- Glasgow-haskell-users

Happy documentation
by George Russell 09 Jan '02

09 Jan '02

Any chance of getting the Happy documentation as HTML in a .tar.gz file? Or do I have to get DocBook running on x86 Linux machine (I normally use Sparc/Solaris) to compile it from source, or do a recursive wget on http://www.haskell.org/happy/doc/html/happy.html?

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GHC Poll: scope in GHCi
by Simon Marlow 09 Jan '02

09 Jan '02

Folks, There's a long-standing problem in GHCi, namely that when you select a compiled module with ':m M' you can only see the exports of M, and even the exports of the Prelude are hidden. Several people have suggested that this should be improved, and I'm just getting around to implementing something more useful. This message is to gather suggestions on what the user interface should look like in a more general setting, from people who use GHCi more than we do :-) Ok, so in general a 'scope' can be constructed by combining: 1. the full top-level scope from zero or more *interpreted* modules 2. the exports of zero or more modules (interpreted or compiled) 3. any temporary bindings made on the command line I'm assuming name clashes are handled in the normal Haskell 98 way, ie. lazilly, so it might actually make sense to combine the top-level scope of more than one module. Whatever user interface we adopt should provide a way to manipulate these sets. Here's one suggestion: :m M1..Mn set sets 1 & 2 from M1..Mn - use list 1 if Mi is interpreted, otherwise list 2. :m +M adds M to set 1 or 2. :m -M removes M from set 1 or 2. Which leaves one remaining case: adding an interpreted module to set 2. Perhaps this could be ':m *M'. Does anyone have any better suggestions? Cheers, Simon

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RE: GHC Poll: scope in GHCi
by Simon Marlow 09 Jan '02

09 Jan '02

> Is there any haskell interpreter done it already? > Hugs and hmake support ":also" command. I don't know > now exactly it works, but quick test showed than > it (sometimes) helps to mix scopes: > > Hi (hmake/nhc98): > ------- begin cut > Prelude> :also Maybe > [Std module... /usr/local/opt/nhc98/include/nhc98/Prelude.hi] > [Std module... /usr/local/opt/nhc98/include/nhc98/Maybe.hi] > Maybe> print "a" > "a" > Maybe> :also IO > [Std module... /usr/local/opt/nhc98/include/nhc98/Prelude.hi] > [Std module... /usr/local/opt/nhc98/include/nhc98/Maybe.hi] > [Std module... /usr/local/opt/nhc98/include/nhc98/IO.hi] > IO> listToMaybe [1] > Just 1 > ------- end cut Hugs's :also is the same as GHC's :add; it causes another module to be loaded without throwing away the existing loaded set, and it changes the scope to the new module. Hi seems to be doing something slightly different, but I can't find any documentation on Hi's :also command. Cheers, Simon

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FORTRAN and HASKELL
by clusterpoli 09 Jan '02

09 Jan '02

Somebody works with together FORTRAN and Haskell. Exists some funcao to transform codigo FORTRAN into codigo HASKELL? Thanks, Allan Bruno __________________________________________________________________________ AcessoBOL, só R$ 9,90! O menor preço do mercado! Assine já! http://www.bol.com.br/acessobol

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RE: Clean 2.0 dynamics
by Simon Peyton-Jones 09 Jan '02

09 Jan '02

I think that "proper" dynamics are one of those things that are easier said than done. Yes, GHC has more of the infrastructure now than it used to have. But I don't think it's a routine matter to come up with a robust design, or to implement that design. But it would certainly be a good and useful project. We don't have any plans here to work on it, though. Simon | -----Original Message----- | From: Krasimir Angelov [mailto:ka2_mail@yahoo.com] | Sent: 09 January 2002 09:00 | To: glasgow-haskell-users(a)haskell.org | Subject: Clean 2.0 dynamics | | | Hi | | Are you known about new Clean 2.0 compiler and your | new features. There is two general extensions in | language: Dinamics and their automatic loading\writing | to files or streams. Clean Dinamics are most similar | to corresponding Haskell Dinamic type. Main difference | is in some language extensions which allow dynamic | types to be dynamicaly unified. See following Clean | function: | | dynApply :: Dynamic Dynamic -> Dynamic | dynApply (f :: a -> b) (x :: a) = dynamic (f x :: b) | dynApply df dx = dynamic ("cannot apply",df,"to",dx) | | In Haskell the only way to define dynApply is with | using of unsafeCoerce# which is type unsafe. Runtime | type unification is useful but not obligatory. I think | that most important thing is automatic loading\writing | of Dynamics. Loading/writing facilities in Clean needs | dynamic linker which can dynamical loading of object | files. As I known in GHC-5.02 we already have such | linker which is part of runtime system. I think that | is'n too difficult to implement this feature in GHC. | Is there any plan to implement this. For functional | programing Dynamics can be same as COM/Corba for OO | programing. While runtime type unification needs some | syntax extensions (As I known using polymorphic types | in pattern type signatures are always implemented | according to rank-N types), dynamic linking needs only | backend changes. | | Krasimir | | __________________________________________________ | Do You Yahoo!? | Send FREE video emails in Yahoo! Mail! | http://promo.yahoo.com/videomail/ | | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-| haskell-users |

