February 2004 - Hugs-Bugs

Undefined variable bug
by John Tromp 27 Feb '07

27 Feb '07

I just found out that I can circumvent the problem by adding a line import Char to my loaded file. regards, -john

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[Hugs-bugs] Hugs needs redundant constraint
by Bjorn Bringert 09 Feb '04

09 Feb '04

I am not sure if this is a bug or not, but I have found a program where Hugs (Nov 2003) requires adding a redundant constraint to class methods. Loading this code (it is quite useless, but it is the smallest example I could come up with that gave the same error message as my much larger actual program): class FromStr a where fromStr :: String -> a typeError :: FromStr a => a -> a typeError t = error "type error" instance FromStr [a] where fromStr _ = typeError undefined -- line 8 instance FromStr [(String,a)] where -- line 10 fromStr _ = typeError undefined -- line 11 with "hugs -98 +o test.hs" gives me: ERROR "test.hs":8 - Cannot justify constraints in instance member binding *** Expression : fromStr *** Type : FromStr [a] => String -> [a] *** Given context : FromStr [a] *** Constraints : FromStr [a] Adding the constraint "FromStr a" to the declaration of fromStr fixes the problem, but that seems like it should be redundant. Removing the second instance (lines 10-11) also fixes the problem, interestingly enough. /Bjorn Bringert

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[Hugs-bugs] the woes of non-cvs haskellers
by Claus Reinke 08 Feb '04

08 Feb '04

Dear all, I'm getting more and more worried about Haskell users who depend on multiple Haskell packages and compilers, but don't want to follow the cvs developments for all of these packages. I have the feeling that Haskellers who rely on pre-packaged binaries are not currently getting a good impression of the state of the art. To give just one concrete example, what packages do I recommend to someone wanting to learn a bit of Haskell, and do some graphics and perhaps windowing, on Windows? - Hugs (Winhugs bug in current binary release, so better avoid that and use plain Hugs?) - HGL (does it work with latest Hugs/GHC, or do I need older versions? which ones?) - GHC (current binary release seems to have serious probs on some Windows versions; has also seen some rapid development breakage recently, e.g., TH syntax, forcing other packages to play catch-up just to get working again) - wxHaskell (works with ghc-6.0.1, will it work with 6.2? what about Hugs? what about ghc-6.4?) - some generic text-editor (but on Windows98, the way that .hs files are associated with Hugs/GHC cannot be modified in the standard dialogues, as they can for other associations, so how do I associate .hs files with an editor? I wouldn't want to recommend some beginner editing the registry for that purpose..) The issues are usually small, but there are many of them, each package has its own, and all too often the response is "fixed in CVS, will be in next release". Of course, the next release is a while a away and by that time, there'll be a different set of small issues plagueing the next set of binary releases. So, just getting someone started requires careful investigation/testing and some thinking (instead of: "just download and install the latest Haskell starters set"). A modular way to fix this would be to have at least once-a-month patch updates of binary packages, so that one would never be more than a month away from the fixed versions (instead of having to wait for the next releases of everything). A broader approach would be to try and show a united Haskell tools front to the general Haskeller: Identify a core set of Haskell tools (the above four would be my initial suggestion), and make sure that the latest binary releases for these are always in synch with each other. In other words, someone could go download them, make a "Haskell tools, Spring 2004" CD, and be sure that they actually work together while he/she's trying to learn Haskell. Both GHC and Hugs have had release candidate testing in the past, but experience and mailing list archives show that there's always a number of issues that are only detected after the binary releases. On Windows at least, it seems that everyone is relying on Sigbjorn to do all the packaging - couldn't the creation of updated installers be automated (or Haskellised), so that he'd only have to be bothered for the initial packaging, not for patchlevel updates? There are similar issues for Haskellers needing a larger set of tools and libraries, but those will hopefully be addressed by the library infrastructure project in the long run, so I'm just asking about the state of the core tools here. Opinions? Claus

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[Hugs-bugs] test of subscription, please ignore
by Byron Hale 04 Feb '04

04 Feb '04

test

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[Hugs-bugs] module system/libraries bug
by Iavor S. Diatchki 04 Feb '04

