let superpositions current_table =
     let r = Stmt.Hashtbl.create (Stmt.Hashtbl.length current_table)
     in
     Stmt.Hashtbl.iter
       (fun k record ->
         let sup2 =
           State_imp.fold
             State_set.add
              record.superposition
             State_set.empty
         in
         Stmt.Hashtbl.add r k sup2)
       current_table;
     r