Re: [Haskell-cafe] Why do I need a 'do'?
On Wed, 29 Apr 2009, michael rice wrote: == import System.Random rollDice :: IO Int rollDice = getStdRandom (randomR (1,6)) rollNDice :: Int - [IO Int] rollNDice 0 = [] rollNDice n = rollDice : rollNDice (n-1) replicateM n rollDice http://www.haskell.org/haskellwiki/Avoiding_IO#State_monad ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] default values in a record structure
Is there anyway when defining a dat type record struct to indicate default values for some of the fields? A bit dated, but still ... http://article.gmane.org/gmane.comp.lang.haskell.general/2078 J.W. -- View this message in context: http://www.nabble.com/default-values-in-a-record-structure-tp23287084p23313391.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Getting started - help
What I need to do is build a type of database. Firstly have a few questions, whether what I have done it right...and how to do something else. This is my algebraic type for the database (correct me if its wrong) data Film = Film String String Int String with this as the data. testDatabase :: [Film] testDatabase = [(Casino Royale, Martin Campbell,2006, Garry, Dave, Zoe)] the last set of strings are the fans to the film. I want to be able to add a new fan, but not sure how to specifically insert it to there this is what I have so far: becomeFan :: String - String - [Film] - [Film] becomeFan = do putStr Which film are you a fan of: filmTitle - getLine do putStr What is your name: fanName - getLine (if filmTitle == filmName then fanName : [Film]) -- View this message in context: http://www.nabble.com/Getting-started---help-tp23314466p23314466.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting started - help
First off, is this homework? You really ought to start with passing your code to GHCi, or the compiler, to see whether it's accepted before sending questions to the mailing list. At least if you are interested in getting constructive replies. On Thu, Apr 30, 2009 at 12:33 PM, applebiz89 applebi...@hotmail.com wrote: What I need to do is build a type of database. Firstly have a few questions, whether what I have done it right...and how to do something else. This is my algebraic type for the database (correct me if its wrong) data Film = Film String String Int String with this as the data. testDatabase :: [Film] testDatabase = [(Casino Royale, Martin Campbell,2006, Garry, Dave, Zoe)] the last set of strings are the fans to the film. I want to be able to add a new fan, but not sure how to specifically insert it to there If the fans is a set of strings why not represent them as a list of strings (`[String]`)? this is what I have so far: becomeFan :: String - String - [Film] - [Film] becomeFan = do putStr Which film are you a fan of: filmTitle - getLine do putStr What is your name: fanName - getLine (if filmTitle == filmName then fanName : [Film]) The type is wrong, you need to do this in the `IO` monad. A more serious issue is that I don't understand at all what you intend this code to do. It isn't valid Haskell, but I think that instead of battling Haskell you should, at this point, go back to your algorithm. Answer the question, given your type, what steps are needed to add a fan to a single film? Then you can progress to answering, what steps are needed to add a fan to a specific film in a list of films? /M -- Magnus Therning(OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Help from C libraries experts
Do you understand very well a C library and would like Haskell to have a binding for it? (...) Could you perhaps then summarise what design rules you're using? Yes. They are summarised at the main module documentation: http://hackage.haskell.org/packages/archive/bindings/0.1/doc/html/Bindings.html For example, why did you pick the new 'Bindings' namespace? The most important guideline is: users guide guidelines. If you have a better sugestion for a base module name, please open a ticket at development website, under 'Issues/Create new issue' (you can do it as anonymous): http://bitbucket.org/mauricio/bindings What are you doing that's different to having standalone small packages? I'm trying to write canonical bindings libraries. One risk I see is that 'bindings' will depend on a large number of C libraries (...) Sure. I would like to have: bindings-common bindings-testsAndExamples bindings-sqlite3 bindings-openusb bindings-agar etc. But I thought I should not polute hackage before this package get at least a few people understanding and agreeing with the concept. Maybe this is a better discussion for librar...@? OK. I'll repost there, with text updated after your thoughts. Thanks, Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting started - help
firstly no it isnt homework. I havent run it through the compiler because I know it won't compile as I havent finished the function as you can see. I was just asking for guidance on how to understand what to do. So now I know to put the fan's into a list, which I have done. So then I can just add the fan's directly to the list of fans if the name of the film matches the desired film to be a fan of. Magnus Therning wrote: First off, is this homework? You really ought to start with passing your code to GHCi, or the compiler, to see whether it's accepted before sending questions to the mailing list. At least if you are interested in getting constructive replies. On Thu, Apr 30, 2009 at 12:33 PM, applebiz89 applebi...@hotmail.com wrote: What I need to do is build a type of database. Firstly have a few questions, whether what I have done it right...and how to do something else. This is my algebraic type for the database (correct me if its wrong) data Film = Film String String Int String with this as the data. testDatabase :: [Film] testDatabase = [(Casino Royale, Martin Campbell,2006, Garry, Dave, Zoe)] the last set of strings are the fans to the film. I want to be able to add a new fan, but not sure how to specifically insert it to there If the fans is a set of strings why not represent them as a list of strings (`[String]`)? this is what I have so far: becomeFan :: String - String - [Film] - [Film] becomeFan = do putStr Which film are you a fan of: filmTitle - getLine do putStr What is your name: fanName - getLine (if filmTitle == filmName then fanName : [Film]) The type is wrong, you need to do this in the `IO` monad. A more serious issue is that I don't understand at all what you intend this code to do. It isn't valid Haskell, but I think that instead of battling Haskell you should, at this point, go back to your algorithm. Answer the question, given your type, what steps are needed to add a fan to a single film? Then you can progress to answering, what steps are needed to add a fan to a specific film in a list of films? /M -- Magnus Therning(OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Getting-started---help-tp23314466p23314963.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Why do I need a 'do'?
