# File lib/core/facets/enumerable/modulate.rb, line 11
  def modulate(modulo)
    return to_a if modulo == 1
    raise ArgumentError, 'bad modulo' if size % modulo != 0
    r = Array.new(modulo, [])
    (0...size).each do |i|
      r[i % modulo] += [self[i]]
    end
    r
  end