type character = rule list
and rule = Rule of state_number list * statement
and statement = 
    If of condition * statement * elseif list * statement 
  | Decision of new_state * string 
  | Case of string * arm list * statement
and elseif =
    Elseif of condition * statement
and arm = 
    Arm of int list * statement
and condition =
    Equals of string * int
  | And of condition list
  | Or of condition list
and new_state = int option
and state_number = int
;;

val to_ast: character -> Ast.character
val from_ast: Ast.character -> character