Prototyping the functors for FSM

test.ml

(*ocamlc -o test test.ml*)
(* the problem we're trying to solve is to have the FSM module 
 * be able to deal with different expression types
 *)
module type BASETYPE = 
  sig
    type 'a var_t
    val set : 'a var_t -> 'a -> unit
    val get_var_name : 'a var_t -> string
    val get_var_val  : 'a var_t -> 'a
  end

(* Concrete type *)
module Logic = struct
  type 'a var_t = { name: string; mutable value: 'a }
  let make_var s v = { name = s; value = v }
  let set v n = v.value <- n
  let get_var_name v = v.name
  let get_var_val  v = v.value
end

module type EXP =
  sig
    type  'a var_t
    val get_var_name : 'a var_t -> string
    val get_var_val  : 'a var_t -> 'a
  end

module B (T : BASETYPE) = 
  struct
    include T
    (*
    type 'a var_t     = 'a T.var_t
    let get_var_name  = T.get_var_name 
    let get_var_val   = T.get_var_val  
    *)
  end

module LogicExp = B(Logic)

module FSM ( Exp : EXP )(*with type 'a var_t = int A.var_t)*) = 
  struct
    let print_var v = Printf.printf "%s = %d\n" (Exp.get_var_name v)
    (Exp.get_var_val v)
    
  end

module MyFSM = FSM(LogicExp) 

let myvar = Logic.make_var "foo" 1;;

MyFSM.print_var myvar ;;