- Glasgow-haskell-users

IArray and MArray
by Marcin 'Qrczak' Kowalczyk 15 Apr '01

15 Apr '01

Is it important to keep the current definition of IArray and MArray classes? I would like to change class operations, without changing the interface, i.e. turn methods into ordinary overloaded functions and have different methods. It would affect users making their own instances of these classes, but not users of these instances. The problem is that translation of the index to an Int is coupled with actual array operations. It's not possible to omit the translation with the range check in an overloaded way; such operations must be coded separately for each element type, which is quite painful. It's not possible to add a method which specifies indexing by Int, because there is no reasonable default definition, except using (!!) on the index range: the class Ix doesn't define translation from Int to indices. Many bulk operations don't need indices but just iterate over the array: elems, listArray, amap, thaw, freeze, (==), compare (actually compare is a more complex issue). The performance is horrible if tight loops do the translation. But if the needed functionality is not in the array, the operation must be coded for each type separately instead of letting the compiler do the specialization, and some of these must be matched with rules. Class operations define too much. Translation of indices to Ints with bounds checking is done in the same way for all arrays. These operations must be polymorphic wrt. index, so they don't have a choice. But they have to hardwire the translation into individual methods. I would let operations in IArray and MArray work on Ints and change current methods to functions overloaded over the array and the index. -- Marcin 'Qrczak' Kowalczyk

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How to convert the type signature of a variable to a String?
by Pasch, Thomas (ACTGRO) 15 Apr '01

15 Apr '01

Hello, it is possible to write module Main(main) where import Dynamic main = putStrLn ( show ( typeOf (f (1::Integer)))) f x = x The output is of course Integer But the typeOf will only work for 'concrete' data types. It will not work for functions. So I can't write main = putStrLn ( show ( typeOf (f))) Thus it is possible to write a function that recognize functions, i.e. functionType arg = case arg of (arg:: a->b) -> "function" So the question is: Is is possible to write a function the gives back a String with the signature of the argument of that function? For example: 'function f' gives the String "a->a" Best regards, Thomas

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win32 4.08.2 install question
by David Bakin 15 Apr '01

15 Apr '01

While waiting for 5.00 for win32 I thought I'd get started with 4.08.2 - downloaded it today and installed it and the latest cygwin as per instructions. However: When following the "test the fruits of your labour" I invoke "ghc -o main main.hs" and get back a bash prompt and that's all. No files created, e.g., no main. Same for "ghc -c main.hs". Something trivial must be wrong with my setup. I've copied the ghc/bin/perl to cygwin/bin. No spaces in any directories (ghc is installed at c:\ghc). My mounted dirs look like this: C:\Cygwin\bin>mount Device Directory Type Flags c:\Cygwin\bin /usr/bin user textmode c:\Cygwin\etc /etc user textmode c:\Cygwin\lib /usr/lib user textmode c: / user textmode Anybody have an idea what's going on? I can't wait to get 5.00 and its integral driver! -- Dave

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Building ghci
by Wolfhard Bu� 12 Apr '01

12 Apr '01

Hello, i just built and installed ghc 5.00 from the sources with the help from ghc 4.08.2. ghci responds with 'ghc-5.00: not built for interactive use'. Q: How to build ghc with support for interactive use? Which configure option or makefile target did i miss? Kind regards, Wolfhard.

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Re: Stack trace on error (and packages)
by Keith Wansbrough 11 Apr '01

11 Apr '01

> > Hi, > > Is it possible to persuade ghc/RTS to provide a stack trace (or > something similar) when an error occurs? I have some code that is > generating a runtime error (appears to be due to division by > almost-zero, provoking very large numbers and then a NaN in a case > statement when coerced to Double) in a function that is used throughout > my code - it would be a big help to know which function called the > function that is generating the error. Yes. Compile your program with -prof -auto-all (you need at least -prof on all modules for the link to work, but -auto-all is only necessary on modules containing functions you want to trace). This turns on automatic profiling. Now run your program with the option `+RTS -xc' . This will turn on a cost-centre stack trace, displayed each time your program throws an exception (including runtime errors). This gives not the program stack (which function demanded which value), but the cost-centre stack (which function called which function which failed), which may or may not be more useful. The former is only available under `gdb' at the moment, with a very hairy user interface. You can read about cost centres in chapter 4 of the manual. My apologies for not having put this properly in the manual yet! HTH.. --KW 8-) -- Keith Wansbrough <kw217(a)cl.cam.ac.uk> http://www.cl.cam.ac.uk/users/kw217/ Cambridge University Computer Laboratory.

