无论选择什么语法，都可以把这种结构从具体的模式范式回溯到抽象范式（参见 清单 3），从而找到确定其定义的语义锚。

Regardless of the syntax you choose, you trace the structure from the concrete schema patterns to the abstract pattern (as in Listing 3), where you find semantic anchors that solidify the definition.

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JRuby 1.6中，在生成回溯时不再需要这个数据结构了，这意味着很多Ruby方法现在的人为调用开销接近于0。

In JRuby 1.6, we have eliminated the need for this data structure for generating backtraces, which means that many Ruby methods now have nearly zero artificial call overhead.

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回溯作为计算机科学中的一种基本的控制结构，在人工智能中有广泛的应用。

As a basic control structure in computer science, backtracking has been widely used in artificial intelligence.

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