flex&bison实例1

事例1：flex事例（计算 英文单词个数）

%{


int wordCount = 0;
int numCount = 0;
FILE *pfin = NULL;
FILE *pfin2 = NULL;
%}

chars [A-za-z\_\'\."]
numbers ([0-9])+
delim [" "\n\t]
whitespace {delim}+
words {chars}+

%%

{words} { wordCount++; }
{whitespace} { }
{numbers} { numCount++; }

%%


void main()
{

yyin = fopen ("in.txt", "r");
pfin = yyin;
pfin2 = fopen("in2.txt", "r");

yyout = fopen ("out.txt", "w");
yylex();

printf(" No of words: %d; num:%d\n", wordCount, numCount);
fprintf(yyout, " No of words: %d ; num:%d \n; lineCnt:%d\n", wordCount, numCount, yylineno);

fclose(pfin);
fclose(pfin2);
fclose(yyout);
}


int yywrap(void)
{
if (pfin == yyin)
{
yyin = pfin2;
return 0;
}
return 1;
}



事例2：flex 与 bison 结合（name=age）

name.y

%{
typedef char* string;


%}


%union {
char* pchr;
int nvalue;

}

%token NAME EQ AGE







%type NAME
%type EQ
%type AGE


%%

file : record file
| record
;
record : NAME EQ AGE {
printf("%s is %d years old!!!\n", $1, $3); }
;
%%

int main()
{
yyparse();
return 0;
}
int yyerror(char *msg)
{
printf("Error encountered: %s \n", msg);
return 0;
}

name.lex

%{

#include "./name.tab.h"
#include
#include

#define YY_NO_UNISTD_H 1
%}

char [A-Za-z]
num [0-9]
eq [=]
name {char}+
age {num}+

%%

{name} { yylval.pchr = strdup(yytext); return NAME; }
{eq} { return EQ; }
{age} { yylval.nvalue = atoi(yytext); return AGE; }

%%

int yywrap()
{
return 1;
}

事例3：flex （自己写的一个简单的 加减乘除）

%{
#define YY_NO_UNISTD_H 1
int nValue = 0;
char* pRet;
char* pExp;
char cOpType[20] = "";
char szBuf[1000];
int nTemp = 0;
%}


char ([a-zA-Z])+
delchr [" "\t\n]

optype ['*''+''/''\-']
result {char}+
whitespace {delchr}+
exp ([0-9])+
eq [=]



%%

{result} { printf("%s\n" , yytext); strncpy(szBuf, yytext, sizeof(szBuf));
if ( strcmp(szBuf, "exit") == 0 )
{return 0;
} }
{whitespace} { }
{exp} {

nTemp = atoi(yytext);
printf("%d\n", nTemp);

if (nTemp != 0)

switch(cOpType[0])
{
case '+':
nValue += nTemp;
printf("var=%s; value=%d; nTemp=%d, cOpType=%s, \n", szBuf, nValue, nTemp, cOpType);
break;
case '-':
nValue -= nTemp;
printf("var=%s; value=%d; nTemp=%d, cOpType=%s, \n", szBuf, nValue, nTemp, cOpType);
break;
case '*':
nValue *= nTemp;
printf("var=%s; value=%d; nTemp=%d, cOpType=%s, \n", szBuf, nValue, nTemp, cOpType);
break;
case '/':
nValue /= nTemp;
printf("var=%s; value=%d; nTemp=%d, cOpType=%s, \n", szBuf, nValue, nTemp, cOpType);
break;
default :
nValue = nTemp;
}
cOpType[0] = '\0';

}

{optype} { printf("%s\n" , yytext); strncpy(cOpType,

yytext, sizeof(cOpType)); }
{eq} { };
%%


int main()
{
yylex();

return 0;
}
int yywrap()
{
return 0;
}