Pre-Pre-HFTP: Decoupling base and GHC

[Ericson2314]

@atravers

Alternately, and if the GHC-centric modules are the minority, ghc-base is initially an empty package which base imports. GHC-centric modules are then replicated or moved, leaving base with the the implementation-independent modules.

We don’t want to do that because we want (the new) base to be portable across GHC versions (and other hypothetical implementations) at all times. The empty library is trivially portable, and we move over definitions only if they are also.

…and right now (2022 Feb) that would require going as close to fully-parameterised (no type classes) as possible

I am interested in these things, but I don’t think overly opinionated instances in GHC are a problem. (Outputable is opinionated but structured errors mean that pretty-printing is increasingly moved to the outskirts!)

If you want to talk to about orphan instances more, would you mind forking that to a new thread? It is orthogonal to the low hanging initial steps for both making GHC a real library and decoupling base.

[atravers]

@Ericson2314

If you want to talk to about orphan instances more, would you mind forking that to a new thread?

Acknowledged. I’ve just searched for orphan here to see if there was an existing Discourse thread - this appeared in the results:

Towards a prevalent alternative prelude?

The tricky part here is that base (unfortunately) currently serves a few, largely orthogonal roles: it serves as the home of GHC’s IO subsystem (the event manager) which is closely tied to GHC’s runtime system (e.g. GHC.Event, GHC.Conc) it serves as the home of several core typeclasses which are closely tied to the compiler (e.g. GHC.Base, GHC.Functor, GHC.Enum, GHC.Generics) it serves as the home for wrappers to GHC primops which could in principle be implemented elsewhere (e.g. Data.IORef)…

…which mentioned this:

split base · Wiki · Glasgow Haskell Compiler / GHC · GitLab

which in turn refers to this:

README.md

May you be more successful.

[Ericson2314]

Thanks! That is very useful. I am generally a fan of rebasing things no matter how ancient, so I should take a crack at rebasing @nomeata’s changes even though they are a decade old.

From it’s readme

Some changes are just work-arounds due to GHC having the package name base hardcoded

Yes we should definitely get that more flexible so we don’t need to rebuild the compiler are stuff merely moves around. Settings file, maybe?

[Ericson2314]

Proposal: Relax instances for Functor combinators; put superclasses on <class>1 to make less-breaking · Issue #10 · haskell/core-libraries-committee · GitHub I wrote up a new benefit that even the most trivial “beachhead” of making ghc-base contain everything and base reexport it all would realize.

[atravers]

Bringing Data.Text into `base`: What is the next step?

Draft: move base to ghc base, #20647 (!7898) · Merge requests · Glasgow Haskell Compiler / GHC · GitLab this is a very simple PR which almost works. Some just needs to debug the remaining Safe Haskell and TH test failures; I would love it if that someone were not me. After that is done I think splitting base up can proceed incrementally with assorted volunteer effort. This is the one and only stumbling block!

[atravers]

santiweight:

For those motivated to make this happen, you should definitely contribute to the efforts […] in getting the ball rolling!

rae:

I have a simple proposal: let there be a new package [which] includes and re-exports modules from base and text (and possibly a few more). We teach cabal to either default to including standard as a dependency or ask users during the interactive init.

• haskell98: Compatibility with Haskell 98

• haskell2010: Compatibility with Haskell 2010

• https://hackage.haskell.org/package/haskell2020

…therefore:

• https://hackage.haskell.org/package/haskell-glasgow2021

• https://hackage.haskell.org/package/haskell-glasgow2024

• https://hackage.haskell.org/package/haskell2028

• …

with each being a “standardised snapshot” of:

• https://hackage.haskell.org/package/haskell

in which all the latest products of active research debuts. The haskell package can also serve as the point of separation (or abstraction) between base and GHC, allowing the two to evolve at their own pace.

Everyone else can then choose the level of stability and compatibility most suitable for their Haskell project.

[Ericson2314]

Standard library reform by Ericson2314 · Pull Request #47 · haskellfoundation/tech-proposals · GitHub I have opened a draft tech proposal on this.