[bitc-dev] Objects without subtypes

[Eric Northup]

Jonathan S. Shapiro wrote:
> So the question is now: how do we recover objects without having
> subtypes?
>
> Actually, this turns out to be separable into two questions:
>
>   1. How do we recover a suitably constrained form of existential
>      type (objects)?
>
>   2. How do we recover inheritance?
>   
This may not be strictly related to subtyping but one other programming 
pattern I associate with "objects" is using them to control visibility.
[...]
> What we now have in mind is to introduce a new constraint:
>
>   (has-field 'a name 'b)
>   
I don't see how you would be able to get "protected" fields out of 
this.  Perhaps that's fine (I've seen it mis-used quite often), but just 
thought I'd mention it.

The module system might be a better way to perform that kind of 
encapsulation anyway.  Is there a module equivalent of "friend"?

-Eric