The dot (.) is now known as the context item expression, and might be a node or an atomic value, depending on the current item in the sequence being processed.

点号(.)在这里称为上下文项表达式，可以是节点或者原子值，视处理的序列中的当前项而定。

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During the single dot cross operation, import the athuard ordinal number arrow, simplify the cross operation of the natural sequence.

在单点交叉过程中引入了逆序数向量进行交叉，简化了自然数序列的交叉过程。

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