(*
    ||M||  This file is part of HELM, an Hypertextual, Electronic        
    ||A||  Library of Mathematics, developed at the Computer Science     
    ||T||  Department, University of Bologna, Italy.                     
    ||I||                                                                
    ||T||  HELM is free software; you can redistribute it and/or         
    ||A||  modify it under the terms of the GNU General Public License   
    \   /  version 2 or (at your option) any later version.              
     \ /   This software is distributed as is, NO WARRANTY.              
      V_______________________________________________________________ *)

module H = Hashtbl
module S = Scanf
module C = Cps

type graph = string * (int -> int)

let sorts = 2
let sort = H.create sorts 
let index = ref 0

(* Internal functions *******************************************************)

let set_sort f (h:int) (s:string) =
   H.add sort h s; f (succ h)

(* Interface functions ******************************************************)

let set_new_sorts f ss =
   let f i = index := i; f i in   
   C.list_fold_left f set_sort !index ss 

let get_sort f h =
   try f (Some (H.find sort h))
   with Not_found -> f None

let string_of_graph f (s, _) = f s

let apply f (_, g) h = f (g h)

let graph_of_string f s =
   try 
      let x = S.sscanf s "Z%u" C.start in 
      if x > 0 then f (Some (s, fun h -> x + h)) else f None
   with
      S.Scan_failure _ | Failure _ | End_of_file -> f None

let graph =
   ref (graph_of_string (function Some g -> g | None -> assert false) "Z2")