Question

I want to read two matrices from two different txt files, and say output them in another one.
I doesn’t write all of them, it only writes the fist one and “Hi” and stops there.
So I believe it cannot read the second file.
Here is the code:

#include <iostream>
#include <fstream>
using namespace std;

#define I 5
#define J 5
#define P 2
int i,j,k;  //for loops

int main ()
{
    ifstream inFile;
    ofstream outFile;

    double C[I][J];
    double u[I][J];
    double UB = 0;

    outFile.open("results.txt");
    // READ U0
    inFile.open("u.txt", ios::in);
    if (! inFile) {
        cerr << "unable to open file u.txt for reading" << endl;
        return 1;
    }
    for(i = 0; i < I; i++)
        for(j = 0; j < J; j++)
            inFile >> u[i][j];

    outFile << "u" << endl;
    for(i = 0; i < I; i++)
    {
        for(j = 0; j < J; j++)
            outFile << u[i][j];
            outFile << endl;
    }
    outFile << "Hi";

    //READ C
    inFile.open("C.txt", ios::in);
    if (! inFile) {
        cerr << "unable to open file C.txt for reading" << endl;
        return 1;
    }
    for(i = 0; i < I; i++)
        for(j = 0; j < J; j++)
            inFile >> C[i][j];
    outFile << "C" << endl;

    outFile << "UB=" << UB;


    inFile.close();
    outFile.close();

    return 0;

}

Answer 1

You have two general choices:

• Use two different variables, such as inFile1 and inFile2, for u.txt and C.txt.
• Close inFile with inFile.close() before trying to use the same variable to open a new file.