unboxed VS ghc-proposals

With Lev as defined here.

Check out unboxed. I think that could be a good starting point. I recently updated it to the 9.2.1 alpha here: https://github.com/noughtmare/unboxed/commit/b6338e68540a2c62a6aae6ded0dcdc3b83106916. I should check again if the this issue is fixed in this rc.

I tried it out and it is really not usable yet unfortunately. There are several problems. I think the main issue is that you need two versions of all functions and data types. And currently classes like Num are not levity-polymorphic (there is a proposal about this), so you can't use + to add two "real" inductive peano naturals. One problem with making type classes levity-polymorphic is that top-level bindings can't be levity-polymorphic, so mempty cannot be levity-polymorphic. A workaround is to use a type class to levitate levity-polymorphic variables, but that has disadvantages too. Levitated values are not shared and must be recomputed at every call site.

This is really just a matter of how much syntax sugar you want to implement. Idris has this already, and there’s a proposal to add it to Haskell too [0]. But none of this changes the core properties of the system which make it monadic.

[0] https://github.com/ghc-proposals/ghc-proposals/issues/527

> I think Haskell needs a way to graduate (or retire) language extensions

https://github.com/ghc-proposals/ghc-proposals/pull/601

Additionally, while this proposal is focused on the simple implementation and so in the current proposal or patterns do not bind any variables as per #522, if we do get settled on syntax and then later wish to expand to allow binding variables as in #43, then the syntax is again clean and discoverable.

Yeah, a relatively natural thing would be to be able to opt-in to having the HasField instances be available in all contexts. The (not yet implemented, but accepted) "Modifiers" GHC proposal might be nice for that.

The local modules proposal imo is excellent as-is.

Why would you drop TypeFamilies? It seems fairly popular, given that it was just one vote short of getting added to GHC2021. Do you consider it a less-ideal compromise, that is subsumed by your second proposal (Core with GRTT)?

as syntax is contentious a topic as ever, David (the main proposal author) and I would like to invite you to give your input on https://github.com/ghc-proposals/ghc-proposals/pull/585, where we propose to change the syntax of the accepted proposal #522 introducing Or patterns. In particular, we'd like to know

This looks great, congratulations on completing it! I assume you didn’t get an opportunity to evaluate the delimited continuations based eff library? It would’ve been nice to see Cont included as one of the effects covered, though perhaps not available in all the systems you looked at? Maybe some future work.

I do hope qualified exports are available someday: https://github.com/ghc-proposals/ghc-proposals/pull/283

Right. Being able to disable "custom type warnings" at use sites was part of an earlier proposal (https://github.com/ghc-proposals/ghc-proposals/pull/454) but it ended up being shelved.