Code help

**Trey Brumley** · 02-06-2013

The following code should determine whether or not a square of numbers is a magic square or not. The code debugs and run just fine, but the command prompt opens, asks me how many squares I would like to calculate for, and after I hit enter with a number, it just sits there and does nothing.

Can anyone tell me why it does that? Have I done anything wrong?

Code:

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


const int size = 5;
void square (int x[size][size]);
void heading();


ifstream infile;
ofstream outfile;


int main()
{
    infile.open("input.txt");
    outfile.open("output.txt");


    int c;


    cout << "How many squares would you like to determine?  ";
    cin >> c;
    cout << endl;


    heading;
    outfile << "The user of this program has chosen to determine whether " << c << " squares are magic squares." << endl << endl;


    int x[size][size];


    for (int c = 1; c > 0; c++)
    {
        for (int d=0; d<size; d++)
            for (int e=0; e<size; e++)
                infile >> x[d][e];


        square(x);
    }


    system("pause");
    return 0;
}


// This function writes the heading in the outfile.
void heading()
{
    outfile << "Trey Brumley" << endl;
    outfile << "CMPS 1063 - Johnson" << endl;
    outfile << "January 29, 2013" << endl;
    outfile << "Program 1 - Magic Squares" << endl;
    outfile << "=========================" << endl << endl;


    outfile << "This program will take a certain number of number squares as determined by the user, and it will compare the sums of each row, column, and diagonal." << endl;
    outfile << "A magic square is a square of numbers with a constant sum of each of its rows, columns, and diagonals." << endl << endl;


    return;
}


// This function will test a square one row at a time
void square (int x[size][size])
{
    infile.open("input.txt");
    outfile.open("output.txt");


    int sum = 0, sum2 = 0;
    int y=1, z=1;


    //This and the following loop will determine a sum, which will remain constant. 
    //A second sum of the next row will be determined, which will repeatedly be tested against the first sum.
    //If the sums are equal, the loop will continue to run.  If not, the function will end.
    for (y; y <= 5; y++)
        sum += x[y][z];
        while (z<5)
        {
            sum2 = 0;


            for (y=1; y<=5; y++)
                sum2 += x[y][z];


            if (sum2 != sum)
            {
                outfile << "This square is not a magic square." << endl;
                return;
            }


            else
                z++;
        }


    for (z=1; z<=5; z++)
        while (y<=5)
        {
        sum2 = 0;
        sum2 += x[y][z];
        if (sum2 != sum)
        {
            outfile << "This square is not a magic square." << endl;
            return;
        }
        else
            y++;
        }


    sum2 = 0;


    //The following loops will test diagonals.
    for (z=1; z<=5; z++)
    {
        y=z;
        sum2 += x[y][z];
        if (sum2 != sum)
        {
            outfile << "This square is not a magic square." << endl;
            return;
        }
    }


    sum2 = 0;


    for (z=1; z<=5; z++)
        {
            y=6-z;
            sum2 += x[y][z];
            if (sum2 != sum)
            {
                outfile << "This square is not a magic square." << endl;
                return;
            }
        }


    outfile << "This square is a magic square.  The constant sum is " << sum << "." << endl;


    return;
}

**grumpy** · 02-06-2013

The cause of your problem is the for loop

Code:

for (int c = 1; c > 0; c++)

c starts with a positive value, is only ever incremented, so is always positive - so c > 0 is always true. Hence an infinite loop. (Strictly speaking, the program will eventually exhibit undefined behaviour when c overflows, so the loop isn't necessarily infinite, but will iterate at least 32766 times before that happens so your program will appear to hang).

Unrelated to your question, but the line

Code:

heading;

does nothing (except evaluate the address of the function named heading). If you want the function to be called, it is necessary to do

Code:

heading();

**std10093** · 02-06-2013

First of all this is wrong:

Code:

void square (int x[size][size])

What you can write is

Code:

void square (int x[][size], int size)

or

Code:

void square (int x[][], int size)

The compiler ignores the first parameter. Why you didn't an error? Because, int size is a global variable (not good technique, I can explain why if you wish after you resolve your infinite loop!).

