first part of r22260

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@22325 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/library/scala/collection/TraversableLike.scala

@@ -330,17 +330,18 @@ trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr]
    *               for which `f(x)` equals `k`.
    * 
    */
-  def groupBy[K](f: A => K): Map[K, Repr] = {
-    var m = Map[K, Builder[A, Repr]]()
+  def groupBy[K](f: A => K): immutable.Map[K, Repr] = {
+    val m = mutable.Map.empty[K, Builder[A, Repr]]
     for (elem <- this) {
       val key = f(elem)
-      val bldr = m get key match {
-        case None => val b = newBuilder; m = m updated (key, b); b
-        case Some(b) => b
-      }
+      val bldr = m.getOrElseUpdate(key, newBuilder)
       bldr += elem
     }
-    m map { case (k, b) => (k, b.result) }
+    val b = immutable.Map.newBuilder[K, Repr]
+    for ((k, v) <- m)
+      b += ((k, v.result))
+    
+    b.result
   }
 
   /** Tests whether a predicate holds for all elements of this $coll.

src/library/scala/collection/TraversableProxyLike.scala

@@ -37,7 +37,7 @@ trait TraversableProxyLike[+A, +Repr <: TraversableLike[A, Repr] with Traversabl
   override def filterNot(p: A => Boolean): Repr = self.filterNot(p)
   override def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = self.collect(pf)(bf)
   override def partition(p: A => Boolean): (Repr, Repr) = self.partition(p)
-  override def groupBy[K](f: A => K): Map[K, Repr] = self.groupBy(f)
+  override def groupBy[K](f: A => K): immutable.Map[K, Repr] = self.groupBy(f)
   override def forall(p: A => Boolean): Boolean = self.forall(p)
   override def exists(p: A => Boolean): Boolean = self.exists(p)
   override def count(p: A => Boolean): Int = self.count(p)

src/library/scala/collection/TraversableViewLike.scala

@@ -216,7 +216,7 @@ self =>
   override def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[This, B, That]): That =
     newForced(thisSeq.scanRight(z)(op)).asInstanceOf[That]
 
-  override def groupBy[K](f: A => K): Map[K, This] =
+  override def groupBy[K](f: A => K): immutable.Map[K, This] =
     thisSeq.groupBy(f).mapValues(xs => newForced(xs).asInstanceOf[This])
   
   override def stringPrefix = "TraversableView"

test/files/run/colltest1.scala

@@ -29,8 +29,8 @@ object Test extends Application {
     val (o, e) = ten.partition(_ % 2 == 0)
     assert(o.size == e.size)
     val gs = ten groupBy (x => x / 4)
-    val vs1 = (for (k <- gs.keysIterator; v <- gs(k).toIterable.iterator) yield v).toList
-    val vs2 = gs.values.toList.flatten
+    val vs1 = (for (k <- gs.keysIterator; v <- gs(k).toIterable.iterator) yield v).toList.sorted
+    val vs2 = gs.values.toList.flatten.sorted
 //    val vs2 = gs.values.toList flatMap (xs => xs)
     assert(ten.head == 1)
     assert(ten.tail.head == 2)