Hey :) On Thu 31 Oct 2019 15:17, Mikael Djurfeldt <mik...@djurfeldt.com> writes:
> How does the record subtyping relate to GOOPS? I do realize that there > are issues related to keeping bootstrapping lean, but shouldn't record > types and classes share mechanisms? They share the struct layer. Records are simple: their fields are laid out in order, are all unboxed, and can be treated as a simple kind of nominal product type. `match' takes advantage of this. GOOPS is more flexible: it can have different slot allocations, unboxed slots, multiple inheritance, and so on. Because of multiple inheritance its accessors have to do dynamic dispatch; whereas for records, if supertype A allocates slot X to index I, all subtypes will have that slot in the same place. A check whether a record is an instance of A is a simple O(1) check, rather than the CPL search of GOOPS. Exceptions have a kind of multiple inheritance, but it's more about object composition than typing. You can make a compound condition from a heterogeneous collection of other conditions. While you could implement compound conditions with subtyping, it's more straightforward to use composition. I think the current status is close to the sweet spot but your thoughts are welcome :) I would dearly like to be able to subtype records in GOOPS, but having looked at it a few times I haven't found quite the right way to do it. Cheers, Andy
