1 / 13

Introduction of Bison/Yacc

Introduction of Bison/Yacc. Yet another compiler-compiler. LALR(1) 分析生成器 安装 Bison 编写 .y 文件，描述文法 Bison *.y 生成 .c 文件 VC 编译 .c 文件生成 exe 文件 运行 exe 分析输入串. Yacc 说明文件 (.h) { 定义 } %% { 规则 } %% 辅助程序. Example. exp -> exp addop term | term addop -> + | - term -> term mulop factor | factor

kyle-dennis
Download Presentation

Introduction of Bison/Yacc

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction of Bison/Yacc

  2. Yet another compiler-compiler • LALR(1)分析生成器 • 安装Bison • 编写.y文件，描述文法 • Bison *.y生成.c文件 • VC编译.c文件生成exe文件 • 运行exe分析输入串

  3. Yacc说明文件(.h) • {定义} • %% • {规则} • %% • 辅助程序

  4. Example • exp -> exp addop term | term • addop -> + | - • term -> term mulop factor | factor • mulop -> * • factor -> (exp) | number • 对应的.y文件

  5. 解释 • exp : exp ‘+’ term { $$ = $1 + $3; } • yylval • yylex • yyerror • yyparse

  6. 分析表以及分析过程 • Bison -v *.y 生成对应 .output 文件 • .output文件即生成的LALR(1)分析表 • 设置yydebug可直接输出分析过程

  7. 处理二义性 • E -> E+E | E-E | E*E | E/E | (E) | -E | E^E | number • 归约-归约冲突：选择说明中最先出现的产生式 • 移进-归约冲突：移进优先 • 算符优先与结合性

  8. 算符的优先级与结合性 • 优先级（越后出现优先级越高） • %left ‘+’ ‘-’ • %left ‘*’ • 结合性 • %left ‘+’ ‘-’ • 12+34-12 • %right （右结合） • %nonassoc （重复的算符不允许出现在相同的层级）

  9. E -> E+E | E-E | E*E | E/E | (E) | -E | E^E | number • 对应的.y文件

  10. Bison与Flex的结合 • Bison –d *.y 生成.h文件 • .h文件中存放需要的token • .l文件定义所有的token • Flex *.l • 替换yylex函数

  11. YYSTYPE • $$, $1, $2的实际值，存放在yylval中 • 默认yylval为int类型 • 可通过#define YYSTYPE double设置为其他类型 • %union设置复杂的类型 • YYSTYPE也可定义为特定的类型(其他头文件中定义), #define YYSTYPE treeNode *

  12. Example • %union{double val; char op} • %token NUM • %type <val> exp term factor NUM • %type <op> addop mulop • exp : exp op term {switch($2) • { • case ‘+’: $$ = S1 + S3; break; • case ‘-’: $$ = S1 – S2; break; • } • } • Tiny程序（编译原理与实践 附录）

  13. Thanks

More Related