> There was no Haskell 2020 meeting this year at ICFP. Sadly, interest seems to have waned here...
Yes that is sad. So either Haskell 2020 won't happen, or it'll be only minor tweaks over H2010, as that was over H98. It's hard to imagine any serious Haskelling without FlexibleInstances/FlexibleContexts, MultiParamTypeClasses, UndecidableInstances -- and yet all of those are beyond Haskell 2010. And they were available in at least 2 compilers by around 2000. (Possibly they weren't by then entirely polished. I saw a claim on a StackOverflow answer that Hugs, last release 2006, is not H2010 compliant: not true; indeed several of the H2010 changes since H98 were proposed by the Hugs dev team, and agreed by the GHC team because GHC had copied Hugs.) I've had comments from non-Haskellers that they won't take Haskell seriously, because it seems to be a bunch of 'risky'/unstable/experimental features. Whereas I know those features have been stable at least a dozen years. And yet we still face the same conundrums as did H2010: With FlexibleInstances we can write overlapping instances. With FlexibleContexts we can put overlapping constraints on an instance, even if the head's types are H98 (non-Flexible). With MultiParamTypeClasses (which were anticipated in Wadler's very earliest 1988 proposal for typeclasses) we're bound to choose FunDeps and/or type families. FunDep instances either need repeated tyvars -- which brings us straight back to FlexibleInstances, or UndecidableInstances -- which will almost certainly lead to FlexibleInstances somewhere. I feel those parts of Haskell have been in suspended animation/arrested development since ~2006: that was the last release of Hugs; the 'FunDeps via CHRs' paper [**]; the start of associated types/type families. [**] AFAICT, that paper was a purely academic exercise: GHC was not changed in light of its findings, so has a bogus implementation of FunDeps that persists to this day. The paper did not address the combo of FunDeps + Overlaps, so said nothing about what had been a stable cottage industry of type-level programming since at least 2004 (the HList paper). Is there a terms of ref for Haskell 2020? Would any of the above issues be within its scope? (Supposing there were any interest ...) AntC
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