我们以递归方式为解析名称和查询群组成员提供了两个帮助器类。
We have provided two helper classes for resolving names and querying group members in a recursive manner.
最后对于递归表达式的情况，当解析器在表达式递归中看到括号时，就应该简单地进行回送，如清单21中所示。
Finally, for the case of recursive expressions, the parser should simply echo parentheses when it sees them within the expression recursion, as illustrated in Listing 21.
此算法递归地重复，直到所有新解析的子组不再包含子组。
This algorithm repeats recursively until all newly resolved subgroups contain no further subgroups.
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