flatten an array of arbitrarily nested integers

flatten

def flatten(list, result=[])
  list.each do |item|
    if item.is_a? Integer
      result << item
    else
      result += flatten(item)
    end
  end
  res
end

flatten [1, 2, [3, 4], [[5, 6], [7], 8]]
=> [1, 2, 3, 4, 5, 6, 7, 8]