Merge pull request #1739 from jedesah/Array_opt

SI-5017 Poor performance of :+ operator on Arrays

3 files changed, 29 insertions, 0 deletions

diff --git a/src/library/scala/collection/mutable/ArrayOps.scala b/src/library/scala/collection/mutable/ArrayOps.scala
index bb938a7aeb..6b778b26f5 100644
--- a/src/library/scala/collection/mutable/ArrayOps.scala
+++ b/src/library/scala/collection/mutable/ArrayOps.scala
@@ -52,6 +52,20 @@ trait ArrayOps[T] extends Any with ArrayLike[T, Array[T]] with CustomParalleliza
       super.toArray[U]
   }
 
+  def :+[B >: T: scala.reflect.ClassTag](elem: B): Array[B] = {
+    val result = Array.ofDim[B](repr.length + 1)
+    Array.copy(repr, 0, result, 0, repr.length)
+    result(repr.length) = elem
+    result
+  }
+
+  def +:[B >: T: scala.reflect.ClassTag](elem: B): Array[B] = {
+    val result = Array.ofDim[B](repr.length + 1)
+    result(0) = elem
+    Array.copy(repr, 0, result, 1, repr.length)
+    result
+  }
+
   override def par = ParArray.handoff(repr)
 
   /** Flattens a two-dimensional array by concatenating all its rows
diff --git a/test/files/run/array-addition.check b/test/files/run/array-addition.check
new file mode 100644
index 0000000000..7bfbd9c711
--- /dev/null
+++ b/test/files/run/array-addition.check
@@ -0,0 +1,4 @@
+Array(1, 2, 3, 4)
+Array(1, 2, 3, 4)
+Array(1)
+Array(1)
diff --git a/test/files/run/array-addition.scala b/test/files/run/array-addition.scala
new file mode 100644
index 0000000000..8def48e85c
--- /dev/null
+++ b/test/files/run/array-addition.scala
@@ -0,0 +1,11 @@
+object Test {
+  def prettyPrintArray(x: Array[_]) = println("Array(" + x.mkString(", ") + ")")
+
+  def main(args: Array[String]): Unit = {
+    prettyPrintArray(Array(1,2,3) :+ 4)
+    prettyPrintArray(1 +: Array(2,3,4))
+    prettyPrintArray(Array() :+ 1)
+    prettyPrintArray(1 +: Array())
+  }
+}
+