04 Feb '04

hello, i am having the following problem (just tried it with the current cvs version, on linux) > import Array > import ST hiding (bounds) > > test x = bounds x ERROR "test.hs":4 - Ambiguous variable occurrence "bounds" *** Could refer to: Data.Array.Base.bounds Hugs.Array.bounds I am not sure why ST is exporting "bounds" at all, but in any case the "hiding" clause of the import should prevent the conflict. a similar thing occurs with "indices", but then adding the "hiding" clause solves the problem. -iavor -- ================================================== | Iavor S. Diatchki, Ph.D. student | | Department of Computer Science and Engineering | | School of OGI at OHSU | | http://www.cse.ogi.edu/~diatchki | ==================================================

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[Hugs-bugs] type-cheker woes
by Iavor S. Diatchki 04 Feb '04

04 Feb '04

hello, sorry for the many posts, today seems to have turned into a bug reporting day. there seems to be a probelm with the type checker of the current cvs version: > class {-(Monad m, Monad n) =>-} HasBaseMonad m n | m -> n where > mapBase :: (forall a. n a -> n a) -> m a -> m a > > instance HasBaseMonad IO IO where > mapBase f x = f x ERROR "hugs-bug.lhs":10 - Illegal type in class constraint if i comment-in the commented-out part (the Monad constraints) i get the following: ERROR "hugs-bug.lhs":11 - Inferred type is not general enough *** Expression : mapBase *** Expected type : HasBaseMonad IO IO => (forall c. a c -> a c) -> IO b -> IO b *** Inferred type : HasBaseMonad IO IO => (forall b. IO b -> IO b) -> IO a -> IO a if i remove the instance the script loads fine. -iavor -- ================================================== | Iavor S. Diatchki, Ph.D. student | | Department of Computer Science and Engineering | | School of OGI at OHSU | | http://www.cse.ogi.edu/~diatchki | ==================================================

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[Hugs-bugs] RE: the woes of non-cvs haskellers
by Simon Marlow 04 Feb '04

04 Feb '04

> To give just one concrete example, what packages do I > recommend to someone wanting to learn a bit of Haskell, and > do some graphics and perhaps windowing, on Windows? > > - Hugs (Winhugs bug in current binary release, so better avoid > that and use plain Hugs?) > - HGL (does it work with latest Hugs/GHC, or do I need older > versions? which ones?) > - GHC (current binary release seems to have serious probs on > some Windows versions; has also seen some rapid > development breakage recently, e.g., TH syntax, forcing > other packages to play catch-up just to get working again) > - wxHaskell (works with ghc-6.0.1, will it work with 6.2? what about > Hugs? what about ghc-6.4?) > - some generic text-editor (but on Windows98, the way that .hs > files are associated with Hugs/GHC cannot be modified in > the standard dialogues, as they can for other associations, > so how do I associate .hs files with an editor? I wouldn't > want to recommend some beginner editing the registry for > that purpose..) > > The issues are usually small, but there are many of them, each > package has its own, and all too often the response is "fixed in > CVS, will be in next release". > > Of course, the next release is a while a away and by that time, > there'll be a different set of small issues plagueing the next set > of binary releases. So, just getting someone started requires > careful investigation/testing and some thinking (instead of: > "just download and install the latest Haskell starters set"). It's been a rough ride in a few ways recently. But let me try to explain our policy and why it's a good compromise, and hopefully this will shed some light on why there might be problems going from GHC 6.0.1 to 6.2, for example. There's always going to be a tension between doing lots of bugfix releases and releasing new development versions so that people can get access to new features quickly. We only have limited resources - and we like to do a bit of development & research too, rather than just fixing bugs and doing releases all the time. So we arrived at the current policy, which is... We start a new *major* release every so often (eg. 6.2 is a major release). It has new features, and might change the interfaces to libraries and tools. At this point we branch the codebase. We then do a number of patchlevel releases (6.2.1, 6.2.2 etc.) that fix bugs *only*: i.e. it's highly unlikely that these releases introduce new bugs, and they definitely don't change interfaces. So those after stable binary releases can follow these patchlevels and get a monotonically improving experience :-) Meanwhile, we can continue development on the main branch (the HEAD). Due to our lack of resources, we can't do releases off both the stable branch and the HEAD (otherwise there would have been a 6.0.2). In due course, the HEAD turns into a new major release (6.4) and so on. We think this is a reasonable compromise and makes good use of the resources we've got. Remember that 6.2 is a new major release, and has had zero time to mature. So it's likely there are going to be bugs in it (eg. the Windows ME problem). 6.2.1 will follow shortly, and fix all/most of the issues that were reported without breaking code that works on 6.2. Also remember that certain features like TH are deemed experimental, and fixing their interfaces too soon would give us an undue maintenance burden. If you use experimental features, be prepared to do some conditional compilation based on compiler versions. Cheers, Simon

