](f: A => Iterable[B]): Stream[B] =
+    if (isEmpty) Stream.empty
+    else Stream.fromIterator(f(head).elements) append (tail flatMap f)
 
   override def toStream = this