require 'generator' 
def coroutine(m, *args)
  Generator.new {|g|
    m.call(*args) {|x| g.yield x}
  }
end

def generate_fibonacci(a, b)
  loop do
    yield a
    a, b = b, a + b
  end
end

fibonacci = coroutine(method(:generate_fibonacci), 1, 1)
10.times do
  puts fibonacci.next
end