[xyproto]

That is pretty neat. Does it mean that one could do something similar for vectors and quaternions?

    let open Quaternion in
    x * y + x

[andrepd]

Yep. You could write

    module Quaternion = struct
      let (+) =
        ...
    
      let ( * ) =
        ...
    end

then

    let open Quaternion in

imports the contents of Quaternion into local scope, so you can write

    x * y + z

[vrotaru]

Yes.