let cfg_of_imp = fun imp_prog -> match imp_prog with
    ImpProg (dec, com) ->
      let rec cfg_of_imp' = fun com cont -> match com with
              Cseq (com1, com2) -> let cfg = cfg_of_imp' com1  cont in
                       let cont' = ultimo_cont cfg in
                       let cfg' = cfg_of_imp' com2 cont' in
                       (match com1 with
                       While (exp, com) -> union_cfg cfg cfg'
                     | _ -> union_cfg cfg (imposta_archi ([string_of_int cont', string_of_int (cont'+1)])
                         (cfg_of_imp' com2 (cont'+1))))
            | Skip -> ([(string_of_int cont, BSkip)], [])
                | AssignVar (ide, n) -> ([string_of_int cont, BAssignVar (ide, n)], [])
        | AssignArray (ide, i, n) -> ([string_of_int cont, BAssignArray (ide, i, n)], [])
        | If (exp, com1, com2) -> let cfg_com1 = cfg_of_imp' com1 (cont+1) in
                      let cont' = ultimo_cont cfg_com1 in
                      let cfg_com2 = cfg_of_imp' com2 cont' in
                      union_cfg (imposta_archi ([string_of_int cont, string_of_int (cont')])
                                ([string_of_int cont, BGuard exp], [string_of_int cont, string_of_int (cont + 1)]))
                                (union_cfg cfg_com1 cfg_com2)
        | While (exp, com) -> let cfg = cfg_of_imp' com (cont+1) in
                      let cont' = ultimo_cont cfg in
                      imposta_archi ([string_of_int cont', string_of_int cont; string_of_int cont, string_of_int (cont' + 1)]) (union_cfg ([string_of_int cont, BGuard exp], [string_of_int cont, string_of_int (cont+1)]) cfg)
      in cfg_of_imp' com 0
;;