Small refactoring in some collection classes

18 files changed, 36 insertions, 52 deletions

diff --git a/src/library/scala/Iterator.scala b/src/library/scala/Iterator.scala
index 1c813543d4..99526ddc41 100644
--- a/src/library/scala/Iterator.scala
+++ b/src/library/scala/Iterator.scala
@@ -430,11 +430,11 @@ mixin class Iterator[+A] {
    *  @return  a list which enumerates all elements of this iterator.
    */
   def toList: List[A] = {
-    var res: List[A] = Nil;
+    val res = new collection.mutable.ListBuffer[A];
     while (hasNext) {
-      res = next :: res;
+      res += next;
     }
-    res.reverse
+    res.toList
   }
 
 }
diff --git a/src/library/scala/collection/Set.scala b/src/library/scala/collection/Set.scala
index 66f571213e..99d7968567 100644
--- a/src/library/scala/collection/Set.scala
+++ b/src/library/scala/collection/Set.scala
@@ -87,5 +87,5 @@ mixin class Set[A] extends AnyRef with Function1[A, Boolean] with Iterable[A] {
      *  @return a string showing all elements of this set.
      */
     override def toString(): String =
-      if (size == 0) "{}" else toList.mkString("{", ", ", "}");
+      if (isEmpty) "{}" else toList.mkString("{", ", ", "}");
 }
diff --git a/src/library/scala/collection/immutable/ListMap.scala b/src/library/scala/collection/immutable/ListMap.scala
index 21ffd72da8..6efe90b4b2 100644
--- a/src/library/scala/collection/immutable/ListMap.scala
+++ b/src/library/scala/collection/immutable/ListMap.scala
@@ -30,7 +30,7 @@ class ListMap[A, B] extends AnyRef with Map[A, B] {
     /** This method returns a new ListMap instance mapping keys of the
      *  same type to values of type <code>C</code>.
      */
-    def empty[C] = new ListMap[A, C];
+    def empty[C] = ListMap.Empty[A, C];
 
     /** Returns the number of mappings in this map.
      *
diff --git a/src/library/scala/collection/immutable/ListSet.scala b/src/library/scala/collection/immutable/ListSet.scala
index e510f4bfc5..2f63aa610e 100644
--- a/src/library/scala/collection/immutable/ListSet.scala
+++ b/src/library/scala/collection/immutable/ListSet.scala
@@ -36,6 +36,8 @@ class ListSet[A] extends AnyRef with Set[A] {
      */
     def size: Int = 0;
 
+    def empty = new ListSet[A];
+
     /** Checks if this set contains element <code>elem</code>.
      *
      *  @param  elem    the element to check for membership.
diff --git a/src/library/scala/collection/immutable/Queue.scala b/src/library/scala/collection/immutable/Queue.scala
index 02a8533383..88b725a656 100644
--- a/src/library/scala/collection/immutable/Queue.scala
+++ b/src/library/scala/collection/immutable/Queue.scala
@@ -25,15 +25,7 @@ object Queue {
 [serializable]
 class Queue[+A](elem: A*) extends Seq[A] {
   protected val in: List[A] = Nil;
-  protected val out: List[A] = itToList(elem.elements);
-
-  protected def itToList[B >: A](elems: Iterator[B]): List[B] =
-    if (elems.hasNext) {
-      val hd = elems.next;
-      hd :: itToList(elems)
-    }
-    else
-      Nil;
+  protected val out: List[A] = elem.elements.toList;
 
   protected def mkQueue[A](i: List[A], o: List[A]): Queue[A] =
     new Queue[A]() {
diff --git a/src/library/scala/collection/immutable/Set.scala b/src/library/scala/collection/immutable/Set.scala
index 8f479d1b50..78e78257d6 100644
--- a/src/library/scala/collection/immutable/Set.scala
+++ b/src/library/scala/collection/immutable/Set.scala
@@ -26,6 +26,10 @@ mixin class Set[A] extends AnyRef with collection.Set[A] {
      */
     def +(elem: A): Set[A];
 
