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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">GADTs must be one of Haskell’s most successful innovations ever. It’s a big feature, but it’s extremely well established now, and widely used. Users like GADTs – it’s #7 in the “popularity” column.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Vote for GADTs </span>
<span style="font-family:"Segoe UI Emoji",sans-serif;mso-fareast-language:EN-US">😊</span><span style="mso-fareast-language:EN-US">.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> ghc-steering-committee <ghc-steering-committee-bounces@haskell.org>
<b>On Behalf Of </b>Alejandro Serrano Mena<br>
<b>Sent:</b> 03 December 2020 09:41<br>
<b>To:</b> Joachim Breitner <mail@joachim-breitner.de><br>
<b>Cc:</b> ghc-steering-committee@haskell.org<br>
<b>Subject:</b> Re: [ghc-steering-committee] #380 GHC2021: Current status<o:p></o:p></span></p>
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<p class="MsoNormal">Joachim, I love your statistics :) And I think I’m less sad that you made it look: I think that NullaryTypeClasses is implied by MultiParamTypeClasses, and that MonadFailDesugaring is already (or is going to be) the default in GHC! :P<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">To get some more discussion, I would be very happy to hear reasons for and against:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">- GADTs:<o:p></o:p></p>
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<p class="MsoNormal"> - Stable and well documented,<o:p></o:p></p>
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<p class="MsoNormal"> - Adding indices to types is one of the main reasons one would like to have MultiParamTypeClasses and TypeFamilies on,<o:p></o:p></p>
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<p class="MsoNormal"> - I find the GADT syntax much nicer (but this is an extremely personal choice.)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">- RankNTypes:<o:p></o:p></p>
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<p class="MsoNormal"> - I originally voted “no”, because I find it to be part of “advanced Haskell”, and because using it may be complicated without ImpredicativeTypes on,<o:p></o:p></p>
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<p class="MsoNormal"> - On the other hand, it’s also been in GHC for ages.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On 3 Dec 2020 at 10:31:18, Joachim Breitner <<a href="mailto:mail@joachim-breitner.de">mail@joachim-breitner.de</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Dear Committee,<br>
<br>
<br>
we have 9 votes in. Dear Cale and Eric, can we have your votes please?<br>
<br>
As always, the table<br>
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fblob%2Fghc2021%2Fproposals%2F0000-ghc2021.rst%23data&data=04%7C01%7Csimonpj%40microsoft.com%7Cd1b5e56aaa764f6028e308d8976f8dc3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637425852654681789%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=rzZgJlwbhSUTgZ2bRgSMRTZiArUtaKdzyCJAdpC2wWk%3D&reserved=0">https://github.com/ghc-proposals/ghc-proposals/blob/ghc2021/proposals/0000-ghc2021.rst#data</a><br>
has the current data.<br>
<br>
We had the most discussion so far about:<br>
<br>
* The innnocence of PostfixOperators<br>
* The effect of UnicodeSyntax on error messages<br>
* Whether InstanceSigs is a good design<br>
* Whether OverloadedString is harmless enough.<br>
<br>
I see that three is less clear signal on odd extensions that are<br>
obsolete, on by default, implied by others etc. That’s probably fine<br>
and no need to worry; some of them will be resolved by virtue of being<br>
implied by others. We can also sanity-check the final result, and<br>
include all implied ones in the final design.<br>
<br>
So where do we stand?<br>
<br>
Applying the actual quota of ⅔ out of 11, i.e. 8 votes, these would go<br>
in no matter how Cale and Eric vote:<br>
<br>
BangPatterns, BinaryLiterals, ConstraintKinds, DeriveDataTypeable,<br>
DeriveFoldable, DeriveFunctor, DeriveGeneric, DeriveLift,<br>
DeriveTraversable, EmptyCase, EmptyDataDecls, EmptyDataDeriving,<br>
ExplicitForAll, FlexibleContexts, FlexibleInstances, GADTSyntax,<br>
HexFloatLiterals, ImportQualifiedPost, KindSignatures,<br>
MultiParamTypeClasses, NamedFieldPuns, NumericUnderscores,<br>
StandaloneDeriving, ViewPatterns<br>
<br>
The following have 6 or 7 votes, i.e. they’d go in if we extrapolate<br>
from the current votes:<br>
<br>
ConstrainedClassMethods, DerivingStrategies,<br>
ExistentialQuantification, GeneralisedNewtypeDeriving, InstanceSigs,<br>
