static RegexExpression _ParseModifier(RegexExpression expr, ParseContext pc) { var line = pc.Line; var column = pc.Column; var position = pc.Position; switch (pc.Current) { case '*': expr = new RegexRepeatExpression(expr); expr.SetLocation(line, column, position); pc.Advance(); break; case '+': expr = new RegexRepeatExpression(expr, 1); expr.SetLocation(line, column, position); pc.Advance(); break; case '?': expr = new RegexOptionalExpression(expr); expr.SetLocation(line, column, position); pc.Advance(); break; case '{': pc.Advance(); pc.TrySkipWhiteSpace(); pc.Expecting('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ',', '}'); var min = -1; var max = -1; if (',' != pc.Current && '}' != pc.Current) { var l = pc.CaptureBuffer.Length; pc.TryReadDigits(); min = int.Parse(pc.GetCapture(l)); pc.TrySkipWhiteSpace(); } if (',' == pc.Current) { pc.Advance(); pc.TrySkipWhiteSpace(); pc.Expecting('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '}'); if ('}' != pc.Current) { var l = pc.CaptureBuffer.Length; pc.TryReadDigits(); max = int.Parse(pc.GetCapture(l)); pc.TrySkipWhiteSpace(); } } else { max = min; } pc.Expecting('}'); pc.Advance(); expr = new RegexRepeatExpression(expr, min, max); expr.SetLocation(line, column, position); break; } return(expr); }