Re: Is Linux Unix?

[Jeronimo Pellegrini <pellegrini@mpcnet.com.br>]

> There's another problem with the above C++ code:  If ny and nz
> aren't constant, you can't write
> 
>     double s[ny][nz];
> 
> Instead, either you allocate the array in two stages:
> 
>     double** s = new (double*)[ny];
>     for (j=0; j < ny; ++j) s[j] = new double[nz];

Actually, the first version works -- and both C and C++ (tested here with
gcc -- not sure it it became a standard or not)) will dynamically allocate
memory for you. Try this:

#include <iostream>

using namespace std;

int main() {
        int size1, size2, i, j;
        cin >> size1;
        cin >> size2;
        double vec[size1][size2];

        for (i=0; i<size1; i++)
                for (j=0; j<size2; j++)
                        vec[i][j] = i+j;
        cout << endl;
        for (i=0; i<size1; i++) {
                for (j=0; j<size2; j++)
                        cout << vec[i][j] << " ";
                cout << endl;
        }
}

And enter something like "1000" and "1000" when asked for the array dimensions.
It compiles, runs, and does not segfault! :-)

The C version:

#include<stdio.h>

int main() {
        int size1, size2, i, j;
        scanf("%d", &size1);
        scanf("%d", &size2);
        double vec[size1][size2];

        for (i=0; i<size1; i++)
                for (j=0; j<size2; j++)
                        vec[i][j] = i+j;
        puts("");
        for (i=0; i<size1; i++) {
                for (j=0; j<size2; j++)
                        printf("%f ",vec[i][j]);
                puts("");
        }
}

J.