learning ruby vtable opening up array

gistfile1.rb

puts 'VTable format'

class Array
  def print_vtable(cols)
    rows = (self.length.to_f / cols).ceil
    
    self.map { |index| 
      x = index % cols
      y = index / cols
      x * rows + y
    }
  end
end

# print_vtable on array
(0...17).to_a.print_vtable(3)