Re: ANNOUNCE: GHC 7.0.1 Release Candidate 2
On 10/29/10 20:19, Bas van Dijk wrote:
I'm not sure this is in rc2 since I'm using the latest ghc-HEAD (7.1.20101029).
In ghc< 7 you needed to import symbols like fromInteger, (>>=) and
fail when you used them indirectly. For example when using integer
literals or do-notation.
I noticed that in my ghc-HEAD this isn't needed anymore:
{-# OPTIONS_GHC -Wall #-}
{-# LANGUAGE NoImplicitPrelude #-}
Yes, in HEAD only, NoImplicitPrelude no longer implies RebindableSyntax.
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=ghc;a=darcs_commitdiff;h=20101022143400-1287e-746a83b4269744bb54177753c8ff67bec542b46c.gz
import Control.Monad ( return )
import System.IO ( IO )
import Data.Int
-- Only needed for ghc< 7.
-- In fact, the following gives a redundancy warning in ghc-7:
import Control.Monad ( (>>=), fail )
import Prelude ( fromInteger )
However, a redundancy warning sounds wrong (or at least confusing). An
"unused import" warning seems more appropriate to me, although it's a
bit of a grey area. If you remove LANGUAGE NoImplicitPrelude from the
module, what warning do you get? (maybe test that in HEAD as well as
6.12 or so)
-Isaac
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Re: ANNOUNCE: GHC 7.0.1 Release Candidate 2
I'm not sure this is in rc2 since I'm using the latest ghc-HEAD (7.1.20101029).
In ghc < 7 you needed to import symbols like fromInteger, (>>=) and
fail when you used them indirectly. For example when using integer
literals or do-notation.
I noticed that in my ghc-HEAD this isn't needed anymore:
{-# OPTIONS_GHC -Wall #-}
{-# LANGUAGE NoImplicitPrelude #-}
import Control.Monad ( return )
import System.IO ( IO )
import Data.Int
-- Only needed for ghc < 7.
-- In fact, the following gives a redundancy warning in ghc-7:
import Control.Monad ( (>>=), fail )
import Prelude ( fromInteger )
main :: IO ()
main = do _ <- return (1 :: Int)
return ()
Is this intentional?
Regards,
Bas
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Re: Type error in GHC-7 but not in GHC-6.12.3
On Fri, Oct 29, 2010 at 5:42 PM, Simon Peyton-Jones
wrote:
> That looks odd.
>
> Can you isolate it for us? The easiest thing is usually to start with the
> offending code:
> withDeviceWhich ∷
> ∀ pr α
> . MonadCatchIO pr
> ⇒ USB.Ctx
> → (USB.DeviceDesc → Bool)
> → (∀ s. RegionalDeviceHandle (RegionT s pr) → RegionT s pr α)
> → pr α
> withDeviceWhich ctx p f = do
> devs ← liftIO $ USB.getDevices ctx
> useWhich devs withDevice p f
>
> Now add local definitions for each of the functions mentioned, with
> definition foo = undefined.
>
> useWhich ∷
> ∀ k desc e (m ∷ * → *) α
> . (GetDescriptor e desc, MonadIO m)
> ⇒ [e]
> → (e → k → m α)
> → (desc → Bool)
> → k
> → m α
> useWhich = undefined.
>
> Now all you need is the types involved, and you can probably define them as
>
> data RegionT s pr a
>
> etc
>
> That should give a standalone test case.
>
> Thanks!
>
> SImon
>
Ok, Here's the more isolated program which still gives the same error
as the full usb-safe (on the latest ghc-HEAD (7.1.20101029)):
USBSafeTest.hs:39:57:
Couldn't match expected type `forall s.
RegionalDeviceHandle (RegionT s pr)
-> RegionT s pr α'
with actual type `RegionalDeviceHandle (RegionT s pr)
-> RegionT s pr α'
In the fourth argument of `useWhich', namely `f'
In the expression: useWhich devs withDevice p f
In the expression:
do { devs <- return [Device];
useWhich devs withDevice p f }
{-# LANGUAGE UnicodeSyntax
, KindSignatures
, RankNTypes
, MultiParamTypeClasses
, FunctionalDependencies
#-}
import Data.List (find)
data Ctx = Ctx
data Device = Device
data DeviceDesc = DeviceDesc
data RegionalDeviceHandle (r ∷ * → *) = RegionalDeviceHandle
data RegionT s (pr ∷ * → *) α = RegionT
instance Monad pr ⇒ Monad (RegionT s pr) where
return = undefined
(>>=) = undefined
runRegionT ∷ (∀ s. RegionT s pr α) → pr α
runRegionT = undefined
openDevice ∷ Device → RegionT s pr (RegionalDeviceHandle (RegionT s pr))
openDevice = undefined
withDevice ∷ Monad pr
⇒ Device
→ (∀ s. RegionalDeviceHandle (RegionT s pr) → RegionT s pr α)
→ pr α
withDevice dev f = runRegionT $ openDevice dev >>= f
withDeviceWhich ∷ ∀ pr α
. Monad pr
⇒ Ctx
→ (DeviceDesc → Bool)
→ (∀ s. RegionalDeviceHandle (RegionT s pr) → RegionT s pr α)
→ pr α
withDeviceWhich ctx p f = do devs ← return [Device]
useWhich devs withDevice p f
useWhich ∷ ∀ k desc e (m ∷ * → *) α
. (GetDescriptor e desc)
⇒ [e]
→ (e → k → m α)
→ (desc → Bool)
→ k
→ m α
useWhich ds w p f = case find (p . getDesc) ds of
Nothing → error "not found"
Just d → w d f
class GetDescriptor α desc | α → desc, desc → α where
getDesc ∷ α → desc
instance GetDescriptor Device DeviceDesc where
getDesc = undefined
I could isolate it a bit more if you want.
