Array Nil, can't figure out why

Ruby
1

The array init becomes nil and so it would never enter the if condition,
any ideas why?

2

In ruby, you can think of variables as referencing to objects. When you
write

deck = init = Array(1…cards)

You are creating a new Array object, and let both deck and init point to
that object. During your loop, you are creating a new array, filling it
and emptying the original array.

deck = table

Deck now points to the newly created array, but init still points to the
array created initially, which is now empty.

To fix this, you can write either

deck = Array(1…cards)
init = Array(1…cards)

or

init = Array(1…cards)
deck = init.clone

or if you really want to do it in one line

deck = (init = Array(1…cards)).clone

Your program then outputs

Woot!!! It took 6 tries.

Also, here’s a slightly shorter version of the program:

i = 0
cards = 10
deck = Array(1…cards)
init = Array(1…cards)

while init!=deck || i==0
table = []
cards.times do
table.unshift(deck.shift)
deck.push(deck.shift)
end
deck = table
i += 1
end

puts “Woot!!! It took #{i} tries.”

3

Thank you dude ! Very helpful :slight_smile:

4

Perhaps I should add that Array#clone only performs a shallow copy. It
won’t clone any of the array’s elements. Consider the following code
example:

x = [0,1,[2,3]]
y = x.clone
y[0] = 9
y[2][1] = 9
p x
p y

This will produce

[0,1,[2,9]]
[9,1,[2,9]]