WINDOWS下bison和flex的使用

以一个简单计算器为例

mycalc.l

%{
#include 
#include "y.tab.h"

int
yywrap(void)
{
    return 1;
}
%}
%%
"+"             return ADD;
"-"             return SUB;
"*"             return MUL;
"/"             return DIV;
"\n"            return CR;
([1-9][0-9]*)|0|([0-9]+\.[0-9]*) {
    double temp;
    sscanf(yytext, "%lf", &temp);
    yylval.double_value = temp;
    return DOUBLE_LITERAL;
}
[ \t] ;
. {
    fprintf(stderr, "lexical error.\n");
    exit(1);
}
%%

mycalc.y

%{
#include 
#include 
#define YYDEBUG 1
%}
%union {
    int          int_value;
    double       double_value;
}
%token       DOUBLE_LITERAL
%token ADD SUB MUL DIV CR
%type  expression term primary_expression
%%
line_list
    : line
    | line_list line
    ;
line
    : expression CR
    {
        printf(">>%lf\n", $1);
    }
expression
    : term
    | expression ADD term
    {
        $$ = $1 + $3;
    }
    | expression SUB term
    {
        $$ = $1 - $3;
    }
    ;
term
    : primary_expression
    | term MUL primary_expression 
    {
        $$ = $1 * $3;
    }
    | term DIV primary_expression
    {
        $$ = $1 / $3;
    }
    ;
primary_expression
    : DOUBLE_LITERAL
    ;                 
%%
int
yyerror(char const *str)
{
    extern char *yytext;
    fprintf(stderr, "parser error near %s\n", yytext);
    return 0;
}

int main(void)
{
    extern int yyparse(void);
    extern FILE *yyin;

    yyin = stdin;
    if (yyparse()) {
        fprintf(stderr, "Error ! Error ! Error !\n");
        exit(1);
    }
}

在命令行输入如下命令

bison --yacc -dv mycalc.y
flex mycalc.l
gcc -o mycalc y.tab.c lex.yy.c