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help getting happy
by Greg Meredith 14 Sep '07

14 Sep '07

Haskellians, The code pasted in below causes Happy to return parE when invoked with happy rparse.y -i . Is there anyway to get Happy to give me just a wee bit more info as to what might be causing the parE (which i interpret a 'parse error'). Best wishes, --greg { module Main where } %name rparse %tokentype { Token } %error { parseError } %token '{' { TokenLCurly } '}' { TokenRCurly } '[' { TokenLSquare } ']' { TokenRSquare } '(' { TokenLRound } ')' { TokenRRound } '@' { TokenAt } ',' { TokenComma } ';' { TokenSemi } lquote { TokenLQuote } rquote { TokenRQuote } %% Molecule : '{' '}' { Zero } | Name Reagent { Locate $1 $2 } | '@' Name { Decode $2 } ReagentList : Reagent { [ $1 ] } | ReagentList ';' Reagent { $1 ++ [$3] } Reagent : '?' '(' NameList ')' Mixture { Abstraction $3 $5 } | '[' Mixture ']' { Concretion $2 } Mixture : Molecule { Mix [ $1 ] } | '{' ReagentList '}' { Mix $2 } NameList : Name { [ $1 ] } | NameList ',' Name { $1 ++ [$3] } Name : lquote Mixture rquote { Name $2 } { parseError :: [Token] -> a parseError _ = error "Parse error" data Molecule = Zero | Locate Name Reagent | Decode Name deriving (Eq, Show) data Reagent = Abstraction [Name] Mix | Concretion Mix deriving (Eq, Show) data Mix = Mix [Molecule] deriving (Eq, Show) data Name = Name Mix deriving (Eq, Show) data Token = TokenLQuote | TokenRQuote | TokenLCurly | TokenRCurly | TokenLSquare | TokenRSquare | TokenLRound | TokenRRound | TokenComma | TokenSemi | TokenAt deriving Show lexer :: String -> [Token] lexer [] = [] lexer (c:cs) | isSpace c = lexer cs lexer ('{':cs) = TokenLCurly : lexer cs lexer ('}':cs) = TokenRCurly : lexer cs lexer ('[':cs) = TokenLSquare : lexer cs lexer (']':cs) = TokenRSquare : lexer cs lexer ('(':cs) = TokenLRound : lexer cs lexer (')':cs) = TokenRRound : lexer cs lexer (',':cs) = TokenComma : lexer cs lexer (';':cs) = TokenSemi : lexer cs lexer ('@':cs) = TokenAt : lexer cs lexer ('<':'<':cs) = TokenLQuote : lexer cs lexer ('>':'>':cs) = TokenRQuote : lexer cs main = getContents >>= print . rparse . lexer } -- L.G. Meredith Managing Partner Biosimilarity LLC 505 N 72nd St Seattle, WA 98103 +1 206.650.3740 http://biosimilarity.blogspot.com

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Basic FFI with GHC
by Ronald Guida 13 Sep '07

13 Sep '07

How do I create C-libraries that I can load into GHCi? I am trying to do some basic FFI, and it's not working. Here's the background. I created three files, foo.h, foo.cpp, and test_foo.lhs. (source code below) Note: I am using MinGW/Msys under Windows XP. If I compile foo.cpp and then try to load test_foo into GHCi, I get an error. OTOH, if I compile test_foo with GHC, it works. I just don't understand why it works one way and not the other. What am I doing wrong? -- Ron ------------------------------ Shell commands ------------------------------ $ gcc -c foo.cpp $ ghci test_foo.lhs foo.o ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.6.1, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base ... linking ... done. Loading object (static) foo.o ... done final link ... done [1 of 1] Compiling Main ( test_foo.lhs, interpreted ) During interactive linking, GHCi couldn't find the following symbol: foo This may be due to you not asking GHCi to load extra object files, [snip] $ ghc --make test_foo.lhs foo.o [1 of 1] Compiling Main ( test_foo.lhs, test_foo.o ) Linking test_foo.exe ... $ test_foo.exe Entering main y = 22 Exiting main $ ar rcs libfoo.a foo.o $ ghc --make test_foo.lhs -lfoo $ test_foo.exe Entering main y = 22 Exiting main $ ghci test_foo.lhs -lfoo ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.6.1, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base ... linking ... done. Loading object (dynamic) foo ... failed. Dynamic linker error message was: addDLL: unknown error Whilst trying to load: (dynamic) foo Directories to search are: : user specified .o/.so/.DLL could not be loaded. ------------------------------ Source code ------------------------------ // foo.h extern "C" { __stdcall int foo(int x); } ------------------------------ // foo.cpp #include "foo.h" __stdcall int foo(int x) { return 3 * x + 1; } ------------------------------ test_foo.lhs > {-# OPTIONS_GHC -fglasgow-exts #-} > module Main > where > import Foreign > import Foreign.C > foreign import stdcall unsafe "foo" > c_Foo :: Word32 -> IO Word32 > main = do > putStrLn "Entering main" > let x = 7::Word32 > y <- c_Foo(x) > putStrLn $ "y = " ++ show y > putStrLn "Exiting main"

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Haskell and State Monad.
by VinyleEm 13 Sep '07

