Ceylon Migration Bot

[@gavinking] Rust, one of the up'n'coming languages for systems programming, has a nice system of type classes (called "traits"). http://pcwalton.github.io/blog/2012/08/08/a-gentle-introduction-to-traits-in-rust/

[@RossTate] From what's in that article, traits are just interfaces. If David Herman's at POPL next week, I'll double-check with him.

[@gavinking] > From what's in that article, traits are just interfaces. Ah ... I'm assuming that the reason they have `&self` as an explicit parameter to methods is that you...

[@gavinking] Oh. Looks like they plan it but [don't have it yet](http://stackoverflow.com/questions/20342436/rust-invoke-trait-method-on-generic-type-parameter). Well, it will fit really nicely in with the rest of what they have, when they add it.

[@Zambonifofex] @GavinKing Sorry, but I'm slightly confused by [your example](/#4005#issuecomment-32317426)... What does `given Other Summable` mean? I'm imagining it's a typo?... And, on `StringMonoid`, why is `zero` a `Float`? Shouldn't...

[@gavinking] > I'm imagining it's a typo? Yes, thanks, I fixed it. > Shouldn't it be a `String`? Yes of course. Also fixed. > I'd say it's creatively thought out,...

[@lukedegruchy] I've noticed that there are currently some rather cryptic compile errors on JVM when using this feature presently. Should there be a separate bug for clearing compile errors (ex...

[@gavinking] So the question is: what would it look like in Ceylon syntax?

[@pthariensflame] A simple way would be to use the existing `alias` and `switch` syntaxes, and just combine them: ``` ceylon alias Plus given M satisfies Nat given N satisfies Nat...

[@pthariensflame] The prior-mentioned syntax would allow so-called _closed_ families; the _open_ ones would require something a bit closer to Haskell's current method: ``` ceylon /** A class that efficiently represents...