infinite enumerator rewind

4
votes

I have a function that generates an enumerator in the following manner:

def create_example_enumerator(starting_value)
  current = starting_value
  e = Enumerator.new do |y|
    loop do
      current += 1
      y << current
    end
  end
end

The current behavior is pretty straightforward.

> e = create_example_enumerator(0)
#<Enumerator: details>
> e.next
1
> e.next
2
> e.rewind
#<Enumerator: details>
> e.next
3

I would like e.rewind to reset the enumerator back to it's starting value. Is there a nice way to do that while still using an infinite enumerator?

1
rubyenumerator

1 Answers

5
votes

This should work:

n = Enumerator.new do |y|
  number = 1
  loop do
    y.yield number
    number += 1
  end
end

n.next #=> 1
n.next #=> 2
n.next #=> 3
n.rewind
n.next #=> 1