enumerable example

class Fibonnaci
   include Enumerable

   def initialize
      @a = @b = 1
   end
   
   def each
      loop do
         yield @a
         @a, @b = @b, @a + @b
      end
   end
end

enumerable with termination

class Fibonnaci
   include Enumerable

   def initialize(limit)
      @a = @b = 1
      @limit = limit
   end
   
   def each
      while @a < @limit
         yield @a
         @a, @b = @b, @a + @b
      end
   end
end

enumerator with termination

def fibonnaci_enumerator(limit)
   Enumerator.new do |y|
      a = b = 1

      while a < limit
         y << a
         a, b = b, a + b
      end
   end
end