- Glasgow-haskell-users

fromEnum (c :: Char)
by Serge D. Mechveliani 09 Sep '09

09 Sep '09

People, I need to convert Char <-> Int in a possibly _standard_ way for Haskell -- and also in an efficient way. In particular, it must not spend 100 comparisons in a look through the listing of Char. I use ord :: Char -> Int and chr :: Int -> Char. Is this all right? Thank you in advance for advice, ----------------- Serge Mechveliani mechvel(a)botik.ru

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no backspace, delete or arrow keys in ghci
by Gabriel Schwanen 08 Sep '09

08 Sep '09

Hello to everybody, I'm currently working with Haskell via the ghc interpreter (version 6.10.4 on Ubuntu 9.10). The problem, if it is really a problem and not a normal comportement, happens when I try, as example, to enter some characters after having execute getLine. Actually, if I make a mistake when typing the string, I can't use neither backspace, delete or even arrow keys to correct it before hitting enter to finish input. In fact, as example, if I hit backspace, I get "^?" in place of deleting the previous character ... :^( As I wrote above, I don't know if it is a "bug" or not. Maybe it is normal. Can someone help me ? Thanks in advance, Gabriel

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ghc --help displays obsolete URL
by Ahn, Ki Yung 08 Sep '09

08 Sep '09

$ ghc --help ... The User's Guide has more information about GHC's *many* options. An online copy can be found here: http://www.haskell.org/ghc/documentation.html ------------------------------------------------------------------------ The above URL does not exist! Hope it gets fixed in 6.12.x

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few questions about GHC RTS
by Peter Hercek 07 Sep '09

07 Sep '09

Hi, I thought I may look at the :next command for GHCi debugger again. If I do, I will not make it before 6.12.1 is out. I have few questions about RTS in relation to :next implementation. If they is easy to answer I would appreciate it, if not, don't bother since I'm not sure I'll do it ... and If I decide to do it I may just figure it out myself or fail again :) Why is stg_nofoceIO_info added as last argument to IO actions in unregistered mode? Do I still need to pass it in even when (I think) my IO action does not need it? E.g. is it required for every IO action by some stack walking code or something? Are there any Cmm functions in RTS with signature (IO()) or signature (Int->IO()) which I could check out as examples to see how they are done? ... and ideally also how they are called from the stack. Are there any special things to do when adding a new field (e.g. simulated stack size) to StgTSO? Thanks, Peter.

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Plans for GHC 6.12.1: release candidate 14 September 2009
by Ian Lynagh 26 Aug '09

26 Aug '09

Hi all, This is a summary of our plans for GHC 6.12.1. We are aiming to have the first release candidate out on the 14th September 2009. Until then, we plan to focus on the bugs in the 6.12.1 milestone, marked high priority; they are listed here: http://hackage.haskell.org/trac/ghc/query?status=new&status=assigned&status… If there is a bug not in that list that is important to you, please let us know. Thanks Ian

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ghc 6.10.4 infix declarations and '\' bug or not ?
by John Lask 23 Aug '09

23 Aug '09

in declaring fixity for an operator (\\) to get it to compile using ghc 6.10.4, I needed to use the following code infixl 9 \\\ (\\) a b = etc ... where I assume the first \ escapes the second \, using infixl 9 \\ generates a syntax error infixl 9 \\ used to compile no problems with ghc 6.8.2 what is going on here ? why do I now need to add an additional \ ?, where is this change documented ?, is this a bug?

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RE: [Haskell-cafe] generalize RecordPuns and RecordWildCards to work with qualified names?
by Simon Peyton-Jones 20 Aug '09

