(def good-sample
  '(:des_system_lib   (:std :synopsys :std_cell_lib :des_system_lib :dw02 :dw01 :ramlib :ieee)
    :dw01             (:ieee :dw01 :dware :gtech)
    :dw02             (:ieee :dw02 :dware)
    :dw03             (:std :synopsys :dware :dw03 :dw02 :dw01 :ieee :gtech)
    :dw04             (:dw04 :ieee :dw01 :dware :gtech)
    :dw05             (:dw05 :ieee :dware)
    :dw06             (:dw06 :ieee :dware)
    :dw07             (:ieee :dware)
    :dware            (:ieee :dware)
    :gtech            (:ieee :gtech)
    :ramlib           (:std :ieee)
    :std_cell_lib     (:ieee :std_cell_lib)
    :synopsys         ()))

(def cyclic-dependence
  '(:dw01 (:dw04)))

(def bad-sample
  (concat cyclic-dependence good-sample))