protected function append(string $val, bool $addPostNewline = false, bool $addIndentation = false, bool $addPreNewline = false) : void
    {
        if ($addPreNewline) {
            $this->output .= "\n";
            ++$this->currentLine;
        }

        if ($addIndentation) {
            $val = $this->prefix.$val;
        }

        $this->output .= $val;

        if ($addPostNewline) {
            $this->output .= "\n";
            ++$this->currentLine;
        }
    }