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內容簡介

flex 與 bison(影印版)》內容簡介：如果你需要分析或處理Linux或Unix中的文本數據，這本有用的書籍就向你講解了如何使用flex和bison迅速解決問題。《flex與bison》被期待已久，是經典O`Reilly系列書籍《lex & yacc》的續篇。在原書出版以來的近20年中，flex和bison已被證明比原來的Unix工具更、更強大。

flex與bison》一書涵蓋了Linux和Unix程序開發中相同的重要核心功能，以及一些重要的新主題。你會找到適用于新手的修訂教程和適用于高級用戶的參考資料，以及對每個程序的基本用法的解釋，并且運用它們創建簡單、獨立的應用程序。有了《flex與bison》，你會發現這些靈活的工具提供的廣泛用途。

包括的主題有：

· 正則表達式工具無法處理的地址語法擠壓(address syrltax crunching

· 生成編譯器和解釋器，并運用大范圍的文本處理功能

· 解釋代碼、配置文件或任何其他結構化的格式

· 學習關鍵編程技術，包括抽象語法樹和符號表

· 用完整的示例代碼實現一個完善的SQI一語法

· 使用新的功能，如純(可重入)詞法分析器(Iexer)和語法分析器(parser)、功能強大的JGLR分析器和C++的接口

作者簡介

John Levine, Taughannock Networks的創始人，著有20余本技術書籍，其中包括《lex & yacc》和《qmail》，均為O`Reilly出版。

在線預覽

A bison specification has the same three-part structure as a flex specification. (Flexcopied its structure from the earlier lex, which copied its structure from yacc, the predecessor of bison.) The first section, the definition section, handles control informationfor the parser and generally sets up the execution environment in which the parser willoperate. The second section contains the rules for the parser, and the third section isC code copied verbatim into the generated C program.

Bison creates the C program by plugging pieces into a standard skeleton file. The rulesare compiled into arrays that represent the state machine that matches the input tokens.The actions have the SN and @N values translated into C and then are put into a switchstatement within yyparse0 that runs the appropriate action each time there's a reduction. Some bits of the skeleton have multiple versions from which bison chooses depending on what options are in use; for example, if the parser uses the locations feature,it includes code to handle location data.

In this chapter we take the simple calculator example from Chapter 1 and extend itsignificantly. First, we rewrite it to take advantage of some handy bison shortcuts andchange it to produce a reusable data structure rather than computing the values on thefly. Later, we'll add more complex syntax for loops and functions and show how toimplement them in a simple interpreter.

One of the most powerful data structures used in compilers is an abstract syntax tree(AST). In Chapter 1 we saw a parse tree, a tree that has a node for every rule used toparse the input string. In most real grammars, there are rules that exist to managegrouping but that add no meaning to the program. In the calculator example, the rulesexp: term and term: factor exist only to tell the parser the relative precedence of theoperators. An AST is basically a parse tree that omits the nodes for the uninterestingrules.