From: Love U Ruby <lists@...>
Date: 2013-02-21T19:19:46+09:00
Subject: How does Array#shuffle! works in ruby?

Here I was trying to see how Array#shuffle! works with array objects. So
I started playing with it in my IRB:

[1,2,3]
#=> [1, 2, 3]
[1,2,3].shuffle!
#=> [3, 1, 2]

In the above code I understood how it works. And the below I was trying
to play with it more hard-way to see it from every corner.

[1,2,5]
#=> [1, 2, 5]
[1,2,5]<<[1,2,5]
#=> [1, 2, 5, [1, 2, 5]]

Till now I am good.

[1, 2, 5, [1, 2, 5]].shuffle!
#=> [5, 1, 2, [1, 2, 5]]

With above piece of code I have confusions. So below the questions came
in my head:

    (a) Why shuffle! not worked recursively? As I expected that the
output of the inner array [1, 2, 5] also will be shuffled. But not
happened.

    (b) Why does shuffle! not shuffle the element array [1, 2, 5] ,
rather works only with the 1, 2, 5, elements of the array [1, 2, 5, [1,
2, 5]] ? I thought the output would come as [[1, 2, 5],5, 1, 2]. So why
the element array didn't change it's position,rather the normal elements
did only?


Very interesting behavior it is showing:

a=[1,2,4]
#=> [1, 2, 4]
a<<[7,8]
#=> [1, 2, 4, [7, 8]]
a.shuffle!
#=> [[7, 8], 1, 4, 2]
a.shuffle!
#=> [4, 1, [7, 8], 2]
a.shuffle!
#=> [[7, 8], 2, 1, 4]
irb(main):006:0>

Does the shuffling really follow any order or its a random shuffling?

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