import System.Random rollDice :: IO Int rollDice = getStdRandom (randomR (1,6)) rollNDice :: Int - [IO Int] rollNDice 0 = [] rollNDice n = rollDice : rollNDice (n-1) replicateM n rollDice http://www.haskell.org/haskellwiki/Avoiding_IO#State_monad Or, if you want the original idea: sequence (rollNDice 10) Check the type of sequence at Control.Monad. Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Why do I need a 'do'?
On Thu, 30 Apr 2009, Maurício wrote: import System.Random rollDice :: IO Int rollDice = getStdRandom (randomR (1,6)) rollNDice :: Int - [IO Int] rollNDice 0 = [] rollNDice n = rollDice : rollNDice (n-1) replicateM n rollDice http://www.haskell.org/haskellwiki/Avoiding_IO#State_monad Or, if you want the original idea: sequence (rollNDice 10) Check the type of sequence at Control.Monad. I'd still propose http://www.haskell.org/haskellwiki/Haskell_programming_tips#Avoid_explicit_recursion___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Help from C libraries experts
Hi, Maurício wrote: My goal is to have a place where one can find reliable and comprehensive low-level bindings to foreign libraries, so that writing higher level bindings becomes an easier task. Like others, I think you should consider making this place not a single package, but a bunch of packages. For example, one could make a convention that a package named bindings-foo contains low-level bindings to a c library foo. In your guidelines, you say: Code should be portable and easy to build. Does your understanding of portable include Windows? The problem with windows is that you usually do not have these c libraries installed, and no easy way to install them, so a binding is not enough. For example, the Haskell package zlib bundles the actual zlib c code for Windows users, which works not too bad. Do you plan to support this kind of thing in your bindings project? I am not sure which kind of c libraries can be reasonably included in cabal packages. I guess the idea breaks with more complicated build systems for the c library, and with libraries written in other languages then c, and with libraries which are supposed to be linked against dynamically, and with complicated license situations, and in all kinds of other situations. Anyway, if there are more such libraries then just zlib, maybe a naming convention would be helpful, like: - bundled-foois a package which contains just the c code of foo - bindings-foo contains the low-level bindings for foo Now bindings-foo could use cabal configurations to depend on the c library directly on most systems, but depend on bundled-foo on Windows. This way, on all systems, you could just install bindings-foo and be able to use the library. If you have special needs, you could still use an explicit flag on Windows to configure bindings-foo not to depend on bundled-foo, and install the c library yourself instead. Tillmann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting started - help
Hi, applebiz89 wrote: data Film = Film String String Int String with this as the data. testDatabase :: [Film] testDatabase = [(Casino Royale, Martin Campbell,2006, Garry, Dave, Zoe)] Try to compile this part of the program, to get a feeling for whether you are on the right track. If it does not compile, try to find out what's wrong and correct it so that it compiles. As you already noted in a different mail, you plan to change the representation of the list of fans to a list of strings (instead of a single string with commas). That is a good idea! So change the data declaration, and change the definition of testDatabase to this new design. Try to compile that program. Now you can add some utility functions to work with your database. This will make it much easier to write a correct user interface later. For example, write a function isFan :: [Film] - String - String - Bool which checks whether someone is a fan of a film in your database. In other words, isFan testDatabase Garry Casino Royale should be True, but isFan testDatabase Peter Matrix should be False. Another useful utility function could be becomeFan :: String - String - [Film] - [Film] which adds the information that someone is a fan of some film to an existing database. Note that this function does not do any user interaction, but gets the name of the fan and the name of the film as arguments. Think about which other utility functions you could use. Try them out in ghci. When you have done that, you can write a user interface which asks for input on the command line and uses the utility functions to keep track of the current database. Tillmann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Help from C libraries experts
Maurício briqueabra...@yahoo.com wrote: bindings-agar http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/51478 -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting started - help
