November 2017 - ghc-steering-committee

Proposal: Or patterns (#43)
by Manuel M T Chakravarty 18 Jun '18

18 Jun '18

Folks, I am sorry for taking a long time to get us going on this proposal. The ”Or pattern” proposal is about an extension to pattern matching: (formatted) https://github.com/osa1/ghc-proposals/blob/or_patterns/proposals/0000-or-pa… (PR thread) https://github.com/ghc-proposals/ghc-proposals/pull/43 Its basic idea is simple: allow multiple alternative patterns for each alternative during pattern matching. Unfortunately, the interaction with guards and some other languages features makes it significantly less straight forward than one might initially think. I propose to accept this proposal provided we can agree to use the ”first semantics” (aka single-match semantics) — see https://github.com/osa1/ghc-proposals/blob/or_patterns/proposals/0000-or-pa… My reason for insisting on the first semantics is that it is a simple extension of the existing pattern semantics in the Report, whereas the second semantics requires a more profound, non-local change. This, in particular, also makes it easier to understand the implications of the first semantics. (Also, OCaml has made that same choice.) However, even with the first semantics, I still have one concern about this proposal. The story about the interaction with existential types is currently only partial and there is no discussion of the interaction with GADTs. It might be reasonable to ask for a complete specification of the interaction with these features before making a final determination on this proposal. Nevertheless, this proposal is quite elaborate and quite some work has gone into it. Hence, I think, we owe it the authors of the proposal to at least make a preliminary determination at this point. (In particular, if it is not going to fly regardless of how GADTs are handled, we should say so now.) Cheers, Manuel PS: It is worth noting that Swift solved the problem of deciding between the first and second semantics by choosing a syntax that avoids the ambiguity: <https://developer.apple.com/library/content/documentation/Swift/Conceptual/…>. It is difficult to adapt this syntax to Haskell. If it where possible, I think, this would be the best solution.

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Please review: Mutable constructor fields, Shepherd: Ryan Newton
by Joachim Breitner 08 May '18

08 May '18

Dear Committee, this is your secretary speaking: https://github.com/ghc-proposals/ghc-proposals/pull/8 was brought before the committee, by our own Simon Marlow. I propose Ryan Newton as the Shepherd, because he asked for it :-) Ryan, please reach consensus as described in https://github.com/ghc-proposals/ghc-proposals#committee-process I suggest you make a recommendation about the decision, maybe point out debatable points, and assume that anyone who stays quiet agrees with you. Greetings, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Committee Discussion : Lazy unboxed tuples
by Ryan Newton 05 May '18

