let

  drvA1 = derivation { name = "a"; builder = "/foo"; system = "i686-linux"; };
  drvA2 = derivation { name = "a"; builder = "/foo"; system = "i686-linux"; };
  drvA3 = derivation { name = "a"; builder = "/foo"; system = "i686-linux"; } // { dummy = 1; };
  
  drvC1 = derivation { name = "c"; builder = "/foo"; system = "i686-linux"; };
  drvC2 = derivation { name = "c"; builder = "/bar"; system = "i686-linux"; };

in [ (drvA1 == drvA1) (drvA1 == drvA2) (drvA1 == drvA3) (drvC1 == drvC2) ]