From: "Jacques Le Normand" <rathereasy@gmail.com>

> is it possible to add methods to an object?
> in other words, if an object has type <a:b,c:d>, is it possible to create an
> object of type <a:b,c:d,e:f> ?

No, you can only add methods to classes.
The only thing you can do with an object is build a wrapper object or
class, which forwards original methods to the base object:

let wrap o =
  object
    method a = o#a
    method c = o#c
    method e = ...
  end

Jacques Garrigue