Help with a class

[Xilonian]

Im supposed to write a class to do various matrix operations. The class has a 2d array to represent the matrix. It uses an add method to add 2 matrices together. The method takes a matrix as it's argument and returns a matrix.

Ignore the first 2 constructors as they have no relation to the methods.
The error is in the add method when i try to use the Matrix argument. I have commented the program for reference. The error only shows up when i use anotherMatrix[i][j].

#include<iostream>
#include<iomanip>
#include<cmath>
#include<cstdlib>

using namespace std;

// The Matrix class definition goes here
class Matrix
{
	public:
                //Constructors
		Matrix();
		Matrix(int, int);
		Matrix(int[][5], int, int);
		//Methods
                void print();
		Matrix add( Matrix );
		Matrix subtract( Matrix );
		//counter variables
                int i;
		int j;
		
		
	private:
                //Constants for maximum array size of 5
  		#define maxRows 5
  		#define maxCols 5
                //The matrix for the class
  		int matrixArray[maxRows][maxCols];  
                //Variables to represent the actual array size (most arrays will not be maximum size)
  		int actualRows, actualCols;
};

//Constructor 1 sets the matrix size to the maximum and initializes it to 0's
Matrix::Matrix()
{
	actualRows=maxRows;
	actualCols=maxCols;

//	  matrixArray[actualRows][actualCols]={0};
	for(i=0;i<actualRows;i++)
	{
		for(j=0;j<actualCols;j++)	 
		{
		matrixArray[i][j]=0;
		}
	}
	
}

//Constructor 2 sets the matrix size to the passed in values and initializes it to 0's
Matrix::Matrix( int newNumRows, int newNumColumns )	
{
	if( newNumRows <=maxRows)
	{
		actualRows=newNumRows;
	}
	else
	{
		actualRows=maxRows;
	}
	
	if( newNumColumns <=maxCols)
	{
		actualCols=newNumColumns;
	}
	else
	{
		actualCols=maxCols;
	}   
}

//Constructor 3 sets the matrix size to the passed in values and initializes it with the passed in 2D array
Matrix::Matrix( int ar[][5], int arRows, int arColumns )
{
	if( arRows <=maxRows)
	{
		actualRows=arRows;
	}
	else
	{
		actualRows<maxRows;
	}
	
	if( arColumns <=maxCols)
	{
		actualCols=arColumns;
	}
	else
	{
		actualCols=maxCols;
	}   
	
	ar[actualRows][actualCols]=matrixArray[actualRows][actualCols];
	
	for(i=0;i<actualRows;i++)
	{
		for(j=0;j<actualCols;j++)	 
		{
		matrixArray[i][j]=ar[i][j];
		}
	}
	
}

int main()
{
	//declaring various 2d arrays for use in the class
	int ar1[5][5] = {{0,1,2},
                 {9,8,7}};

	int ar2[5][5] = {{6,5,4},
                 {3,4,5}};

	int ar3[5][5] = {{-1,2,0,15,9},
                 {0,3,6,7,-11},
                 {-4,50,12,0,6},
                 {1,1,1,1,1},
                 {-8,16,4,6,22}};

	int ar4[5][5] = {{0,-4,3},
                 {9,-4,-3}};

	int ar5[5][5] = {{1,2,3,4,5},
                 {2,3,4,5,6},
                 {3,4,5,6,7},
                 {4,5,6,7,8},
                 {5,6,7,8,9}};

	int ar6[5][5] = {{7,8},
                 {9,10},
                 {11,12}};

	
        //the following line copies array 3 to the array declared in the class
	Matrix m3( ar1, 2, 3);
        
        
	<< "Test 2: add method" << endl << endl;

	Matrix m4( ar4, 2, 3);
	
	cout << "Matrix m3 contains" << endl;
	m3.print();

	cout << endl << endl << "Matrix m4 contains" << endl;
	m4. print();
	
	cout << endl << endl << "The result of adding matrices m3 and m4" << endl;

	m5 = m3.add( m4 );

	return 0;
}

// Code the Matrix class methods below this line


void Matrix::print()
{
	cout<<"\n\n";	 
	for(i=0;i<actualRows;i++)
	{
		for(j=0;j<actualCols;j++)
		{
			cout<<matrixArray[i][j]<<"   ";
		}	 
		cout<<"\n";
	}
}


Matrix Matrix::add( Matrix anotherMatrix )
{
	int aMatrix[3][3];
	
	for(i=0;i<actualRows;i++)
	{
		for(j=0;j<actualCols;j++)
		{
//error is here: No match for operator[] in anotherMatrix[((Matrix*)this)->Matrix::i]
	    	aMatrix[i][j]=anotherMatrix[i][j]+matrixArray[i][j];
		}
	}  	   
}
	

[keskiverto]

Like the error says: class Matrix does not have operator[]. If it would have, then the probable error would be that the return type of Matrix::operator[] (size_t) does not have operator[].

Just try in main

Matrix m42;
cout << m42[0];

Within add() you can get around the error because it is a member function and has therefore access to members:
aMatrix[i][j] = anotherMatrix.matrixArray[i][j] + this->matrixArray[i][j];

Your add() has more problems though:
1. this and anotherMatrix might be of different size.
2. int aMatrix[3][3];
3. no return of value

[Xilonian]

Thanks for the quick reply. I will try what you suggested.

As for the last 3 things I know about them and will be fixing them.

[Xilonian]

I am having trouble returning the matrix back to the main function. In the info from the prof it states: "This method adds a Matrix object to another Matrix object. It takes a Matrix object as its argument and returns a Matrix object."

I have done searching and everywhere i go i am told returning a 2d array is not possible. This line of code was supplied by the prof: m5 = m3.add( m4 );
It indicates that after the member is called a matrix array should be returned to m5. But I cant seem to do this.

[keskiverto]

You have to create a Matrix object in the function and return that one object.

Matrix foo()
{
  Matrix m42;
  // fill m42 with meaningful data
  return m42;
}