IMO it is just a matter of choosing your own poison. Some people avoid type extension and deferred bindings, others don’t like reverse communication. I think @victotronics has described reverse communication fairly when he says:
The idea is to make the function data-independent by keeping
the data entirely outside its scope. Thus for every operation on that data
you have to return, with a request parameter indicating what
operation has to be performed outside, and you have to have a way
to indicate where you resume after the operation is done.I’ve written code like this, and it’s kinda neat, but I’m not
entirely unconvinced that it’s not totally evil. Or not.
[emphasis added]