Double pointer in C?

[JonTheBaller]

How do I initialize a double pointer of type int (2D matrix) in C (**foo)?

Is new part of the C++ language?

 

[JonTheBaller]

help please

 

[singh]

Example:

const int num_rows = 5;
const int num_cols = 5;


int **pMatrix = new int [num_rows];
for(int i=0; i < num_rows; ++i)
{
pMatrix = new int [num_cols];
}


To Delete:
for(int i=0; i < num_rows; ++i)
{
delete pMatrix;
}

delete pMatrix;

 

[dighn]

new and delete are C++ keywords. and it realy should be delete [] in those cases.
also int **pMatrix = new int [num_rows]; should really be = new int*[num_rows];

instead use int **pMatrix = (int**)malloc(sizeof(int*) * num_rows);
then pMatrix(subscripti) = (int*)malloc(sizeof(int) * num_cols);

(i used (subscripti) because forum software interprets square brackets with i as italic)

and free() instead of delete

 

[JonTheBaller]

Originally posted by: dighn
new and delete are C++ keywords. and it realy should be delete [] in those cases.
also int **pMatrix = new int [num_rows]; should really be = new int*[num_rows];

instead use int **pMatrix = (int*)malloc(sizeof(int*) * num_rows);

and free() instead of delete

Do I still need to use the for loop to allocate the "inner" array?

 

[dighn]

Originally posted by: johnnytightlips

Originally posted by: dighn
new and delete are C++ keywords. and it realy should be delete [] in those cases.
also int **pMatrix = new int [num_rows]; should really be = new int*[num_rows];

instead use int **pMatrix = (int*)malloc(sizeof(int*) * num_rows);

and free() instead of delete

Do I still need to use the for loop to allocate the "inner" array?

yes you do. i fixed a little typo too

 

[Ameesh]

Originally posted by: singh
Example:

const int num_rows = 5;
const int num_cols = 5;


int **pMatrix = new int [num_rows];
for(int i=0; i < num_rows; ++i)
{
pMatrix = new int [num_cols];
}


To Delete:
for(int i=0; i < num_rows; ++i)
{
delete pMatrix[ I ];
}

delete pMatrix;

edited to show you the [ i ]

 

[singh]

new and delete are C++ keywords. and it realy should be delete [] in those cases.

Yup. I guess I ignored the "C" part in the title 🙂

 

[singh]

edited to show you the [ i ]

Thanks 🙂