From 436a7d8636498d855a6792c2d1597d13e1c0ee4c Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Sun, 13 Jun 2010 16:16:47 +0000
Subject: Changed groupBy to return immutable.Map.

---
 src/library/scala/collection/TraversableLike.scala        | 15 ++++++++-------
 src/library/scala/collection/TraversableProxyLike.scala   |  2 +-
 src/library/scala/collection/TraversableViewLike.scala    |  2 +-
 .../scala/collection/parallel/ParallelSeqViewLike.scala   |  2 +-
 4 files changed, 11 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/library/scala/collection/TraversableLike.scala b/src/library/scala/collection/TraversableLike.scala
index 04d9002eae..2169dcdd02 100644
--- a/src/library/scala/collection/TraversableLike.scala
+++ b/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.
diff --git a/src/library/scala/collection/TraversableProxyLike.scala b/src/library/scala/collection/TraversableProxyLike.scala
index 05c4c44f12..f2d91ded0c 100644
--- a/src/library/scala/collection/TraversableProxyLike.scala
+++ b/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)
diff --git a/src/library/scala/collection/TraversableViewLike.scala b/src/library/scala/collection/TraversableViewLike.scala
index 7b443e54b8..9b5be82dd6 100644
--- a/src/library/scala/collection/TraversableViewLike.scala
+++ b/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"
diff --git a/src/parallel-collections/scala/collection/parallel/ParallelSeqViewLike.scala b/src/parallel-collections/scala/collection/parallel/ParallelSeqViewLike.scala
index 40f5231fbe..2e9ebb1df3 100644
--- a/src/parallel-collections/scala/collection/parallel/ParallelSeqViewLike.scala
+++ b/src/parallel-collections/scala/collection/parallel/ParallelSeqViewLike.scala
@@ -135,7 +135,7 @@ extends SeqView[T, Coll]
   override def span(p: T => Boolean): (This, This) = (takeWhile(p), dropWhile(p))
   override def scanLeft[S, That](z: S)(op: (S, T) => S)(implicit bf: CanBuildFrom[This, S, That]): That = newForced(thisSeq.scanLeft(z)(op)).asInstanceOf[That]
   override def scanRight[S, That](z: S)(op: (T, S) => S)(implicit bf: CanBuildFrom[This, S, That]): That = newForced(thisSeq.scanRight(z)(op)).asInstanceOf[That]
-  override def groupBy[K](f: T => K): collection.Map[K, This] = thisSeq.groupBy(f).mapValues(xs => newForced(xs).asInstanceOf[This])
+  override def groupBy[K](f: T => K): collection.immutable.Map[K, This] = thisSeq.groupBy(f).mapValues(xs => newForced(xs).asInstanceOf[This])
   override def +:[U >: T, That](elem: U)(implicit bf: CanBuildFrom[This, U, That]): That = newPrepended(elem).asInstanceOf[That]
   override def reverse: This = newReversed.asInstanceOf[This]
   override def patch[U >: T, That](from: Int, patch: Seq[U], replaced: Int)(implicit bf: CanBuildFrom[This, U, That]): That = newPatched(from, patch, replaced).asInstanceOf[That]
-- 
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