C / C++ / MFC

Sauce! wrote:

Each element of ppArrayColumns only points to one element of pArray. As such, when we use the [] operator, the whole thing falls apart because we've managed to walk into funny memory.

Array2D<int> arr(10, 10);

int main(int, char**)
{
   for (int i=0;i<10;++i)
      std::cout << (int)arr[i] << std::endl;
   return 0;
}

~Array2D()
{
  delete []ppArrayColumns;
  delete [] pArray;
}

Stuart Dootson wrote:

I think you'll find that's the way C/C++ arrays work - they are just pointers really. Your code works fine - when I run this code, it prints out addresses that are 40 bytes apart, which is what I'd expect for rows of 10 ints.

Array2D<int> arr(10, 10);

int main(int, char**)
{
   for (int i=0;i<10;++i)
      std::cout << (int)arr[i] << std::endl;
   return 0;
}</int>

main.cpp<br />
<br />
<pre>#include <iostream><br />
#include "Array2D.h"<br />
<br />
typedef unsigned int UINT;<br />
using namespace std;<br />
<br />
int main()<br />
{<br />
	UINT width = 3, height = 5;<br />
	Array2D<int> *theArray;<br />
	theArray = new Array2D<int>(width, height);<br />
<br />
<br />
        //Get input to fill theArray<br />
	for(UINT i = 0; i < width; i++)<br />
	{<br />
		for(UINT j = 0; j < height; j++)<br />
		{<br />
			cout << " [" << i << "][" << j << "]:";<br />
			int temp = 0;<br />
			cin >> temp;			<br />
			*theArray[i][j] = temp;<br />
		}<br />
		cout << "\n";<br />
	}<br />
<br />
        //Print the contents of theArray<br />
	for(UINT i = 0; i < width; i++)<br />
	{<br />
		for(UINT j = 0; j < height; j++)<br />
		{<br />
			int temp = 0;<br />
			temp = *theArray[i][j];<br />
			cout << temp << " ";<br />
		}<br />
		cout << "\n";<br />
	}<br />
	<br />
	return 0;<br />
}</pre><br />
You'll find that we are able to assign <code>temp

Stuart Dootson wrote:

Also - your template class won't really be usable, as your client code won't be able to instantiate the size constructor or destructor - you don't define template class methods in .cpp files!

Sauce! wrote:

*theArray[i][j]

Sauce! wrote:

Can anyone link me to a good article that explains why template functions must be defined in the header

Stuart Dootson wrote:

why the * - the dereference is implied when you use array indexing.

Sauce! wrote:

Error 1 error C2440: '=' : cannot convert from 'int' to 'int *' c:\users\bryce\documents\visual studio 2008\projects\array2d\array2d\main.cpp 20

visual studio tells me otherwise

The real reason is that theArray is a pointer to an object of type Array2D. Re-read the code and it makes sense.

Array2D<int> theArray(width, height);

class someclass
{
public:
     someclass();
     ~someclass();

private:
     Array2D<int> *myArray;
};

someclass::someclass(UINT width, UINT height)
{
     myArray = new Array2D<int>(width, height);
}

someclass::~someclass()
{
     delete myArray;
}

class someclass
{
public:
     someclass(UINT width, UINT height):myArray<int>(width)(height);
     ~someclass();

private:
     Array2D<int> myArray;
};

someclass::~someclass()
{

}

blokkies wrote:

Don't i need to create the .exe?

blokkies wrote:

How do I create an .exe for this new project?

blokkies wrote:

I am using Visual C++ 6.0.