variable length arrays as arguments to functions

[Alcino Dall Igna Junior]

As I see, in fact, matrices doesn't exist, so, the easiest way seems to
me to be:

On Tue, 2003-06-03 at 05:28, Maarten Speekenbrink wrote:
> I am trying to write a function in c++ that takes a square matrix of variable dimension as its argument. I read in the manual that this should be possible in g++. However, I am experiencing some trouble. I am a novice in c++, so it could be in my code or in the compiler. For instance, when I try the code below, I get an error for the function declaration that N is not specified. Is there a way to write functions for variable-size two dimensional arrays? (I am using the Mingw port of g++). 
> Thanks for your help,
> Maarten
> 
> // Program
> 
> #include <iostream>
> using namespace std;
> 
> void MyFunc(int N, float my_matrix[N][N])
  void MyFunc(int N, float my_matrix[])
> 
> int main()
> {
>     float Q[5][5] = {
>         {0.90, 0.85, 0.70, 0.85, 0.70},
>         {0.85, 0.90, 0.70, 0.85, 0.70},
>         {0.60, 0.60, 0.90, 0.60, 0.60},
>         {0.60, 0.60, 0.60, 0.90, 0.60},
>         {0.50, 0.50, 0.50, 0.50, 0.50}
>     };
    float Q[5*5] = {
       0.90, 0.85, 0.70, 0.85, 0.70,
        0.85, 0.90, 0.70, 0.85, 0.70,
        0.60, 0.60, 0.90, 0.60, 0.60,
        0.60, 0.60, 0.60, 0.90, 0.60,
        0.50, 0.50, 0.50, 0.50, 0.50
    };

> 
>     MyFunc(5, Q);
> 
>     return 0;
> 
> }
> 
> void MyFunc(int N, float my_matrix[N][N])
  void MyFunc(int N, float my_matrix[]) 
> {
      int size = N * N;
> 
>     for (int i=0; i<N; i++){
      for (int i=0; i< size; i+=N){
>         float sum = 0;
> 	  for (int j=0; j<N; j++) {
>             sum = sum + Q[i][j];
              sum = sum + Q[i+j];
>         }
>         cout << "Rowsum is: " << sum << '\n';
>     }
> }
> 
> 
In this way the changes are minimal, as clear as, and more efficient,
or in a even more efficient way, it could be done using pointers
directly.

The use of many indexes appear to be clearer, but adds a lot of
overhead, what is not the C/C++ way.

>        
> ---------------------------------------------------------------------
>   Maarten Speekenbrink
>   Psychological Methodology
>   Department of Psychology, Faculty of Social and Behavioral Sciences
>   address: Roetersstraat 15, 1018 WB Amsterdam, Netherlands
>   tel: +31 20 525 6876 / +31 20 525 6870
>   fax: +31 20 639 0026
> ---------------------------------------------------------------------
> 
>