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February 2004

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System.system
by Ian Lynagh 11 Feb '04

11 Feb '04

Hi, In src/prelude/System/SystemFun.hs the OS's system function is called to implement System.system. However, the various checks are not done and WEXITSTATUS is not applied as appropriate. It looks like src/runtime/Builtin/cSystem.c does the same thing. src/libraries/base/System/Cmd.hs uses systemCmd when __GLASGOW_HASKELL__ is defined, which is defined in libraries/base/cbits/system.c. This looks like it is doing the right stuff. This causes this: -----8<----------8<----------8<----------8<----- main :: IO () main = mapM_ f [0..5] f :: Int -> IO () f i = do x <- system $ "exit " ++ show i print x -----8<----------8<----------8<----------8<----- to output this for me: ExitSuccess ExitFailure 256 ExitFailure 512 ExitFailure 768 ExitFailure 1024 ExitFailure 1280 Thanks Ian

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Re: cvs commit: nhc98/src/libraries/base/Data Tree.hs
by Ross Paterson 04 Feb '04

04 Feb '04

On Wed, Feb 04, 2004 at 02:51:18AM -0800, Malcolm Wallace wrote: > malcolm 2004/02/04 02:51:18 PST > > Modified files: > src/libraries/base/Data Tree.hs > Log: > Exclude functions 'unfoldTreeM' and 'unfoldForestM' in nhc98. > For some unknown reason they result in a type inference error: > "No default for Prelude.Monad" Curious bug (in nhc98) -- it seems you need mutual recursion to trigger it, as in: mapM_1 :: Monad m => (a -> m b) -> [a] -> m () mapM_1 f [] = return () mapM_1 f (x:xs) = f x >> mapM_2 f xs mapM_2 :: Monad m => (a -> m b) -> [a] -> m () mapM_2 f [] = return () mapM_2 f (x:xs) = f x >> mapM_1 f xs Delete either signature and it goes away.

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