Yielder & Enumerator pure Ruby example implementation

enum.rb

# Using standard library
fib = Enumerator.new do |y|
  a = b = 1
  loop do
    y << a
    a, b = b, a + b
  end
end

p fib.take(10)
# => [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]

# Re-implemented
class FYielder
  def initialize(&block)
    @f = Fiber.new do
      puts "Starting fiber"
      block.call(self)
    end
  end 

  def <<(value)
    puts "<< called"
    Fiber.yield(value)
  end

  def get_val
    puts "get_val called"
    @f.resume
  end
end

class FEnumerator
  def initialize(&block)
    @yielder = FYielder.new(&block)
  end 

  def next
    @yielder.get_val
  end

  def take(x)
    x.times.map { self.next }
  end
end

fib = FEnumerator.new do |y|
  puts "block called"
  a = b = 1
  loop do
    puts "inner loop"
    y << a
    a, b = b, a + b
  end
end

p fib.take(10)