November 2002 - Hugs-Bugs

Instalation fails everytime....*g*
by Everyone 10 Nov '02

10 Nov '02

Hi there Hugs-Bugs-team, Now you think: >>Boy, again somebody who doesn't know how to handle our smooth msi-installation file...but I got a problem here of a different kind... I start the installation, agree to the license and don't change the directory where to install, but if I click next...I instantly see this Page: Installation Incomplete the installer was interrupted before Hugs98 - December 2001 could be installed. You need to restart the installer to try again. Click "Close" to exit. What can I do, to get Hugs installed on my computer... A computer-science-student of the Freie Universtät Berlin

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M�jde - ProHack.Net A��ld� !!!
by ProHack.Net 10 Nov '02

10 Nov '02

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(no subject)
by Pedro Fialho 10 Nov '02

10 Nov '02

hi! can u tell me why does my system don't let me open any file, displaying the following message: Prelude> :l maiuscu Reading file "maiuscu": ERROR "maiuscu" - Unable to open file "maiuscu" Prelude> How should I solve this???tks

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GC bug
by John Hughes 09 Nov '02

09 Nov '02

The attached program (needs the Hugs Graphics Library) reveals what I presume is a GC bug in the Dec 2001 hugs. John ----- Original Message ----- From: "John Hughes" <john.hughes(a)swipnet.se> To: "Alastair Reid" <alastair(a)reid-consulting-uk.ltd.uk> Sent: Friday, November 08, 2002 2:58 PM Subject: Re: HGL > > > > > > Alastair, Just for a bit of fun, I solved the first programming lab > > > on our Java course using HGL instead. You might like to run the > > > attached program to see the result! > > > > That's pretty cool. Thanks. > > > > > Give it a BIG heap, or you'll hit the same GC bug in Hugs that I did. > > > > I do indeed need a big heap. > > > > How do you know it's a GC bug and not just a space leak? > > If we can, I'd like to fix it if it's a bug (or even if it's not a 'bug' > > but can be fixed.) > > > > Well, I get different behaviour depending on the heap size. For example, > with a heap size of 250000, > > Main> main > > Thread raised exception: {{Cell ...}} > Uncaught Error: {{Cell ...}} > > or, in a fresh winhugs, > > Main> foldr1 (.+) (take 10000 (points ())) > > Program error: {primIntegerToInt (-2147483648)} > > Repeating that, by the way, gives > > Main> foldr1 (.+) (take 10000 (points ())) > > ERROR - Garbage collection fails to reclaim sufficient space > > With a heap size of 249999, I get¨ > > Main> main > > ERROR - Garbage collection fails to reclaim sufficient space > > Main> foldr1 (.+) (take 10000 (points ())) > > Program error: {primIntegerToInt 352126429244364} > > Behaviour that depends on the heap size looks like a GC bug to me. > > I would have liked to pare the program down to a small one exhibiting the > same problem, but that proved difficult. What I did discover is that the > type signature on transform is crucial: removing it changes the behaviour, > for reasons which are not at all clear to me. > > Good luck with bug-hunting! > > John > >

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WinHugs Problem
by Mark Cummins 07 Nov '02

07 Nov '02

Hi, Im having trouble with WinHugs on Windows ME. When I installed it a few days ago it worked fine. Now it crashes on startup with "Winhugs has caused an error in Winhugs.EXE". I've uninstalled any software I installed after Hugs, and reinstalled Hugs multiple times, but I still get exactly the same error. The command line Hugs works fine. Mark.

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winhugs can't start
by Phat Tran 07 Nov '02

07 Nov '02

Hi! I have a strange problem after a confliction. Well first, I had winhugs in edit-mode then I opened the same file with Jcreator and did some changes and tried to reload the haskell program. At this point there was some thing wrong that it adwised me that it have to turn winhugs off. This was don't automatically by win2000. After this apposal the same precedure kept repeating. I don't know if I have to reinstall my windows or if there is a better way to fix this. I have already try reinstall Hugs98 but have not solve anything. So if you can help me it would be very nice. Sincerely, Phat

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winhugs window disappears
by Mordechai Ben-Ari 07 Nov '02

