John M. Dlugosz wrote: > TSa Thomas.Sandlass-at-barco.com |Perl 6| wrote: > > Take e.g. my supertyping proposal. I guess it was regarded as > > a curiosity rather than an innovative feature. > > Which idea was that? Maybe I already took the wind into account when I > rounded up the ideas in need of documentation/elaboration in the first > place.
IIRC, the supertyping proposal involved being able to "anti-derive" roles from existing roles or classes, working from subtypes to supertypes (or from derived roles to base roles) instead of the other way around. The proposal got hung up on terminology issues, specifically a discussion involving intensional sets vs. extensional sets. I find this unfortunate, as I see a lot of potential in the idea if only it could be properly (read: unambiguously) presented. >From an "intensional set" perspective, a supertype would be a role that includes the structure common to all of the classes and/or roles for which it's supposed to act as a base role. From an "extensional set" perspective, the range of values that it covers should span the range of values that any of its pre-established "subtypes" cover. A proposal was put forward to use set operations to create anonymous supertypes, and then to provide them with names via aliasing; where it got hung up was whether it should be based on a union of extensional sets (i.e., combining the potential set of values) or on an intersection of intensional sets (i.e., identifying the common attributes and methods). -- Jonathan "Dataweaver" Lang