20 Aug '09

Evan, Lennart Thanks for the provocation. I've committed a patch that fixes all these issues. Try now! Simon Thu Aug 20 13:34:43 BST 2009 simonpj(a)microsoft.com * Improvements to record puns, wildcards * Make C { A.a } work with punning, expanding to C { A.a = a } * Make it so that, with -fwarn-unused-matches, f (C {..}) = x does not complain about the bindings introduced by the "..". * Make -XRecordWildCards implies -XDisambiguateRecordFields. * Overall refactoring of RnPat, which had become very crufty. In particular, there is now a monad, CpsRn, private to RnPat, which deals with the cps-style plumbing. This is why so many lines of RnPat have changed. * Refactor the treatment of renaming of record fields into two passes - rnHsRecFields1, used both for patterns and expressions, which expands puns, wild-cards - a local renamer in RnPat for fields in patterns - a local renamer in RnExpr for fields in construction and update This make it all MUCH easier to understand * Improve documentation of record puns, wildcards, and disambiguation | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On | Behalf Of Evan Laforge | Sent: 12 August 2009 23:59 | To: Simon Peyton-Jones | Cc: Augustsson, Lennart; haskell; GHC users | Subject: Re: [Haskell-cafe] generalize RecordPuns and RecordWildCards to work with | qualified names? | | > | Even is suggesting that instead of reporting an error, in the second | > | case we could use the translation: | > | | > | f (A.A { A.a }) = a --> f (A.A { A.a = a }) | > | | > | (i.e., when punning occurs with a qualified name, use just the | > | unqualified part of the name in the pattern) | > | > Yes, that'd be possible. But it seems debatable -- it doesn't *look* as if the | pattern (A.A { A.a }) binds 'a' -- and it seems even less desirable in record | construction and update. To be concrete, would you expect these to work too? | > | > g a = A.A { A.a } --> g a = A.A { A.a = a } | > h x a = x { A.a } --> h x a = a { A.a = a } | | Oh, I didn't realize that record punning included construction as | well. Yeah, that's a little funky looking. I don't mind seeing the | binding form and I think a new reader could figure it out without too | much trouble but I would be a little confused by the construction form | and think a new reader would also be confused. | | > With -XDisambiguateRecordFields you could say | > | > g a = A.A { a } | > | > which seems better. (But there's no help for record update, since we don't know | which data constructor is involved.) | | I didn't know about DisambiguateRecordFields! Looks like that also | makes the wildcard work like I want it to. | | The ghc docs for DisambiguateRecordFields don't make this very clear | to me... it talks about disambiguating names in scope, but if I say | "R.R { a = val}" I wouldn't expect it to "disambiguate" 'a', which is | not in scope at all, to 'R.a' which looks like a completely different | name. Rereading the paragraph at 7.3.11 I'm still surprised this | works. Maybe add something like: | | ... preceeding docs ... | | This also means that if you use qualified imports you can still use | unqualified field names. E.g. in the pattern @(R.R { a = a_val })@, | @a@ will be disambiguated to @R.a@, even if @R@ is imported qualified. | | I gather we're not supposed to call them "records" anymore, they're | supposed to be something I forget now, but the rest of the ghc docs | says records, so... | | > So my current conclusion is: improve the error message, perhaps suggesting the | flag -XDismabiguateRecordFields, but don't add the change you suggest. | > | > Comments? | | Sounds good to me. I'll try adding DisambiguateRecordFields and try | out the new punning, thanks! | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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Building just a stage 1 compiler?
by Tim Chevalier 19 Aug '09

19 Aug '09

Hi, Is there a way to tell the GHC build system that I only want to build a stage 1 compiler and the libraries, not a stage 2 compiler? Executing: $ sh boot $ ./configure $ make stage=1 in my build tree still builds the stage 2 compiler as well. Thanks, Tim -- Tim Chevalier * http://cs.pdx.edu/~tjc/ * Often in error, never in doubt

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Generating valid Haskell code using the GHC API pretty printer
by Jan Schaumlöffel 18 Aug '09

18 Aug '09

Hello everyone, we are trying to use the GHC API for a source-to-source transformation on Haskell programs. The result of parsing and typechecking a module enables us to apply the transformation, but writing the transformed module back using the pretty printer (Outputable) generates invalid Haskell code. For one thing, since even the names defined in the current module are fully qualified, the resulting code is not valid anymore. This can be worked around, but there is another issue: Simply reading the following program and then writing it out using the pretty printer renders the resulting code invalid. > module Main where > main = do > if True then putStrLn "longlonglonglonglonglongline" > else return () > longlonglonglonglonglonglonglonglonglonglonglongname $ "test" > longlonglonglonglonglonglonglonglonglonglonglongname = putStrLn The result looks like this: > Main.main = do if GHC.Bool.True then > System.IO.putStrLn "longlonglonglonglonglongline" > else > GHC.Base.return () > Main.longlonglonglonglonglonglonglonglonglonglonglongname > GHC.Base.$ > "test" > Main.longlonglonglonglonglonglonglonglonglonglonglongname = System.IO.putStrLn There are two different problems in this output: 1) the indentation of "if ... then ... else" violates the "do"-block layout rule 2) the indentation of the long function call is invalid It looks like those problems could be avoided if the pretty printer could be configured to consistently use "do { ... ; ... }" notation, but we have been unable to figure out how. Is there a canonical way to use the GHC API to pretty print to valid Haskell code? Kind regards, Jan Appended is our current code to execute the transformation above (the module to be read is expected in a file "dummy.hs" for simplicity). Please excuse if this might not be a minimal example. module Main where import GHC import GHC.Paths import Outputable main = do x <- runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags (dflags { hscTarget = HscNothing, ghcLink = NoLink }) target <- guessTarget "dummy.hs" Nothing setTargets [target] load LoadAllTargets graph <- getModuleGraph let unparsedmod = head graph parsedmod <- parseModule unparsedmod typecheckedmod <- typecheckModule parsedmod let Just renamedsource = renamedSource typecheckedmod (group,_,_,_,_) = renamedsource moduledings = (ms_mod unparsedmod) return (showSDoc (ppr group)) putStr $ x ++ "\n" -- If you're happy and you know it, syntax error!

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what is the path to a particular module?
by S. Alexander Jacobson 15 Aug '09

15 Aug '09

Is there a way from GHCi to discover the path to a particular module that you have imported or loaded? -Alex-

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