Lazy evaluated fibonacci sequence

fib.rb

class Fib
  def self.fib
    a, b = [0, 1]
    s = 1..Float::INFINITY
    Enumerator::Lazy.new(s.lazy) do |yielder, val|
      a, b = b, a + b
      yielder << a
    end
  end
end

puts Fib.fib.take(10).force
# =>
1
1
2
3
5
8
13
21
# =>
34
55