You define a language by defining the structure of its abstract syntax tree, its abstract grammar.

定义语言就是定义它的抽象句法树，它的抽象文法。

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Generate the tree structure of the abstract class diagram by selecting the Explore in Browse diagram from the context menu.

通过选择内容菜单中Explore in Browse Diagram选项来产生抽象类图的树状结构。

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With the emphasis on the abstraCt syntax tree (AST), the paper also discusses the structure of a disk file as well as the functions designed for saving and recovering the AST.

主要分析了抽象语法树(ast)，讨论了磁盘文件的结构及ast的写入和复原技术。

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