Question

Here we are once again good people of the internet.

This is the code I’m using:

//This is what is in the header file
int *myArr[]; // A two-dimensional array representing holding the matrix data

//This is what is in the definition file
Matrix::Matrix(int n, int m)
{
    myRows = n;
    myColumns = m;
    initialize();
}

void Matrix::initialize()
{
    *myArr = new int[myRows];

    for (int i=0; i < 3; i++)//Only set to 3 since myRows is acting crazy
    {
        myArr[i] = new int[myColumns];
    }
}

For some reason when I use myRows variable to create the myArr array it just seems to stop referencing the value it was pointing towards before.

For instance I give it the value 3 and after the *myArr = new int[myRows] has been executed it changes the value of myRows to 9834496, which I don’t understand.

Does the “new” de-reference the variable or something?
Or am I doing something wrong?

Oh and since this is a school practice project (so I won’t blame you if you don’t answer) I would prefer an answer over working code, so that I could know what I did wrong for future projects.

Answer 1

int *myArr[];

This is wrong! You’ve to tell the compiler the size also, of your array of pointer. How about if you declare int a[]. You’re telling the compiler to create an array of int, of unknown size, which is not allowed in C++. That is why you cannot do that.

I would suggest you to do this:

int **myArr;

void Matrix::initialize()
{
    myArr = new int*[myRows]; //note int* here!

    for (int i=0; i < myRows; i++)
    {
        myArr[i] = new int[myColumns];
    }
}

This should work now.