December 2001 - Hugs-Bugs

Re: --+ not treated as a start of a comment
by Sigbjorn Finne 11 Dec '01

11 Dec '01

Thanks, I've made Hugs98 comply with the Report. --sigbjorn ----- Original Message ----- From: "Ian Lynagh" <igloo(a)earth.li> To: <glasgow-haskell-bugs(a)haskell.org> Sent: Sunday, December 09, 2001 10:43 Subject: --+ not treated as a start of a comment > > If I have > > foo = 0 --+ 1 > > then ghc tells me > > tt.lhs:2: Variable not in scope: `--+' > > while the report (and hugs) believe "--+ 1" is a comment. > > > Thanks > Ian > > > _______________________________________________ > Glasgow-haskell-bugs mailing list > Glasgow-haskell-bugs(a)haskell.org > http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

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Hugs RPMs for Redhat 7.1
by Niklas Elmqvist 10 Dec '01

10 Dec '01

Hello, I am having a slight problem with using the Hugs RPMs on a Linux Redhat 7.1 system. It seems that the RPM has a dependency to libreadline.so.4.1, but on this system, libreadline.so.4.2 is installed. Is there a way to bypass this (for instance, would it work if I tried to force the install) and fix it for the future? Surely the dependency should be 4.1 or better? best, Niklas Elmqvist -- Niklas Elmqvist (elm(a)cs.chalmers.se) -------------------------------- "Gravity is a habit that is hard to shake off." -- Terry Pratchett, Small Gods

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Export list (,) not allowed
by Ian Lynagh 09 Dec '01

09 Dec '01

With this module: module Foo (,) where foo = 0 hugs gives me: ERROR tt.lhs:2 - Syntax error in module definition (unexpected comma) while the report (and GHC) allow it. hugs seems to be OK with import lists. Thanks Ian

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loading modules
by rdt＠cs.queensu.ca 07 Dec '01

07 Dec '01

> * When you evaluate an expression in the interpreter, it has to use some > symbol table for looking up the ids you use. What symbol table does it use? > The only credible alternatives are: > > * The export list of the "current module" (see :module command) > * The symbol table of the "current module" > > Hugs uses the latter (which seems more useful) but you might reasonably > expect Hugs to use the export list and wonder why Hugs doesn't seem to > implement abstract data types correctly when you do experiments from the > command line. This begs the question of exactly what it means to "load modules". The Hugs documentation AFAIK seems to assume it's self-evident. But, as the "not a bug it's a feature" message above makes clear, it isn't, even when just a single module is loaded. I would have thought module loading could be defined in terms of something *in* Haskell (as did presumably the bug reporters the message is responding to); but at the moment the best that could be said is that module loading is an undocumented hack. Bob T.

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Type-checker bug
by John Hughes 07 Dec '01

07 Dec '01

The program below produces this error message (with -98 in the February 2001 version): ERROR Bug.hs:5 - Instance of Num Int required for definition of f Pardon? data T class C a b | b->a where m :: a -> (Bool, b) instance C Int T instance C a b => C [a] [b] f () = located :: [T] where (_,located) = m [0]

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Functional dependencies
by Josef Svenningsson 06 Dec '01

06 Dec '01

Hi! It seems as the functional dependencies are not working as well as they should. Suppose I have the following class: \begin{code} class A a b | a -> b where foo :: a b \end{code} and then I declare the following type: \begin{code} newtype Foo = Bar (forall a b. A a b => a Int) \end{code} Loading this in hugs gives the following error message: ERROR HugsBug.lhs:9 - Ambiguous type signature in type component *** ambiguous type : A a b => a Int But the type is clearly not ambiguous since the functional dependency determines b whenever a is known. /Josef

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Hugs feb 01
by Frank Dellaert 06 Dec '01

06 Dec '01

Hi I'm considering whether to use Hugs in a class this spring, but it would be significantly better if the graphics library would work. Is there an ETA on when that will work ? Cheers Frank -Frank Dellaert (dellaert(a)cc.gatech.edu)

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Problem with "\t" in Winhugs
by Andreas Grommek 03 Dec '01

03 Dec '01

Hi! I recently encountered a problem using Winhugs. Hugs does not seem to recognize "\t", it is always ignored. "\n" on the other hand works fine (see Hugs.jpg). No other user of Winhugs that I know has ever encountered this problem. This problem only appears in Winhugs, on DOS-Level, "\t" works fine, either with or without "+98"-Option. Is this a real bug or is there an option I have not discovered yet? What can I do about it (aside from using Hugs on DOS-Level)? Greetings Andreas Grommek, Germany

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Re: hugs-Linux
by Alastair David Reid 03 Dec '01

03 Dec '01

> wenn i try to run hugs on my suse linux i get the error: cannot load > shared library libreadline.so.4.1 It seems like we've heard reports like this a number of times. Do we need (to get the package maintainer) to add a dependency to the package or perhaps statically link libreadline? [Sorry if this has already been dealt with.] -- Alastair

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