Can someone please tell me why this code doesnt print anything? - c++

Question

I have to write a code that compares three text files and i cant for the life of me find out why this wont print anything:
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
using namespace std;
int main (int argc, char *argv[])
{
ifstream mousefile;
mousefile.open(argv[1]);
string mouse_dna;
getline(mousefile, mouse_dna);
ifstream humanfile;
humanfile.open(argv[2]);
string human_dna;
getline(humanfile, human_dna);
ifstream unknownfile;
unknownfile.open(argv[3]);
string unknown_dna;
getline(unknownfile, unknown_dna);
int len = mouse_dna.size();
int mouseDistance = 0, humanDistance = 0;
for(int i=0; i<len; i++)
if(mouse_dna[i] != unknown_dna[i])
mouseDistance++;
return mouseDistance;
for(int i=0; i<len; i++)
if(human_dna[i] != unknown_dna[i])
humanDistance++;
return humanDistance;
double similarity_scoreH = (len - humanDistance) / len;
double similarity_scoreM = (len - mouseDistance) / len;
cout << "MouseCompare = " << similarity_scoreM << endl;
cout << "HumanCompare = " << similarity_scoreH << endl;
if (similarity_scoreH == similarity_scoreM)
cout << "identity cannot be determined" << endl;
else if (similarity_scoreH > similarity_scoreM)
cout << "human" << endl;
else if (similarity_scoreM > similarity_scoreH)
cout << "mouse" << endl;
}
It compiles properly, and doesn't give any errors, but when i rut it as:
./DNA mouseDNA.txt humanDNA.txt unknownDNA.txt
it still does nothing.
I appreciate any help. Thanks!

Answer 1

It doesn't print anything because it's returning before the instructions to print (return mouseDistance; or return humanDistance;). Make your function more verbose by printing progress messsages before each return statement.

Answer 2

As already has pointed out, you return too early. I modify your code:
I put brackets around the if block and for block.
I have a return statement at the end.
This is a start. You may have to add more checking, for example, if the file is open correctly.
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
using namespace std;
int main (int argc, char *argv[])
{
ifstream mousefile;
mousefile.open(argv[1]);
string mouse_dna;
getline(mousefile, mouse_dna);
ifstream humanfile;
humanfile.open(argv[2]);
string human_dna;
getline(humanfile, human_dna);
ifstream unknownfile;
unknownfile.open(argv[3]);
string unknown_dna;
getline(unknownfile, unknown_dna);
int len = mouse_dna.size();
int mouseDistance = 0, humanDistance = 0;
for(int i=0; i<len; i++)
{
if(mouse_dna[i] != unknown_dna[i])
{
mouseDistance++;
}
}
for(int i=0; i<len; i++)
{
if(human_dna[i] != unknown_dna[i])
{
humanDistance++;
}
}
double similarity_scoreH = (len - humanDistance) / len;
double similarity_scoreM = (len - mouseDistance) / len;
cout << "MouseCompare = " << similarity_scoreM << endl;
cout << "HumanCompare = " << similarity_scoreH << endl;
if (similarity_scoreH == similarity_scoreM)
cout << "identity cannot be determined" << endl;
else if (similarity_scoreH > similarity_scoreM)
cout << "human" << endl;
else if (similarity_scoreM > similarity_scoreH)
cout << "mouse" << endl;
return 0;
}

Answer 3

You use arg[1], arg[2], and arg[3]. You may want arg[0], arg[1], and arg[2].