07 Nov '02

Hello I have used hugs98 with the winhugs gui for a couple of weeks with no problem. Suddenly, every time i try to run it, the window flashes briefly and disappears. Running hugs.exe from a command line still works. I tried uninstalling/rebooting/reinstalling, to no avail. My system is windows xp. Any ideas? Thanks Moti Prof. Moti Ben-Ari Department of Science Teaching, Weizmann Institute of Science and Department of Computer Science University of Joensuu PO Box 111, FIN-80101 Joensuu, Finland Tel: +358-13-251-7951, Fax: -7955 mailto:moti.ben-ari@cs.joensuu.fi http://cs.joensuu.fi/~moti

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Help me!!!!
by Hai 07 Nov '02

07 Nov '02

Please help me,I have just study FP for a while!!!!And I can not execute my file using Hugs!!!Please help me doing this!!!!!!!Thank you very much!!!

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RE: "Could not unambiguously deduce"..
by Simon Peyton-Jones 06 Nov '02

06 Nov '02

| Yes, but isn't that an implementation problem surfacing at the | language level? All the dictionaries needed to delay the decision to | the point of use could also be made available when compiling the | original program, no? After all, that's the reason why there's an | ambiguity in the first place. No, it's not. It's tricky to understand and tricky to explain. I'll have one more go. Consider just this: | > | class C t where | > | expl :: t -> String | > | expl x "default" | > | | > | instance C String where expl s = "String" | > | instance C a => C [a] where expl l = "[a]" Now try this: f :: C a => [a] -> String f xs = expl xs ++ "\n" foo1 = f "wig" foo2 = expl "wig" ++ "\n" baz1 = f [True] baz2 = expl [True] ++ "\n" I think we'll agree that foo2 should return "String\n" and baz2 should return "[a]\n".] But what about foo1 and baz1? Both execute the code for 'f'. What does f do? It needs a dictionary for C[a] to deal with the call (expl xs). BUT it does not know what 'a' is going to be. It can't choose the String instance. So perhaps it should choose the C [a] instance? Well, it could, but then (f xs) would always return "[a]\n". And 'f' must choose one of the two instances right now, because all it's passed is a dictionary for (C a). If, instead, we say f :: C [a] => [a] -> String then f doesn't have to choose which instance... it can just use the C[a] dictionary that is passed. Then in foo1, the compiler knows that it should pass a (C String) dictionary, and in baz1 it should pass a (C [Boo]) dictionary and all is well. In your example things are slightly more complicated because it's the instance decl that gives rise to the problem, but it's just the same issue. Simon | | Not to mention that in the case for which there is an overlap, the | String instance will always be chosen as the more specific one.. | | Claus | | > | data T a ý [a] | > | | > | class C t where | > | expl :: t -> String | > | expl x ÿdefault" | > | | > | instance C String where expl s "String" | > | instance C a ÿC [a] where expl l "[a]" | > | | > | instance (C a {- ,C [a] -} ) ÿC (T a) where | > | expl (D xs) þxpl xs | > | | > | main ÿutStrLn $ expl "hi" | > | | > | ------------ | > | | > | As is, both ghc and hugs reject the program, whereas | > | both accept it with the extra constraint in the C (T a) | > | instance.. Now, I think I can see how the right-hand-side | > | expl could come either from the C String or from the C [a] | > | instance - hence ghc's message: | > | | > | $ ghc --make Tst.hs | > | c:\ghc\ghc-5.04\bin\ghc.exe: chasing modules from: Tst.hs | > | Compiling Main ( Tst.hs, ./Tst.o ) | > | | > | Tst.hs:15: | > | Could not unambiguously deduce (C [a]) | > | from the context (C (T a), C a) | > | The choice of (overlapping) instance declaration | > | depends on the instantiation of `a' | > | Probable fix: | > | Add (C [a]) to the class or instance method `expl' | > | Or add an instance declaration for (C [a]) | > | arising from use of `expl' at Tst.hs:15 | > | In the definition of `expl': expl xs | > | | > | | > | Confused, | > | Claus | > | | > | PS. Perhaps related, but why does Hugs seem to ignore the | > | C a constraint in the context of the original version? | > | | > | $ hugs -98 Tst.hs | > | __ __ __ __ ____ ___ | > | _________________________________________ | > | || || || || || || ||__ Hugs 98: Based on the Haskell 98 | > | standard | > | ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2001 | > | ||---|| ___|| World Wide Web: | > | http://haskell.org/hugs | > | || || Report bugs to: | > | hugs-bugs(a)haskell.org | > | || || Version: December 2001 | > | _________________________________________ | > | | > | Hugs mode: Restart with command line option +98 for Haskell 98 | > mode | > | | > | Reading file "c:\Program Files\Hugs98\\lib\Prelude.hs": | > | Reading file "Tst.hs": | > | Type checking | > | ERROR "Tst.hs":15 - Cannot justify constraints in instance member | > | binding | > | *** Expression : expl | > | *** Type : C (T a) ÿT a -> String | > | *** Given context : C (T a) | > | *** Constraints : C [a] | > | | > | Prelude> | > | _______________________________________________ | > | Glasgow-haskell-bugs mailing list | > | Glasgow-haskell-bugs(a)haskell.org | > | http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs |

