[Pharo-project] recompiling class

Can we do this in Pharo: "in Java, the computation of numeric o ffsets for instance elds in memory is done by the run-time system. This permits updating a class with new instance elds or methods without aff ecting existing code. In other words, it is possible to run an existing bytecode fi le for a subclass after updating and recompiling the class, but without recompiling the subclass."