Data commit

Task/Stack/F-Sharp/stack.fs

@@ -0,0 +1,20 @@
+type Stack<'a> //'//(workaround for syntax highlighting problem)
+  (?items) =
+  let items = defaultArg items []
+
+  member x.Push(A) = Stack(A::items)
+
+  member x.Pop() =
+    match items with
+      | x::xr ->  (x, Stack(xr))
+      | [] -> failwith "Stack is empty."
+
+  member x.IsEmpty() = items = []
+
+// example usage
+let anEmptyStack = Stack<int>()
+let stack2 = anEmptyStack.Push(42)
+printfn "%A" (stack2.IsEmpty())
+let (x, stack3) = stack2.Pop()
+printfn "%d" x
+printfn "%A" (stack3.IsEmpty())