I thought that the RFC for a virtual fn alternative pushed a couple days ago by Bill Myers looked interesting: https://github.com/bill-myers/rfcs/blob/5e62f881421fc6aa34e85ffc5b2a91a7d6666370/active/0000-oop-with-enums.md
I can’t tell if it is elegant or an evil contortion of existing Rust features though. I’m curious what people think of it since it is much different then the other proposals out there. Eric On Mar 17, 2014, at 3:19 PM, Jan Klesnil <kles...@centrum.cz> wrote: > Hi, > > I've just read your proposal. It is pretty similar to an idea I had over the > weekend. However, there is one thing I want to ask about. But I will present > my idea because it may be the case that I misunderstood some part from your > proposal. > > My idea was to introduce few orthogonal concepts and use them together to > solve the DOM problem: > > 1) single static inheritance and static cast to base types > 2) virtual struct WITHOUT any virtual methods > 3) dynamic cast to derived type or implemented trait for virtual structs > > Structs that are declared virtual will have a hidden pointer to some > vtable-like structure that allows dynamic casting to derived types and to > traits. So the layout is similar to C++'s virtual classes, but there are no > virtual methods. Instead, you would be able to cast to any implemented trait > dynamically. If I understand your proposal correctly, it is the same as the > Fat<T as U> relation. > > I see that this Fat<T as U> relation is absolutely doable, but I was not able > to come up with any efficient solution and I see performance of the dynamic > cast as very important property. Otherwise the feature will be very useful. > > My baseline solution was to build hashtable for every crate with key of pair > (T,U) and search the hashtables when the dynamic cast is requested. That was > just a proof that it is doable because it is not efficient solution. I also > expect that some v-table structure can be generated for each virtual struct > as far as we know all the implemented traits. (E.g., at link time for entire > crate.) But when I considered implementing traits for virtual struct from > different crate, it became more difficult and I stopped examining the problem. > > So my questions would be: > Did I understood the meaning of the Fat<> relation correctly? > > Is the Fat<> relation already implemented? Or is there a proposal for the > implementation somewhere? > > J > > On 03/15/2014 05:30 AM, Micah Chalmer wrote: >> I wrote up an alternative proposal that I think, if I’m understanding them >> correctly, meets all the requirements. I submitted it as an RFC, so >> discussion of it is probably better put on github on the mailing list, but >> in case anyone interested is watching this thread and not watching the RFCs: >> >> https://github.com/rust-lang/rfcs/pull/9 >> >> -Micah >> >> _______________________________________________ >> Rust-dev mailing list >> Rust-dev@mozilla.org >> https://mail.mozilla.org/listinfo/rust-dev >> > _______________________________________________ > Rust-dev mailing list > Rust-dev@mozilla.org > https://mail.mozilla.org/listinfo/rust-dev _______________________________________________ Rust-dev mailing list Rust-dev@mozilla.org https://mail.mozilla.org/listinfo/rust-dev
