September 2004 - Glasgow-haskell-users

RE: Dynamic loading problem
by Simon Marlow 18 Feb '05

18 Feb '05

On 30 April 2004 11:26, Duncan Coutts wrote: > Could someone remind me what the remaining issues are in getting ghc > to build Haskell modules/packaged into unix .so shared libraries? > > As I recall it seems to nearly work. Andre Pang got them to load and > function but it was a bit fragile and the rts would complain after a > short while: > http://www.mail-archive.com/glasgow-haskell-users@haskell.org/msg03923.h tml It might be possible to do this, but only if you want to do dlopen()-style linking at runtime. Linking a haskell binary against Haskell .so libraries still isn't possible - I had another look at this recently, and although one of the obstacles has been removed, there are others (details available on request). Any remaining issues to do with dlopen()ing a Haskell .so library are probably to do with CAFs. The dynamically loaded code needs to call newDynCAF() instead of newCAF() in a CAF's entry code - this is normally arranged by the RTS linker, but for a .so you'll have to do it some other way, like getting the compiler to emit the different call, or doing some CPP magic (but only for -fvia-C). Any reasonable patches to implement this will be incorporated. Oh, and strictly speaking we should run the __stginit_Foo() function from each dynamically loaded module. But the RTS linker still doesn't do this. Cheers, Simon

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RE: Double -> CDouble, realToFrac doesn't work
by Simon Peyton-Jones 05 Nov '04

05 Nov '04

| Hmmm, this is a little bit of a dark corner in the H98 report, but there are | probably other people on this list who know better than me. :-] The problem | is that 'realToFrac' is defined as 'fromRational . toRational', so the first | question is: How is 'toRational' supposed to handle NaN? One thing coming to | my mind is '0 :% 0', but this is normally a value which can't be constructed. | So the next question is: Would this be allowed? +Infinity and -Infinity could | be represented similarly then ('1 :% 0' and '(-1) :% 0'), and 'fromRational' | could handle these values specially. But I can't believe that this has been | discussed for the first time. SPJ? Malcolm? I don't recall a discussion about this, and a quick search in my mail archive didn't turn up anything except the enclosed from George Russell. I'm pretty ignorant about the dark corners of numerics, but it does seem bad that passing through Rational loses information. Perhaps the Report should specify normalised representations for +Inf, -Inf and NaN as Rationals (1:%0, -1:%0, and 0:%0 seem like plausible candidates). If someone wants to try this out, and send us a patch for the Rational library, we could incorporate it. And so far as the report goes, perhaps the Errata could contain a note identifying the issue, and suggesting a solution. It's a bit late to *specify* a solution unless we are really sure about it. Simon -----Original Message----- From: George Russell [mailto:ger@informatik.uni-bremen.de] Sent: 25 February 2000 10:19 To: glasgow-haskell-users(a)haskell.org Subject: Floating-point nitpicking: floor(Inf) and floor(NaN) floor(Inf) and floor(NaN) do not appear to be defined in Standard Haskell. (They both come down to "properFraction" which is only defined for Ratio.) This differs from (for example) the Standard ML Basis Library, where it is specified that floor(Int) should raise Overflow and floor(NaN) should raise Domain. Hence Hugs and GHC do different things. Hugs returns floor(Inf) = 0 and floor(NaN) = 0 GHC returns floor(Inf) = very very large integer and floor(NaN) = even larger integer. (This is because the GHC implementation of properFraction simply ignores the case of Inf/NaN and treats the artificially high exponent encoded in those floating-point numbers as if it were a real one.) My own opinion is that Standard ML is right here and that floor(x) should raise an exception (In Haskell terms, fail) when x does not correspond to a real number. | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Sven Panne | Sent: 08 August 2004 17:02 | To: Hal Daume III | Cc: GHC Users Mailing List; Malcom Wallace | Subject: Re: Double -> CDouble, realToFrac doesn't work | | Hal Daume III wrote: | > [...] | > Prelude Foreign.C> (0 :: CDouble) / 0 | > NaN | > Prelude Foreign.C> (0 :: Double) / 0 | > NaN | > Prelude Foreign.C> realToFrac ((0 :: Double) / 0) :: CDouble | > -Infinity | > | > yikes! the NaN got turned into a -Infinity!!! | > | > aside from manually checking for 'strange' Double/CDouble values and | > wrapping realToFrac, is there a better way? also, does this count as a | > bug? | | Hmmm, this is a little bit of a dark corner in the H98 report, but there are | probably other people on this list who know better than me. :-] The problem | is that 'realToFrac' is defined as 'fromRational . toRational', so the first | question is: How is 'toRational' supposed to handle NaN? One thing coming to | my mind is '0 :% 0', but this is normally a value which can't be constructed. | So the next question is: Would this be allowed? +Infinity and -Infinity could | be represented similarly then ('1 :% 0' and '(-1) :% 0'), and 'fromRational' | could handle these values specially. But I can't believe that this has been | discussed for the first time. SPJ? Malcolm? | | When you compile the stuff above with optimizations on, you get what you've | expected, thanks to RULES which shortcut the route via Rational completely. | | Cheers, | S. | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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BeOS port
by Waldemar Kornewald 02 Oct '04

