> On Jun 25, 2016, at 12:00 AM, L. Mihalkovic <[email protected]> > wrote: > > Inline > Regards > (From mobile) > >> On Jun 25, 2016, at 1:00 AM, Joe Groff via swift-evolution >> <[email protected]> wrote: >> >> >>> On Jun 23, 2016, at 8:55 PM, Jordan Rose via swift-evolution >>> <[email protected]> wrote: >>> >>> [Proposal: >>> https://github.com/apple/swift-evolution/blob/master/proposals/0095-any-as-existential.md >>> ] >>> >>> I’ve gone on record before as against this syntax, although when I set out >>> earlier today to record my usual rebuttal I found that it really was mostly >>> a matter of taste. Yes, this looks weird to me: >>> >>> let callback: (Data) -> NSCoding & NSCopying >>> >>> but I’m sure the infix ‘->’ for functions looked weird to everyone the >>> first time they saw it as well, and it really is pretty clear in argument >>> position. >> >> We could conceivably bracket the 'where' constraints somewhere. It's nice >> not to have to punish the common case syntax. In my personal ideal vision of >> the world, I'd like to see us support opening existentials via >> path-dependent types (e.g., let a: Collection; let element: a.Element). If >> we support them in decl-level 'where' clauses, we provide a nice, clean >> syntax for complex generic relationships that doesn't require angle brackets >> or per-existential where clauses at all, something like: >> >> func intersect(a: Collection, b: Collection) -> Collection >> where a.Element == b.Element, b.Element == return.Element { >> } >> >> which doesn't completely define away the need for 'where' as part of >> existential types, but would shrink it quite a bit. > > For some reason it had not clicked until your 'path dependent type' reference > how reminicent of (U+00B7) this is. I watched nada's 2014 presentation > again... but then it means intersection types would add a lot... you guys > seem ok to add P&Q now, so why not take that opportunity to allow P|Q at the > same time. Does it also mean that you might consider at some point expanding > 'assoctype U' into: T where <:U , :>U opening the door to lower/higher > type bounds?
Let's not rathole on the P|Q thing. Disjunctions are difficult to make much sense of in a parametric type system like ours; there are plenty of other threads on this mailing list discussing it. -Joe _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
