Hello all,

I'm having trouble with making a 2d vector array class. Would anyone have time to help with a couple of questions?

I think my problem is with overloading (). I notice that this:

```
template <typename T>
T& Array2d<T>::operator() ( int x, int y)
{
if( x >= rows || y >= cols )
{
cout << "Problem with dimensions ";
else
return matrix[x][y];
}
}
```

produces the following warning: "Control reaches end of non-void function." I googled this and it appears to mean that the thing the function SHOULD return (matrix[x][y]) is not being returned. This must mean that there is some problem with my indexing. Also, there's a segmentation fault when I try to run my code. Am I correct? If so, can anyone see what the indexing issue is?

If this is not the problem, is there something else I'm missing? I'm pretty new at this and I'm not sure that I understand the STL containers as well as I should. I read that I don't need a destructor, copy constructor or assignment operator. But an example I saw does contain a destructor (I included one just in case). Could someone clarify this? Am I missing a constructor that I do need, or is my destructor a problem?

Also, someone told me that it would be better to use 1-D vectors for making 2-D matrices than the vector "wrapper" style I have used. But I find the vector wrapper style easier to deal with. Is there a particular advantage of using the 1-D style? Is it faster, maybe?

Here is my code:

Header file

```
#ifndef ARRAY_H
#define ARRAY_H
#include <iostream>
#include <vector>
template <typename T>
class Array2d
{
private:
unsigned int rows, cols;
std::vector<std::vector<T> > matrix;
public:
// Constructors
Array2d( unsigned int rowsPub, unsigned int colsPub );
~Array2d();
// Functions
// Various functions for doing things to the matrix.
std::vector<T>& operator() ( unsigned int x, unsigned int y );
const std::vector<T>& operator() ( unsigned int x, unsigned int y ) const;
T& operator() ( int x, int y );
const T& operator() ( int x, int y ) const;
};
#endif
```

Definitions file

```
#include "Array2d.h"
#include <stdlib.h>
#include <iostream>
#include <iomanip>
#include <cmath>
#include <new>
using namespace std;
template <typename T>
Array2d<T>::Array2d(unsigned int rowsPub, unsigned int colsPub)
: matrix(rows, vector<T>(cols,0))
{
for(int i=0; i<rows; ++i)
{
matrix.push_back(std::vector<T>(cols));
}
}
template <typename T>
Array2d<T>::~Array2d()
{
}
// Functions (not included)...
template <typename T>
T& Array2d<T>::operator() ( int x, int y)
{
if( x >= rows || y >= cols || x < 0 || y < 0)
{
cout << "Problem with dimensions ";
else
return matrix[x][y];
}
}
template <typename T>
const T& Array2d<T>::operator()( int x, int y) const
{
if( x >= rows || y >= cols || x < 0 || y < 0)
{
cout << "Problem with dimensions ";
else
return matrix[x][y];
}
}
template class Array2d<int>;
template class Array2d<double>;
template class Array2d<long>;
```