05 May '18

Dear Committee, The public discussion <https://github.com/ghc-proposals/ghc-proposals/pull/35> for this one <https://github.com/goldfirere/ghc-proposals/blob/unbanged-strict-patterns/p…> has happened, now for 4 weeks of committee discussion and final accept/reject. In that public discussion, you can see on Jan 11 options broken down as (1),(2),(3), with this proposal being (1). This seems to have stopped in a weird place where there was some substantial argument for (2) and (3) in the latter half of the comments, but the proposal is for (1). Richard, one bit that threw me off was this: *"we should require the bang even on bare variables, but that would break a lot of code I think."* Because that makes it seem like in spite of this cleaning-up proposal, GHC still has a basically inconsistent position on how to interpret variable-bindings of unlifted kind in patterns. Discuss? -Ryan On Tue, Jul 11, 2017 at 11:08 AM, Joachim Breitner <mail(a)joachim-breitner.de > wrote: > Hi, > > it is by Richard, I just got the URL wrong. The right pull request is > https://github.com/ghc-proposals/ghc-proposals/pull/35 > sorry for that. > > Using this thread is fine. > > Joachim > > Am Dienstag, den 11.07.2017, 10:58 -0400 schrieb Ryan Newton: > > Just to clarify, this is proposed by a user "winterland". I.e. not > > Richard, right? In the process document it is the author that "brings > > it before the committee" correct? > > > > I checked and it looks like our process document does not specify the > > means of our committee discussion. I propose we discuss this one > > right here on this thread, which we've already got sitting in our > > inboxes. > > > > Best, > > -Ryan > > > > > > On Tue, Jul 11, 2017 at 2:58 AM, Joachim Breitner <mail@joachim-breit > > ner.de> wrote: > > > Dear Committee, > > > > > > this is your secretary speaking: > > > > > > https://github.com/ghc-proposals/ghc-proposals/pull/45 > > > was brought before the committee, by our own Richard. > > > > > > I propose Ryan Newton as the Shepherd, just to rotate this role > > > properly. > > > > > > Ryan, please reach consensus as described in > > > https://github.com/ghc-proposals/ghc-proposals#committee-process > > > > > > I suggest you make a recommendation about the decision, maybe point > > > out > > > debatable points, and assume that anyone who stays quiet agrees > > > with > > > you. > > > > > > > > > Greetings, > > > Joachim > > > > > > > > > -- > > > Joachim Breitner > > > mail(a)joachim-breitner.de > > > http://www.joachim-breitner.de/ > > > > > > > > -- > Joachim “nomeata” Breitner > mail(a)joachim-breitner.de • https://www.joachim-breitner.de/ > XMPP: nomeata(a)joachim-breitner.de • OpenPGP-Key: 0xF0FBF51F > Debian Developer: nomeata(a)debian.org > _______________________________________________ > ghc-steering-committee mailing list > ghc-steering-committee(a)haskell.org > https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee > >

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Underscores in literals
by Iavor Diatchki 05 Dec '17

05 Dec '17

Hello, This e-mail is about pull request #76, to allow underscores in numeric literals: https://github.com/takenobu-hs/ghc-proposals/blob/numeric-underscores/propo… In short, this is a very simply feature, which modifies the notation for numeric literals to allow writing underscores (_) in the middle of literals. The underscores are only to increase readability, and have no effect on the meaning of the program. So, for example, I could write things like: 10_000_072 or 0xFFFF_FA10. Many other languages have a similar feature (especially hardware specification languages) and I see no downsides to it, so I think we should accept it. Please respond to this e-mail if you have objections. Cheers, -Iavor

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Proposal: BlockArguments (Shepherd: Joachim)
by Joachim Breitner 05 Dec '17

05 Dec '17

Dear committee, the BlockArguments (former ArgumentDo) proposal was brought before us: https://github.com/ghc-proposals/ghc-proposals/pull/90 I’ll shepherd this myself. The idea is to not require parenthesis around block syntax elements such as lambda expressions, let bindings, if-then-else, case-of and (in particular) do expressions. The change to the grammar to enable that is actually a simplificiation (it removes one non-terminal, lexp). Variants proposed are: * do this only for `do` in argument position, or * do it for all blocks, but only in function argument positions. I am fond of this proposal, because it allows code with less parenthesis to be written. If Haskell was written from ground up, I believe there would be little opposition to this setup, and maybe we would not have had to hack higher-rank support into ($), as the idiom `runST $ do …` would just be `runST do …`. Another argument in favor of it is the mentioned simplificiation of the grammar rules. I am aware that reading the parenthesis-free code feels strange to many, but I not overly worried about that: Every change feels strange, and in this case, only code that is otherwise illegal is affected. Akio has indicated that he is willing to work on the implementation. Therefore, I suggest that we accept this proposal. Please discuss (or voice you silent agreement). Regards, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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What do we need from the linear-types proposal?
by Joachim Breitner 29 Nov '17

