ScannerByRegularExpression

------------
test.y:

%{
#include <stdio.h>

int yylex();
int yyerror(char *s);

%}

%token STRING NUM OTHER SEMICOLON

%type <name> STRING
%type <number> NUM

%union{
	  char name[20];
    int number;
}

%%

prog:
  stmts
;

stmts:
		| stmt SEMICOLON stmts

stmt:
		STRING {
				printf("Your entered a string - %s", $1);
		}
		| NUM {
				printf("The number you entered is - %d", $1);
		}
		| OTHER
;

%%

int yyerror(char *s)
{
	printf("Syntax Error on line %s\n", s);
	return 0;
}

int main()
{
    yyparse();
    return 0;
}

------------
test.l:

%{
#include <stdio.h>
#include <string.h>
#include "test.tab.h"
void showError();
%}


numbers     ([0-9])+
alpha       ([a-zA-Z])+

%%

{alpha}			   {sscanf(yytext, "%s", yylval.name); return (STRING);}
{numbers}      {yylval.number = atoi(yytext); return (NUM);}
";"      		   {return (SEMICOLON);}
.      		     {showError(); return(OTHER);}

%%


void showError(){
    printf("Other input");
}
int yywrap(){
    return 1;
}
------------
TO RUN:

win_flex test.l
win_bison -d test.y
gcc lex.yy.c test.tab.c
a