Yes, the difference is between internal iterators vs. external iterators. For external iterators, Ruby's Enumerator syntax is a little less convenient. But I

Yes, the difference is between internal iterators vs. external iterators. For external iterators, Ruby's Enumerator syntax is a little less convenient. But I think it's a small price to pay for not having 2 colors of functions [1]. In Ruby, an Enumerator is just an object with methods like any other object. And there are things built in to core to make working with lazy enumerators just as easy as regular ones. To GP's point, you rarely actually need enumerators because of a block's ability to break in Ruby. It's the most useful thing that's in so few languages [2]. For example, if I really wanted to write an infinite loop yielding fib -- not saying I would do it this way but -- the quickest way to do it in Ruby, adapting the Stack Overflow example, is probably more like this: def fib() puts "Enter function" a = b = 1 i = 0 loop do puts "Inside loop" yield i, a puts "i: #{i}, a: #{a}, b: #{b}" a, b = b, a + b i += 1 end end n_from_user_input = 5 fib do |i, x| break if i == n_from_user_input puts "Use value: #{x}" end 1: https://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/ https://journal.stuffwithstuff.com/2015/02/01/what-color-is-... 2: https://yehudakatz.com/2012/01/10/javascript-needs-blocks/ https://yehudakatz.com/2012/01/10/javascript-needs-blocks/