Hey thanks, that was really helpful actually. I know it must be annoying for you, and im sorry but ive done what you said, try and compile it to see if it does and fix it. I have tried every possible way of using brackets in different place's etc (as u can tell Im not good with haskell at all) but it still isnt, it must be to do with my data type. -- Film as datatype data Film = String String Int [String] -- List of films testDatabase :: [Film] testDatabase = [Casino Royale, Martin Campbell ,2006, [Garry, Dave, Zoe] ] I get this error: *** Expression : [Casino Royale,Martin Campbell,2006,[(Garry,Dave,Zoe)]] *** Term : [(Garry,Dave,Zoe)] *** Type : [([Char],[Char],[Char])] *** Does not match : [Char] Thanks alot! applebiz Tillmann Rendel-3 wrote: Hi, applebiz89 wrote: data Film = Film String String Int String with this as the data. testDatabase :: [Film] testDatabase = [(Casino Royale, Martin Campbell,2006, Garry, Dave, Zoe)] Try to compile this part of the program, to get a feeling for whether you are on the right track. If it does not compile, try to find out what's wrong and correct it so that it compiles. As you already noted in a different mail, you plan to change the representation of the list of fans to a list of strings (instead of a single string with commas). That is a good idea! So change the data declaration, and change the definition of testDatabase to this new design. Try to compile that program. Now you can add some utility functions to work with your database. This will make it much easier to write a correct user interface later. For example, write a function isFan :: [Film] - String - String - Bool which checks whether someone is a fan of a film in your database. In other words, isFan testDatabase Garry Casino Royale should be True, but isFan testDatabase Peter Matrix should be False. Another useful utility function could be becomeFan :: String - String - [Film] - [Film] which adds the information that someone is a fan of some film to an existing database. Note that this function does not do any user interaction, but gets the name of the fan and the name of the film as arguments. Think about which other utility functions you could use. Try them out in ghci. When you have done that, you can write a user interface which asks for input on the command line and uses the utility functions to keep track of the current database. Tillmann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Getting-started---help-tp23314466p23318195.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting started - help
I'm intermediate-level myself so I hesitate to say something wrong, but I'll go ahead and point out the obvious. applebiz89 wrote: Hey thanks, that was really helpful actually. I know it must be annoying for you, and im sorry but ive done what you said, try and compile it to see if it does and fix it. I have tried every possible way of using brackets in different place's etc (as u can tell Im not good with haskell at all) but it still isnt, it must be to do with my data type. -- Film as datatype data Film = String String Int [String] This time you left something off what's called the constructor. (You had it there the first time!) data Film = Film String String Int [String] Because an algebraic data type can be constructed in potentially more than one way, you need a constructor. In this case, you have only one way of constructing a Film, so you just name the constructor Film also. -- List of films testDatabase :: [Film] testDatabase = [Casino Royale, Martin Campbell ,2006, [Garry, Dave, Zoe] ] And here your problem is that (1) you need to prefix the constructor when making a Film, and (2) don't use commas between arguments to the constructor. (In Haskell commas are for lists and tuples, and not for function arguments.) So this would be how to make one Film: aFilm :: Film aFilm = Film Casino Royale Martin Campbell 2006 [Garry, Dave, Zoe] or testDatabase = [ Film Casino Royale Martin Campbell 2006 [Garry, Dave, Zoe] ] I get this error: *** Expression : [Casino Royale,Martin Campbell,2006,[(Garry,Dave,Zoe)]] *** Term : [(Garry,Dave,Zoe)] *** Type : [([Char],[Char],[Char])] *** Does not match : [Char] Thanks alot! applebiz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting started - help
On Thu, Apr 30, 2009 at 4:04 PM, applebiz89 applebi...@hotmail.com wrote: Hey thanks, that was really helpful actually. I know it must be annoying for you, and im sorry but ive done what you said, try and compile it to see if it does and fix it. I have tried every possible way of using brackets in different place's etc (as u can tell Im not good with haskell at all) but it still isnt, it must be to do with my data type. -- Film as datatype data Film = String String Int [String] Change that to data Film = Film String String Int [String] that way you get a constructor called `Film` for the data type `Film`: casinoRoyale = Film CR MC 2006 [G, D, Z] -- List of films testDatabase :: [Film] testDatabase = [Casino Royale, Martin Campbell ,2006, [Garry, Dave, Zoe] ] Then you can create your test database either like this: testDatabase = [(Film CR MC 2006 [G, D, Z])] or if you have defined `casinoRoyale` like above the like this: testDatabase = [casinoRoyale] I get this error: *** Expression : [Casino Royale,Martin Campbell,2006,[(Garry,Dave,Zoe)]] *** Term : [(Garry,Dave,Zoe)] *** Type : [([Char],[Char],[Char])] *** Does not match : [Char] I think you would benefit from reading chapter 3 of RWH http://book.realworldhaskell.org/read/defining-types-streamlining-functions.html it offers a good introduction to defining your own types. /M -- Magnus Therning(OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Arrow preprocessor and *** combinator
Thanks Ross. Does anyone know how to tackle this? Combining GHC's builtin arrow processor and rewrite rules? On Wed, Apr 29, 2009 at 3:43 PM, Ross Paterson r...@soi.city.ac.uk wrote: On Wed, Apr 29, 2009 at 03:07:25PM +0200, Peter Verswyvelen wrote: After doing some pragmatic tests, it seems that neither the arrow preprocessor nor GHC's builtin one generate / optimize to the (***) combinator. Right, neither of them do that. It might be possible to do that using GHC rules, but it isn't done at the moment. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to install HOpenGL to Windows?