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[Hugs-bugs] RE: the woes of non-cvs haskellers
by Simon Peyton-Jones 04 Feb '04

04 Feb '04

| I'm getting more and more worried about Haskell users who | depend on multiple Haskell packages and compilers, but don't | want to follow the cvs developments for all of these packages. You are right to be worried. That is why, with strong encouragement from the last Haskell workshop, Isaac has been running the Haskell Library Infrastructure Project. http://www.haskell.org/libraryInfrastructure/ This is not a little private project of Isaac's. It's a major service to us all, for the reasons Claus describes. The more people that offer to help him, the faster we'll get to the point where Claus's problems will be at least ameliorated. Of course, even with a completed library infrastructure, someone has to do the work to fix bugs, and compile wxhaskell with the next version of GHC etc. But at least the dependency tracking, distribution and installation should be much easier. So, all you would-be library writers and users out there... volunteer to Isaac! Meanwhile, the idea of a set of mutually-consistent core Haskell tools has been mooted before, and a very good idea it is too. All it needs is someone to do the work. Simon | -----Original Message----- | From: glasgow-haskell-bugs-bounces(a)haskell.org [mailto:glasgow-haskell-bugs- | bounces(a)haskell.org] On Behalf Of Claus Reinke | Sent: 04 February 2004 13:38 | To: glasgow-haskell-bugs(a)haskell.org | Cc: hugs-bugs(a)haskell.org | Subject: the woes of non-cvs haskellers | | Dear all, | | I'm getting more and more worried about Haskell users who | depend on multiple Haskell packages and compilers, but don't | want to follow the cvs developments for all of these packages. | I have the feeling that Haskellers who rely on pre-packaged | binaries are not currently getting a good impression of the | state of the art. | | To give just one concrete example, what packages do I | recommend to someone wanting to learn a bit of Haskell, and | do some graphics and perhaps windowing, on Windows? | | - Hugs (Winhugs bug in current binary release, so better avoid | that and use plain Hugs?) | - HGL (does it work with latest Hugs/GHC, or do I need older | versions? which ones?) | - GHC (current binary release seems to have serious probs on | some Windows versions; has also seen some rapid | development breakage recently, e.g., TH syntax, forcing | other packages to play catch-up just to get working again) | - wxHaskell (works with ghc-6.0.1, will it work with 6.2? what about | Hugs? what about ghc-6.4?) | - some generic text-editor (but on Windows98, the way that .hs | files are associated with Hugs/GHC cannot be modified in | the standard dialogues, as they can for other associations, | so how do I associate .hs files with an editor? I wouldn't | want to recommend some beginner editing the registry for | that purpose..) | | The issues are usually small, but there are many of them, each | package has its own, and all too often the response is "fixed in | CVS, will be in next release". | | Of course, the next release is a while a away and by that time, | there'll be a different set of small issues plagueing the next set | of binary releases. So, just getting someone started requires | careful investigation/testing and some thinking (instead of: | "just download and install the latest Haskell starters set"). | | A modular way to fix this would be to have at least once-a-month | patch updates of binary packages, so that one would never be | more than a month away from the fixed versions (instead of having | to wait for the next releases of everything). | | A broader approach would be to try and show a united Haskell | tools front to the general Haskeller: Identify a core set of Haskell | tools (the above four would be my initial suggestion), and make | sure that the latest binary releases for these are always in synch | with each other. In other words, someone could go download | them, make a "Haskell tools, Spring 2004" CD, and be sure that | they actually work together while he/she's trying to learn Haskell. | | Both GHC and Hugs have had release candidate testing in the | past, but experience and mailing list archives show that there's | always a number of issues that are only detected after the | binary releases. On Windows at least, it seems that everyone | is relying on Sigbjorn to do all the packaging - couldn't the | creation of updated installers be automated (or Haskellised), | so that he'd only have to be bothered for the initial packaging, | not for patchlevel updates? | | There are similar issues for Haskellers needing a larger set of | tools and libraries, but those will hopefully be addressed by | the library infrastructure project in the long run, so I'm just | asking about the state of the core tools here. | | Opinions? | Claus | | | _______________________________________________ | Glasgow-haskell-bugs mailing list | Glasgow-haskell-bugs(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

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