02 Oct '04

Hi, is there someone doing a BeOS port of GHC? If not, I would like to try it (if not too time-consuming). What problems did you run into when porting GHC to FreeBSD or any other POSIX platform? Why do you not offer .hc packages of different builds (FreeBSD and/or Linux)? I could use them as a very good starting point. Or could anyone please create a zip with those files generated from such a build? Thank you very much. Bye, Waldemar Kornewald

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RE: Registering packages
by Simon Marlow 01 Oct '04

01 Oct '04

On 22 September 2004 21:37, Geoff C wrote: > Howdy, > > I am trying to set up GHC with wxHaskell and run a couple of samples > in Win2K Professional. > > I have GHC in c:\Program Files\ghc-6.2.1\ > and wxHaskell in c:\Program Files\wxhaskell-0,8\ > > The setup batch file for wxHaskell could not register the packages, or > copy the DLL to the system32 directory. I manually copied the DLL, > and tried to register the packages with GHC. I set the PATH > environment variable to include the GHC directory. > > I am typing the following commands and the command prompt: > > ghc-pkg -u -i "c:\progra~1\wxhaskell-0.8\bin\wxcore.pkg" > ghc-pkg -u -i "c:\progra~1\wxhaskell-0.8\bin\wx.pkg" > > Each time, I get an error 'Unable to expand variable "wxhlibdir"' when > the program is trying to expand embedded variables. > > I went ahead and put GHC in my program file directory because I did > not intend to use cygwin (which I understand has a problem with spaces > in file/dir names). Usually, however, using "Progra~1" instead of > "Program Files" allows programs which don't like spaces to run. Could > this be the problem? Looks like wxHaskell needs to set an environment variable when installing the package, but because you did it by hand you didn't have this environment variable set. Why didn't the normal wxHaskell install work for you? Cheers, Simon

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RE: constant space `minimum'
by Simon Peyton-Jones 30 Sep '04

30 Sep '04

| I meant that the implementation like | | minimum [x] = x | minimum (x:y:xs) = if x > y then minimum (y:xs) | else minimum (x:xs) It would be great if this was the defn of minimum in the Report. But it isn't. Consider data T = T1 | T2 instance Ord T where min x T2 = T2 min x y = error "urk" Now try minimum [T1,T2,T2] your defn gives "urk", but the Report gives T2. Stupid, I know, but that's what it says. So the best thing seems to be to give monomorphic instances of minimum for types where we know the instances! Simon

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ghc-6.2.2-sep-26 tested
by Serge D. Mechveliani 30 Sep '04

