[ghc-steering-committee] #380 GHC2021: Forth status update / kialo.com

Tue Dec 15 12:48:12 UTC 2020

On 15 Dec 2020 at 13:18:20, Simon Peyton Jones via ghc-steering-committee <
ghc-steering-committee at haskell.org> wrote:

> Writing down the summary here
>
> https://docs.google.com/document/d/1BMJtUQGk1HKOFgLnczybAwd1HgqbNpZA7elM4VnANa8/edit?usp=sharing
>
> allows me to ask:
>
> * It can't be sensible to propose NamedWildCards (8 votes) without
> ParitalTypeSignatures (2 votes), can it?
>

As far as I understand it, they have different purposes:

- NamedWildCards instructs GHC to treat names starting with underscore as
unknown variables when unifying. So for example, the following would not
work, since _a would need to be Char and Bool at the same time.

> f :: _a -> _a
> f ‘x’ = True

If you do not enable NamedWildCards, names starting with an underscore are
taken to be regular variables. So the type ‘_a -> _a’ is completely
equivalent to ‘a -> a’.

- PartialTypeSignatures is about *accepting* those signatures by the
compiler. If you don’t have this on, a partial type signature gives you an
error with the inferred type, but does not continue compiling your program.

Personally, I think this is the right behaviour: do not accept partial
signatures unless explicitly told so.

> Simon
>
> |  -----Original Message-----
> |  From: ghc-steering-committee <ghc-steering-committee-
> |  bounces at haskell.org> On Behalf Of Joachim Breitner
> |  Sent: 14 December 2020 22:23
> |  To: ghc-steering-committee at haskell.org
> |  Subject: [ghc-steering-committee] #380 GHC2021: Forth status update /
> |  kialo.com
> |
> |  Dear Committe,
> |
> |  three weeks in, we have all votes. So now things are looking more
> |  concrete.
> |
> |  As always, the table
> |  https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
> |  ub.com%2Fghc-proposals%2Fghc-
> |  proposals%2Fblob%2Fghc2021%2Fproposals%2F0000-
> |  ghc2021.rst%23data&data=04%7C01%7Csimonpj%40microsoft.com%7C10d0e7
> |  09a1dd4525973708d8a07ecdad%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%
> |  7C637435813779684920%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQI
> |  joiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=3i5Pfxw2%2B
> |  XKtfsbkhbwjreFArYCfvMDGyw%2F0ctxJfKs%3D&reserved=0
> |  has the current data.
> |
> |  Would it be helpful to add columns to that table for each committee
> |  member? So that you can quickly see who voted what?
> |
> |  The following in are safely in (= need more than one vote to change to
> |  get out):
> |
> |  BangPatterns, BinaryLiterals, ConstrainedClassMethods,
> |  ConstraintKinds, DeriveDataTypeable, DeriveFoldable, DeriveFunctor,
> |  DeriveGeneric, DeriveLift, DeriveTraversable, EmptyCase,
> |  EmptyDataDecls, EmptyDataDeriving, ExplicitForAll, FlexibleContexts,
> |  FlexibleInstances, GADTSyntax, GeneralisedNewtypeDeriving,
> |  HexFloatLiterals, ImportQualifiedPost, InstanceSigs, KindSignatures,
> |  MultiParamTypeClasses, NamedFieldPuns, NumericUnderscores, PolyKinds,
> |  PostfixOperators, RankNTypes, StandaloneDeriving, StarIsType,
> |  TypeApplications, TypeSynonymInstances
> |
> |  The following are barely in (exactly 8 votes in favor, and 3 against):
> |
> |  ExistentialQuantification, NamedWildCards, StandaloneKindSignatures,
> |  TypeOperators
> |
> |  The following are short one vote (7 in favor, 4 against):
> |
> |  DerivingStrategies, ForeignFunctionInterface, GADTs, MonoLocalBinds,
> |  NegativeLiterals, RecordWildCards, ScopedTypeVariables, TupleSections,
> |  TypeFamilies
> |
> |
> |  I am sure we can have plenty of discussion for each of these. Probably
> |  without end. As Simon says, mailing lists don't scale. So I think we
> |  have two choices:
> |
> |  1. Let the numbers decide, and accept whatever comes out. According to
> |  the process (which we should only follow if we find it helpful) we'd
> |  maybe update our votes, and maybe point out new facets, for one week,
> |  and then just take whatever has 8 votes.
> |
> |  or
> |
> |  2. Explore a more efficient discussion format.
> |
> |  For the latter I mentioned kialo.com before, and maybe it is worth a
> |  try, so I set up a discussion there:
> |  https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.
> |  kialo.com%2Fwhich-haskell-extensions-should-go-into-ghc2021-
> |  43548%3Fpath%3D43548.0&data=04%7C01%7Csimonpj%40microsoft.com%7C10
> |  d0e709a1dd4525973708d8a07ecdad%7C72f988bf86f141af91ab2d7cd011db47%7C1%
> |  7C0%7C637435813779684920%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiL
> |  CJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=I8nLXqK
> |  Mf32ctvlrPcPS%2BKBD%2FSw5vrV%2B0Fv%2BYvP%2Bbho%3D&reserved=0
> |
> |  So what do you see there?
> |
> |  There is a discussion tree:
> |
> |  The root is "what goes in GHC2021"
> |
> |  The next layer are all extensions with 7 or 8 votes.
> |  (I assume we should focus on those initially, but feel free to add
> |  more or ask me to.) For example:  TupleSections
> |
> |  And then each of these has a column where we can collect Pros and
> |  cons.
> |  For example:
> |  Pro: Opt-in Syntax
> |  Con: Possible clash with extra-comma syntax extensions.
> |
> |  So you can treat it like a wiki, but with structure to organize the
> |  discussion.
> |
> |  In fact, each pro and con is itself a node where you can add
> |  supporting and disagreeing comments. This means that if you _disagree_
> |  that TupleSections are actually Opt-in syntax, there is a dedicated
> |  place to raise that point, rather than putting "Not actually opt-in"
> |  in the Con column of TupleSections...
> |
> |  A good way to navigate the discussion seems to be the radial icon in
> |  the top left; it opens a radial view of the whole discussion, and you
> |  can read arguments by hovering.
> |
> |
> |  The site doesn't offer voting, it is only about structuring the
> |  discussion, and it is designed for much larger and much more
> |  contentious debates (e.g. "Brexit"). So we'll see how well it works
> |  for us and if it's helpful.
> |
> |  Cheers,
> |  Joachim
> |
> |
> |  --
> |  Joachim Breitner
> |    mail at joachim-breitner.de
> |
> |  https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.j
> |  oachim-
> |  breitner.de%2F&data=04%7C01%7Csimonpj%40microsoft.com%7C10d0e709a1
> |  dd4525973708d8a07ecdad%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63
> |  7435813779684920%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV
> |  2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=7N%2FDBw%2BRwVr
> |  DcVqSS7BQroJAg8R3ccoLQ9Hua%2FgwbAE%3D&reserved=0
> |
> |
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