Shuffle

[Oskar Linde]

Walter Bright wrote:

>     /* Shuffle the files[] array
>      */

To be nitpicky, your algorithm will not give a perfect shuffling. 
Consider shuffling the sequence 012. The algorithm has 3^3 = 27 
different ways it can shuffle the sequence, and there exists 3! = 6 
different permutations of the sequence. Since 27 isn't divisible by 6, 
the algorithm will give a slight bias towards some end sequences. 
(021,102 and 120 in this case). A quick fix is to change the first line 
of the loop body:

>     for (size_t i = 0; i < files.length; i++)
>     {
>     auto j = std.random.rand() % files.length;

       auto j = std.random.rand() % (files.length - i) + i;

>     // swap [i] and [j]
>     auto tmp = files[i];
>     files[i] = files[j];
>     files[j] = tmp;
>     }

(the last iteration will be a nop, so the loop condition could be 
changed into i < files.length-1)

Regards,

-- 
Oskar