Ok, so you have an infinite loop, I guess inside square function.

Also, the index of the arrays, start at zero, not at one! (learn this one and for all! You are not fortran programmer!).

Then I would check if the files really open. On line 42 I would check if the x array (x is not really a good name a suppose, but ok), is really filled up as you expect it is. Then I would fill square function with cout's on lines that are prone to infinite loops and I would run the code with a small amount of data. That way you debug yourself the code and you feel good

EDIT: Well obviously, grumpy found the mistake while I was typing, but I think you will be benefited a bit by reading my post

**Elysia** · 02-06-2013

>>int x[][]
You can't do that. You must specify the outer dimension, so it must be something like
int x[][size]
Where size is some constant expression (eg, a number).

**std10093** · 02-07-2013

Correct, so you use my first suggestion

**Trey Brumley** · 02-07-2013

Okay, so I edited the code. The offending code now looks like this:

for (c; c > 0; c--)

which should work, but now nothing at all is printing. Not even "The user has chosen to determine whether X squares are magic squares," which was printing just fine earlier.

**std10093** · 02-07-2013

Hmm.. Can you post a bit more code?

**Trey Brumley** · 02-07-2013

Originally Posted by std10093

Hmm.. Can you post a bit more code?

Code:

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


const int size = 5;
void square (int x[size][size]);
void heading();


ifstream infile;
ofstream outfile;


int main()
{
    infile.open("input.txt");
    outfile.open("output.txt");


    int c;


    cout << "How many squares would you like to determine?  ";
    cin >> c;
    cout << endl;


    heading();
    outfile << "The user of this program has chosen to determine whether " << c << " squares are magic squares." << endl << endl;


    int x[size][size];


    for(c; c > 0; c--)
    {
        for (int d=0; d<size; d++)
            for (int e=0; e<size; e++)
                infile >> x[d][e];


        square(x);
    }


    system("pause");
    return 0;
}


// This function writes the heading in the outfile.
void heading()
{
    outfile << "Trey Brumley" << endl;
    outfile << "CMPS 1063 - Johnson" << endl;
    outfile << "January 29, 2013" << endl;
    outfile << "Program 1 - Magic Squares" << endl;
    outfile << "=========================" << endl << endl;


    outfile << "This program will take a certain number of number squares as determined by the user, and it will compare the sums of each row, column, and diagonal." << endl;
    outfile << "A magic square is a square of numbers with a constant sum of each of its rows, columns, and diagonals." << endl << endl;


    return;
}


// This function will test a square one row at a time
void square (int x[size][size])
{
    infile.open("input.txt");
    outfile.open("output.txt");


    int sum = 0, sum2 = 0;
    int y=1, z=1;


    //This and the following loop will determine a sum, which will remain constant. 
    //A second sum of the next row will be determined, which will repeatedly be tested against the first sum.
    //If the sums are equal, the loop will continue to run.  If not, the function will end.
    for (y; y <= 5; y++)
        sum += x[y][z];
        while (z<5)
        {
            sum2 = 0;


            for (y=1; y<=5; y++)
                sum2 += x[y][z];


            if (sum2 != sum)
            {
                outfile << "This square is not a magic square." << endl;
                return;
            }


            else
                z++;
        }


    for (z=1; z<=5; z++)
        while (y<=5)
        {
        sum2 = 0;
        sum2 += x[y][z];
        if (sum2 != sum)
        {
            outfile << "This square is not a magic square." << endl;
            return;
        }
        else
            y++;
        }


    sum2 = 0;


    //The following loops will test diagonals.
    for (z=1; z<=5; z++)
    {
        y=z;
        sum2 += x[y][z];
        if (sum2 != sum)
        {
            outfile << "This square is not a magic square." << endl;
            return;
        }
    }


    sum2 = 0;


    for (z=1; z<=5; z++)
        {
            y=6-z;
            sum2 += x[y][z];
            if (sum2 != sum)
            {
                outfile << "This square is not a magic square." << endl;
                return;
            }
        }


    outfile << "This square is a magic square.  The constant sum is " << sum << "." << endl;


    return;
}

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