| It occurred to me that rather than moving just these instances to a new | module, we could move the large tuples themselves to a new module | Data.LargeTuple and put the instances there. Yes, that's what I intended to suggest. Good plan. Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Reid | Barton | Sent: 05 January 2017 15:27 | To: ghc-devs@haskell.org | Subject: Large tuple strategy | | Hi all, | | https://phabricator.haskell.org/D2899 proposes adding Generic instances for | large tuples (up to size 62). Currently GHC only provides Generic instances | for tuples of size up to 7. There's been some concern about the effect that | all these instances will have on compilation time for anyone who uses | Generics, even if they don't actually use the new instances. | | There was a suggestion to move these new instances to a separate module, but | as these instances would then be orphans, I believe GHC would have to read | the interface file for that module anyways once Generic comes into scope, | which would defeat the purpose of the split. | | It occurred to me that rather than moving just these instances to a new | module, we could move the large tuples themselves to a new module | Data.LargeTuple and put the instances there. The Prelude would reexport the | large tuples, so there would be no user-visible change. | According to my experiments, GHC should never have to read the | Data.LargeTuple interface file unless a program actually mentions a large | tuple type, which is presumably rare. We could then also extend the existing | instances for Eq, Show, etc., which are currently only provided through 15- | tuples. | | A nontrivial aspect of this change is that tuples are wired-in types, and | they currently all live in the ghc-prim package. I'm actually not sure why | they need to be wired-in rather than ordinary types with a funny-looking | name. In any case I need to look into this further, but the difficulties | here don't seem to be insurmountable. | | Does this seem like a reasonable plan? Anything important I have missed? | | Regards, | Reid Barton | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.haskell | .org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc- | devs&data=02%7C01%7Csimonpj%40microsoft.com%7Cd3262b1204df407f65ce08d4357f4b | d8%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636192268229980651&sdata=NV% | 2BaCgD7Xo5EIwuL5cZaTrCBHihNxAiZvT0VCNQl6Z8%3D&reserved=0