He should look into C, not C++. With Duff's device[1] trick, it becomes surprisingly lisp- and forth-y. It can be used to implement coroutines in 100% portable C[2]. And I'm pretty sure you can use the same trick to implement infinite recursion (stack on heap) and maybe even backtracking a la prolog.

[1] https://en.m.wikipedia.org/wiki/Duff%27s_device

[2] https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html