Initial data commit

Task/Polymorphic-copy/F-Sharp/polymorphic-copy.fs

@@ -0,0 +1,14 @@
+type T() =
+  // expose protected MemberwiseClone method (and downcast the result)
+  member x.Clone() = x.MemberwiseClone() :?> T
+  // virtual method Print with default implementation
+  abstract Print : unit -> unit
+  default x.Print() = printfn "I'm a T!"
+
+type S() =
+  inherit T()
+  override x.Print() = printfn "I'm an S!"
+
+let s = new S()
+let s2 = s.Clone()  // the static type of s2 is T, but it "points" to an S
+s2.Print() // prints "I'm an S!"