March 2003 - Hugs-Bugs

Hugs internal error, parsing
by Scott Turner 17 Mar '03

17 Mar '03

I'm using :version -- Hugs Version November 2002 If I make a .hs file with the two lines: import Maybe Need. And do a :load IE.hs, the output is Reading file "IE.hs": Reading file "/usr/local/lib/hugs/lib/Maybe.hs": Reading file "IE.hs": INTERNAL ERROR: parseInput

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Direct use of if-then-else with function type cause "Program error"
by Mike Gunter 14 Mar '03

14 Mar '03

With the following code > run f = f 7 (-3) > programError wd initVal = (if initVal < 0 then showAsUnsiged else const show) wd initVal > noProblem wd initVal = f wd initVal where f = if initVal < 0 then showAsUnsiged else const show > showAsUnsiged width nIn = show n where n | nIn < 0 = 2^width + nIn > | otherwise = nIn I get: $ hugs HugsIfFuncBug.lhs __ __ __ __ ____ ___ _________________________________________ || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2002 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Report bugs to: hugs-bugs(a)haskell.org || || Version: November 2002 _________________________________________ Haskell 98 mode: Restart with command line option -98 to enable extensions Reading file "/usr/lib/hugs/libraries/Hugs/Prelude.hs": Reading file "/usr/lib/hugs/libraries/Prelude.hs": Reading file "HugsIfFuncBug.lhs": Hugs session for: /usr/lib/hugs/libraries/Hugs/Prelude.hs /usr/lib/hugs/libraries/Prelude.hs HugsIfFuncBug.lhs Type :? for help Main> run noProblem "125" Main> run programError " Program error: {instShow_v14_v1224 (showAsUnsiged instIntegral_v34 instOrd_v27 instNum_v30 (Num_fromInt (Real__sc0_Real (Integral__sc0_Integral instIntegral_v34)) 7))} Main> :q [Leaving Hugs] Thanks. mike

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Hugs documentation update
by Henk-Jan.van.Tuyl 06 Mar '03

06 Mar '03

L.S., The web page http://cvs.haskell.org/Hugs/pages/hugsman/libs.html states: The libraries Directory, Time, and CPUTime, are not currently supported. As there are files Directory.hs, Time.hs, and CPUTime.hs in the {Hugs}\lib directory, I suppose this is not true anymore. Greetings, Henk-Jan van Tuyl --

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type inference bug
by Mark Tullsen 05 Mar '03

05 Mar '03

Here's a (serious) bug in the type-inferencer of the November 2002 Hugs (tested using hugs98-Nov2002-rh7.3-1.i386.rpm): data T a b = T {f1 :: a, f2 :: b} updateF1 x t = t{f1 = x} the type inferred for updateF1: observed behavior: updateF1 :: a -> T b c -> T a d expected behavior: updateF1 :: a -> T b c -> T a c FYI, this bug didn't exist in the Dec 2001 version. - Mark

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Concurrent Haskell bug?
by Daniel McNeill 02 Mar '03

02 Mar '03

{- Hi, Possible Concurrent Haskell bug Here is an attempt at concurrent, data-driven assertions for Haskell. The code has been simplified to just work for type Char: -} import Concurrent import IOExts(unsafePerformIO) assert :: (Char -> Bool) -> Char -> Char assert p x = unsafePerformIO $ do mv <- newEmptyMVar forkIO $ check p (listen mv) return (demand mv x) check :: (a -> Bool) -> a -> IO () check p x | p x = return () | otherwise = putStrLn "Assertion failed!" demand :: MVar Char -> Char -> Char demand mv c = unsafePerformIO $ do putMVar mv c; yield; return c listen :: MVar Char -> Char listen mv = unsafePerformIO $ takeMVar mv main :: IO () main = putChar (assert (isLower) 'z') {- When main is evaluated, it causes evaluation of assert, which returns the data it was called on, but also forks a "check" IO action to check predicate p on the data. This check is synchronised using "listen" which waits on an MVar into which the data will be placed when available. The data is placed here by evaluation of "demand" (which is returned by assert). Demand yields after putting the data, to allow the check to be carried out before computation is continued. In this example, the data is immediately available so the result should simply be 'z'. However, the actual output is: Thread raised exception: no more threads (deadlock?) which must then be interrupted with Ctrl-C. If listen is replaced with the following version, the printout "takeMVar: 'z'" occurs after the message about the exception, but execution still halts. listen mv = unsafePerformIO $ do val <- takeMVar mv putStrLn ("takeMVar: " ++ show val) return val I've tried the code in GHC and it works fine. Any ideas? Cheers, Dan -}

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Your message to Hugs-Users awaits moderator approval
by hugs-users-admin＠haskell.org 01 Mar '03

01 Mar '03

Your mail to 'Hugs-Users' with the subject Sos! Is being held until the list moderator can review it for approval. The reason it is being held: Message body is too big: 131572 bytes but there's a limit of 40 KB Either the message will get posted to the list, or you will receive notification of the moderator's decision.

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