Question

I am new to C++ programming and am obviously missing something. In the following code the compiler doesn’t seem to recognize this line: lengths[counter] = findDups(crtLine); I get an error: variable “lengths” set but not used. I cannot figure out why it is not recognizing this line, when the names[counter] = getNameOnly(crtLine) works perfectly and it is essentially the same format. Any insight into this issue is appreciated!

#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>

using namespace std;


string getNameOnly (string line) {
    return line.substr(0, line.find(' '));
}

int findDups (string line) {
    string lnCpy = line;
    sort(lnCpy.begin(), lnCpy.end());   
    int i = 0; 
    int dups = 0;
    int j = 1;
    int len = lnCpy.length();
    while (j < len) {
        if (lnCpy.at(i) == lnCpy.at(j))
                dups++;
        i++;
        j++;
    }

    if (dups != 0)
        return 0;
    else
            return lnCpy.length();
}

int main() {

string names[1219];
int lengths[1219];
string crtLine;
int counter = 0;

ifstream myfile ("dist.male.first");
if (myfile.is_open()) {
    while (!myfile.eof()) {
        getline(myfile,crtLine);
        lengths[counter] = findDups(crtLine);           
        names[counter] = getNameOnly(crtLine);                  
        counter++;
    }
    myfile.close();
}   
else cout << "Unable to open file";


return (0);

}

Answer 1

That’s a warning, not an error, and it tells you exactly what the problem is: you put things into the variable named lengths, but never check what’s in it, you might as well never store anything there in the first place.

You don’t get a similar warning for names, because the assignment operator of std::string has side effects, and the compiler assumes you were interested in the side effect (rather than getting the value out later).