Grouping array ruby

Create arrays inside an array.

require 'enumerator'

>> a = (0..12).to_a
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
>> b = a.enum_for(:each_slice,4).to_a
=> [[0, 1, 2, 3], [4, 5, 6, 7], [8, 9, 10, 11], [12]]

below is how to iteration

>> b.each do |c|
?>   c.each do |value|
?>     puts value
>>   end
>> end