(*
    ||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 Y = Entity

(* internal functions *******************************************************)

let rec rename ns n =
   let token, mode = n in
   let n = token ^ "_", mode in
   if List.mem n ns then rename ns n else n

let alpha_name acc attr =
   let ns, a = acc in
   match attr with
      | Y.Name n ->
	 if List.mem n ns then
            let n = rename ns n in
	    n :: ns, Y.Name n :: a
	 else 
	    n :: ns, attr :: a
      | _        -> assert false 

(* interface functions ******************************************************)

let alpha ns a =
   let f a names =
      let _, names = List.fold_left alpha_name (ns, []) (List.rev names) in
      List.rev_append a names
   in
   Y.get_names f a