Changed from type to module for cfg and moved to separate lib

lib/cfg/Cfg.mli

@@ -0,0 +1,38 @@
+module type PrintableType = sig
+  type t
+  val pp : out_channel -> t -> unit
+  val pplist : out_channel -> t list -> unit
+end
+
+module Node : sig
+  type t
+  val compare : t -> t -> int
+  val create : unit -> t
+end
+
+module NodeMap : Map.S with type key = Node.t
+module NodeSet : Set.S with type elt = Node.t
+
+module type C = sig
+  type elt
+  type t = {
+    empty: bool;
+    nodes: NodeSet.t;
+    edges: (Node.t * (Node.t option)) NodeMap.t;
+    reverseEdges: (Node.t list) NodeMap.t;
+    inputVal: elt option;
+    outputVal: elt option;
+    initial: Node.t option;
+    terminal: Node.t option;
+    content: elt list NodeMap.t
+  }
+
+  val create : unit -> t
+  val merge : t -> t -> Node.t -> Node.t -> t
+  val concat : t -> t -> t
+  val addToLastNode : elt -> t -> t
+
+  val pp : out_channel -> t -> unit
+end
+
+module Make (M: PrintableType) : C with type elt = M.t