One more test

Author: odersky

tests/pos/Orderings.scala

@@ -0,0 +1,20 @@
+object Orderings {
+
+  // A type class:
+  trait Ord[T] { def less(x: T, y: T): Boolean }
+
+  implicit val intOrd: Ord[Int] = new {
+    def less(x: Int, y: Int) = x < y
+  }
+
+  implicit def listOrd[T](implicit ev: Ord[T]): Ord[List[T]] = new {
+    def less(xs: List[T], ys: List[T]): Boolean =
+      if ys.isEmpty then false
+      else if xs.isEmpty then true
+      else if xs.head == ys.head then less(xs.tail, ys.tail)
+      else ev.less(xs.head, ys.head)
+  }
+
+  def isLess[T]: T => T => implicit Ord[T] => Boolean =
+    x => y => implicitly[Ord[T]].less(x, y)
+}