Created Mutable and Immutable SetFactories to d...

Created Mutable and Immutable SetFactories to deal with the spectacular
performance regression which accompanies the use of AddingBuilder on
mutable Sets. Because '+' now creates a new collection even on mutable
sets, AddingBuilder on a 100K element collection will create garbage
sets of size 1,2,3...,99,999 before finishing. Thankfully there is
already GrowingBuilder.

See test/files/run/adding-growing-set.scala for a demonstration.

This patch is not complete: in particular, SortedSet and SetBuilder need
attention. Unfortunately there is a combinatorial jump in the number of
Addable/Growable divisions which arises once one tries to accomodate
both Sorted signatures (taking an Ordering) and unsorted signatures, so
will come back to it after receiving counsel.

Review by odersky.

1 files changed, 11 insertions, 0 deletions

diff --git a/test/files/run/adding-growing-set.scala b/test/files/run/adding-growing-set.scala
new file mode 100644
index 0000000000..5903813ed1
--- /dev/null
+++ b/test/files/run/adding-growing-set.scala
@@ -0,0 +1,11 @@
+/** This will run a a loooong time if Set's builder copies a
+ *  complete new Set for every element.
+ */
+object Test {
+  def main(args: Array[String]): Unit = {
+    val a = new Array[Long](1000000)
+    (1 to 10000) foreach (i => a(i) = i)
+    val s = collection.mutable.Set(a: _*)
+    assert(s.sum > 0)
+  }
+}