SI-6642 Adds iteratorFrom, keysIteratorFrom, and valuesIteratorFrom

Adds the ability to efficiently create an iterator that starts at a
given key or element of a sorted set or map. Similar work is done for
key and value only iterators on maps.

The bulk of the work is in RedBlackTree. Most of the rest is pushing
the new api methods throughout the appropriate spots in the collection
API.

This commit leaves undone some similar work possible on mutable TreeSets

1 files changed, 1 insertions, 0 deletions

diff --git a/src/library/scala/collection/immutable/TreeSet.scala b/src/library/scala/collection/immutable/TreeSet.scala
index 8bceb936aa..67668b3bef 100644
--- a/src/library/scala/collection/immutable/TreeSet.scala
+++ b/src/library/scala/collection/immutable/TreeSet.scala
@@ -144,6 +144,7 @@ class TreeSet[A] private (tree: RB.Tree[A, Unit])(implicit val ordering: Orderin
    *  @return the new iterator
    */
   def iterator: Iterator[A] = RB.keysIterator(tree)
+  override def keysIteratorFrom(start: A): Iterator[A] = RB.keysIterator(tree, Some(start))
 
   override def foreach[U](f: A =>  U) = RB.foreachKey(tree, f)