+    /** @return an empty set of the same type as this set
+     */
+    def empty: Set[A];
+
     /** <code>incl</code> can be used to add many elements to the set
      *  at the same time.
      */
diff --git a/src/library/scala/collection/immutable/Tree.scala b/src/library/scala/collection/immutable/Tree.scala
index d069ca82ad..fdeea70f1f 100644
--- a/src/library/scala/collection/immutable/Tree.scala
+++ b/src/library/scala/collection/immutable/Tree.scala
@@ -90,11 +90,9 @@ abstract class Tree[A <% Ordered[A], B]() extends AnyRef {
   */
   protected type aNode = GBTree[A,B];
 
-  private val empty: aNode = GBLeaf[A,B]();
-
   /** The nodes in the tree.
   */
-  protected def tree: aNode = empty;
+  protected def tree: aNode = GBLeaf[A,B]();
 
   /** This abstract method should be defined by a concrete implementation
   **   C[T] as something like:
diff --git a/src/library/scala/collection/immutable/TreeSet.scala b/src/library/scala/collection/immutable/TreeSet.scala
index d681f01fb7..24a11c8b81 100644
--- a/src/library/scala/collection/immutable/TreeSet.scala
+++ b/src/library/scala/collection/immutable/TreeSet.scala
@@ -41,6 +41,8 @@ class TreeSet[A <% Ordered[A]]() extends Tree[A, A] with Set[A] {
      */
     def +(elem: A): TreeSet[A] = updateOrAdd(elem, elem);
 
+    override def empty: Set[A] = New(0, GBLeaf[A,A]());
+
     /** <code>-</code> can be used to remove a single element from
      *  a set.
      */
diff --git a/src/library/scala/collection/mutable/ArrayBuffer.scala b/src/library/scala/collection/mutable/ArrayBuffer.scala
index 8f56d42447..1986964280 100644
--- a/src/library/scala/collection/mutable/ArrayBuffer.scala
+++ b/src/library/scala/collection/mutable/ArrayBuffer.scala
@@ -35,11 +35,10 @@ class ArrayBuffer[A] extends Buffer[A] with ResizableArray[A] {
      *
      *  @param elem  the element to append.
      */
-    def +(elem: A): Buffer[A] = {
+    def +=(elem: A): Unit = {
         ensureSize(size+1);
         array(size) = elem;
         size = size + 1;
-        this
     }
 
     /** Appends a number of elements provided by an iterable object
diff --git a/src/library/scala/collection/mutable/Buffer.scala b/src/library/scala/collection/mutable/Buffer.scala
index f04c2dbe1e..da89424865 100644
--- a/src/library/scala/collection/mutable/Buffer.scala
+++ b/src/library/scala/collection/mutable/Buffer.scala
@@ -33,13 +33,16 @@ mixin class Buffer[A] extends AnyRef
      *
      *  @param elem  the element to append.
      */
-    def +(elem: A): Buffer[A];
+    def +(elem: A): Buffer[A] = {
+      this += elem;
+      this
+    }
 
     /** Append a single element to this buffer.
      *
      *  @param elem  the element to append.
      */
-    def +=(elem: A): Unit = this + elem;
+    def +=(elem: A): Unit;
 
     /** Appends a number of elements provided by an iterable object
      *  via its <code>elements</code> method. The identity of the
diff --git a/src/library/scala/collection/mutable/BufferProxy.scala b/src/library/scala/collection/mutable/BufferProxy.scala
index 463f537841..f21ad6c339 100644
--- a/src/library/scala/collection/mutable/BufferProxy.scala
+++ b/src/library/scala/collection/mutable/BufferProxy.scala
@@ -34,13 +34,13 @@ mixin class BufferProxy[A] extends Buffer[A] with Proxy {
      *
      *  @param elem  the element to append.
      */
-    def +(elem: A): Buffer[A] = self.+(elem);
+    override def +(elem: A): Buffer[A] = self.+(elem);
 
