SI-5151 - Add firstKey and lastKey to LongMap.

3 files changed, 24 insertions, 0 deletions

diff --git a/src/library/scala/collection/immutable/LongMap.scala b/src/library/scala/collection/immutable/LongMap.scala
index fab1b7f00b..60300c2a9e 100644
--- a/src/library/scala/collection/immutable/LongMap.scala
+++ b/src/library/scala/collection/immutable/LongMap.scala
@@ -12,6 +12,7 @@ package immutable
 
 import scala.collection.generic.{ CanBuildFrom, BitOperations }
 import scala.collection.mutable.{ Builder, MapBuilder }
+import scala.annotation.tailrec
 
 /** Utility class for long maps.
  *  @author David MacIver
@@ -416,5 +417,20 @@ extends AbstractMap[Long, T]
 
   def ++[S >: T](that: LongMap[S]) =
     this.unionWith[S](that, (key, x, y) => y)
+
+  @tailrec
+  final def firstKey: Long = this match {
+    case LongMap.Bin(_, _, l, r) => l.firstKey
+    case LongMap.Tip(k, v) => k
+    case LongMap.Nil => sys.error("Empty set")
+  }
+
+  @tailrec
+  final def lastKey: Long = this match {
+    case LongMap.Bin(_, _, l, r) => r.lastKey
+    case LongMap.Tip(k , v) => k
+    case LongMap.Nil => sys.error("Empty set")
+  }
+
 }
 
diff --git a/test/files/run/longmap.check b/test/files/run/longmap.check
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/files/run/longmap.check
diff --git a/test/files/run/longmap.scala b/test/files/run/longmap.scala
new file mode 100644
index 0000000000..1f18eebd31
--- /dev/null
+++ b/test/files/run/longmap.scala
@@ -0,0 +1,8 @@
+object Test extends App{
+  import scala.collection.immutable.LongMap;
+
+  val it = LongMap(8L -> 2, 11L -> 3, 1L -> 2, 7L -> 13);
+
+  assert(it.firstKey == 1L);
+  assert(it.lastKey == 11L);
+}