(*
    ||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_______________________________________________________________ *)

type csys = {
           buri: Entity.uri;
   mutable tp  : int list;
   mutable t1  : int list;
   mutable tn  : (int * int) list;
}

val init: unit -> csys

val add_nonzero: csys -> Entity.attrs -> unit

val add_zero: csys -> Entity.attrs -> unit

val add_equal: csys -> Entity.attrs -> Entity.attrs -> unit