Pure Haskell implementation of GHC.Unicode

[wismill]

Following this discussion, the goal of this proposal is to refactor GHC.Unicode from a C implementation to a pure Haskell implementation.

Motivation

• Reportedly up to 4× faster
• Simplified maintenance (no FFI).
• More portable code.

Implementation

I opened a merge request with a working implementation.

This work is based on the package unicode-data, developed by @Bodigrim, @harendra-kumar, @adithyaov, me and others.

The re-licensing is discussed in this issue.

Relevant links

• Package unicode-data: Github, Hackage and Discourse.
• GHC ticket
• GHC MR

Further discussion

Other interesting functions could be imported from unicode-data. This proposal only use those already in base, in order to keep the interface unchanged.

Aknowledgement

I would like to thank @Bodigrim, @harendra-kumar and @adithyaov for making unicode-data and @nomeata for his guidance.

[tomjaguarpaw]

This sounds absolutely tremendous!

[nomeata]

Thanks for pushing this forward! Highly appreciated

[harendra-kumar]

Nice to see one significant dependency on C libraries removed. I appreciate the contributions of @wismill to the unicode-data package, making it a drop-in replacement for Data.Char and now pushing this into GHC, actually replacing Data.Char! And thanks to @nomeata for taking the initiative and helping out on getting this done.

[Bodigrim]

I conducted a technical review of https://gitlab.haskell.org/ghc/ghc/-/merge_requests/8072 and it looks good to me.

Dear CLC members, let's vote on the proposal to speed up Data.Char 4 times :-P
@tomjaguarpaw @cigsender @cgibbard @emilypi @chessai

+1 from me.

[chessai]

+1

[tomjaguarpaw]

+1

[mixphix]

+1

[cgibbard]

+1

[Bodigrim]

With 5 votes in favor out of 6 possible, the proposal is now approved by CLC. Thanks @wismill.

[chshersh]

I'm trying to summarise the state of this proposal as part of my volunteering effort to track the progress of all approved CLC proposals.

Field	Value
Authors	@wismill
Status	merged
base version	4.18.0.0
Merge Request (MR)	https://gitlab.haskell.org/ghc/ghc/-/merge_requests/8072
Blocked by	nothing
CHANGELOG entry	missing (please, raise an MR to base to update changelog)
Migration guide	not needed

Please, let me know if you find any mistakes 🙂

---

@wismill I find it hard to determine the exact version of base that implemented this proposal. Could you open an MR to base with the CHANGELOG entry for the corresponding base version?

[wismill]

@chshersh thanks for your effort. base-4.18.0.0 implements this proposal. I think there is no changelog entry because it is not an API change, merely an implementation one.

[chshersh]

@wismill Thanks for confirming the base version!

In my understanding, if a change requires a CLC proposal, it should go to CHANGELOG, and I don't view CHANGELOG as API-only list of changes. But views of other CLC members may differ 😌

[parsonsmatt]

I would personally prefer to see nearly all changes in the changelog - subtle implementation differences can be hard to track down, and a changelog makes that much easier

[chessai]

I would personally prefer to see nearly all changes in the changelog - subtle implementation differences can be hard to track down, and a changelog makes that much easier

I agree, and that base should be held to a very strict standard of this

[wismill]

MR sent.