Question

I am working on an exercise in operator overloading. I’ve created a matrix class and I am supposed to overload operators so I can do arithmetic on matrices efficiently.

My directions say that I am supposed to make two matrix arrays using the class constructor that has 2 parameters and a third matrix array that will be used to store the result of arithmetic using the default constructor (1 parameter).

Since I am going to use these arrays to overload operators they are going to need to be data members of the class (I think). However, I thought that classes were supposed to be as representative of real life things as possible so making a matrix class with multiple arrays doesn’t make sense to me (a matrix is only one matrix).

Am I misunderstanding classes or is there a different way to make additional matrices using the class constructor I am not thinking of? Thanks all, here is the code in question.

class matrix
{
    friend ostream& operator << (ostream&, const matrix&); // << overloader 

    private:
    int size // size indicates length of rows and cols, so size 3 means a 3 x 3 matrix
    int array[10][10];

    public:
    matrix(int);
    matrix(int, int);
};

matrix:: matrix (int sizeIn) //default constructor, use to make result matrix
{
    int MAX_SIZE = 10;

    if (0 > sizeIn && sizeIn > 10)
    {
     size = MAX_SIZE;
    }
    else
    {
     size = sizeIn;
    }

    for (int i = 0; i < size; i++)
        for (int j = 0; j < size; j++)
             array[i][j] = 0;
}

matrix:: matrix (int sizeIn, int rangeIn) //use to make first 2 matrices that will be added
{
    int range;
    int MAX_SIZE = 10;
    int MAX_RANGE = 20;

    if (0 > sizeIn && sizeIn > 10)
    {
     size = MAX_SIZE;
    }
    else
    {
     size = sizeIn;
    }

    if (0 > rangeIn && rangeIn > 20)
    {
      range = MAX_RANGE;
    }
    else
    {
     range = rangeIn;
    }

    for (int i = 0; i < size; i++)
        for (int j = 0; j < size; j++)
            array[i][j] = (rand() % (2 * range + 1) - range); //random number for each index
}

ostream & operator << (ostream & os, const matrix & arrayPrint) // << overloader
{
    for (int i = 0; i < arrayPrint.size; i++)
    {
        cout << '|';
        for (int j = 0; j < arrayPrint.size; j++)
            {
            os << setw(4) << arrayPrint.array[i][j] << " ";
            }
        os << setw(2) << '|' << endl;
    }
return os;
}

Answer 1

You are misunderstanding the question. You are required to make a Matrix class that has 1 two dimensional array and then use the constructor to make two different matrices and then add them and store the result into a third one. So you will end up with something like this

    matrix::matrix(int Size, int Range)
    {
         if(Range < 0 || Range > RANGE_MAX)
             Range = RANGE_MAX;

         if(Size < 0 || Size > SIZE_MAX)
             Size = SIZE_MAX;

        for (int i = 0; i < Size; i++)
            for (int j = 0; j < Size; j++)
               array[i][j] = (rand() % (2 * Range + 1) - Range);
    }

Then you will make two matrices A and B as follows

matrix A(4,10); // Create a Matrix A size 4 with random entries in range of 10
matrix B(3,8); // Create a Matrix B with size 3 with random entries in range of 8

You will then overload the = operator and + operator to let you do the following (of course you need to check if the sizes allow the operation first)

matrix C = A + B

To overload the “=” operator

matrix& matrix::operator=(const matrix &rhs)
{
   // if we have A = B then A is me and B is the rhs
   // assuming all members are public you might need to write get/set functions
   size = rhs.size;         // my size equals the right hand side's size
   range = rhs.range;
   for(int i = 0; i < size; i++)
     for(int j = 0; j < size; j++)
        array[i][j] = rhs.array[i][j];

    return *this;   // return me
}