Returns the character (Unicode code point) at the specified index.
返回指定索引的字符(Unicode码的位置)。
The only collation URI defined by XPath 2.0 is for the Unicode code point collation, according to which strings are compared by the Unicode code points of their individual characters.
XPath 2.0仅定义了一种排序uri，即Unicode代码点排列法，字符串根据每个字符的Unicode代码点进行比较。
Unicode character encoding standard is a fixed-length character that provides a unique code point for every character in the world regardless of the platform, program, or the language.
Unicode字符编码标准是固定长度的字符，它为世界上的每一个字符都提供了一个惟一的代码点，无论平台、程序或语言如何。
Unicode character encoding standard is a fixed-length character that provides a unique code point for every character in the world regardless of the platform, program, or the language.
Unicode字符编码标准是固定长度的字符，它为世界上的每一个字符都提供了一个惟一的代码点，无论平台、程序或语言如何。
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