Giving error at accessing the array, in

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Giving error at accessing the array, in

Giving error at accessing the array, in a class Matrix

Mar 27, 2020 at 10:42am

Please see the following code

#include<iostream>
#include<ctime>
using namespace std;
class Matrix
{
public:
	Matrix();
	Matrix(int r, int c);//----------overloaded
	Matrix(const Matrix &obj);
	~Matrix();
	//
	Matrix Add(Matrix m);
	Matrix Subtract(Matrix m);
	void input();
	void Print_Matrix();
	void Print(); 
private:
	int** p;
	int rows;
	int cols;
};
Matrix::Matrix()
{
	rows = 2;
	cols = 2;
	p = new int*[2];
	for (int i = 0; i < 2; i++)
		p[i] = new int[2];
}
Matrix::Matrix(int r, int c)
{
	rows = r;
	cols = c;
	p = new int*[rows];
	for (int i = 0; i < rows; i++)
		p[i] = new int[cols];
}
Matrix::Matrix(const Matrix &obj)
{
	this->rows = obj.rows;
	cols = obj.cols;  
	this->p = new int*[obj.rows]; 
	for (int i = 0; i < obj.rows; i++)
		p[i] = new int[obj.cols]; 

	for (int i = 0; i < obj.rows; i++)
	{
		for (int j = 0; j < obj.cols; j++)
			p[i][j] = obj.p[i][j]; 
	}

}
Matrix Matrix::Add(Matrix m) 
{
	Matrix P(rows, cols);
	if (rows == cols)
	{
		for (int i = 0; i < rows; i++)
		{
			for (int j = 0; j < cols; j++)
			{
				P.p[i][j] = this->p[i][j] + m.p[i][j];
			}
		}
		return P;
	}
	else
	{
		cout << "CAN'T BE ADDED\n";
		return P;
	}
}
Matrix Matrix::Subtract(Matrix m) 
{
	Matrix Q(rows, cols);
	if (rows == cols)
	{
		for (int i = 0; i < rows; i++)
		{
			for (int j = 0; j < cols; j++)
			{
				Q.p[i][j] = this->p[i][j] - m.p[i][j];  
			}
		}
		return Q;
	} 
	else
	{
		cout << "CAN'T BE SUBTRACTED\n";
		return Q;
	}
}
void Matrix::input()
{
	cout << "INPUT :\n";
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < cols; j++)
		{
			this->p[i][j] = rand() % 10 + 1;
		}
	}
}
void Matrix::Print_Matrix()
{
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < cols; j++)
		{
			cout << "i: " << i << endl << "j: " << j << endl; 
			cout << this->p[i][j] << " ";
		}
		cout << endl;
	}
}
Matrix::~Matrix()
{
	for (int i = 0; i < rows; i++)
	{
		delete p[i];
	}
	delete[] p;
}

int main()
{


	int rows = 0, cols = 0;
	cout << "ENTER ROWS AND COLUMNS :";
	cin >> rows >> cols;
	if (rows == cols)
	{
		Matrix p1(rows, cols);
		Matrix p2(p1), p3(p1);
		cout << "ENTER FOR 1st:\n";
		p1.input();
		cout << endl;
		p1.Print_Matrix();

		cout << "ENTER FOR 2nd :\n ";
		p2.input();
		cout << endl;
		p2.Print_Matrix();

		cout << "ADDED :\n";
		p3 = p1.Add(p2);
		cout << endl;
		p3.Print_Matrix();
		cout << endl;
		cout << "SUBTRACTED :\n";
		p3 = p1.Subtract(p2);
		cout << endl;
		p3.Print_Matrix();

	}
	else
	{
		cout << "SIZES ARE DIFFERENT";
		return 0;
	}


	getchar();
	return 0; 
}

Edit & run on cpp.sh

What it is doing is this that it is calling the destructor of Local Variable (P) made in "Add" function BEFORE copying the values of "P" in "p3" in int main...

I want to store the result of the add function in my int main object "p3" but because "P"'s destructor is already called... the result don't get stored and so, the compiler is giving error when it tries to print values of "p3".

anyone who probably can help solving this?

Last edited on Mar 27, 2020 at 11:27am

Mar 27, 2020 at 10:58am

Repeater (3046)

What's the problem? What does it do that you wish it didn't do, or what does it not do that you wish it did?

Mar 27, 2020 at 11:08am

lastchance (6980)

Write a copy assignment operator.
https://en.cppreference.com/w/cpp/language/rule_of_three

Mar 27, 2020 at 11:26am

sindhu05 (32)

Topic archived. No new replies allowed.

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Giving error at accessing the array, in a class Matrix