解析XPath表达式时出错

Question

调试xslt时出现以下错误。

xslt

    <xsl:variable name="is_embedded_mode" select="if ($embedded_mode_root_path_prefix != '' and $invalid_embedded_mode_request != '1') then '1' else '0'" />

错误消息

[ERROR]: Syntax error in 'if ($embedded_mode_root_path_prefix != '' and $invalid_embedded_mode_request != '1') then '1' else '0''.
[ERROR]: file:default_frontend.xsl: line 62: Error parsing XPath expression 'if ($embedded_mode_root_path_prefix != '' and $invalid_embedded_mode_request != '1') then '1' else '0''.