Fun with Recursive Anonymous Functions

Did you know that an anonymous function can call itself?

All you need is something like this:

```ruby
factorial_of = -> (n) { n <= 1 ? 1 : n * factorial_of.call(n - 1) }
factorial_of.call(5)
# => 120
```

This came in handy when I had a recursive method which needed to be wrapped inside an enumerator to navigate a very complex hierarchy of objects.

Instead of something as complex as that, let's wrap our anonymous factorial function around an enumerator:

```ruby
factorial_of = -> (n) { n <= 1 ? 1 : n * factorial_of.call(n - 1) }

f = Enumerator.new do |y|
  num = 0
  loop do
    y << factorial_of.call(num)
    num += 1
  end
end

f.next
=> 1
f.next
=> 1
f.next
=> 2
f.next
=> 6
```
Now we can fetch the next number whenever we want, or enumerate over the numbers until we don't have any left (which is infinite in this case)

douglasgreyling
July 4, 2022