Windows下 flex + bison 小例子

2023-02-22 07:17:04

.下载flex和bison，网址是http://gnuwin32.sourceforge.net/packages/flex.htm

和http://gnuwin32.sourceforge.net/packages/bison.htm，如果这两个链接不好使了就自己搜吧。

这两个链接里面下载那两个Setup文件就好了。然后把他们安装了。

主要需要 lib文件夹下的 libfl.a 和 liby.a 这两个库。

.从 http://sourceforge.net/projects/winflexbison/ 下载已经编译好的压缩文件 win_flex_bison-2.5.1.zip（不到700kb）

.把2中的路径添加到环境变量

.编写两个文件，实现简单的计算器功能。

fb1-5.l代码：

/* Companionsource code for "flex & bison", published by O'Reilly

* Media, ISBN 978-0-596-15597-1

* Copyright (c) 2009, Taughannock Networks.All rights reserved.

* See the README file for license conditionsand contact info.

* $Header: /home/johnl/flnb/code/RCS/fb1-5.l,v2.1 2009/11/08 02:53:18 johnl Exp $

*/ 

/* recognizetokens for the calculator and print them out */ 

%{ 

# include"fb1-5.tab.h" 

%} 

%% 

"+" { return ADD; }

"-" { return SUB; }

"*" { return MUL; }

"/" { return DIV; }

"|" { return ABS; }

"(" { return OP; }

")" { return CP; } 

[0-9]+ { yylval = atoi(yytext); return NUMBER; } 

\n { return EOL; }

"//".*

[ \t] { /* ignore white space */ }

. { yyerror("Mystery character%c\n", *yytext); } 

%%

fb1-5.y代码：

/* Companionsource code for "flex & bison", published by O'Reilly

* Media, ISBN 978-0-596-15597-1

* Copyright (c) 2009, Taughannock Networks.All rights reserved.

* See the README file for license conditionsand contact info.

* $Header: /home/johnl/flnb/code/RCS/fb1-5.y,v2.1 2009/11/08 02:53:18 johnl Exp $

*/ 

/* simplestversion of calculator */ 

%{ 

# include <stdio.h> 

%} 

/* declare tokens*/

%token NUMBER

%token ADD SUB MUL DIV ABS

%token OP CP

%token EOL 

%% 

calclist: /*nothing */

| calclist exp EOL { printf("= %d\n>", $2); }

| calclist EOL { printf("> "); }/* blank line or a comment */

; 

exp: factor

| exp ADD exp { $$ = $1 + $3; }

| exp SUB factor { $$ = $1 - $3; }

| exp ABS factor { $$ = $1 | $3; }

; 

factor: term

| factor MUL term { $$ = $1 * $3; }

| factor DIV term { $$ = $1 / $3; }

; 

term: NUMBER

| ABS term { $$ = $2 >= 0? $2 : - $2; }

| OP exp CP { $$ = $2; }

; 

%% 

main()

{

	printf("> ");

	yyparse();

} 

yyerror(char *s)

{

	fprintf(stderr, "error: %s\n", s);

}