flatten with loop (no recursion)

flatten_with_loop.rb

class Array
  # flatten without recursion but loop
  def myflatten!
    i = 0

    while i < self.size
      unless self[i].is_a?(Array)
        i += 1
        next
      end

      f = self[i]
      self.slice!(i)
      self.insert(i, *f)
    end
  end
end


if __FILE__ == $0
  # we need these annoying lines just only to use 'assert_equal' ... sigh.
  require "minitest"
  include Minitest::Assertions
  class << self
    attr_accessor :assertions
  end
  self.assertions = 0

  # main
  [1,["foo", ["bar"]], [[9]], []].tap do |arr|
    arr.myflatten!
    assert_equal(arr, [1, "foo", "bar", 9])
  end
end