On Mon, 7 Oct 2002, Fogle Cpl Shawn B wrote:
> I have studied
> the fisher_yates_shuffle but I can't seem to implement it to save my life.
> It would help quite a bit if I understood what "@$" is and how to
> effectively use it. I don't see it in the beginners manual (and haven't
> searched the perldocs yet). Please feel free to diff me any improvements you
> have, I'd love to see what improvements can be made (be it known I am
> working on the short getopts).
>
> Thanks in advance
> shawn
I will post the parts of your code that can be changed along with my
comments.
$SIG{'INT'} = 'terminate';
# This is better written as $SIG{'INT'} = \&terminate;
# perldoc perlipc, look at the first page
sub find_flac { foreach (@root) { find ( \&wanted, "$_" ); } }
# You don't need the foreach here, the second argument to find is a list
# this can be rewritten as find (\&wanted, @root)
# perldoc File::Find
sub wanted {
if ( /\.(flac)$/ ) { push (@music_list, "$File::Find::dir/$_\n") }
}
# You are pushing a string with a newline only to chomp it later on, why so?
# $File::Find::name contains the complete pathname to the file, you don't need
# a $File::Find::dir/$_
sub random { my $music_phile = $_[rand @_]; }
# The @$ is used to get to the array from the array reference that is
# passed into the sub. I will explain the code as given in
# perldoc -q shuffle
sub fisher_yates_shuffle {
my $deck = shift; # $deck is a reference to an array
my $i = @$deck; # @$deck gets to the array from the reference
# In scalar context this will give the number
# of elements in the array.
while ($i--) {
my $j = int rand ($i+1);
# perldoc -f rand, rand returns a value greater than or equal to 0
# and less than it's argument. In this case, greater than or equal to 0
# and less than the current index + 1. This makes sure that the indices
# that have been shuffled do not get shuffled again
@$deck[$i,$j] = @$deck[$j,$i];
# This is how you swap array elements in perl. Swap the value of the
# current index with the one returned from rand.
# This style (@$deck[$i,$j]) is called an array slice
}
}
# You also have a choice to use the shuffle function from List::Util.
# You can get this module from
# http://search.cpan.org/author/GBARR/Scalar-List-Utils-1.0701/
# You can shuffle your array by including this function and calling
# it as fisher_yates_shuffle (\@music_list)
sub count { foreach (@music_list) { $flac_count++; }; }
# @music_list used in a scalar context will give you the no of elements in that array.
# You don't need the foreach loop here just a $flac_count = @music_list should do
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