     /** Append a single element to this buffer.
      *
      *  @param elem  the element to append.
      */
-    override def +=(elem: A): Unit = self.+=(elem);
+    def +=(elem: A): Unit = self.+=(elem);
 
     /** Appends a number of elements provided by an iterable object
      *  via its <code>elements</code> method. The identity of the
diff --git a/src/library/scala/collection/mutable/DoubleLinkedList.scala b/src/library/scala/collection/mutable/DoubleLinkedList.scala
index 4bc79652ca..610dc3f6e5 100644
--- a/src/library/scala/collection/mutable/DoubleLinkedList.scala
+++ b/src/library/scala/collection/mutable/DoubleLinkedList.scala
@@ -25,7 +25,7 @@ abstract class DoubleLinkedList[A, This >: AllRef <: DoubleLinkedList[A, This]]
          extends SingleLinkedList[A, This]
 {
 
-    var prev: This = _;
+    var prev: This;
 
     override def append(that: This): Unit =
         if (that == null)
diff --git a/src/library/scala/collection/mutable/ImmutableMapAdaptor.scala b/src/library/scala/collection/mutable/ImmutableMapAdaptor.scala
index cd90a3e2d0..29e1e36161 100644
--- a/src/library/scala/collection/mutable/ImmutableMapAdaptor.scala
+++ b/src/library/scala/collection/mutable/ImmutableMapAdaptor.scala
@@ -22,9 +22,9 @@ package scala.collection.mutable;
  *  @version 1.0, 21/07/2003
  */
 [serializable]
-class ImmutableMapAdaptor[A, B](m: immutable.Map[A, B]) extends Map[A, B] {
-
-    protected var imap = m;
+class ImmutableMapAdaptor[A, B](protected var imap: immutable.Map[A, B])
+extends Map[A, B]
+{
 
     def size: Int = imap.size;
 
@@ -54,13 +54,11 @@ class ImmutableMapAdaptor[A, B](m: immutable.Map[A, B]) extends Map[A, B] {
 
     def -=(key: A): Unit = { imap = imap - key; }
 
-    override def clear: Unit = { imap = empty; }
+    override def clear: Unit = { imap = imap.empty; }
 
     override def map(f: (A, B) => B): Unit = { imap = imap.map(f); }
 
     override def filter(p: (A, B) => Boolean): Unit = { imap = imap.filter(p); }
 
     override def mappingToString(p: Pair[A, B]) = imap.mappingToString(p);
-
-    protected def empty: scala.collection.immutable.Map[A, B] = m;
 }
diff --git a/src/library/scala/collection/mutable/ImmutableSetAdaptor.scala b/src/library/scala/collection/mutable/ImmutableSetAdaptor.scala
index 80db910c1c..b6f1cfd710 100644
--- a/src/library/scala/collection/mutable/ImmutableSetAdaptor.scala
+++ b/src/library/scala/collection/mutable/ImmutableSetAdaptor.scala
@@ -22,9 +22,7 @@ package scala.collection.mutable;
  *  @version 1.0, 21/07/2003
  */
 [serializable]
-class ImmutableSetAdaptor[A](s: immutable.Set[A]) extends Set[A] {
-
-    protected var set = s;
+class ImmutableSetAdaptor[A](protected var set: immutable.Set[A]) extends Set[A] {
 
     def size: Int = set.size;
 
@@ -46,7 +44,6 @@ class ImmutableSetAdaptor[A](s: immutable.Set[A]) extends Set[A] {
 
     def -=(elem: A): Unit = { set = set - elem; }
 
-    def clear: Unit = { set = empty; }
+    def clear: Unit = { set = set.empty; }
 
