module Hamster::List

def flat_map(&block)

def flat_map(&block)
  return self unless block_given?
  Stream.new do
    next self if empty?
    head_list = Hamster.list(*yield(head))
    next tail.flat_map(&block) if head_list.empty?
    Sequence.new(head_list.first, head_list.drop(1).append(tail.flat_map(&block)))
  end
end

Instance Methods