Am Mittwoch, 29. April 2009 11:25:31 schrieb Duncan Coutts: On Mon, 2009-04-27 at 19:03 +0200, Sven Panne wrote: [...] As usual, things are always a bit trickier than they appear initially: On non- Windows systems it is not always sufficient to link against libGL alone, sometimes you'll have to link against several X11 libs, too. I am not sure if this is still a widespread problem, but in the past it was. Right. It's still possible to use custom code in Setup.hs to test these kinds of things. It's a bit less easy however. That's why the autoconf macros are so tricky. Re-inventing the wheel in Haskell is not something I'd like to do. Note: I see autoconf as a necessary evil, not as a glorious tool. The predefined autoconf macros contain man years (if not man decades) of sweat and tears from people trying to make their SW portable. If you only know 1 or 2 platforms, everything looks easy, but this is not the case at all. Good luck for everybody trying to ignore that accumulated knowledge... I didn't know that there was any working GHC for Cygwin. Or do you mean building a non-cygwin lib but under the cygwin shell? [...] I don't know if GHC currently builds under Cygwin, but in former times it was *the* way (read: one and only way) to build it on Windows. On *nices you look into /usr/include and /usr/local/include, and that's it, unless the user tells you something different. And Apple is always a very creative company, so they decided to put *their* OpenGL headers in a completely different path where no -I flag can help... But you have some way of finding them right? Even if it's platform dependent. We can do the same in the .cabal file or the Setup.hs. There's also a Cabal flag users can pass to tell us about extra lib and include dirs. I even have standard, well-documented, platform-independent way: Tell configure about it via the environment variable CPPFLAGS for headers and LDFLAGS for libraries. Cabal is buggy in this respect, IIRC, it passes no or incorrectly named variables to configure. Absolutely, finding headers is important. Cabal now checks at configure time that all header files and libs listed in the .cabal file can actually be found. I don't know what Cabal does internally, but simply checking for the existence of a header file or a library file is *far* too naive, look into the autoconf docs and/or mailing lists to see why. You actually have to compile for header checks and link for library checks, everything else is plainly wrong, because you'll probably miss dependencies, pick up the wrong stuff, etc. One suggestion I've seen is just to improve the ffi pre-processors. The c2hs tool is in a position to discover if the calling convention is stdcall or ccall so it could generate the foreign imports correctly. [...] This wouldn't help much: The foreign imports in OpenGL are written by hand, and when the OpenGL ARB ever manages to release some consistent, machine- usable and complete API description (the current .spec files fail in almost all these aspects), they will be generated from that, not from C headers, because, not surprisingly, the latter lack a lot of information. In practise I've not found that most configure scripts actually do feature based tests. There's some, but half of it degenerates into if we've not got the OSX framework for this then do that. I mean they just end up doing platform-specific conditionals. [...] This is often correct for hobby projects of inexperienced people, but not necessarily for larger or more mature projects. And in a (very) few cases, platform-specific conditionals are even the right thing to do, but not in the vast majority of cases, of course. And this has nothing to say about autoconf itself: Seeing e.g. ugly Haskell code is not a reason to condemn Haskell itself, either. Anyway, so that's why I'd like us to look in detail at what features we need in Cabal to let us switch most packages from using ./configure scripts to using Setup.hs scripts. As I said in another email: I'll happily review and accept patches for this, but I won't spend any effort on re-inventing the autoconf wheel in Haskell. Cheers, S. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Google SoC: Space profiling reloaded
Hello all, I'm one of the lucky individuals accepted for this year's Summer of Code. Here's the abstract of my proposal: http://socghop.appspot.com/student_project/show/google/gsoc2009/haskell/t124022468245 There's less than a month left before I'm supposed to jump into coding, and I'd love to hear about any little idea you think would make this project even better! I created a project page with a rough draft of what I intend to concentrate on, but the issue tracker is obviously begging for content, so feel encouraged to populate it. :) http://code.google.com/p/hp2any/ I also intend to expand the description later. Gergely -- http://www.fastmail.fm - The professional email service ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to install HOpenGL to Windows?
On Thu, 2009-04-30 at 19:44 +0200, Sven Panne wrote: That's why the autoconf macros are so tricky. Re-inventing the wheel in Haskell is not something I'd like to do. Note: I see autoconf as a necessary evil, not as a glorious tool. The predefined autoconf macros contain man years (if not man decades) of sweat and tears from people trying to make their SW portable. If you only know 1 or 2 platforms, everything looks easy, but this is not the case at all. Good luck for everybody trying to ignore that accumulated knowledge... The thing is, it doesn't really matter if autoconf macros work fine for every Unix ever invented. The Windows users simply cannot use packages with configure scripts. They complain about it a lot. We can call them foolish for not installing cygwin/mingw, but they will not do it and instead will simply not use our software and/or continue to complain. But you have some way of finding them right? Even if it's platform dependent. We can do the same in the .cabal file or the Setup.hs. There's also a Cabal flag users can pass to tell us about extra lib and include dirs. I even have standard, well-documented, platform-independent way: Tell configure about it via the environment variable CPPFLAGS for headers and LDFLAGS for libraries. Cabal is buggy in this respect, IIRC, it passes no or incorrectly named variables to configure. Right then lets fix it, lets work out exactly which flags or env vars to pass. See: http://hackage.haskell.org/trac/hackage/ticket/458 Doing it is not hard, it's working out exactly what to pass that's the important matter. Absolutely, finding headers is important. Cabal now checks at configure time that all header files and libs listed in the .cabal file can actually be found. I don't know what Cabal does internally, but