Lexical Analyzer using LEX

Question

I am using the LEX generator to do a lexical analysis of a simple C++ code. The following code is from the generator:

%{
    #include<stdio.h>
%}

extern FILE *yyin;

%%
"<"         {printf("(Identifier, %s)\n",&yytext[0]);}
">"         {printf("(Identifier, %s)\n",&yytext[0]);}
"+"         {printf("operador de soma %s\n",&yytext[0]);}
"-"         {printf("operador de subtracao %s\n",&yytext[0]);}
%%

int yywrap(){
    return 1;
}

    int main(){

        yyin=fopen("cpp.cpp","r");

        yylex();
        fclose(yyin);   
        return;
    }

As you can see, I used the 'yyin' variable to call the cpp.cpp file for lexical analysis. I would like instead of printing the text to be written in the cpp.cpp file. That is, the result for each lexema was written in the analyzed code itself. cpp file:

#include<iostream>

using namespace std;

int main(){

    int a = 0;
    int b = 2;
    int c = a + b;

    cout << c << endl;

    return 0;
}

*I know you have lexemas that will not be found by grammar, but it’s just an example to explain that I want the lexemas found to be written inside the cpp.cpp file(as if instead of the 'printf' function was a fprintf function - which writes to a file, using C, or a RETURN so that I can write to the file inside the main method).

Answer 1

Do you need to write at the end of the file ? or can you overwrite it ? if you are using linux and can overwrite the cpp.cpp file do the following:.

int main(int argc, char **argv){

    yyin=fopen(argv[1],"r");

    yylex();
    fclose(yyin);   
    return 0;
}

And when you run open the terminal with Ctrl+alt+t and do . /executable < cpp.cpp