From: "Jan E." <lists@...>
Date: 2012-06-11T07:25:54+09:00
Subject: Re: Beginner question: Bubble sort using array.each_index

Hi,

You misunderstand the code. "first" and "second" aren't fixed values. 
They are the block parameters belonging to the two iterators, so their 
value will change on each iteration.

Have a look at the outer iterator first:

array.each_index do |first|

end

This iterator loops over the indices of "array". On each iteration, the 
current index is assigned to the "first" parameter. So if array is ['x', 
'z', 'y'] for example, the parameter will be assigned the values 0, 1 
and 2 subsequently.

You can test this:

array.each_index do |first|
  puts first
end

Then there is also an inner iterator, which also loops over the indices 
of array. This means: While the outer iterator is going through the 
indices 0, 1, 2, 3, ..., the inner iterator will do the same on every 
step.

See for yourself:

array.each_index do |first|
  array.each_index do |second|
    puts "first (outer): #{first}, second (inner): #{second}"
  end
end


By the way, the code you posted is *not* bubble sort. I do not even know 
it, but it is definitely a bad algorithm, since it involves a lot of 
unnecessary element swapping.

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