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Stack trace on error (and packages)
by Andrew Cooke 11 Apr '01

11 Apr '01

Hi, Is it possible to persuade ghc/RTS to provide a stack trace (or something similar) when an error occurs? I have some code that is generating a runtime error (appears to be due to division by almost-zero, provoking very large numbers and then a NaN in a case statement when coerced to Double) in a function that is used throughout my code - it would be a big help to know which function called the function that is generating the error. Also, less importantly, how do I generate packages? I have a bunch of .o files (modules) all compiled using -package-name and -c, but I can't find the correct ghc flag to link them into a library (.a/Linux). Apologies if both/either of these are covered in the docs - I couldn't find a simple way of getting a stack trace and no info on actually linking to create a package (when I try various "obvious" things I get errors indicating a missing main). Thanks, Andrew PS Away from home, so having to use my work address. Please reply to the list (which I can read on the 'net and will subscribe to when I get home) or, if you want to avoid that, andrew(a)andrewcooke.free-online.co.uk, which I will read this weekend. Work isn't happy about non-work-related emails to this account. Sorry.

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ghc5.00 binary on Sparc?
by George Russell 10 Apr '01

10 Apr '01

GHC 5.00 looks wonderful. Would it be possible to make a binary distribution available for Sparc? As you may remember, I've had difficulty compiling it myself for Sparc, for some reason I don't know, and even if I find a way of hacking things to compile it, I'd rather users (= students) didn't have to . . .

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RE: How to box/unbox values?
by Julian Seward (Intl Vendor) 10 Apr '01

10 Apr '01

| -----Original Message----- | From: Thomas Pasch [mailto:pasch@netzGeneration.com] | Sent: Tuesday, April 10, 2001 12:55 AM | To: glasgow-haskell-users(a)haskell.org | Subject: How to box/unbox values? | | | Hello, | | is there an easy way to box/unbox Types. | I need this for Int's, so is there | a function that does: | | Int# -> Int | Int -> Int# import GlaExts ( Int(..) ) iBox x = I# x iUnbox (I# x) = x

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How to box/unbox values?
by Thomas Pasch 10 Apr '01

10 Apr '01

Hello, is there an easy way to box/unbox Types. I need this for Int's, so is there a function that does: Int# -> Int Int -> Int# Regards, Thomas

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failed when trying to compile FranTk with ghc
by luc 09 Apr '01

09 Apr '01

I tried FranTk with ghc 4.08 and got : (this is the "fixed" FrankTk, alledged working with 4.06, if im not wrong) are there any difference with 4.06 and 4.08 ? ------------------------------------------------------------------------ ==fptools== gmake boot - --no-print-directory -r; in /home/luc/tmp/FranTk/src/FranSrc ------------------------------------------------------------------------ ghc -M -optdep-f -optdep.depend -optdep-o -optdepo -O -fglasgow-exts -recomp -dcore-lint -fvia-C -syslib concurrent -i../TclHaskellSrc Compatibility.ghc.hs BaseTypes.hs Force.hs MutSet.hs Event.hs BPrim.hs WorkPool.hs FranTime.hs Behavior.hs FranPrim.hs Listener.hs ColorCore.hs Vector2.hs VectorSpace.hs Point2.hs Vector3.hs Point3.hs Transform2.hs Rect.hs Transform3.hs StaticTypes.hs ColorCoreB.hs Point2B.hs Point3B.hs Vector2B.hs Vector3B.hs RectB.hs Transform2B.hs Transform3B.hs BehaviorTypes.hs VectorSpaceB.hs BehaviorIO.hs FranCore.hs FranBehavior.hs No file `PrelNumExtra.hi', `PrelNumExtra.lhs', `PrelNumExtra.hs' (reqd from file `Compatibility.ghc.hs') among import directories: ../TclHaskellSrc:. gmake[2]: *** [depend] Error 1 gmake[1]: *** [boot] Error 1

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