November 2001 - Glasgow-haskell-users

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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Socket library ghc 5.02.1
by Sven Eric Panitz 30 Dec '01

30 Dec '01

It seems that the Socket library does still not work with ghc 5.02.1. I tried the simple test: > main = > do > d <- connectTo "localhost" (PortNumber 80) > hPutStr d "GET / HTTP/1.0\n\n" > hFlush d > c <- hGetContents d > putStr c On Windows2000 I get the known error: *** Exception: does not exist Action: getProtocolByName Reason: no such protocol entry whereas on Linux I get the following error: *** Exception: failed Action: connect Reason: Unknown error 142731264 The error number changes for every invocation and every 20th time or so it works on the linux machine. Can anyone recommend me, how to get a working Socket library with ghc 5.02. (I really need it now...) Sven Eric

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Communicating with other programs (Win32)
by Jan de Wit 05 Dec '01

05 Dec '01

Hi all, In my free time, I'm writing a Go program in Haskell. Main platform is GHC and GHCi under Win32. It is coming along nicely: it has a GUI and the moves it comes up with are starting to make some sense. For testing (and maybe later training :) purposes I want it to be able to play against GnuGo (the strongest Open Source Go program) on its own. Currently, to get GnuGo to think up a move, I use something like (SGF is the standard way of outputting Go games): | do writeFile "in.sgf" (showAsSGF game) | let cmd = "echo quit > gnugo --quiet --infile in.sgf --color " ++ | (show computerColor) ++ | " --mode ascii > out.txt" | system cmd | result <- readFile "out.txt" | return (parseResultMove result) I think this both ugly and inefficient: for every move a new instance of GnuGo gets started and an SGF file is output! Instead, I want to start GnuGo only once per game and communicate with it like a human player would, by typing commands at it; or by using the Go Text Protocol which is specifically designed for computer-computer play. Does anybody here know a way - under Win32 - to start a process in the background and communicate with it via its stdin/stdout? I've poked around a bit in the Win32 library source, looking for an FFI interface to CreateProcess (the API function which does what I want) but found nothing. The Posix library looks like it should be up to the job, but unfortunately that isn't supported under Win32... (I'm not using Cygwin) Any help would be appreciated! Cheers, Jan de Wit

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Re: FORTRAN and HASKELL
by heron_carvalho 30 Nov '01

30 Nov '01

Hello GHC users, We want to reuse FORTRAN libraries within Haskell code. How can we use FFI to implement this interface directly ? We know that we can use C to implement it indirectly with FFI, but how can we do this directly ? Any suggestion ? Thanks, Heron de Carvalho > --- clusterpoli <clusterpoli(a)bol.com.br> wrote: > > Somebody works with together FORTRAN and Haskell. Exists > > some funcao to transform codigo FORTRAN into codigo > > HASKELL? > > TXL might help, but it's its own functional language. > It can probably convert FORTRAN to Haskell given the > EBNF for each language, but I'm not sure how it works... > http://www.research.avayalabs.com/user/wadler/realworld/l s2000.html > http://gatekeeper.dec.com/pub/misc/txl/ > > Otherwise, I would look at what algorithm the FORTRAN is > implementing, the either write it in Haskell, or look for it > on the Internet using http://www.google.com/ > > For example: http://www.cs.chalmers.se/pub/haskell/library/ > http://www.cs.chalmers.se/pub/haskell/library/bevan/index > > __________________________________________________ > Do You Yahoo!? > Yahoo! GeoCities - quick and easy web site hosting, just $8.95/month. > http://geocities.yahoo.com/ps/info1 > > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users(a)haskell.org > http://www.haskell.org/mailman/listinfo/glasgow- haskell-users > __________________________________________________________________________ AcessoBOL, só R$ 9,90! O menor preço do mercado! Assine já! http://www.bol.com.br/acessobol

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ghc and hierarchical module names
by Tim Barbour 29 Nov '01

29 Nov '01

The release notes for ghc 5.02.1 say: 1.4.4. New experimental features Partial support for hierarchical module names. - but I could not find a document describing how to use this feature. Is it possible to use hierarchical module names with ghc at present, and if so, how does one write and use a hierarchically-named module ? Tim -- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -- Benjamin Franklin

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[qforeign] CursesTest segfaults
by Jens Petersen 29 Nov '01

29 Nov '01

I built qforeign from cvs under Linux. Any idea why tests/CursesTest segfaults? Is my ncurses too new? (I have had it working previously - 6 months ago or so.) version info: ghc-5.02.1 ncurses-5.02 glibc-2.2.4 gmp-3.1.1 readline-4.2 If you need more info or traces, please let me know. Jens

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Re: Casting dynamic values
by Marcin 'Qrczak' Kowalczyk 28 Nov '01

