MATRIXES - Dinamic Memory

[Jose Garcia]

Hi there,

Can somebody explain me how can i use matrixes with dinamic memory? I
use malloc and free (NOT new & delete). I want to access to the matrix
like Matrix[r][c] but i don't know how to do that with pointers and
malloc & free...

If I declare 4 statics matrixs of 576x720, the program brokes down (how
is it posible!?), so i must use dinamic memory (i suppose)...

Can somebody help me?


Txs a lot! ;)
Good luck for all time

[Phil Staite]

The usual way to implement [][] syntax is something like this:
class Row
{
public:

int& operator[]( int colIndex );
int operator[]( int colIndex ) const;

private:

// some collection of data (vec/deq)

};
class Matrix
{
public:

Row& operator[]( int rowIndex );
const Row& operator[]( int rowIndex ) const;

private:

// some collection of Row object (eg. std::vector or std::deque)

};

Jose Garcia wrote:

Hi there,

Can somebody explain me how can i use matrixes with dinamic memory? I
use malloc and free (NOT new & delete). I want to access to the matrix
like Matrix[r][c] but i don't know how to do that with pointers and
malloc & free...

If I declare 4 statics matrixs of 576x720, the program brokes down (how
is it posible!?), so i must use dinamic memory (i suppose)...

Can somebody help me?


Txs a lot! ;)
Good luck for all time

[E. Robert Tisdale]

Jose Garcia wrote:

Can somebody explain [to] me how can I use matrixes with dinamic memory?
I use malloc and free (NOT new & delete).
I want to access to the matrix like Matrix[r][c]
but I don't know how to do that with pointers and malloc & free.

If I declare 4 static matrices of 576x720,
the program breaks down (How is it possible?)
So I must use dinamic memory (I suppose).
Try increasing the stack size limit first.
Can somebody help me?

Try using a matrix class library.
Take a look at
The C++ Scalar, Vector, Matrix and Tensor class Library

http://www.netwood.net/~edwin/svmtl/

Then, take a look at
The Object-Oriented Numerics Page

http://www.oonumerics.org/oon/

[Axter]

> Can somebody explain [to] me how can I use matrixes with dinamic
memory?

I use malloc and free (NOT new & delete).
I want to access to the matrix like Matrix[r][c]
but I don't know how to do that with pointers and malloc & free. If I declare 4 static matrices of 576x720,
the program breaks down (How is it possible?)
So I must use dinamic memory (I suppose).

Use a class who's operator[] returns a pointer to the type.
Example:
template < class T>
class dynamic_2d_array
{
public:
dynamic_2d_array(int row, int col):m_row(row),m_col(col),
m_data((row!=0&&col!=0)?new T[row*col]:NULL){}
dynamic_2d_array(const
dynamic_2d_array&src):m_row(src.m_row),m_col(src.m _col),
m_data((src.m_row!=0&&src.m_col!=0)?new T[src.m_row*src.m_col]:NULL){
for(int r=0;r<m_row;++r)for(int c=0;c<m_col;++c) (*this)[r][c] =
src[r][c];
}
~dynamic_2d_array(){if(m_data) delete []m_data;}
inline T* operator[](int i) {return (m_data + (m_col*i));}
inline T const*const operator[](int i) const {return (m_data +
(m_col*i));}
protected:
dynamic_2d_array& operator=(const dynamic_2d_array&);
private:
const int m_row;
const int m_col;
T* m_data;
};

For more information, check out the following link:
http://www.tek-tips.com/faqs.cfm?fid=5575