A quick way to make enumerable objects from an arbitrary block

any_enumerable.rb

class AnyEnumerable
  include Enumerable

  def initialize(&each_impl)
    @each_impl = each_impl
  end

  def each(&block)
    @each_impl.call(&block)
  end
end

sequence = AnyEnumerable.new do |&block|
  last = 12
  i = 0
  while i <= last
    block.call i
    i += 1
  end
end

sequence.map do |i|
  i.to_s
end # => ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"]

sequence.take(5) # => [0, 1, 2, 3, 4]