From 57edf1ab5ec40364d19a84b2db78dc284ff9dad9 Mon Sep 17 00:00:00 2001 From: michelou Date: Thu, 9 Mar 2006 13:51:32 +0000 Subject: added file docs/examples/gadts.scala --- docs/examples/gadts.scala | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 docs/examples/gadts.scala diff --git a/docs/examples/gadts.scala b/docs/examples/gadts.scala new file mode 100644 index 0000000000..88e1ff9fdb --- /dev/null +++ b/docs/examples/gadts.scala @@ -0,0 +1,22 @@ +package examples + +object gadts extends Application { + + abstract class Term[T] + case class Lit(x: int) extends Term[int] + case class Succ(t: Term[int]) extends Term[int] + case class IsZero(t: Term[int]) extends Term[boolean] + case class If[T](c: Term[boolean], + t1: Term[T], + t2: Term[T]) extends Term[T] + + def eval[T](t: Term[T]): T = t match { + case Lit(n) => n + case Succ(u) => eval(u) + 1 + case IsZero(u) => eval(u) == 0 + case If(c, u1, u2) => eval(if (eval(c)) u1 else u2) + } + Console.println( + eval(If(IsZero(Lit(1)), Lit(41), Succ(Lit(41))))) +} + -- cgit v1.2.3