Memory allocation C++

[Benzaa]

Hi,

Im working with a small class in C++. I want to create a matrix class that can store a bunch of numbers on it.

It should be easy, but im having an issue with the destructor. As soon as the program finishes, the destructor generates an error that I can not understand.

The error only happens when I use the method "set" at 1,0

Please, could someone help me with this

here is the code that I made:


//Matrix object
#include <iostream>

class Matrix {
protected:
int m_iRow, m_iCol;
double* m_pdData;
void copy(const Matrix&);

public:
Matrix(int, int);
~Matrix();
Matrix(const Matrix&);
Matrix& operator=(const Matrix&);
int nRow(void);
int nCol(void);
double get(int, int);
void set(int,int,double);
void create(void);
};

Matrix::Matrix(int a, int b) {
//Initialise the matrix with the row and column
m_iRow = a;
m_iCol = b;
create();
}

Matrix::~Matrix() {
//Deletes the space of the data
delete m_pdData;
}

void Matrix::create(void) {
//Creates container with zeros
m_pdData = new double[m_iRow*m_iCol];
}

Matrix::Matrix(const Matrix& mat) {
//Copy constructor
//Used when a copy of an object is produced
this->copy(mat);
}

Matrix& Matrix::operator=(const Matrix& mat) {
//Assignment operator function
//Overloads the equal sign operator to work
//with Matrix objects
if (this==&mat) return *this;
delete [] m_pdData;
this->copy(mat);
return *this;
}

int Matrix::nRow(void) {
//Returns number of rows
return m_iRow;
}

int Matrix::nCol(void) {
//Returns number of columns
return m_iRow;
}

double Matrix::get(int i, int j) {
//Parenthesis operator function
//Allows acces to values of matrix via (i,j)
return m_pdData[m_iCol*(i-1) + (j-1)];
}

void Matrix::set(int i,int j,double val) {
//set the value val into the matrix
if (i < m_iRow && j < m_iCol)
m_pdData[m_iCol*(i-1) + (j-1)] = val;
}

void Matrix::copy(const Matrix& mat) {
//private copy functions
//copies values from one matrix to another
m_iRow = mat.m_iRow;
m_iCol = mat.m_iCol;
int iData = m_iRow * m_iCol;
create();
for (int i=0; i<iData; i++)
m_pdData[i] = mat.m_pdData[i];
}

int main() {
int n=3;
Matrix A(n,n);
A.set(1,0,9.0);

for (int i=0; i<n; i++)
for (int j=0; j<n; j++) {
std::cout << i << "," << j << ":" << A.get(i,j) << "\n";
}

return 0;
}

[Martin Witte]

It is not the destructor but it is the get method which gives problems. Change it to

double Matrix::get(int i, int j) {
//Parenthesis operator function
//Allows acces to values of matrix via (i,j)
std::cout << i << j << std::endl;
return m_pdData[m_iCol*(i-1) + (j-1)];
}

to get a hint whats going wrong

[Benzaa]

It is not the destructor but it is the get method which gives problems. Change it to

double Matrix::get(int i, int j) {
//Parenthesis operator function
//Allows acces to values of matrix via (i,j)
std::cout << i << j << std::endl;
return m_pdData[m_iCol*(i-1) + (j-1)];
}

to get a hint whats going wrong


I found the mistake
the index had to be [m_iCol*(i) + (j)]

This small mistakes make your programing life a bit disturbing.

Thanks for the help