29 Nov '17

Dear committee, Mathieu Boespflug asks on https://github.com/ghc-proposals/ghc-proposals/pull/91#issuecomment-3471232… > Could the Committee define the items it expects before it can make a > determination about this proposal? We've heard in this thread members > of the Committee ask for a fleshed out linear base, more examples > than are already in the proposal and in the paper, and also full code > from other users at large. I can certainly understand where they are > coming from. But at the same time, I am concerned about scope creep. > Defining where the goal posts are from now would certainly help. and I am not sure what to reply here… but “we’ll know that once we made a determination” is probably not helpful. Does anyone here feel like he could define the requirements that are necessary to allow us to consider the proposal properly? Thanks, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Please review: add incomplete-uni-patterns and incomplete-record-updates to -Wall, Shepherd: Simon Marlow
by Joachim Breitner 21 Nov '17

21 Nov '17

Dear Committee, this is your secretary speaking: The question of whether the meaning of -Wall out to include incomplete- uni-patterns and incomplete-record-updates was brought before the committee. https://github.com/ghc-proposals/ghc-proposals/pull/71 I propose Simon Marlow as the Shepherd. Simon, please reach consensus as described in https://github.com/ghc-proposals/ghc-proposals#committee-process I suggest you make a recommendation about the decision, maybe point out debatable points, and assume that anyone who stays quiet agrees with you. Thanks, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Our process and BIG ideas
by Manuel M T Chakravarty 15 Nov '17

15 Nov '17

In the light of the linear types proposal PR, SimonPJ’s comment https://github.com/ghc-proposals/ghc-proposals/pull/91#issuecomment-3434578… and some uncertainty about the proposal process that has been communicated to me via a side channel, it might be worthwhile clarifying our expectations for large complex proposals. (I know, we basically punted on these questions in our initial discussion on the process with the intention to revisit after we gained some experience. It seems this time has come.) Firstly, we usually require proposals to be self-contained. This makes a lot of sense for small to medium-sized proposals to limit the time needed by the committee to hunt down all the required information. However, in a case, such as the linear types work, where there is a highly polished text in the form of a research paper (or similar), it seems reasonable to refer to that existing work — not only because type rules are a lot nicer to read when rendered by LaTeX instead of Markdown. Concretely, I’d like us to give some guidance wrt to this issue to proposal authors and document that at https://github.com/ghc-proposals/ghc-proposals#ghc-proposals Secondly, Simon, you seem to suggest that a large proposal like this wouldn’t be either accepted or rejected, but put into a kind a limbo state of further evaluation as seen fit. I agree that instead of outright rejection of a proposal that we consider flawed but not hopeless, we might request further elaboration and resubmission as we have done in the past. However, if a proposal passes muster, I think, we should accept it unconditionally, even if it is a large change. (If, say, at the end, the implementation is not up to scratch, then it is up to the code reviewers to reject the patches, but I don’t think, it is this committee’s job anymore.) In any case, I think, it is important make the process as clear as possible to authors, so they know what they are in for. What do you all think? Cheers, Manuel

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Please review: Deprecate STM invariant, Shepherd: Manuel M T Chakravarty
by Joachim Breitner 10 Nov '17

10 Nov '17

Dear Committee, this is your secretary speaking: Deprecate STM invariant mechanism https://github.com/ghc-proposals/ghc-proposals/pull/77 was brought before the committee, by our own Ben Gamari I propose Manuel M T Chakravarty as the Shepherd. Roman, please reach consensus as described in https://github.com/ghc-proposals/ghc-proposals#committee-process I suggest you make a recommendation about the decision, maybe point out debatable points, and assume that anyone who stays quiet agrees with you. Thanks, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Please review: visible dependent quantification, Shepherd: Roman Leshchinskiy
by Joachim Breitner 10 Nov '17

10 Nov '17

Dear Committee, this is your secretary speaking: Visible dependent quantification (TL;DR: forall k -> k -> *) https://github.com/ghc-proposals/ghc-proposals/pull/81 was brought before the committee, by our own Richard Eisenberg. I propose Roman Leshchinskiy as the Shepherd. Roman, please reach consensus as described in https://github.com/ghc-proposals/ghc-proposals#committee-process I suggest you make a recommendation about the decision, maybe point out debatable points, and assume that anyone who stays quiet agrees with you. Thanks, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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