I don't know about that link, but in general you would use a fix point combinator. The Fit library has a fix point combinator here: http://pfultz2.github.io/Fi

I don't know about that link, but in general you would use a fix point combinator. The Fit library has a fix point combinator here: http://pfultz2.github.io/Fit/doc/html/fix/ http://pfultz2.github.io/Fit/doc/html/fix/ So you could implement a generic factorial like this: auto factorial = fit::fix([](auto self, auto x) -> decltype(x) { return x == 0 ? 1 : x * self(x-1); });