Comment by OskarS
Indeed, that is exactly the case, lambdas are essentially syntax sugar for doing this.
The one thing the author's solution does which this solution (and lambdas) does not is type erasure: if you want to pass that closure around, you have to use templates, and you can't store different lambdas in the same data structure even if they have the same signature.
You could solve that in your case by making `void operator()` virtual and inheriting (though that means you have to heap-allocate all your lambdas), or use `std::function<>`, which is a generic solution to this problem (which may or may not allocate, if the lambda is small enough, it's usually optimized to be stored inline).
I get where the author is coming from, but this seems very much like an inferior solution to just using `std::function<>`.
The author of the article freely admits that `std::function<>` is more flexible. He still prefers this solution, as it is easier for him to reason about. This is covered in the "Fringe Benefits" part of the document.