protected override IEnumerable <ParseStep> GetSuccessParseStep(IRegexEngine engine, State initialState)
{
var matchedText = engine.Input.Substring(initialState.Index, engine.State.Index - initialState.Index);
engine.AddCapture(Number, initialState.Index, matchedText);
yield return(ParseStep.Capture(this, matchedText, Number, initialState, engine.State));
yield return(ParseStep.Pass(this, matchedText, initialState, engine.State));
yield return(ParseStep.Break(this));
}