Question

I’m new to c++, I’m writing a program that reads code from a file, and classifies each part of it as an identifier, bracket, keyword, etc..

I’m doing this using if else statements, it works fine except with brackets and semicolons.

for example if(a== "=" ) cout << "a is the equal operator" works, but if(a== ";" ) cout << "a is a semicolon" doesn’t. I also tried using the compare method, it didn’t work either.

Can someone please tell me why that’s happening?

Thanks

void checkString(string a)

        if(a=="("){
                cout << "RPAR: " << a + "\n";
        }

        else if(a==")"){
                cout << "LPAR: " << a + "\n";
        }

        else if(a.compare("{") == 0){
                cout << "LBRAC: " << a + "\n";
        }

        else if(a=="}"){
                cout << "RBRAC: " << a + "\n";
        }

        else{
                cout << "IDENTIFIER: " << a + "\n";
        }
}

int  main (){

    std::vector<string> STRINGS;
    string STRING;
    ifstream infile;
    infile.open("m.c");
    while(getline(infile,STRING,' ')){
            STRINGS.push_back(STRING);
    }

    infile.close();
    for(int i=0; i<STRINGS.size(); i++){
            checkString(STRINGS[i]);
    }

    return 0;
}

If a is a bracket or a semicolon the program prints IDENTIFIER: {.

Answer 1

It looks like the problem is with getline(infile,STRING,' ').

What happens if your code hits a \n, \t, etc? It will be extracted together with your token and you will end up with a string such as ";\n", which is not the same as ";"

Either change the logic that you use to tokenize your file:

std::ifstream fin("m.c");
while (fin >> STRING ){
   STRINGS.push_back(STRING);
}
fin.close();

Or trim your string.

---

Update:

And keep in mind that this kind of tokenizer will only work if your tokens are separated by whitespaces (return 0 ; will work as expected, return 0; will be tokenized to return and 0;)