simply checking for the existence of a header file or a library file is *far* too naive, look into the autoconf docs and/or mailing lists to see why. You actually have to compile for header checks and link for library checks, everything else is plainly wrong, because you'll probably miss dependencies, pick up the wrong stuff, etc. Right, that's exactly what it does. We checked used the autoconf macros as guidance. One suggestion I've seen is just to improve the ffi pre-processors. The c2hs tool is in a position to discover if the calling convention is stdcall or ccall so it could generate the foreign imports correctly. [...] This wouldn't help much: The foreign imports in OpenGL are written by hand, and when the OpenGL ARB ever manages to release some consistent, machine- usable and complete API description (the current .spec files fail in almost all these aspects), they will be generated from that, not from C headers, because, not surprisingly, the latter lack a lot of information. I don't see that the two approaches are exclusive. For example with Gtk+ we also generate from an incomplete API description with manual adjustments because of lack of info. However we generate .chs files that then get processed by c2hs so that we can check if our binding at least matches the C header files. Certainly the C headers are not enough (no info about memory management) but the bindings do at least have to be consistent with the C headers on the current platform. And the C headers do say if the calling convention is ccall or stdcall (otherwise the C progs would not work). But this is not a short term fix, it'd be a complete change for the binding so I'm not seriously suggesting it. Anyway, so that's why I'd like us to look in detail at what features we need in Cabal to let us switch most packages from using ./configure scripts to using Setup.hs scripts. As I said in another email: I'll happily review and accept patches for this, but I won't spend any effort on re-inventing the autoconf wheel in Haskell. I'm not asking you personally to do that. I'm asking for help from you or others on identifying the tests that we need to do to support our most common Haskell bindings packages. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Help from C libraries experts
My goal is to have a place where one can find reliable and comprehensive low-level bindings to foreign libraries, so that writing higher level bindings becomes an easier task. (...) In your guidelines, you say: Code should be portable and easy to build. Does your understanding of portable include Windows? My thought on that was: anyone trying to wrap a library will have to solve this kind of problem. So, if it is possible to write such wrap, at least one solution exist, and 'bindings' set will try to select the best one for general use. Sometimes, this may be adding the C code itself, as is my current attempt on sqlite3. Sometimes the task can be delegated to pkg-config. Actually, that is the reason why my first post was a call for help from libraries experts. This has to be solved on a per library base. Thanks, Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] unsafeSTToIO and stToIO
I gather that ...making it possible to use ST code directly on IORef's. is what we have today? -- Jason Dusek |...making it possible to use ST code directly on IORef's.| http://www.mail-archive.com/glasgow-haskell-b...@haskell.org/msg03568.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Arrow preprocessor and *** combinator
On Thu, Apr 30, 2009 at 11:42 AM, Peter Verswyvelen bugf...@gmail.comwrote: Thanks Ross. Does anyone know how to tackle this? Combining GHC's builtin arrow processor and rewrite rules? Another possibility is to make an optimizer arrow transformer that encodes the rules. Eg. data Optimize a b c where Arr :: (b - c) - Optimize a b c (:) :: Optimize a b c - Optimize a c d - Optimize a b d First :: Optimize a b c - Optimize a (b,d) (c,d) Second :: Optimize a b c - Optimize a (b,d) (c,d) (:***) :: Optimize a b b' - Optimize a c c' - Optimize a (b,b') (c,c') optimize :: Optimize a b c - Optimize a b c optimize (First f : Second g) = f :*** g ... compile :: (Arrow a) = Optimize a b c - a b c compile (Arr f) = arr f compile (f : g) = compile f compile g ... I have of course handwaved over optimize, which will have some interesting traversal structure; esp. if you want to take advantage of the associativity of . Unfortunately, Arr is not quite transparent enough to do everything one might want with this. e.g.,this rule cannot be encoded: swap (x,y) = (y,x) first f arr swap first g = f *** g arr swap If you are serious about arrow optimizations, it might be worthwhile to modify the original preprocessor to output a richer GADT (with cases for things like ArrSwap) with all the information it knows, so that user code can experiment with optimizations. Godspeed on this interesting problem. Please publish :-) Luke On Wed, Apr 29, 2009 at 3:43 PM, Ross Paterson r...@soi.city.ac.ukwrote: On Wed, Apr 29, 2009 at 03:07:25PM +0200, Peter Verswyvelen wrote: After doing some pragmatic tests, it seems that neither the arrow preprocessor nor GHC's builtin one generate / optimize to the (***) combinator. Right, neither of them do that. It might be possible to do that using GHC rules, but it isn't done at the moment. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] unsafeSTToIO and stToIO
On Thu, Apr 30, 2009 at 12:44:49PM -0700, Jason Dusek wrote: I gather that ...making it possible to use ST code directly on IORef's. is what we have today? No, we have stToIO :: ST RealWorld a - IO a, but STRef and IORef are still incompatible types. (I now think that's a good thing, because STRefs have more equations than IORefs.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Arrow preprocessor and *** combinator
If you are serious about arrow optimizations, it might be worthwhile to modify the original preprocessor to output a richer GADT (with cases for things like ArrSwap) with all the information it knows, so that user code can experiment with optimizations. Godspeed on this interesting problem. Please publish :-) Thanks for the tips Luke. I didn't think of that. But would doing these optimizations at runtime be as efficient as using rewrite rules? I know Yampa uses these GADTs for optimization. No I won't be able to make such a big optimizer myself - but Paul Liu and Paul Hudak are working on something like that I think (see the Causal Commutative Arrows paper). But my code made use of a non-default *** and I found it odd that it was never called, so I hoped it would be easy to add a couple of simple rewrite rule so that *** was generated. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to install HOpenGL to Windows?
