Collections refactoring.

1 files changed, 25 insertions, 0 deletions

diff --git a/src/library/scala/collection/mutable/LazyBuilder.scala b/src/library/scala/collection/mutable/LazyBuilder.scala
new file mode 100644
index 0000000000..7ddcb4a1f1
--- /dev/null
+++ b/src/library/scala/collection/mutable/LazyBuilder.scala
@@ -0,0 +1,25 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003-2009, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+// $Id$
+
+package scala.collection
+package mutable
+
+/** A builder that constructs its result lazily. Iterators or iterables to
+ *  be added to this builder with `++=` are not evaluated until `result` is called.
+ */
+abstract class LazyBuilder[Elem, +To] extends Builder[Elem, To] {
+  /** The different segments of elements to be added to the builder, represented as iterators */
+  protected var parts = new ListBuffer[scala.collection.Traversable[Elem]]
+  def +=(x: Elem): this.type = { parts += List(x); this }
+  override def ++=(xs: Iterator[Elem]): this.type = { parts += xs.toStream; this }
+  override def ++=(xs: scala.collection.Traversable[Elem]): this.type = { parts += xs; this }
+  def result(): To
+  def clear() { parts.clear() }
+}