August 2002 - Glasgow-haskell-users

RE: withStorableArray making IORefs
by Simon Marlow 13 Aug '02

13 Aug '02

> I'm guessing it's not safe to use "newIORef" as the function > argument to > withStorableArray, but in a simple case [1], it seems to work okay. I > suppose the danger is if the RTS decides to move the array. Does this > happen IRL? The danger is rather that the array might get freed. A StorableArray contains a ForeignPtr to the array, and the finalizer on the ForeignPtr will free the array after the last use. If you obtain a pointer to the array by nefarious means (ie. 'withStorableArray return' would do it) then the RTS might free the array while you still have a pointer to it. Cheers, Simon

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(not) catching ^C in ghc-built application
by Malcolm Wallace 12 Aug '02

12 Aug '02

Hi ghc users, I have a program, written in a mixture of Haskell and C, in which the C part is supposed to handle a ^C interrupt, accomplished through the usual signal() call. It works as expected when the Haskell part is compiled by nhc98. But when it is compiled by ghc, for some reason the ghc RTS appears to trap the interrupt itself, and halts the program with the message prog: interrupted instead of allowing the newly installed C signal handler to run. I have looked through the ghc user manual for some means to turn off or divert the RTS signal-handling, but I couldn't find anything relevant. The nearest thing is Exception.block, which excludes an asynchronous exception from happening whilst the `block' is in operation, but that doesn't seem to stop a ^C from interrupting the program, so I guess that isn't its real purpose. So, what should I use instead? Regards, Malcolm

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RE: FFI
by Simon Marlow 12 Aug '02

12 Aug '02

> I have one program in haskell that function in C passes two > arrays for one > which adds the two and returns one 3º. How I make to import > this function > and to use it in my program? Which is the mapping of the > arrays of haskell > for the C? Perhaps you should take a look at the FFI spec, here: http://www.cse.unsw.edu.au/~chak/haskell/ffi/ and the information specific to using GHC with the FFI, here: http://www.haskell.org/ghc/docs/latest/html/users_guide/ffi.html Cheers, Simon

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by pretty 11 Aug '02

11 Aug '02

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HOpenGL quo vadis?
by Sven Moritz Hallberg 10 Aug '02

10 Aug '02

GHC 5.04 builds the incomplete port of HOpenGL to the new hierarchical library structure. Why not the old but working hslibs version? Sven Moritz

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withStorableArray making IORefs
by Hal Daume III 09 Aug '02

09 Aug '02

I'm guessing it's not safe to use "newIORef" as the function argument to withStorableArray, but in a simple case [1], it seems to work okay. I suppose the danger is if the RTS decides to move the array. Does this happen IRL? - Hal [1]: the example program is something like: module Main where import Data.Array.Storable import Foreign import Data.IORef mkArray :: Int -> IO (StorableArray Int Int) mkArray sz = newArray_ (1,sz) >>= \arr -> mapM_ (\i -> writeArray arr i i) [1..sz] >> return arr foo :: Ptr Int -> IO Int foo ptr = peek ptr >>= \v -> poke ptr (v+1) >> return v bar = do arr <- mkArray 10 ptr <- withStorableArray arr newIORef >>= readIORef foo ptr >> foo ptr >> foo ptr withStorableArray arr foo main = bar >>= print >> bar >>= print >> bar >>= print -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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by haskell-admin＠haskell.org 09 Aug '02

09 Aug '02

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calling a seperate program and supplying command line args.
by Jason Smith 08 Aug '02

08 Aug '02

How to basically? I've not had much luck finding much in the way of doc's in ghc on how to do this?...basically I have a compiler in haskell and I want to call a parser which is written in Java. The parser is a .NET binary, it spits out a text file containing the parse tree which I then suck up and do the usual compiler things with. I need to supply the java parser command line args i.e the file to parse etc.. Thanks heaps Jason.

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specializations on float
by Hal Daume III 08 Aug '02

08 Aug '02

the ghc docs suggest using Doubles instead of Floats because GHC specializes Double but not float...I want to use floats to save memory and to test this claim, i grepped through the libraries for the SPECIALIZE keyword and find that with the exception of a few complex routines (which I don't care about), floats are just as specialized as doubles...is this the case, or am I missing something? the results of grepping are: moussor:libraries/ grep "SPECIALI[SZ]E" `find . | grep 'hs$'` | cut -d':' -f2- | grep Float {-# SPECIALISE instance Num (Complex Float) #-} {-# SPECIALISE instance Fractional (Complex Float) #-} {-# SPECIALISE instance Floating (Complex Float) #-} {-# SPECIALISE instance Floating (Complex Double) #-} {-# SPECIALIZE properFraction :: Float -> (Int, Float) #-} {-# SPECIALIZE round :: Float -> Int #-} {-# SPECIALIZE ceiling :: Float -> Int #-} {-# SPECIALIZE floor :: Float -> Int #-} {-# SPECIALIZE properFraction :: Float -> (Integer, Float) #-} {-# SPECIALIZE truncate :: Float -> Integer #-} {-# SPECIALIZE round :: Float -> Integer #-} {-# SPECIALIZE ceiling :: Float -> Integer #-} {-# SPECIALIZE floor :: Float -> Integer #-} {-# SPECIALIZE showEFloat :: {-# SPECIALIZE showFFloat :: {-# SPECIALIZE showGFloat :: moussor:libraries/ grep "SPECIALI[SZ]E" `find . | grep 'hs$'` | cut -d':' -f2- | grep Double {-# SPECIALISE conjugate :: Complex Double -> Complex Double #-} {-# SPECIALISE mkPolar :: Double -> Double -> Complex Double #-} {-# SPECIALISE cis :: Double -> Complex Double #-} {-# SPECIALISE polar :: Complex Double -> (Double,Double) #-} {-# SPECIALISE magnitude :: Complex Double -> Double #-} {-# SPECIALISE phase :: Complex Double -> Double #-} {-# SPECIALISE instance Num (Complex Double) #-} {-# SPECIALISE instance Fractional (Complex Double) #-} {-# SPECIALISE instance Floating (Complex Double) #-} {-# SPECIALIZE properFraction :: Double -> (Int, Double) #-} {-# SPECIALIZE round :: Double -> Int #-} {-# SPECIALIZE ceiling :: Double -> Int #-} {-# SPECIALIZE floor :: Double -> Int #-} {-# SPECIALIZE properFraction :: Double -> (Integer, Double) #-} {-# SPECIALIZE truncate :: Double -> Integer #-} {-# SPECIALIZE round :: Double -> Integer #-} {-# SPECIALIZE ceiling :: Double -> Integer #-} {-# SPECIALIZE floor :: Double -> Integer #-} {-# SPECIALISE fromRat :: Rational -> Double, -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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FFI
by Allan Bruno 07 Aug '02

07 Aug '02

Hi, my name is Allan, i'm from Brazil, and I have a doubt. I have one program in haskell that function in C passes two arrays for one which adds the two and returns one 3º. How I make to import this function and to use it in my program? Which is the mapping of the arrays of haskell for the C? Thanks !

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