30 Sep '04

Dear GHC team, I have tested ghc-6.2.2-september-26 under our RedHat Linux: compiling of GHC by itself, automatic test of the DoCon and prover programs, -Onot, -O, profiling with -auto-all. It looks all right. I was lazy to re-run manually the examples from the DoCon Manual: they were all right in ghc-6-2-2-branch-CVS and hope will be so in the official ghc-6.2.2. I need official and reliable ghc-6.2.2 greatly. ----------------- Serge Mechveliani mechvel(a)botik.ru

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RE: Haddock: how to disable the JavaScript menus?
by Simon Marlow 30 Sep '04

30 Sep '04

On 30 September 2004 10:08, Simon Marlow wrote: > On 28 September 2004 16:06, Malcolm Wallace wrote: > >> On the theme of improving Haddock, do you think it could be fixed to >> generate valid HTML? Here are some examples of the errors I get when >> running Haddock output through "validate" (the Web Design Group's >> HTML and XML validator). > > Oops! I did check the output with a validator at one point, but it > looks like I've broken it since. Thanks for pointing it out. > It appears that the current CVS Haddock sources generate valid HTML, according to the W3C validator. Cheers, Simon

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RE: Haddock: how to disable the JavaScript menus?
by Simon Marlow 30 Sep '04

30 Sep '04

On 28 September 2004 16:06, Malcolm Wallace wrote: > On the theme of improving Haddock, do you think it could be fixed to > generate valid HTML? Here are some examples of the errors I get when > running Haddock output through "validate" (the Web Design Group's > HTML and XML validator). Oops! I did check the output with a validator at one point, but it looks like I've broken it since. Thanks for pointing it out. Cheers, Simon

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constant space `minimum'
by Serge D. Mechveliani 29 Sep '04

29 Sep '04

Simon Marlow responds on the subject of constant space `minimum': > In 6.4, minimum & maximum will have specialised versions for Int & > Integer, which will run in constant stack space. We can't do this in > general, because minimum/maximum have the type > > (Ord a) =3D> [a] -> a > > and we can't assume that the comparison operations for any given type > are always strict. > I meant that the implementation like minimum [x] = x minimum (x:y:xs) = if x > y then minimum (y:xs) else minimum (x:xs) is correct, and on the other hand, GHC compiles it more readily into an efficient code than the version done via foldl or such. ----------------- Serge Mechveliani mechel(a)botik.ru

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RE: Deforestation of literal lists
by Simon Peyton-Jones 29 Sep '04

29 Sep '04

Carsetn This, plus your earlier message about unfold, certainly make sense. But with the rules below, there's a danger that long literal lists would give rise to a huge nest of cons/build rule firings, which are ultimately all undone again. So I'm a bit cautious about building these rules in. But you can just add them yourself, by writing RULES. (Use the rules in the prelude for guidance). If you get noticeable performance wins, without obvious downside, then I'd certainly think about adding them to GHC. Simon | -----Original Message----- | From: glasgow-haskell-users-bounces(a)haskell.org [mailto:glasgow-haskell-users- | bounces(a)haskell.org] On Behalf Of Carsten Schultz | Sent: 17 September 2004 15:09 | To: glasgow-haskell-users(a)haskell.org | Subject: Deforestation of literal lists | | Hi! | | Just a thought... | | Would it be a sensible thing to not desugar | | [x, y, z] | | into | | (:) x ((:) y ((:) z [])), | | but into | | build (\ c n -> c x (c y (c z n)))? | | Alternatively, how about the following rules? | | {-# RULES | "singleton" [~1] forall x . (:) x [] = build (\c n -> c x n) | #-} | | {-# RULES | "cons/build" [~1] forall (x::a) (f:: forall b . (a->b->b) -> b -> b) . | (:) x (build f) = build (\c n -> c x (f c n)) | #-} | | This should be useful for example in conjuction with sequence_ or // | applied to short lists. Has this been discussed before? | | Greetings, | | Carsten | | -- | Carsten Schultz (2:38, 33:47), FB Mathematik, FU Berlin | http://carsten.codimi.de/ | PGP/GPG key on the pgp.net key servers, | fingerprint on my home page.

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