NegativeLiterals, PostfixOperators, RankNTypes, RecordWildCards,<br>
ScopedTypeVariables, TupleSections, TypeApplications, TypeFamilies,<br>
TypeOperators, TypeSynonymInstances<br>
<br>
These extensions are short one vote:<br>
<br>
DataKinds, DerivingVia, GADTs, LambdaCase, PolyKinds<br>
<br>
<br>
<br>
So how sad would we all be? This is the sadness report for each<br>
committee member, showing the symmetric difference between their ballot<br>
and the (extrapolated) result.<br>
<br>
<br>
alejandro<br>
would miss:<br>
DataKinds, DerivingVia, GADTs, LambdaCase, MonadFailDesugaring,<br>
NamedWildCards, NoMonomorphismRestriction, NullaryTypeClasses,<br>
NumDecimals, OverloadedLists, OverloadedStrings, PolyKinds,<br>
StandaloneKindSignatures<br>
doesn’t want:<br>
RankNTypes<br>
<br>
arnaud<br>
would miss:<br>
Arrows, ExplicitNamespaces, ForeignFunctionInterface,<br>
FunctionalDependencies, GADTs, MonadFailDesugaring, MonoLocalBinds,<br>
PartialTypeSignatures, StarIsType, TypeFamilyDependencies<br>
doesn’t want:<br>
ExistentialQuantification, ImportQualifiedPost, InstanceSigs,<br>
NamedFieldPuns, RankNTypes, RecordWildCards, ScopedTypeVariables,<br>
TupleSections, TypeSynonymInstances<br>
<br>
iavor<br>
would miss:<br>
BlockArguments, MultiWayIf, NoMonomorphismRestriction,<br>
NullaryTypeClasses, OverloadedStrings, ParallelListComp, RecursiveDo<br>
doesn’t want:<br>
ConstrainedClassMethods, ConstraintKinds, DeriveFoldable,<br>
DeriveFunctor, DeriveTraversable, DerivingStrategies, EmptyCase,<br>
GADTSyntax, GeneralisedNewtypeDeriving, InstanceSigs, KindSignatures,<br>
NegativeLiterals, PostfixOperators, TupleSections, TypeApplications,<br>
TypeFamilies, TypeOperators<br>
<br>
joachim<br>
would miss:<br>
DataKinds, DerivingVia, ForeignFunctionInterface, GADTs, LambdaCase,<br>
MonoLocalBinds, NamedWildCards, NondecreasingIndentation,<br>
RoleAnnotations, StarIsType, UnicodeSyntax, UnliftedFFITypes,<br>
UnliftedNewtypes<br>
doesn’t want:<br>
ConstrainedClassMethods, ScopedTypeVariables, TypeSynonymInstances<br>
<br>
richard<br>
would miss:<br>
BlockArguments, DefaultSignatures, DerivingVia,<br>
DisambiguateRecordFields, ExplicitNamespaces, LexicalNegation,<br>
NamedWildCards, NumDecimals, ParallelListComp, PolyKinds,<br>
RoleAnnotations, StandaloneKindSignatures, TemplateHaskellQuotes,<br>
UnicodeSyntax, UnliftedNewtypes<br>
doesn’t want:<br>
NegativeLiterals, RecordWildCards, ScopedTypeVariables, TypeFamilies<br>
<br>
simonm<br>
would miss:<br>
DataKinds, DefaultSignatures, ForeignFunctionInterface, GADTs,<br>
LambdaCase, LiberalTypeSynonyms, MonoLocalBinds, MultiWayIf,<br>
NoMonomorphismRestriction, NondecreasingIndentation, NumDecimals,<br>
OverloadedStrings, PatternSynonyms, PolyKinds, UnicodeSyntax<br>
doesn’t want:<br>
DeriveLift, DerivingStrategies, NumericUnderscores, TypeApplications,<br>
TypeOperators, ViewPatterns<br>
<br>
spj<br>
would miss:<br>
MonoLocalBinds, NoMonomorphismRestriction, NullaryTypeClasses,<br>
OverloadedLists, OverloadedStrings, ParallelListComp, PolyKinds,<br>
RecursiveDo, RoleAnnotations, StandaloneKindSignatures, StarIsType<br>
doesn’t want:<br>
DerivingStrategies, GeneralisedNewtypeDeriving, NegativeLiterals,<br>
RecordWildCards, TupleSections, TypeFamilies<br>
<br>
tom<br>
would miss:<br>
BlockArguments, DataKinds, DefaultSignatures, DerivingVia,<br>
DisambiguateRecordFields, DuplicateRecordFields, ExplicitNamespaces,<br>
FunctionalDependencies, LambdaCase, LexicalNegation,<br>
LiberalTypeSynonyms, MagicHash, MultiWayIf, NamedWildCards,<br>
NullaryTypeClasses, NumDecimals, PackageImports, ParallelListComp,<br>
PolyKinds, QuasiQuotes, RoleAnnotations, StandaloneKindSignatures,<br>
TemplateHaskell, TemplateHaskellQuotes, TypeFamilyDependencies,<br>
UnboxedSums, UnboxedTuples, UnicodeSyntax, UnliftedNewtypes<br>
doesn’t want:<br>
none!<br>
<br>
vitaly<br>
would miss:<br>
DataKinds, DerivingVia, GADTs, LambdaCase, MonadFailDesugaring,<br>
StarIsType<br>
doesn’t want:<br>
ConstrainedClassMethods, ExistentialQuantification, PostfixOperators<br>
<br>
<br>
-- <br>
Joachim Breitner<br>
<a href="mailto:mail@joachim-breitner.de">mail@joachim-breitner.de</a><br>
<a href="https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.joachim-breitner.de%2F&data=04%7C01%7Csimonpj%40microsoft.com%7Cd1b5e56aaa764f6028e308d8976f8dc3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637425852654691785%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=5ZVahXxGFqEyoTMqj5ZitQaTKIIsSxu1G64gFcUFvjU%3D&reserved=0">http://www.joachim-breitner.de/</a><br>
<br>
<br>
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