Matrices and pointers

[Compulsive D]

HI all,

I'm trying to compile the following code:

void fibFillMat(int mat[][COL], int n)
{
	int position=1;
	int temp=1;
	int i;
	**mat=0; //First number is zero
	for(i=1;i<=n;i++)
	{
		*(*(mat+i))=(position*i);
		position+=temp; //finds next relevant position
		temp=*(*(mat+i));
		*(mat+i)+=(position-temp); //moves the pointer to next relevant position
	}
}

The function is supposed to fill a matrix with the Fibonacci sequence.

The error i get is:

"invalid operands to binary + (have ‘int[3]’ and ‘int’)"

(I use Eclipse for Linux).

I'm obviously new to this pointers thing, but i'm pretty sure *(mat+i) points to another pointer wich i can increment, right?

so i can't understand why it's not compiling.

[kmdv]

*(mat + i) += position - temp; //moves the pointer to next relevant position

When you dereference mat+i you get an array. I'm a little bit confsued, because I don't know what is supposed to be your 'pointer'. Do you want to modify 'mat' pointer?
The array should be 1-dimentional:

void fibFillMat(int mat[], int n);

Then you can use:

++mat;

To get the next position.

[Compulsive D]

When you dereference mat+i you get an array. I'm a little bit confsued, because I don't know what is supposed to be your 'pointer'. Do you want to modify 'mat' pointer?

Basically, i'm trying to move inside the 'i' row in the matrix mat.
In my understanding, *(mat+i) gives me the address of the beginning of row 'i' in the matrix.

Am i wrong?

[Bayint Naung]

mat is pointer to an array of COL int.
so *(mat+i) = mat[i] is an array of COL int.
And you cannot modify array. like int array[10];
array++; array += 1; all will produce compiler error.

[kmdv]

Basically, i'm trying to move inside the 'i' row in the matrix mat.
In my understanding, *(mat+i) gives me the address of the beginning of row 'i' in the matrix.

Am i wrong?

I still don't get why you need NxM array instead of N array. Yes, it indeed gives this address, but this is just address of array.

EDIT:
<mat points here>[0,0][0,1][0,2][0,3][0,4]<mat + 1 points here>[1,0][1,1][1,2][1,3][1,4]<mat + 2 points here>[2,0][2,1][2,2][2,3][2,4]

You get address mat+1, but this is not a pointer which you can modify, it's just an array.