Objects use cases in OCaml

[echowuhao]

off topic for newbie question: for the student example.

module rec S1 : Student = Base(Younger(S1))
let s1 = S1.(say@@create 20);;
module rec S2 : Student = Base(Younger(S2))
let s2 = S2.(say@@create 20);;

1. how to interpret the ‘module rec’ for self?

the explain I can find is

Module but no module type recursion?

I haven’t worked through your example, but one thing to note is that for modules which consist of only types, you can recursively define them to be themselves: module rec ... and S : sig type t = ... end = S This trick might provide a way to accomplish what you mean with and type ...

2. Is not the S1 and S2 the same?