28 Nov '01

27 Nov 2001 17:31:10 -0700, Alastair David Reid <reid(a)cs.utah.edu> pisze: > If GHC is able to inline these functions, construction and > deconstruction of the pair can probably be eliminated. cast is compiled to something similar to this: coerce :: a -> b -- this generates no runtime code type Typeable a = a -> TypeRep cast :: Typeable a -> Typeable b -> a -> Maybe b cast t1 t2 x = case t1 x of rep1 -> case t2 (coerce x) of rep2 -> case eqTypeRep rep1 rep2 of True -> Just (coerce x) False -> Nothing Instances of Typeable should not look at their argument to determine TypeRep of its type but unfortunately the compiler can't in general assume that. > But I don't think GHC can do this because AFAIK, GHC will not reduce > literal string comparisions at compile time. Since Oct 1 it tries to. Unfortunately string literals seem to be floated out to toplevel before there are recognized as literals being arguments of (==), and the rule doesn't work. > [This is assuming that GHC's implementation of Typeof still uses > strings. This may not be true though since there was talk of adding > direct compiler support to make the implementation of typeof more > efficient and, more importantly, less prone to programmer error. It doesn't use strings for comparison but uniquely generated numbers. But it's not safe either: uniqueness of these numbers relies on TyCon objects being defined at the toplevel, with {-# NOINLINE #-}, and I'm not sure if common subexpression elimination doesn't mess this up (it corrupts similar cases). Anyway equality on statically known TypeRep is not done at compile time. I don't know why. -- __("< Marcin Kowalczyk * qrczak(a)knm.org.pl http://qrczak.ids.net.pl/ \__/ ^^ QRCZAK

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Re: Socket library ghc 5.02.1
by Sven Eric Panitz 28 Nov '01

28 Nov '01

From: "Sigbjorn Finne" <sof(a)galois.com> Cc: <glasgow-haskell-users(a)haskell.org> Date: Tue, 27 Nov 2001 09:30:04 -0800 > > Conclusion: you're hosed with ghc-5.02.1 and its socket libs under > Win32. Sorry. > If you don't mind getting your hands a (little) bit dirty, here's a story that will work ghc-5.02.1: * edit SocketPrim.hi (and SocketPrim.p_hi), to instead of saying "Socket" in its __export section it says "Socket{MkSocket}" (you'll find the .hi file in imports/net/ inside your 5.02.1 tree). * compile up the attached NetExtra.hs as follows: foo$ ghc -c NetExtra.hs -fvia-C -fglasgow-exts -package net * import and include NetExtra with your socket code, e.g., Thanks Danke Mercie, this works (although I did not fully understand, what I was doing). Sven Eric

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Casting dynamic values
by George Russell 27 Nov '01

27 Nov '01

It would occasionally be nice to have a function cast :: (Typeable a,Typeable b) => a -> Maybe b which returns Just a if a and b have the same type, and Nothing otherwise. This may seem rather a curious need, but it arises with existential types; if you have data A = forall a . (context) => A a (context including Typeable a) then this allows you to getB :: (Typeable b) => A -> Maybe b getB (A a) = cast a and so extract a value from A, if you can guess its type. Clearly we can implement cast = fromDynamic . toDyn My question is: is this the most efficient way of doing it, or is there a better way?

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Re: Socket library ghc 5.02.1
by Sven Eric Panitz 27 Nov '01

27 Nov '01

From: "Sigbjorn Finne" <sof(a)galconn.com> Cc: <glasgow-haskell-users(a)haskell.org> References: <200111220959.KAA29614(a)softwareag.com> Date: Mon, 26 Nov 2001 12:30:47 -0800 "Sven Eric Panitz" <sep(a)softwareag.com> writes: > > It seems that the Socket library does still not work > with ghc 5.02.1. > I tried the simple test: > > > main = > > do > > d <- connectTo "localhost" (PortNumber 80) > > hPutStr d "GET / HTTP/1.0\n\n" > > hFlush d > > c <- hGetContents d > > putStr c > > On Windows2000 I get the known error: > > *** Exception: does not exist > Action: getProtocolByName > Reason: no such protocol entry > (You, of course, need to wrap up that code with Socket.withSocketDo to start up WinSock first). FYI, in case you're planning on doing socket programming with GHC-5.02 on a Win32 platform, stay away from using the higher-level Socket module, since its IO.Handle based view of sockets is just broken. Stick with the lower-level SocketPrim interface instead. Specifically, stay away from using the following: * Socket. connectTo * Socket.accept * Socket.sendTo * Socket. recvFrom * SocketPrim.socketToHandle --sigbjorn Thanks for the help and valuable information. I tried the following little test, which stays away from above functions: > module Main where > > import BSD > import SocketPrim > import Socket (withSocketsDo) > > main = > Socket.withSocketsDo > (do > protNum <- getProtocolNumber "tcp" > s <- socket AF_INET Stream protNum > hostAddr <- inet_addr "157.189.164.68" > let sAddr = (SockAddrInet (toEnum 8080) hostAddr) > connect s sAddr > i <- sendTo s "GET / HTTP/1.0\r\n\r\n" sAddr > (str,l,imsAddr) <- recvFrom s 1000 > putStr str > ) But something I seem to be doing wrong. During evaluation of 'recvFrom s 1000' I get the following error message (consistently for unix and windows): Fail: SocketPrim.hsc:241: Non-exhaustive patterns in case As the log of the webserver reveals the sendTo works fine. Any idea what could be my problem? Sven Eric

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