The thing is, it doesn't really matter if autoconf macros work fine for every Unix ever invented. The Windows users simply cannot use packages with configure scripts. They complain about it a lot. We can call them foolish for not installing cygwin/mingw, but they will not do it and instead will simply not use our software and/or continue to complain. Windows users - that's a lot of different people to generalize over. From what I've heard, most complaints are about assumptions made by non-windows users that turn out not to hold on windows, causing things to fail on windows. Which seems reason enough for failure reports, otherwise known as complaints. If someone wants to use a unix shell on an unknown platform, they should at least check that one exists there or -even better- provide one, not just assume that there'll always be one (and then be surprised about getting complaints from those windows users). Same for autoconf, make co. If someone mixes up GCC's standard layout, they need to adjust everything for those changes, and when that turns out to be rather difficult, it is no surprise if GCC seems unable to pick the right include or library paths. This particular issue has just recently been fixed in GHC head, I understand (will that fix cause problems for cabal, btw, when the existing path hacks are no longer needed?). http://hackage.haskell.org/trac/ghc/ticket/1502#comment:12 Apart from causing lots of other path issues (and confusing tools like cabal, which tried to compensate by special-case code), this complicated the process of installing headers and libraries used by FFI bindings, at least for those windows users who didn't build their own GHCs, with the help of a full GCC install. And so on.. Listen to the complaints, there is (usually) a real issue behind them. A couple more examples of why installing the tools that some cabal packages rely on isn't straightforward: I like and use cygwin, but when installing it, one has to be careful to include all the bits that are needed, preferably leaving out the bits that might cause confusion when used for GHC/Cabal (such as a second GCC installation). I once tried to capture the list of dependencies needed for building GHC in a cygwin pseudo-package (no contents, only dependencies), which made that easy. http://www.haskell.org/pipermail/cvs-ghc/2005-May/025089.html http://hackage.haskell.org/trac/ghc/wiki/Building/Windows/Cygwin But then cygwin's installer added security signatures, and I don't think such were ever added to the pseudo-package, the dependencies are also not uptodate anymore (I don't have write access to where it was put). Nowadays, one could put the cygwin pseudo-package into a cabal package on hackage, including the necessary signature, and that cabal package could run the cygwin installer with the dependencies given in the cygwin package (assuming there's a commandline interface to the cygwin installer) or at least users could run the cygwin installers with an updated version of that cygwin package, and get a cygwin setup useable for cabal packages. Others like msys, but for some reason the msys developers hardly ever put up a simple installer, one usually has to collect various bits and pieces in the right version, then unpack them on top of each other - very far from automated one-click installation. Simon recently collected the pieces needed for building GHC, so one could now point windows users to http://hackage.haskell.org/trac/ghc/wiki/Building/Preparation/Windows for one-stop shopping. One could probably do better by collecting those pieces into a cabal package (assuming the license is favourable), but I could never find documentation for using the mingw/msys installers from the commandline, as a cabal package would need to do. Someone familiar with those installers might not find this difficult. Improving Cabal to replace autoconf is a nice long-term goal, but in the meantime, things could be made a lot easier for those windows users. GHC using the standard layout for its GCC is one step, packaging up the msys and cygwin dependencies would make it straightforward to install those correctly (someone with installer knowledge might even be able to automate that from the cabal commandline..). Then windows users could easily install either msys or cygwin, and the remaining issue would be how to install the headers and libraries for cabal packages with ffi bindings. Just as on other platforms. Claus PS. Don't think of them and they vs we and us and our software. It doesn't help. Neither does classifying bug reports as complaints. -- It is not that we think of other as bad, -- it is that we think of bad as other. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] swish - semantic web in Haskell
Hello, http://www.ninebynine.org/Software/swish-0.2.1.html I am trying to get permission from the author of Swish to move it into Hackage. I will write cabalize it get up to current Haskell standards. Before I go to this effort is anybody attempting to do this? Kind regards, Vasili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Google SoC: Space profiling reloaded
http://socghop.appspot.com/student_project/show/google/gsoc2009/haskell/t124022468245 There's less than a month left before I'm supposed to jump into coding, and I'd love to hear about any little idea you think would make this project even better! I created a project page with a rough draft of what I intend to concentrate on, but the issue tracker is obviously begging for content, so feel encouraged to populate it. :) http://code.google.com/p/hp2any/ Hi there, I'm sure lots of Haskellers are looking forward to profiling improvements!-) The wxHaskell applications page http://wxhaskell.sourceforge.net/applications.html mentions http://dready.org/projects/HPView/ which seems relevant. Shortening the song and dance needed to get profiles would be nice (eliminating the PS viewer dependency in the process). So would not having to select profile type in advance (and not having to repeat the profile runs again and again, with only one view each time). I assume you're only going to look into visualization, not semantics?-) http://www.haskell.org/pipermail/cvs-ghc/2008-October/045981.html Also, there is a lot of space profiling support, but I'd sometimes like more detailed time profiling (not just end-of-run summaries, but time sliced profiling - in this time slice, most of the time was spent in x, in the next time slice, most of the time was spent in y, these functions are frequented in the beginning, but are not used towards the end, etc). Perhaps the recent support for code coverage could be bent to support something like this without too much hacking? Keep us informed! Claus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to install HOpenGL to Windows?