13 Sep '07

Hello all, I am Vinay Emani, new to this forum. I am doing an academic project of writing an assembler cum linker in Haskell as part of building a compiler set written entirely in Haskell. Since i am new to the language, i thought it would do me good to look at some of the existing haskell code, be it in whatever project and written for whatever purpose. This should help me get started. In particular i need to find some project/program which extensively uses the State Monad. I tried looking at some of the existing open source projects at sourceforge. There are only limited number of projects there, some of them being incomplete. Could you please suggest me some project, from which i can learn the State Monad. Thanks very much Vinay Emani India -- View this message in context: http://www.nabble.com/Haskell-and-State-Monad.-tf4427176.html#a12629170 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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"Functional dependencies conflict between instance declarations"
by Peter Verswyvelen 13 Sep '07

13 Sep '07

The Haskell mailing list seems to be filled with people requesting information about this error, so I cannot resist to include myself in it ;-) I've read the information about funcdeps in the GHC user guide, and I think I understand how it works, but I get the error a lot, without having a clue why. Sometimes I get the error even when all the types of all the type parameters are completely different, so even when all parameters would be one-to-one dependent, I still don't get why I would get a conflict error. Does a wiki exists with possible reasons why this error occured and how to fix it? Thanks, Peter

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Re: [Haskell-cafe] Re: Is "take" behaving correctly?
by PR Stanley 13 Sep '07

13 Sep '07

>Hi > > > The same should apply to head and tail. head or tail of [] should be []. > > > > What does the list think? > >Disagree, strongly. Its not even possible for head, since [a] -> a. >Wadler's theorems for free states that if head is given an empty list >the _only_ thing it can do is crash. What's the logic behind this? Thanks, Paul

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Haddock/hscolour integration broken on Hackage?
by David Menendez 12 Sep '07

12 Sep '07

I was looking at the Data.Binary documentation[1] on Hackage, and I've noticed some problems with the associated source listings[2]. First, none of the "Source" links work. They all refer to fragment IDs (e.g., "#Binary") that are not defined. I'm not sure if this is a problem with hscolor, haddock, or hackage. Second, the source listing itself[2] is invalid HTML[3]. The W3C validator lists 678 errors. Of these, 677 are have to do with the line number anchors, all of which start with parentheses. This is bad not only because HTML requires fragment ids to start with a letter, but because parentheses are not allowed to occur in URIs. As a result, links to line numbers will come out looking like "Data-Binary.html#%28line100%29". [1] <http://hackage.haskell.org/packages/archive/binary/0.3/doc/html/Data-Binary…> [2] <http://hackage.haskell.org/packages/archive/binary/0.3/doc/html/src/Data-Bi…> [3] <http://validator.w3.org/check?uri=http%3A%2F%2Fhackage.haskell.org%2Fpackag…>

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Re: Tiny documentation request
by manu 12 Sep '07

12 Sep '07

On Sep 11, 2007, Simon Marlow wrote: > > Please, please, someone do this for me. I tried, and failed, to > get the > layout right for the contents list in all browsers at the same > time. The > semantics of CSS is beyond my comprehension. > > Cheers, > Simon Hi Simon, On the page http://www.haskell.org/ghc/docs/latest/html/libraries/ index.html, you only need tables to display the foldable lists of modules (HTML tables were commonly used to display many "things" on a same line), but they can be replaced by nested lists with a bit of CSS : Check this page out : http://la.di.da.free.fr/haddock/ I can help further, if need be. Emmanuel

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Developing XPCOM components (Firefox extensions) in Haskell
by Pasqualino 'Titto' Assini 12 Sep '07

12 Sep '07

Hello, I wondered if anyone could advice on how to develop XPCOM components in Haskell. I am aware that HDirect supports COM and that there are some similarities with XPCOM but I do not have the time to extend/fix HDirect to support XPCOM. Would using FFI directly be simpler? What problems should I expect? Would you anticipate platform specific issues ? The components should work under both Linux and Windows and ideally Mac as well. Thanks in advance, titto

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Re: Tiny documentation request
by manu 12 Sep '07

12 Sep '07

On Sep 11, 2007, at 9:58 PM, Miguel Mitrofanov wrote: > > > Well, I'm not a web designer, but I did work with few of them, and it > seems to me that you either create a table design in two hours or > spend three days trying to create a CSS one and THEN create a table > design in two hours. That's an exaggeration. It's widely accepted than tables can straightforwardly be dropped in most cases. They are intented to be used to present tabular datas, NOT for layout. (This ideas is not new, Zeldman talked about it in 2001) It does require a bit of CSS-Fu, however, as CSS support in browsers varies... But hey, you've got to occupy these HTML-CSS guys ! Emmanuel

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GraphicsMagick binding for Haskell
by Tim Chevalier 12 Sep '07

12 Sep '07

As a Hackathon project, I'm thinking of trying to write a Haskell binding for the GraphicsMagick image manipulation library (http://www.graphicsmagick.org/) Has anyone done this already? If not, would anyone else besides me use it? If you think there's a better library out there that serves a similar purpose, feel free to tell me about it as well. Cheers, Tim -- Tim Chevalier * catamorphism.org * Often in error, never in doubt "Work is there when love is gone" -- Greg Brown

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