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Clean 2.0 dynamics
by Krasimir Angelov 09 Jan '02

09 Jan '02

Hi Are you known about new Clean 2.0 compiler and your new features. There is two general extensions in language: Dinamics and their automatic loading\writing to files or streams. Clean Dinamics are most similar to corresponding Haskell Dinamic type. Main difference is in some language extensions which allow dynamic types to be dynamicaly unified. See following Clean function: dynApply :: Dynamic Dynamic -> Dynamic dynApply (f :: a -> b) (x :: a) = dynamic (f x :: b) dynApply df dx = dynamic ("cannot apply",df,"to",dx) In Haskell the only way to define dynApply is with using of unsafeCoerce# which is type unsafe. Runtime type unification is useful but not obligatory. I think that most important thing is automatic loading\writing of Dynamics. Loading/writing facilities in Clean needs dynamic linker which can dynamical loading of object files. As I known in GHC-5.02 we already have such linker which is part of runtime system. I think that is'n too difficult to implement this feature in GHC. Is there any plan to implement this. For functional programing Dynamics can be same as COM/Corba for OO programing. While runtime type unification needs some syntax extensions (As I known using polymorphic types in pattern type signatures are always implemented according to rank-N types), dynamic linking needs only backend changes. Krasimir __________________________________________________ Do You Yahoo!? Send FREE video emails in Yahoo! Mail! http://promo.yahoo.com/videomail/

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XML-RPC For Haskell
by Ronald Legere 08 Jan '02

08 Jan '02

Is anyone out there working on an XML-rpc binding for haskell? This probably is not so hard, using HaXml and Sockets (as soon as sockets is working again...) But if someone has/is already done/doing it/it then i would rather just use that :) Cheers! __________________________________________________ Do You Yahoo!? Send FREE video emails in Yahoo! Mail! http://promo.yahoo.com/videomail/

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Re: State Transformer
by Ketil Z Malde 08 Jan '02

08 Jan '02

Jorge Adriano <jadrian(a)mat.uc.pt> writes: > Anyway, I was coding some simple GA, and as you probably know I need to use > random values. The most elegant way I could think of was to generate some [...] > Monads! (right?) Well, I suppose so. Generally speaking. But, you might want to consider using the standard random generation routines from the (IO) top level of your program, and just split the random generator for each function that uses it. IOW, passing each function its own random generator, instead of worrying about returning the "rest" of a global random sequence. (I don't have any good example code, I'm afraid, but at leat have a look at the chapter on Random in the library report on http://haskell.org) -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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State Transformer
by Jorge Adriano 07 Jan '02

