May 2004 - Glasgow-haskell-users

RE: Prelude/main magicks?
by Simon Peyton-Jones 10 May '04

10 May '04

| Is there some simple way to make GHC treat our own base library in the same | magic way as the Prelude, so that it is always implicitly available? Note | that we don't want to exchange the existing Prelude for our own, we want to | leave that one as it stands, rather we want one or more other libraries to | be treated the same way as the Prelude. | If the answer is no, that cannot be done, I would humbly request this as a | feature in upcomming versions of GHC, I believe it's generally useful | feature to have. =) A -fprelude-is flag would certainly be implementable. The questions are a) Would it be desirable? After all, there isn't much difference between module Main where { ... } ghc -fprelude-is Foo Main.hs and module Main where { import Foo ... } ghc Main.hs And arguably the latter it better because the code is more self-describing. b) GHC has a myriad of flags. Every time we add one, even a simple one, it costs us an hour or two, and (worse) potentially interacts with stuff in the future. Each one is "just one little flag" but they do add up! I'd be interested to know if lots of people thought this particular one was very important, though. | And while I'm asking about magicks; In our language we have a special | function, called "page", that we require be present in "executable" modules, | much like a main-function. Once again, is there some way of tweaking GHC to | check this for us? We cannot simply use a 'main-is' flag since this function | is not executed the same way that a main function would be, and its type | should not be IO (). | I don't expect to be able to tell GHC what function must have what type with | a command line flag, but is there some other way? This seems less widely applicable to me; I suggest you use the ideas suggested by others in their replies. Simon

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Re: Prelude/main magicks?
by Niklas Broberg 09 May '04

09 May '04

> > I am currently co-developing a language[1] as an extension to Haskell, >by > > means of a preprocessor to GHC. In this language we want to supply the > > programmer with a number of functions by default, as with the functions >in > > the GHC Prelude. > > Is there some simple way to make GHC treat our own base library in the >same > > magic way as the Prelude, so that it is always implicitly available? > >Perhaps your preprocessor could just place a suitable 'import' in the >generated Haskell module? Indeed, and that is precisely what we are doing right now. And it's not really all that much work for us either, but I can envision other uses for such a feature as well, so my question still stands. > > And while I'm asking about magicks; In our language we have a special > > function, called "page", that we require be present in "executable" > > modules, much like a main-function. Once again, is there some way of > > tweaking GHC to check this for us? > >Along the same lines: put something like this in the generated module > > requirePage :: () > requirePage = f page > where > f :: PageType -> () > f _ = () Hmm, this is an interesting idea. I see a problem though, since (just like with main) we don't require just all modules to contain such a function, only the "executable" ones. That would correspond to the one that we invoke ghc (with the preprocessor) on, but ghc in turn will invoke the preprocessor on all modules that are loaded. In other terms, ghc can know which module is the first, but the preprocessor has no idea. Thanks for the input, /Niklas _________________________________________________________________ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail

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Prelude/main magicks?
by Niklas Broberg 09 May '04

09 May '04

Hello, fellow GHCees, I am currently co-developing a language[1] as an extension to Haskell, by means of a preprocessor to GHC. In this language we want to supply the programmer with a number of functions by default, as with the functions in the GHC Prelude. Is there some simple way to make GHC treat our own base library in the same magic way as the Prelude, so that it is always implicitly available? Note that we don't want to exchange the existing Prelude for our own, we want to leave that one as it stands, rather we want one or more other libraries to be treated the same way as the Prelude. If the answer is no, that cannot be done, I would humbly request this as a feature in upcomming versions of GHC, I believe it's generally useful feature to have. =) And while I'm asking about magicks; In our language we have a special function, called "page", that we require be present in "executable" modules, much like a main-function. Once again, is there some way of tweaking GHC to check this for us? We cannot simply use a 'main-is' flag since this function is not executed the same way that a main function would be, and its type should not be IO (). I don't expect to be able to tell GHC what function must have what type with a command line flag, but is there some other way? Any leads are appreciated, even if they only lead into the source code of GHC... /Niklas Broberg [1] Haskell Server Pages: http://www.dtek.chalmers.se/~d00nibro/hsp/ _________________________________________________________________ The new MSN 8: advanced junk mail protection and 2 months FREE* http://join.msn.com/?page=features/junkmail

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What happened to constrFields?
by Stefan Reich 09 May '04

09 May '04

In recent versions of the GHC libraries, constrFields (as defined here http://www.cs.vu.nl/boilerplate/library/Data.Generics.Basics.html) has disappeared. I failed to figure out another way to get the names of all fields of a constructor. Have I overlooked anything? Do I have to use Template Haskell? -Stefan

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RE: Two problems with heap profiling
by Simon Marlow 09 May '04

