Re^2: array shuffle

I'm trying to test my skills without using the shuffle function. I was def using the wrong loop.

Here's my problem now though, I want to shuffle the "deck" twice.

using the while (@deck) I can get the deck shuffled once, but when I use:

@hand = shuf(@deck);

print "deck shuffled once:\n";
print"@hand\n";

@deck = @hand;
@newhand = shuf(@deck);

print"deck shuffled twice:\n";
print"@newhand\n";
[download]

I don't get the result I'm hoping for, what am I doing wrong now?

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Re^3: array shuffle by davido (Cardinal) on Aug 18, 2011 at 04:19 UTC
Assuming that shuffling is simple is a mistake, and yet once you see an unbiased algorithm on paper (or screen) you will probably say, "Oooh, I get it." But done wrong, shuffling can introduce bias, and it's easy to do wrong. There is a nice article on Wikipedia: Fisher-Yates Shuffle. Implemented as a computer algorithm, it is sometimes known as the Knuth Shuffle. Also looking at the Pure Perl version of List::Util (here: Source for List::Util::PP) you will see a Perlish implementation of Fisher-Yates. Another post here pointed you to perlfaq4, which shows another Fisher-Yates implementation that is easier to read than the List::Util::PP version. For the masochistic or exceptionally curious: The Art of Computer Programming vol. 2 (3rd ed.), pg 145-146. Dave	[reply]
Re^3: array shuffle by jwkrahn (Abbot) on Aug 18, 2011 at 04:02 UTC
See the FAQ How do I shuffle an array randomly? for a shuffle algorithm.	[reply]
Re^3: array shuffle by ikegami (Patriarch) on Aug 18, 2011 at 06:03 UTC
You're using a global variable which you empty the first time around instead of passing the deck to your function. You need to properly scope your variables.	[reply]