1 files changed, 2 insertions, 0 deletions
diff --git a/src/library/scala/math/Ordering.scala b/src/library/scala/math/Ordering.scala
index 1660cdb99e..04c2d96aba 100644
--- a/src/library/scala/math/Ordering.scala
+++ b/src/library/scala/math/Ordering.scala
@@ -133,6 +133,8 @@ object Ordering extends LowPriorityOrderingImplicits {
     override def lteq(x: T, y: T): Boolean = !cmp(y, x)
   }
 
+  def by[T, S: Ordering](f: T => S): Ordering[T] = fromLessThan((x, y) => implicitly[Ordering[S]].lt(f(x), f(y)))
+
   trait UnitOrdering extends Ordering[Unit] {
     def compare(x: Unit, y: Unit) = 0
   }