On Thu, 2009-04-30 at 23:31 +0100, Claus Reinke wrote: The thing is, it doesn't really matter if autoconf macros work fine for every Unix ever invented. The Windows users simply cannot use packages with configure scripts. They complain about it a lot. We can call them foolish for not installing cygwin/mingw, but they will not do it and instead will simply not use our software and/or continue to complain. Windows users - that's a lot of different people to generalize over. Yes, I was generalising. There are those users who are prepared, even happy to install cygwin, and there's everyone else. From what I've heard, most complaints are about assumptions made by non-windows users that turn out not to hold on windows, causing things to fail on windows. Which seems reason enough for failure reports, otherwise known as complaints. If someone wants to use a unix shell on an unknown platform, they should at least check that one exists there or -even better- provide one, not just assume that there'll always be one (and then be surprised about getting complaints from those windows users). Same for autoconf, make co. You mean that we should be shipping a haskell platform with a full copy of mingw + all the tools to make configure scripts run? I doubt that'll make people happy. They'll complain about it not being native. If someone mixes up GCC's standard layout, they need to adjust everything for those changes, and when that turns out to be rather difficult, it is no surprise if GCC seems unable to pick the right include or library paths. This particular issue has just recently been fixed in GHC head, I understand (will that fix cause problems for cabal, btw, when the existing path hacks are no longer needed?). http://hackage.haskell.org/trac/ghc/ticket/1502#comment:12 Apart from causing lots of other path issues (and confusing tools like cabal, which tried to compensate by special-case code), this complicated the process of installing headers and libraries used by FFI bindings, at least for those windows users who didn't build their own GHCs, with the help of a full GCC install. And so on.. In principle there is no problem with finding the mingw headers on Windows. All we need is that the rts or base package specify them in the include-dirs in the package registration info. Cabal uses the same info. Listen to the complaints, there is (usually) a real issue behind them. I don't think the problem is that we've had a messed up mingw. A couple more examples of why installing the tools that some cabal packages rely on isn't straightforward: But there is a significant number of Windows users who do not care to install these tools at all. Making the stuff work better for people who choose to use cygwin is great. I have no objections to that. But the majority want stuff to work without them having to install cygwin. In this case stuff often means random hackage packages and many of them are using configure scripts. Improving Cabal to replace autoconf is a nice long-term goal, but in the meantime, things could be made a lot easier for those windows users. GHC using the standard layout for its GCC is one step, packaging up the msys and cygwin dependencies would make it straightforward to install those correctly (someone with installer knowledge might even be able to automate that from the cabal commandline..). Then windows users could easily install either msys or cygwin, and the remaining issue would be how to install the headers and libraries for cabal packages with ffi bindings. Just as on other platforms. Making them easier to install would probably convince many Windows users to install one of them. PS. Don't think of them and they vs we and us and our software. It doesn't help. Neither does classifying bug reports as complaints. I'm not complaining about people complaining. :-) I'd like to see things work better on windows. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to install HOpenGL to Windows?
If someone wants to use a unix shell on an unknown platform, they should at least check that one exists there or -even better- provide one, not just assume that there'll always be one (and then be surprised about getting complaints from those windows users). Same for autoconf, make co. You mean that we should be shipping a haskell platform with a full copy of mingw + all the tools to make configure scripts run? I doubt that'll make people happy. They'll complain about it not being native. The platform includes GHC, which already includes mingw (GCC)!-) What I meant was a cabal package bundling the pieces of msys (sh, autoconf, make,..). And, no, the haskell platform doesn't need this, so it should be a separate package. But cabal install should know that this package would be nice to have at hand if building a package that uses build-type:configure on windows. just fixed: http://hackage.haskell.org/trac/ghc/ticket/1502#comment:12 In principle there is no problem with finding the mingw headers on Windows. All we need is that the rts or base package specify them in the include-dirs in the package registration info. Cabal uses the same info. In practice, we have instructions like these circulating (these being examples of the better kind, as they actually got things working): http://joelhough.com/blog/2008/04/14/haskell-and-freeglut-at-last/ http://netsuperbrain.com/blog/posts/freeglut-windows-hopengl-hglut/ And I've lost count of the number of times the finding of mingw headers or libs has caused bugs (which usually went unnoticed on the author's machine because the author would have a full copy of mingw in c:/mingw, where gcc looks for things when everything else fails - oh, unless you're using ghc's gcc on d:, when this failsafe would suddenly fail as well, until recently). Perhaps cabal had no problems with this, but problems were plenty and initially non-obvious. So I'm happy that this fix has eliminated one common cause of problems with installing Haskell software on windows. Every little bit helps. A couple more examples of why installing the tools that some cabal packages rely on isn't straightforward: But there is a significant number of Windows users who do not care to install these tools at all. Making the stuff work better for people who choose to use cygwin is great. I have no objections to that. But the majority want stuff to work without them having to install cygwin. In this case stuff often means random hackage packages and many of them are using configure scripts. If cabal can do autoconf/configure stuff without having autoconf/ configure installed, great. Someone could write SH as a Haskell DSEL, for starters, then replicate the autoconf stuff (its all just SH libraries and some macro processing, right?). But I'm not optimistic about that in general. There probably are windows users who don't want to have msys or cygwin on their machine, but I suspect there are more windows users who simply don't want to bother with msys (so if cabal installed and used it internally, they might accept that, just as they accept, or at least live with, GHC installing and using mingw internally). Then windows users could easily install either msys or cygwin, and the remaining issue would be how to install the headers and libraries for cabal packages with ffi bindings. Just as on other platforms. Making them easier to install would probably convince many Windows users to install one of them. It would also simplify cabal package installation instructions, and avoid the it doesn't work and it thinks it is on unix so I don't see how it could possibly work feeling. Instead, cabal install would simply point out another package dependency that needs installing. I'm not complaining about people complaining. :-) I'd like to see things work better on windows. I'm not surprised!-) Claus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Few Alex questions
Hi,
Q1: I am trying to create an Alex equivalent of the following flex file:
http://code.haskell.org/yc2js/es-idl/lexer.ll (lexer for Web IDL which
is a dialect of OMG IDL)
I haven't been able to find Alex equivalent for the following line:
PoundSign ^{WhiteSpace}*#
that is any amount of whitespace at the beginning of line followed by '#'
I defined a @WhiteSpace macro some place earlier, but Alex gives me
parser error on the line I created:
@PoundSign = ^...@whitespace*#
in the position 28 that is position of '@', next to caret, that is,
caret is not recognized by Alex.
