- Haskell-Cafe - Haskell.org

more runhaskell question
by Galchin, Vasili 18 May '08

18 May '08

vigalchin@ubuntu:~/FTP/Haskell/unix-2.2.0.0/tests/mlock$ runhaskell Setup.lhs configure --prefix=$HOME Configuring mlock-1.0... vigalchin@ubuntu:~/FTP/Haskell/unix-2.2.0.0/tests/mlock$ runhaskell Setup.lhs build Setup.lhs: error reading dist/setup-config; run "setup configure" command? No dist/setup-config is being generated! what is the "setup configure" command?? Regards, Vasili

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Calling haddock in a portable way
by Misha Aizatulin 17 May '08

17 May '08

hello, the new version of haddock (2.0.0) needs a new option -B that tells it the GHC lib directory. How do I find out the correct value for this option in a makefile, so that the makefile stays portable? Cheers, Misha

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Mapping Haskell Concepts To C# 3
by Kaveh Shahbazian 17 May '08

17 May '08

I have question on mapping some Haskell concepts to C# 3 ones. Maybe there are not any strict equivalents; yet it helps: 1 - What is the equivalent of "Type Constructor" in C#? 2 - What is the equivalent of "Data Constructor" in C#? 3 - What is the logical implementation of pattern matching in C#? (For example using structures with indicator fields or using interfaces and inheritance and dynamically dispatch in calling overloaded methods. Also this question contain a hidden one...GADTs!) Best Regards -- Kaveh Shahbazian email: kaveh.shahbazian(a)gmail.com

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[ANN] Next Bay FP Meeting: Bryan O'Sullivan on Concurrent and multicore programming in Haskell
by Keith Fahlgren 17 May '08

17 May '08

Hi, Our next BayFP meeting will be this Thursday, May 8th, 2008 at 7:30pm. We'll feature Bryan O'Sullivan on Concurrent and multicore programming in Haskell. Bryan is a co-author of the upcoming O'Reilly book Real World Haskell [http://book.realworldhaskell.org/] (among all sorts of other snazzy endeavors) Talking about multicore is all the rage, so I expect folks to bring a lot of people! :-) Details here: http://www.bayfp.org/blog/2008/05/02/may-8th-meeting-bryan-osullivan-on-con… Many thanks to Alex Payne at Twitter for hosting this month's meeting. They've been very supportive of BayFP and we appreciate their continued hosting. Twitter's address is: 164 South Park St San Francisco, CA 94107 Alex says: It's a building with a dark green door. People can just come on in and walk to their right to a large conference room. We'll start at 7:30pm. As always, this is a free event. If you want pizza, please select which type here (and bring a few $$s): Pizza Selection Form [http://bayfp.wufoo.com/forms/bryan-osullivan-bay-fp/] Keith

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Haskell-Cafe Info Page
by D. Gregor 17 May '08

17 May '08

Hello, Common Lisp is a multiparadigm, general purpose programming language that supports imperative, functional, and object-oriented programming paradigms. Haskell is purely functional. Is this a reason why there is not macro feature in Haskell? I feel the object-oriented paradigm of CL and Scheme is the reason for the macro feature in these two languages. If it's not, then what does the macro feature provide, and why isn't it in Haskell? Douglas

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A point in favour of -XOverlappingInstances (and -XTypeSynonymInstances)
by Achim Schneider 17 May '08

17 May '08

Token.hs:103:15: Overlapping instances for Show (SourcePos, Tok) arising from a use of `anyToken' at Token.hs:103:15-22 Matching instances: instance (Show a, Show b) => Show (a, b) -- Defined in GHC.Show instance [overlap ok] Show Token -- Defined at Token.hs:(39,0)-(40,23) I was just trying _not_ to show the a of (a,b) -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited.

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ghc on Ubuntu Linux?
by Galchin, Vasili 17 May '08

17 May '08

Hello, I am running ghc and tools on Ubuntu. I seem to be running into very strange problems between ghc-pkg and the Ubuntu package manager. Suddenly "runhaskell Setup.hs configure" just stops working ... Are any other ghc/Ubuntu users running into problems? If so, please tell me what problems. This is killing my Haskell work! Regards, Vasili

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Couple of formal questions
by Creighton Hogg 17 May '08

17 May '08

Hello Haskell, So there's two questions that have been bothering me lately & while they are, as usual, a little off topic I figured this might be a good forum: Where could I find a good treatment on data vs. codata & the difference between well-founded recursion & well-founded(?) corecursion? Where could I find a proof that the initial algebras & final coalgebras of CPO coincide? I saw this referenced in the "Bananas.." paper as a fact, but am not sure where this comes from. Thanks, Creighton Hogg

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alex + happy parser problem
by Sean McLaughlin 17 May '08

17 May '08

Hi, To learn alex and happy, I'm trying to write a parser for a simple expression language. When I wrote my own lexer and just used happy, it was fine. When I used the basic wrapper of alex it was also fine. However, when I use the posn wrapper to get position information, I get a strange exception when the parse error occurs at the end of the input. For example, parsing "1 + " yields "Internal Happy error" rather than something like "Parse error at line 1, column 5" The lexer and parser are attached. Can anyone see what I'm doing wrong? calling parse "1+" yields a "Internal Happy error" instead of a parse error as I would expect. Thanks, Sean ------------------ -- Lexer ------------------ { module ExprLexer ( Token(..), AlexPosn(..), alexScanTokens, tokenPosn ) where } %wrapper "posn" $digit = 0-9 tokens :- $digit+ { (\p s -> Int p (read s)) } [\+] { (\p s -> Sym p (head s)) } { data Token = Sym AlexPosn Char | Int AlexPosn Int deriving (Eq, Show) tokenPosn (Sym p _) = p tokenPosn (Int p _) = p } -------------------------- --- Parser -------------------------- { module ExprParser where import ExprLexer (Token(..), alexScanTokens, tokenPosn, AlexPosn(..)) } %name parseExp %tokentype { Token } %token int { Int _ $$ } '+' { Sym _ '+' } %right '+' %% Exp : Exp '+' Exp { Add $1 $3 } | int { Const $1 } { data Expr = Const Int | Add Expr Expr deriving Show parse :: String -> Expr parse = parseExp . alexScanTokens happyError :: [Token] -> a happyError tks = error ("Parse error at " ++ lcn ++ "\n") where lcn = case tks of [] -> "end of file" tk:_ -> "line " ++ show l ++ ", column " ++ show c where AlexPn _ l c = tokenPosn tk }

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Proving my point
by Achim Schneider 16 May '08

16 May '08

"test.l" (line 7, column 1): unexpected end of input expecting "(", Lambda abstraction, Let binding, Atom, end of input or Function application I obviously don't know anything about Parsec's inner workings. I'm going to investigate as soon as I stopped despairing. -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited.

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