Include generated flex and bison code

I am working with Flex and Bison in C ++. I am learning to use these tools and the best way to get started is with a simple calculator. After creating an application (executable) from my calc.y and calc.l files, I can run the .exe file and use it, but now I want to include it in the C ++ file so I can use it in my application, but I cannot ... I believe this is my fault because I am including a bad generated file or creating bad code to import.

main.cpp

#include <iostream>

extern "C" {
    #include "y.tab.h"
}

int main ( int argc, char *argv[] ) {
    yyparse();
    printf(elementos);
    return 0;
}

      

        
        
        
      

    

calc.l

%{
#include "y.tab.h"
#include <stdlib.h>
void yyerror(char *);
%}

%%

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

[-+()\n]    {
    return *yytext;
}

[ \t]   ;

.       {
    yyerror("Invalid character.");
}

%%

int yywrap(void) {
    return 1;
}

      

        
        
        
      

    

calc.y

%{
    #include <stdio.h>
    int yylex(void);
    void yyerror(char *);
    int sym[26];
    int elementos = 0;
%}

%token INTEGER VARIABLE
%left '+' '-'
%left '*' '/'

%%

program:
        program expr '\n' { printf("%d\n", $2 ); }
    |
;

statement:
        expr                { printf("%d\n", $1); }
    |   VARIABLE '=' expr   { sym[$1] = $3; }
;

expr:
        INTEGER             { $$ = $1; }
    |   expr '+' expr       { $$ = $1 + $3; elementos = elementos + 1;}
    |   expr '-' expr       { $$ = $1 - $3; }
    |   expr '*' expr       { $$ = $1 * $3; }
    |   expr '/' expr       { $$ = $1 / $3; }
    |   '(' expr ')'        { $$ = $2; }
;

%%

void yyerror(char *s) {
    fprintf(stderr, "%s\n", s);
}


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

      

        
        
        
      

    

Y.tab.h is generated by bison. When I try to compile main.cpp I get an error:

: gcc main.cpp -o main.exe

result: main.cpp: In function 'int main(int, char**)': main.cpp:8:10: error: 'yyparse' was not declared in this scope main.cpp:9:9: error: 'elementos' was not declared in this scope

How can I fix this?

I am using gcc version 4.7.2, bison 2.4.1 and 2.5.4 on windows 8.1.

Thank!

EDIT

Y.tab.h file:

/* Tokens.  */
#ifndef YYTOKENTYPE
# define YYTOKENTYPE
   /* Put the tokens into the symbol table, so that GDB and other debuggers
      know about them.  */
   enum yytokentype {
     INTEGER = 258,
     VARIABLE = 259
   };
#endif
/* Tokens.  */
#define INTEGER 258
#define VARIABLE 259




#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
typedef int YYSTYPE;
# define YYSTYPE_IS_TRIVIAL 1
# define yystype YYSTYPE /* obsolescent; will be withdrawn */
# define YYSTYPE_IS_DECLARED 1
#endif

extern YYSTYPE yylval;

      

        
        
        
      

    

There is no "elementos" variable, but looking at the generated y.tab.c file I found it was defined!