internal Group() : base(new WrappedString(String.Empty))
{
success = false;
captures = new CaptureCollection(0);
}
// internal
internal Group(IString text, int index, int length, int n_caps) : base(text, index, length)
{
success = true;
captures = new CaptureCollection(n_caps);
captures.SetValue(this, n_caps - 1);
}