February 2014 - ghc-devs

RE: [GHC] #8704: Use GHC.Exts.build in randoms, randomRs to achieve fusion
by Simon Peyton Jones 04 Feb '14

04 Feb '14

Hi Ryan Are you on this thread? You probably should be! Simon | -----Original Message----- | From: ghc-tickets [mailto:ghc-tickets-bounces@haskell.org] On Behalf Of | GHC | Sent: 27 January 2014 18:49 | Cc: ghc-tickets(a)haskell.org | Subject: Re: [GHC] #8704: Use GHC.Exts.build in randoms, randomRs to | achieve fusion | | #8704: Use GHC.Exts.build in randoms, randomRs to achieve fusion | -------------------------------------+--------------------------------- | --- | Reporter: ion1 | Owner: | Type: feature request | Status: patch | Priority: normal | Milestone: | Component: libraries/random | Version: 7.6.3 | Resolution: | Keywords: fusion | Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple | Type of failure: None/Unknown | Difficulty: Unknown | Test Case: | Blocked By: | Blocking: | Related Tickets: #4218 | -------------------------------------+--------------------------------- | --- | | Comment (by nomeata): | | Thanks. From my POV it is worth adding even if you can’t measure a | performance gain; it is still good to know that nice code is being | generated. But of course it is up to Ryan Newton (random maintainer) | to | decide this. | | -- | Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8704#comment:4> | GHC <http://www.haskell.org/ghc/> | The Glasgow Haskell Compiler | _______________________________________________ | ghc-tickets mailing list | ghc-tickets(a)haskell.org | http://www.haskell.org/mailman/listinfo/ghc-tickets

2 1

please elaborate on comment for base:Data.Type.Equality.(==)?
by Nicolas Frisby 04 Feb '14

04 Feb '14

[CC'ing Richard, as I'm guessing he's the author of the comment.] I have a question regarding the comment on the type family Data.Type.Equality.(==). "A poly-kinded instance [of ==] is *not* provided, as a recursive definition for algebraic kinds is generally more useful." Can someone elaborate on "generally more useful". Thank you.

2 2

GHC boot-library package changelogs & release-notes
by Herbert Valerio Riedel 04 Feb '14

04 Feb '14

Hello fellow GHC devs, As some of you might have noticed, I added a changelog.md file to libraries/base: https://github.com/ghc/packages-base/blob/c8634027d4e3315a2276fb1be8168c486… (please feel free to fix any typos/omissions/whatever you notice) My hope/motivation is that since Hackage gained the ability to display changelog files, the rather extensive changes in `base` might be a bit more easily/conveniently accessible on Hackage. I chose to use Markdown format, as I believe it may be more convenient to maintain/edit the `base` changelog as plain text rather than having to edit XML after each noteworthy change in `base`. And as the release-notes typically only exploit a subset of the Docbook facilities, the conversion to Docbook XML could be performed semi-automatically shortly before a release. Moreover, the release notes from previous major GHC release (which in the past contained the major changes in `base` et al.) are usually removed again. While a separate changelog file would usually retain (more) version history. Therefore, I'd propose to switch from editing the user's guide release note for library release notes to using Hackage-changelog files in Markdown format (following a common structural convention) and make it the release-manager's responsibility to integrate the respective package's changelog content into the user's guide. Any comments? Cheers, hvr

4 3

TypeNats trial on new ghc branch 7.8
by Gabriel Riba 01 Feb '14

01 Feb '14

I know that the TypeNats solver may not have been merged with 7.8 branch but the compiler error looks so simple: Couldn't match type ‛(n + m) - 1’ with ‛(n - 1) + m’ --------------------------------- {-# LANGUAGE DataKinds, GADTs, KindSignatures, TypeOperators, PolyKinds, ExistentialQuantification #-} import GHC.TypeLits data Vect :: Nat -> * -> * where Nil :: Vect 0 a Cons :: a -> Vect (n-1) a -> Vect n a data MyProxy (n::Nat) = forall a. MyProxy (Vect n a) toProxy :: Vect (n::Nat) a -> MyProxy n toProxy v = MyProxy v len :: KnownNat n => Vect (n::Nat) a -> Integer len v = (natVal . toProxy) v -- Ok append :: Vect n a -> Vect m a -> Vect (n+m) a append Nil ys = ys append (Cons x xs) ys = Cons x (append xs ys) -- compiler error main = do print $ len Nil -- Ok print $ len (Cons (1::Int) Nil) -- Ok ------------------------------------------------------ Error on "append (Cons x xs) ys = ..." Couldn't match type ‛(n + m) - 1’ with ‛(n - 1) + m’ Expected type: Vect ((n + m) - 1) a Actual type: Vect ((n - 1) + m) a

4 3