Condtional and Lookbehind in Dart

gistfile1.txt

void main() {
  // Lookbehind example
  final String phrase = "fooback";
  final RegExp lookbehindPattern = new RegExp(r'(?<=foo)back');
  
  print('Does lookbehind work? ${lookbehindPattern.hasMatch(phrase)}');
  
  // Negative Lookbehind example
  // It would match .text or text= but not Me.text or FtextABC
  final RegExp negativeLookbehind = new RegExp(r'(?<!(Me\.)|[frFR])(text)(?!\w)');

  final String phrase1 = ".text";
  final String phrase2 = "text=";
  final String phrase3 = "Me.text";
  final String phrase4 = "FtextABC";
  
  print('Negative lookbehind test 1: ${negativeLookbehind.hasMatch(phrase1)}');

  print('Negative lookbehind test 1: ${negativeLookbehind.hasMatch(phrase2)}');
  
  print('Negative lookbehind test 1: ${negativeLookbehind.hasMatch(phrase3)}');
  
  print('Negative lookbehind test 1: ${negativeLookbehind.hasMatch(phrase4)}');
  
  RegExp condition = new RegExp(r'(?((?<=foo)back)[0-9]|[a-z])');
  
  print('Conditional Test: ${condition.hasMatch('fooback')}');
}