09 May '04

On 16 April 2004 10:39, Stefan Reich wrote: > I'm using GHC 6.2.1 on Windows 2000. > > Problem 1: -hr crashes in some circumstances. > > Take this program (Test.hs): > > module Main where > import IO > main = do > readFile "large.csv" > putStrLn "OK" > > where large.csv is an 800K CSV file (with very small files, the bug > doesn't occur). I compile with: > > ghc -prof -auto-all Test.hs > > and run with: > > a.out +RTS -hr I can't reproduce this bug. Just to make sure I'm doing exactly the same thing, could you send me the source code for Test.hs and "large.csv" (compressed), please? Cheers, Simon

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Haddock can't parse data declaration involving operator
by Stefan Reich 09 May '04

09 May '04

Hi, I hope this is the right place to ask about Haddock problems? I'm using Haddock 0.6 (RedHat RPM module) under RedHat 9. When I invoke haddock on this file (Op.hs): module Op where infixl 4 := data a := b = a := b I get the error "Op.hs:Illegal data/newtype declaration". Is this a known problem? Asking more broadly - maybe there is another tool that does what I need: I just want an overview of all my modules including their exported identifiers and all type signatures (including inferred signatures). Thanks in advance, -Stefan

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RE: Haddock bug?
by Simon Marlow 07 May '04

07 May '04

On 07 May 2004 06:11, Adrian Hey wrote: > There seems to be a bug in Haddock 0.6, which causes it not to list > indexes which don't contain an upper case identifier. > > At the moment I'm fixing the problem by creating a dummy data type > in my top level wrapper module.. > > data Dummy = A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z > > ..which seems to fix this problem, but I'd rather not have to do > this:-) Is there a better work around for this? There has been a fix for this in CVS for a while. You could build Haddock from CVS, or wait for version 0.7 (I dunno when that will be, though). > Also, reading the release notes, there's mention of --gen-contents > and --use-contents flags, but these don't seem to be documented in > the user guide AFAICS. Oops, looks like I forgot to document those. Thanks. They work just like the --gen-index and --use-index flags. Cheers, Simon

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RE: how to peform a 'make install' in a windows + cygwin + ghcenvironment?
by Simon Marlow 07 May '04

07 May '04

On 06 May 2004 14:50, Mauro La Salete Costa Lima de Araujo wrote: > Hi folks, > > I would like to know what I have to do if I wanna have a ghc, built by > myself, avaliable to my shell environment, so I can invoke it as > normal ('ghc' :P). > I've built the fptools according the instructions at > 'http://www.haskell.org/ghc/docs/latest/html/building/winbuild.html' > and did a 'make install' under the fptools/ghc directory. But when I > invoke the ghc, I get the following error: > > ------------------------------------------------------------------------ ------------------------ > $ ghc > ghc.exe: Can't find package.conf as > C:\haskell\cygwin\usr\local\ghc\driver\package.conf.inplace > ------------------------------------------------------------------------ ------------------------ > > what does it means? what I have to do to use my own copy of ghc > instead of the '.msi' one? GHC on Windows doesn't support 'make install', I'm afraid. Making a binary package on Windows is something of a black art. You can run ghc directly from the build tree, as fptools/ghc/compiler/ghc-inplace. Cheers, Simon

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Haddock bug?
by Adrian Hey 07 May '04

07 May '04

Hello, There seems to be a bug in Haddock 0.6, which causes it not to list indexes which don't contain an upper case identifier. At the moment I'm fixing the problem by creating a dummy data type in my top level wrapper module.. data Dummy = A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z ..which seems to fix this problem, but I'd rather not have to do this:-) Is there a better work around for this? Also, reading the release notes, there's mention of --gen-contents and --use-contents flags, but these don't seem to be documented in the user guide AFAICS. Regards -- Adrian Hey

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how to peform a 'make install' in a windows + cygwin + ghc environment?
by Mauro La Salete Costa Lima de Araujo 06 May '04

06 May '04

Hi folks, I would like to know what I have to do if I wanna have a ghc, built by myself, avaliable to my shell environment, so I can invoke it as normal ('ghc' :P). I've built the fptools according the instructions at 'http://www.haskell.org/ghc/docs/latest/html/building/winbuild.html' and did a 'make install' under the fptools/ghc directory. But when I invoke the ghc, I get the following error: ------------------------------------------------------------------------------------------------ $ ghc ghc.exe: Can't find package.conf as C:\haskell\cygwin\usr\local\ghc\driver\package.conf.inplace ------------------------------------------------------------------------------------------------ what does it means? what I have to do to use my own copy of ghc instead of the '.msi' one? Cheers, ------------------------------------------------- | Mauro La-Salette C. L. de Araújo | | Undergraduating Computer Science Student | | mscla at cin.ufpe.br | | http://www.cin.ufpe.br/~mscla | ------------------------------------------------- "If this is true, building software will always be hard. There is inherently no silver bullet." (F.P.Brooks)

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