Re: Fisher-Yates shuffle

[_brian_d_foy]

In article <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> wrote:

> I'd prefer to just fix the error in fy1, and put
> 
>        sub fy1 {
>            my $deck = shift;  # $deck is a reference to an array
>            my $i = @$deck;
>            while ($i--) {
>                my $j = int rand ($i+1);
>                @$deck[$i,$j] = @$deck[$j,$i];
>            }
>        }

and here's the proposed patch for comments:

localhost_brian[3004]$ cvs diff -u -d perlfaq4.pod
Index: perlfaq4.pod
===================================================================
RCS file: /cvs/public/perlfaq/perlfaq4.pod,v
retrieving revision 1.19
diff -u -d -r1.19 perlfaq4.pod
--- perlfaq4.pod        11 Mar 2002 22:15:19 -0000      1.19
+++ perlfaq4.pod        4 Apr 2002 17:59:34 -0000
@@ -1335,28 +1335,21 @@
 If you either have Perl 5.8.0 or later installed, or if you have
 Scalar-List-Utils 1.03 or later installed, you can say:
 
-        use List::Util 'shuffle';
+    use List::Util 'shuffle';
 
        @shuffled = shuffle(@list);
 
-If not, you can use this:
+If not, you can use a Fisher-Yates shuffle.
 
-    # fisher_yates_shuffle
-    # generate a random permutation of an array in place
-    # As in shuffling a deck of cards
-    #
     sub fisher_yates_shuffle {
         my $deck = shift;  # $deck is a reference to an array
         my $i = @$deck;
-        while (--$i) {
+        while ($i--) {
             my $j = int rand ($i+1);
             @$deck[$i,$j] = @$deck[$j,$i];
         }
     }
 
-And here is an example of using it:
-
-    #
     # shuffle my mpeg collection
     #
     my @mpeg = <audio/*/*.mp3>;