Can beginning of line (caret) be recognized by Alex?
Q2: The original line says:
MultiLineComment\/\*(([^*])|(\*[^/]))*\*\/
basically same as comments in C or Java.
I had to prefix star and slash even within square brackets with
backslashes to make it compile.
So I got:
@MultiLineComment = \/\*(([^\*])|(\*[^\/]))*\*\/
Is this correct understanding that if we want to match any character
except for an asterisk, then Alex would like to see [^\*] rather than
[^*]? And [^\/] rather than [^/]?
Or would it be better to use a hex code for the asterisk and slash?
Thanks.
--
Dimitry Golubovsky
Anywhere on the Web
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[Haskell-cafe] [tryReadAdvChan :: AdvChan a - IO (Maybe a)] problems
Hi!
I need this function with requirement of heavy reads, *possibly under DDoS
attack*.
Was trying to write such function, but discovered some serious problems of
** possible racings,
** possible starvations
** unbalance: readAdvChan users may get better service than ones of
tryReadAdvChan
These are totally unacceptible for my case of DDoS risk.
Actually, am I wrong thinking, that it can't be helped - and the degradation
from cute concurency synchronization model of Chan is unavoidable?
My (untested) code:
---
---
module AdvChan ( AdvChan
, newAdvChan
, readAdvChan
, writeAdvChan
, writeList2AdvChan
, advChan2StrictList
, withResourceFromAdvChan
, tryReadAdvChan
, isEmptyAdvChan
) where
import Control.Concurrent.Chan
import Control.Concurrent.MVar
data AdvChan a = AdvChan {
acInst:: MVar Chan a
, acWrite :: a - IO ()
, acIsEmpty :: IO Bool
}
newAdvChan :: IO AdvChan a
newAdvChan = do ch- newChan
mv_ch - newMVar ch
return AdvChan {
acInst= mv_ch
, acWrite = writeChan ch
, acIsEmpty = isEmptyChan ch
}
readAdvChan :: AdvChan a - IO a
readAdvChan ach = modifyMVar (acInst ach)
(\ ch - do a - readChan ch
return (ch, a)
)
writeAdvChan :: AdvChan a - a - IO ()
writeAdvChan = acWrite
writeList2AdvChan :: AdvChan a - [a] - IO ()
writeList2AdvChan ach[] = return ()
writeList2AdvChan ach (h:t) = writeAdvChan ach h writeList2AdvChan ach t
advChan2StrictList :: AdvChan a - IO [a]
advChan2StrictList ach = modifyMVar (acInst ach)
(\ ch - let readLoop = do emp -
isEmptyChan ch
case emp of
True -
return []
False -
do _head - readChan ch
_rest - readLoop
return (_head : _rest)
in liftTuple (return ch,
readLoop)
)
withResourceFromAdvChan :: AdvChan a - (\ a - IO (a, b)) - IO b
withResourceFromAdvChan ach f = do res - readAdvChan ach
(res_processed, result) - f res
writeAdvChan ach res_processed
return result
isEmptyAdvChan :: AdvChan a - IO Bool
isEmptyAdvChan = acIsEmpty
microDelta = 50
tryReadAdvChan :: AdvChan a - IO (Maybe a)
tryReadAdvChan ach = emp2Maybeness $ do mb_inst - tryTakeMVar (acInst ach)
case mb_inst of
Nothing - emp2Maybeness
(threadDelay microDelta tryReadAdvChan ach)
Just chan - do emp -
isEmptyChan ch
result - case
emp of
True - return Nothing
False - Just `liftM` readChan ch
putMVar (acInst
ach) chan
return result
where emp2Maybeness f = do emp - isEmptyAdvChan ach
case emp of
True - return Nothing
False - f
---
---
Later after writing my own code, and understanding the problem I checked
Hackage. Found synchronous-channels package there
(http://hackage.haskell.org/cgi-bin/hackage-scripts/package/synchronous-channels),
but it isn't any further in solving my the unbalacedness problems.
Any suggestions on the fresh matter are welcome.
Belka.
--
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[Haskell-cafe] The Haskell Reddit is 1 year old
Just a reminder, the Haskell Reddit is live and active: http://www.reddit.com/r/haskell/ It is a a place for fast, daily, comprehensive news about what's going on in the Haskell community, combining blogs, mail, irc, ghc's patches, the freaking types@ mailing list! It's all here, with comments. Enjoy. Contribute. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
