Array#by

gistfile1.rb

class Array
  def by(n)
    buff, self_ = [], self.clone
    
    if self.size % n == 0
      (self.size/n).times{ buff << self_.shift(n) }
    end
    
   buff
  end
end

# by @mvoto
class Array
  def by(n)
    self.enum_for(:each_slice, n).to_a
  end
end

[1,2,3,4,5,6].by(2) #=> [[1, 2], [3, 4], [5, 6]]

#:P

[*0...9].each_slice(3).to_a => [[0, 1, 2], [3, 4, 5], [6, 7, 8]]