Thanks,
Bas
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ANNOUNCE: GHC 7.0.1 Release Candidate 2
We are pleased to announce the second release candidate for GHC 7.0.1: http://new-www.haskell.org/ghc/dist/7.0.1-rc2/ This includes the source tarball, installers for OS X and Windows, and bindists for amd64/Linux, i386/Linux, amd64/FreeBSD and i386/FreeBSD. Amongst the changes since RC 1 are: * -fglasgow-exts now gives a deprecated warning, and no longer enables GADTs or TypeFamilies. * The haskell98 packge is no longer automatically linked, although this often won't make a difference as --make is now enabled by default. Please test as much as possible; bugs are much cheaper if we find them before the release! Thanks Ian, on behalf of the GHC team ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Type error in GHC-7 but not in GHC-6.12.3
Hello, I'm updating my usb-safe package for GHC-7: darcs get http://code.haskell.org/~basvandijk/code/usb-safe It depends on the HEAD version of regions: darcs get http://code.haskell.org/~basvandijk/code/regions I think I'm suffering from the new implied MonoLocalBinds extension (I'm using GADTs) as described in: http://hackage.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 However, I'm not sure this is the problem because I'm not using local bindings and use explicit type signatures everywhere. I try to make a small isolated example when I have time but for now let's use the actual definitions: The following function type-checked fine in GHC-6.12.3 but fails in GHC-7.1.20101027: withDeviceWhich ∷ ∀ pr α . MonadCatchIO pr ⇒ USB.Ctx → (USB.DeviceDesc → Bool) → (∀ s. RegionalDeviceHandle (RegionT s pr) → RegionT s pr α) → pr α withDeviceWhich ctx p f = do devs ← liftIO $ USB.getDevices ctx useWhich devs withDevice p f The error I get is: Couldn't match expected type `forall s. RegionalDeviceHandle (RegionT s pr) -> RegionT s pr α' with actual type `RegionalDeviceHandle (RegionT s pr) -> RegionT s pr α' In the fourth argument of `useWhich', namely `f' These are the types and definitions of the other functions involved: useWhich ∷ ∀ k desc e (m ∷ * → *) α . (GetDescriptor e desc, MonadIO m) ⇒ [e] → (e → k → m α) → (desc → Bool) → k → m α useWhich ds w p f = case find (p ∘ getDesc) ds of Nothing → throw USB.NotFoundException Just d → w d f withDevice ∷ MonadCatchIO pr ⇒ USB.Device → (∀ s. RegionalDeviceHandle (RegionT s pr) → RegionT s pr α) → pr α withDevice dev f = runRegionT $ openDevice dev >>= f Note that when I inline the definition of useWhich it type-checks fine: withDeviceWhich ctx p f = do devs ← liftIO $ USB.getDevices ctx case find (p ∘ getDesc) devs of Nothing → throw USB.NotFoundException Just d → withDevice d f Since I'm not using local bindings and use explicit type signatures everywhere, I'm not sure MonoLocalBinds is the problem. Note that other applications of useWhich which also use RankNTypes type-check just fine in both GHC-6.12.3 and GHC-7.1.20101027: --- setConfigWhich ∷ ∀ pr cr α . (pr `AncestorRegion` cr, MonadCatchIO cr) ⇒ RegionalDeviceHandle pr → (USB.ConfigDesc → Bool) → (∀ sCfg. ConfigHandle sCfg → cr α) → cr α setConfigWhich h = useWhich (getConfigs h) setConfig getConfigs ∷ RegionalDeviceHandle r → [Config r] setConfig ∷ ∀ pr cr α . (pr `AncestorRegion` cr, MonadCatchIO cr) ⇒ Config pr → (∀ sCfg. ConfigHandle sCfg → cr α) → cr α --- withInterfaceWhich ∷ ∀ pr sCfg α . MonadCatchIO pr ⇒ ConfigHandle sCfg → (USB.Interface → Bool) → (∀ s. RegionalInterfaceHandle sCfg (RegionT s pr) → RegionT s pr α) → pr α withInterfaceWhich h = useWhich (getInterfaces h) withInterface getInterfaces ∷ ConfigHandle sCfg → [Interface sCfg] withInterface ∷ ∀ pr sCfg α . MonadCatchIO pr ⇒ Interface sCfg → (∀ s. RegionalInterfaceHandle sCfg (RegionT s pr) → RegionT s pr α) → pr α --- setAlternateWhich ∷ ∀ pr cr sCfg α . (pr `AncestorRegion` cr, MonadCatchIO cr) ⇒ RegionalInterfaceHandle sCfg pr → (USB.InterfaceDesc → Bool) → (∀ sAlt. AlternateHandle sAlt pr → cr α) → cr α setAlternateWhich h = useWhich (getAlternates h) setAlternate getAlternates ∷ RegionalInterfaceHandle sCfg r → [Alternate sCfg r] setAlternate ∷ ∀ pr cr sCfg α . (pr `AncestorRegion` cr, MonadCatchIO cr) ⇒ Alternate sCfg pr → (∀ sAlt. AlternateHandle sAlt pr → cr α) → cr α --- I'm happy to provide more info when needed. Regards, Bas ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