-    protected def empty: scala.collection.immutable.Set[A] = s;
 }
diff --git a/src/library/scala/collection/mutable/LinkedList.scala b/src/library/scala/collection/mutable/LinkedList.scala
index b6b80fa3e0..e5045950d6 100644
--- a/src/library/scala/collection/mutable/LinkedList.scala
+++ b/src/library/scala/collection/mutable/LinkedList.scala
@@ -19,11 +19,9 @@ package scala.collection.mutable;
  *  @version 1.0, 08/07/2003
  */
 [serializable]
-class LinkedList[A](head: A, tail: LinkedList[A])
+class LinkedList[A](var elem: A, var next: LinkedList[A])
   extends SingleLinkedList[A, LinkedList[A]]
 {
-  elem = head;
-  next = tail;
 
   override def equals(obj: Any): Boolean = (
     obj.isInstanceOf[LinkedList[A]]
diff --git a/src/library/scala/collection/mutable/ListBuffer.scala b/src/library/scala/collection/mutable/ListBuffer.scala
index 815a34b014..eabeabeaa1 100644
--- a/src/library/scala/collection/mutable/ListBuffer.scala
+++ b/src/library/scala/collection/mutable/ListBuffer.scala
@@ -21,13 +21,6 @@ final class ListBuffer[A] extends Buffer[A] {
   private var last: ::[A] = _;
   private var exported: boolean = false;
 
-  /** Append a single element to this buffer and return
-   *  the identity of the buffer. Same as ``this += x; this''
-   *
-   *  @param x  the element to append.
-   */
-  def + (x: A): Buffer[A] = { this += x; this }
-
   /** Prepend a single element to this buffer.
    *
    *  @param x  the element to prepend.
diff --git a/src/library/scala/collection/mutable/SingleLinkedList.scala b/src/library/scala/collection/mutable/SingleLinkedList.scala
index 67151cb29e..32b4690d4d 100644
--- a/src/library/scala/collection/mutable/SingleLinkedList.scala
+++ b/src/library/scala/collection/mutable/SingleLinkedList.scala
@@ -20,15 +20,14 @@ package scala.collection.mutable;
  *  @author  Matthias Zenger
  *  @version 1.0, 08/07/2003
  */
-[serializable]
 abstract class SingleLinkedList[A, This >: AllRef <: SingleLinkedList[A, This]]
          requires This
          extends AnyRef with Seq[A]
 {
 
-    var elem: A = _;
+    var elem: A;
 
-    var next: This = null;
+    var next: This;
 
     def length: Int = 1 + (if (next == null) 0 else next.length);
 
@@ -62,7 +61,6 @@ abstract class SingleLinkedList[A, This >: AllRef <: SingleLinkedList[A, This]]
         }
     }
 
-    override def toList: List[A] =
-        if (next == null) (elem :: Nil) else (elem :: next.toList);
+    override def toList: List[A] = elements toList;
 
 }
diff --git a/src/library/scala/collection/mutable/SynchronizedBuffer.scala b/src/library/scala/collection/mutable/SynchronizedBuffer.scala
index 5c41720732..ed692d4f1b 100644
--- a/src/library/scala/collection/mutable/SynchronizedBuffer.scala
+++ b/src/library/scala/collection/mutable/SynchronizedBuffer.scala
@@ -37,7 +37,7 @@ mixin class SynchronizedBuffer[A] extends Buffer[A] {
      *
      *  @param elem  the element to append.
      */
-    abstract override def +(elem: A): Buffer[A] = synchronized {
+    override def +(elem: A): Buffer[A] = synchronized {
         super.+(elem);
     }
 
@@ -45,7 +45,7 @@ mixin class SynchronizedBuffer[A] extends Buffer[A] {
      *
      *  @param elem  the element to append.
      */
-    override def +=(elem: A): Unit = synchronized {
+    abstract override def +=(elem: A): Unit = synchronized {
         super.+=(elem);
     }