begin work on new device module system

lib/Device.ml

@@ -0,0 +1,34 @@
+module type DEVICE = sig
+  type state
+
+  val state : state
+  val can_handle : int -> bool
+  val dei : Machine.machine -> int -> int option
+  val dei2 : Machine.machine -> int -> int option
+  val deo : Machine.machine -> int -> int -> unit
+end
+
+module Compose (D1 : DEVICE) (D2 : DEVICE) : DEVICE = struct
+  type state = D1.state * D2.state
+
+  let state = (D1.state, D2.state)
+  let can_handle port = D1.can_handle port || D2.can_handle port
+
+  let dei mach port =
+    match (D1.can_handle port, D2.can_handle port) with
+    | true, false -> D1.dei mach port
+    | false, true -> D2.dei mach port
+    | _ -> None
+
+  let dei2 mach port =
+    match (D1.can_handle port, D2.can_handle port) with
+    | true, false -> D1.dei2 mach port
+    | false, true -> D2.dei2 mach port
+    | _ -> None
+
+  let deo mach port value =
+    match (D1.can_handle port, D2.can_handle port) with
+    | true, false -> D1.deo mach port value
+    | false, true -> D2.deo mach port value
+    | _ -> ()
+end