how would you switch to pointer arithmatic?

[irishpoison]

We have to write a program that multiplies matricies, and i showed her the code below and she told me it had to use pointer arthimatic and I have no clue how to make the switch. It is probably a simple procedure but C programming and I make nothing easy...

thanks if anyone can help.

void matrix_mul( int *mat1, int *mat2, int *mat3 )
{
  int i,j,k;
  for ( i=0; i<9; i++) mat3[i]=0;
  for ( i=0; i<3; i++ )
  for ( j=0; j<3; j++ )
  for ( k=0; k<3; k++ )
   mat3[i+3*j] += mat1[i+3*k] * mat2[k+3*j];
}

[irishpoison]

i wish I could say that your post helped me Salem but my problem lies in the fact that I dont understand anything with pointer arithmatic and my teacher has been less helpful then i would like...thanks though, ill try to figure it out

[Vber]

Salem's post is trying to show you that:

mat3[i+3*j] += mat1[i+3*k] * mat2[k+3*j];

is the same as:

*(mat3 + i + 3 * j) += (*(mat3 + i + 3 * k) ) * (*(mat2 + k + 3 * j));

Well, I didn't understand your question.

[irishpoison]

oh, that makes sense...

thanks to both of you