> A closure is an object that supports exactly one method: "apply". What's more, this enforces good object-orientation: this is a reimagining of the single-res

> A closure is an object that supports exactly one method: "apply". What's more, this enforces good object-orientation: this is a reimagining of the single-responsibility principle because closures are objects that literally do one thing. Closures also enforce the open-close principle. Once it's closed it's closed. The result is that you get a lot of good OO practices for free.