private void classify()
    {
        switch (_char)
        {
            case '$':
                _char_classification = I_DOLLAR;
                break;

            case ' ':
            case '\t':
            case '\n':
            case '\r':
                _char_classification = I_WHITESPACE;
                break;

            case '\\':
                _char_classification = I_ESCAPE;
                break;

            case (char) -1:
                _char_classification = I_EOL;
                break;

            default:
                _char_classification = I_OTHER;
                break;
        }
    }