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Re: "Could not unambiguously deduce"..
by C.Reinke 06 Nov '02

06 Nov '02

> | What I don't understand, however, is why adding that extra > | constraint helps in any way? Shouldn't the addition of new > | things in the context only make more options available? Why > | does it make some of the existing, amgibuous options go away? > > With the extra constraint, the instance decl can build a C (T a) > dictionary from a (C a, C [a]) dictionary, by choosing the expl > method from the C [a] dictionary it is passed (ignoring the C a > one). That defers the choice of which of the overlapping instance > decls we are going to use. Perhaps it'll be postponed to a point > at which 'a' is known, in which case the choice is easy. The > point is that we don't want to have to choose between the C String > and C [a] instance decls until we know enough about 'a' to choose > the right one. Yes, but isn't that an implementation problem surfacing at the language level? All the dictionaries needed to delay the decision to the point of use could also be made available when compiling the original program, no? After all, that's the reason why there's an ambiguity in the first place. Not to mention that in the case for which there is an overlap, the String instance will always be chosen as the more specific one.. Claus > | data T a ý [a] > | > | class C t where > | expl :: t -> String > | expl x ÿdefault" > | > | instance C String where expl s ÿString" > | instance C a ÿC [a] where expl l ÿ[a]" > | > | instance (C a {- ,C [a] -} ) ÿC (T a) where > | expl (D xs) þxpl xs > | > | main ÿutStrLn $ expl "hi" > | > | ------------ > | > | As is, both ghc and hugs reject the program, whereas > | both accept it with the extra constraint in the C (T a) > | instance.. Now, I think I can see how the right-hand-side > | expl could come either from the C String or from the C [a] > | instance - hence ghc's message: > | > | $ ghc --make Tst.hs > | c:\ghc\ghc-5.04\bin\ghc.exe: chasing modules from: Tst.hs > | Compiling Main ( Tst.hs, ./Tst.o ) > | > | Tst.hs:15: > | Could not unambiguously deduce (C [a]) > | from the context (C (T a), C a) > | The choice of (overlapping) instance declaration > | depends on the instantiation of `a' > | Probable fix: > | Add (C [a]) to the class or instance method `expl' > | Or add an instance declaration for (C [a]) > | arising from use of `expl' at Tst.hs:15 > | In the definition of `expl': expl xs > | > | > | Confused, > | Claus > | > | PS. Perhaps related, but why does Hugs seem to ignore the > | C a constraint in the context of the original version? > | > | $ hugs -98 Tst.hs > | __ __ __ __ ____ ___ > | _________________________________________ > | || || || || || || ||__ Hugs 98: Based on the Haskell 98 > | standard > | ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2001 > | ||---|| ___|| World Wide Web: > | http://haskell.org/hugs > | || || Report bugs to: > | hugs-bugs(a)haskell.org > | || || Version: December 2001 > | _________________________________________ > | > | Hugs mode: Restart with command line option +98 for Haskell 98 > mode > | > | Reading file "c:\Program Files\Hugs98\\lib\Prelude.hs": > | Reading file "Tst.hs": > | Type checking > | ERROR "Tst.hs":15 - Cannot justify constraints in instance member > | binding > | *** Expression : expl > | *** Type : C (T a) ÿT a -> String > | *** Given context : C (T a) > | *** Constraints : C [a] > | > | Prelude> > | _______________________________________________ > | Glasgow-haskell-bugs mailing list > | Glasgow-haskell-bugs(a)haskell.org > | http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

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