07 Jan '02

Hi, I'm studying, among other things, Genetic Algorithms and Neural Networks and I decided I'd use haskell to code some simple GAs and NNs along with my study. Well, maybe it was not such a good idea after all, because I've been spending way more time learning more Haskell then GAs and NNs :( Anyway, I was coding some simple GA, and as you probably know I need to use random values. The most elegant way I could think of was to generate some infinite list of random values and pass them around as arguments to the functions that need those values. I called data which wraped this list Environment, and at first it seemed a nice way to solve the problem. Well, now I think it gets kind of weird because some functions will end up to have type something -> (otherthing, Environment), to update those lists... it's just ugly. Beside those lists I'd also like to control some statistics like the number of mutations, n. of crossovers, best fitness value in each generation, etc... I figured out that there should be a better way to do this then just chaging all the signatures and passing all this values around. Monads! (right?) Till then I had just read what I needed to be able to use the IO Monad. Seems to me like having a State Transformer monad its the best way to do it. Now I've read a great deal of Richard Birds Book chap 10 (Monads), as well as the "Monads for the Haskell Working Programmer"[1] by Theodore Norvell. I was going to try to make my own simple examples using a ST. A State Monad seemed something like would most probably be in some Standard Library, or at least in some GHC library. And it was (section 4.31.ST in the hslibs documentation) I wanted to use this ST, but then I noticed it was different from the one described in tutorial[1]. I was expecting the ST Monad ghc module to provide an apply function, analogue to the > applyST :: StateTrans s a -> s -> (s, a) > applyST (ST p) s = p s in the tutorial. I also expected to have general functions to access and change State. I can't implement them myself since the ST constructor is (obviously) not exported. But this ST module seems to work in a completely diferent way. >From what I can tell it is not suposed to be applyed to an initial state, instead it starts with an 'empty' state... State is controled with Referencies (mutable variables). Ok, now my problem, how do I use this? I can't really see how to change this referencies from within some function. (Got an example in the end to explain better waht I mean with that [Example1]) I'd also appreciate some coments on: Using a ST monad (good idea, bad?) Using the Ghc ST monad? Chromosomes defined as arrays? - either IArray or Diff array got to give it some more thought... (don't want Ints + bitwise operations right now...) Well, any other comments or hints that you think that might be usefully are welcome. I've already checked out the paper from the TAIGA project[2], it's not exactly done the way I'm thinking about doing it, but I got some usefull tips from there, like the use of a Monad to control statistics. One of my main problems so far as been *knowing what do I need to know*! I don't know anyone that codes in haskell, not having anyone to talk to and share ideas doesn't helps much either. Things get complicated where you (you - the guy that comes from the imperative paradigm) less expects it too... the space leaks, using monads to control state... if you still have not read about this stuff, IMO, it is easy to feel like you already know enough to do some solve some kind of problems when you actually don't. Any newbie to C or Pascal can make a few randoms here and there, and keep track of statistics... when you already spent some time with haskell you don't even question whether you already know enough to do something like *that*. Only when you start to work, and thing start to get messy, you begin to think that *maybe you need something you still don't know about*, and then you got to find out what it is... Documentation, I also feel like it could be more and better... the ST module in ghc for instance... would it be that hard to put at least some simple example there? No, just the type signatures... Well, this is just my opinion anyway. Thanks for your atention, and happy 2002 ;-) J.A. [Example1] How can I do this for instance, with the Ghc ST Monad: ------------------------------------------------------------------------ -- the State Trans defined as in the tutorial newtype StateTrans s a = ST( s -> (s, a) ) instance Monad (StateTrans s) where -- (>>=) :: StateTrans s a -> (a -> StateTrans s b) -> StateTrans s b (ST p) >>= k = ST( \s0 -> let (s1, a) = p s0 (ST q) = k a in q s1 ) -- return :: a -> StateTrans s a return a = ST( \s -> (s, a) ) applyST :: StateTrans s a -> s -> (s, a) applyST (ST p) s = p s -- just change the state putST :: (Char,Int) -> StateTrans (Char,Int) () putST (c',n') = ST(\(c,n)->((c',n'),())) -- get the state getST :: StateTrans (Char,Int) (Char,Int) getST = ST(\(x,y)-> ((x,y), (x,y))) testfunc :: StateTrans (Char,Int) Int testfunc = do foo bar (c,n)<-getST return n foo = do (c,n)<-getST putST ('a',n+1) bar = do (c,n)<-getST putST (c,n+2) tryTestFunc = applyST testfunc ('x',0) ------------------------------------------------------------------------ I is something like this? ---------------------------------------- stupidFunc runST ( do { initstate <- newSTRef ('x',0) -- and now what? }) ----------------------------------------- [1] http://www.engr.mun.ca/~theo/Misc/haskell_and_monads.htm [2] http://www.scms.rgu.ac.uk/staff/db/Taiga/ http://www.scms.rgu.ac.uk/staff/db/Taiga/APGA2000.ps.gz

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RE: weird compiler bug/failed to load interface
by Simon Peyton-Jones 07 Jan '02

07 Jan '02

Hal, Do please say what version of GHC you are using when reporting bugs! I can reproduce this with -O2, but not with -O. That's good, because it's a bug we fixed last week. It'll be fixed in the upcoming 5.02.2 release. thanks for reporting it. The workaround is not to use -O2 for Pattern.hs Simon | -----Original Message----- | From: Hal Daume III [mailto:hdaume@ISI.EDU] | Sent: 04 January 2002 17:36 | To: GHC Users Mailing List | Subject: weird compiler bug/failed to load interface | | | There's one module I wrote that I use in a lot of my programs | and for some reason, whenever I compile a program using this | module with -O or -O2, make changes to the Main, and then | recompile, I get the following error from ghc: | | Skipping Pattern ( Pattern.hs, Pattern.o ) | | failed to load interface for `Pattern': | Could not find interface file for `Pattern' | | Failed to find interface decl for `Pattern.a' | from module `Pattern' | | if I "ls Pattern.*" I get Pattern.hi, Pattern.hs and Pattern.o. | | In order to get it to compile correctly, I have to rm | Pattern.o and then rerun ghc on the Main module. | | I've attached the Pattern.hs fyi. If anyone has any | suggestions, please let me know. (btw, I'm using --make) | | Thanks! | | - Hal | | -- | Hal Daume III | | "Computer science is no more about computers | hdaume(a)isi.edu | than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume |

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