class Hamster::Trie

def delete_at(index = @entries.index { |e| e })
  yield(@entries[index]) if block_given?
  if size > 1
    entries = @entries.dup
    child = @children[index]
    if child
      children = @children.dup
      children[index] = child.delete_at do |entry|
        entries[index] = entry
      end
    else
      entries[index] = nil
    end
    self.class.new(@significant_bits, @size - 1, entries, children || @children)
  end
end