1 /// A case of catastrophic backtracking in Dart

     2 ///---------------------------------------------

     3 /// example provided by Martin Todorov

     4 ///

     5 /// regex: (a*)*b

     6 /// strings: aa...a

     7 ///

     8 /// run with

     9 ///

    10 ///    dart catastrophic.dart n

    11 

    12 

    13 main(List<String> args) {

    14   final n = int.parse(args[0]);

    15   final evilRegex = RegExp("(a*)*b");

    16 

    17   for(int i = 1; i <= n; i++) {

    18     final toMatch = "a" * i;

    19     final stopwatch = Stopwatch()..start();

    20     evilRegex.hasMatch(toMatch);

    21     print("$i a's matched in ${stopwatch.elapsed}");

    22   }

    23 }