April 2003 - Glasgow-haskell-users

irg.ssu.ac.kr
by CoolStats Reseller 26 Apr '03

26 Apr '03

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RE: Immutable CStrings
by Simon Marlow 24 Apr '03

24 Apr '03

> How would one implement an CStringLen-style type that > (a) was efficient, in particular could be read and written to Handles > efficiently; > (b) would get automatically deallocated by the Haskell > garbage collector, > when Haskell no longer referred to it; > (c) was immutable, so that once created the character data could not > be changed; > (d) consequently had the property that conversion to and from > String would > be a pure operation; > (e) could be passed to and from C using the FFI. (Of course > C would need you > to split the length and character data up; the character data > would presumably > have type "const char *".) > ? > It would be rather nice to have such a type. Data.PackedString is *almost* what you want, and could be tweaked to do the right thing (at least in GHC). There are two problems: (1) the representation is currently as an array of 32-bit unicode chars, whereas you probably want 8-bit ISO-8859 or something. (2) Passing to FFI functions: to make this work you can use pinned byte-arrays instead of ordinary byte-arrays to store the string, and an explicit touch# after the FFI call. Cheers, Simon

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RE: Immutable CStrings
by Simon Marlow 24 Apr '03

24 Apr '03

> | How would one implement an CStringLen-style type that > | [...] > > Take a look at: > > http://www.cs.chalmers.se/Cs/Grundutb/Kurser/afp/Lab2/Chunk.hs > > Is that what you want? Only one comment: use mallocForeignPtr and it'll go a lot faster with GHC! Cheers, Simon

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RE: Immutable CStrings
by Simon Marlow 24 Apr '03

24 Apr '03

> Other options may exist using packed string objects, pinning them in > the GHC heap, etc. but they are not portable and probably not much > more efficient. If you use mallocForeignPtr and don't need finalizers, then I agree - the ForeignPtr method is about as efficient as PackedStrings. But if you need finalizers and real ForeignPtrs then it will be significantly less efficient in GHC. I guess it depends on whether the reference count is important for George's application. Cheers, Simon

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Chipworks' Image Sensor, Analog, RF, and Memory Reports
by Chipworks 23 Apr '03

23 Apr '03

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eta-expansion
by David Sabel 23 Apr '03

23 Apr '03

I have some questions about the eta-expansion, which is perfomed in the simplifier. I found in [1], that the transformation "eta-expansion" is of the form v = \a1 ... an -> f a1 ... an ===> v = \a1 ...an ... am -> f a1 ... an ...am assuming f has arity m > n. arity is something like "how many arguments can be applied, without perfoming work" My questions: 1) How do you compute this arity. 2) What's the expression f in the general rule, is it a variable or a term, or could it be both? In the same paper is the case-eta-expansion, but I don't understand the correctness of this transformation: case e of {p1 -> e1,...,pn -> en} ===> \y -> case e of {p1 -> e1 y, ..., pn -> en y} The rhs is a WHNF, but the lhs isn't, so the rule can't be correct in general. For example, assume that e is bot. Regards, David [1] André Santos, Compilation by Transformation in Non-Strict Functional Languages, PhD thesis, TR-1995-17, Department of Computing Science, University of Glasgow, 1995. --------------------------------------------------------------------- David Sabel sabel(a)cs.uni-frankfurt.de JWGU Frankfurt

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Problem Building Package
by Matthew Donadio 23 Apr '03

23 Apr '03

Hi all, I am having a bit of trouble builing local packages. I have three libraries, A, B, and C, that I want to make into local packages. A and B depend only on base, while C depends on base, A, and B. The souces gets built with ghc --make -package-name=A {list of files} ghc --make -package-name=B {list of files} ghc --make -package-name=C {list of files} and I create the archives libHS[A,B,C].a This all works fine. I have three simple .pkg. If I add the dependencies into package-deps, then ghc-pkg says that the dependencies do not exist. If I leave that blank, then I can create my local .conf file. If I do this, I cannot get ghc to use the .conf file. For example, if I try ghc --make -package-conf foo.conf -package C -o SomeApp SomeApp.hs Then ghc complains that it can't find the interface files, even though import-dirs is correct in foo.conf. Can anyone shed some light on this, or point me to a small library that builds a GHC package? I know I am doing something stupid, but I can't figure it out. I tried looking at the GHC Makefiles, but I am having trouble following them because of all the includes. Thanks. -- Matthew Donadio (m.p.donadio(a)ieee.org)

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Immutable CStrings
by George Russell 23 Apr '03

23 Apr '03

How would one implement an CStringLen-style type that (a) was efficient, in particular could be read and written to Handles efficiently; (b) would get automatically deallocated by the Haskell garbage collector, when Haskell no longer referred to it; (c) was immutable, so that once created the character data could not be changed; (d) consequently had the property that conversion to and from String would be a pure operation; (e) could be passed to and from C using the FFI. (Of course C would need you to split the length and character data up; the character data would presumably have type "const char *".) ? It would be rather nice to have such a type.

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RE: ghc-[45].X on mips-sgi-irix65 (not yet)
by Rafael Martinez Torres 23 Apr '03

23 Apr '03

Well , after 8 months of hard-hacking to port ghc into mips-sgi-irix65, this is my modest contribution to the Haskell community: just a stauts-report. :-| . I hope to be usefull for future portes, not only for those for mips-sgi-irix65, saving time on things I have spent months on... For the time beeing I can not upload it at http://segovia.sip.ucm.es/~rmartine , so the links to download the "unstable" patches will not be available...However, they would be usefull for porters, not for final users... But I hope them to be available in the next days... I will announce... If some one is interesting , please e-mail to rmartine(a)fdi.ucm.es, and I will send them...

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Hdirect with ghc 5.04.3, building problems
by Petter Egesund 23 Apr '03

23 Apr '03

Hi, I am trying to build Hdirect with ghc 5.04.3. The sources are from http://galois.com/~sof/hdirect-0.19-src.tar.gz I follow the instructions in INSTALL. make boot works fine, but make lib gives this errs; make -C lib boot && make -C lib all make[1]: Entering directory `/cygdrive/h/download/hdirect-0.19/lib' ghc -M -optdep-f -optdep.depend -optdep-o -optdepo -cpp -DBEGIN_GHC_ONLY='-}' -DEND_GHC_ONLY='{-' -DBEGIN_NOT_FOR_GHC='{-' -DEND_NOT_FOR_GHC='-}' -DELSE_FOR_GHC='-}-}' -package-name hdirect -fglasgow-exts -fvia-C -Wall -fno-warn-deprecations -package lang -static Pointer.lhs HDirect.lhs PointerPrim.hs WideString.hs make[1]: Leaving directory `/cygdrive/h/download/hdirect-0.19/lib' make[1]: Entering directory `/cygdrive/h/download/hdirect-0.19/lib' ghc -cpp -DBEGIN_GHC_ONLY='-}' -DEND_GHC_ONLY='{-' -DBEGIN_NOT_FOR_GHC='{-' -DEND_NOT_FOR_GHC='-}' -DELSE_FOR_GHC='-}-}' -package-name hdirect -fglasgow-exts -fvia-C -Wall -fno-warn-deprecations -package lang -static -c HDirect.lhs -o HDirect.o -osuf o HDirect.lhs:1218: Variable not in scope: `getTag#' make[1]: *** [HDirect.o] Error 1 make[1]: Leaving directory `/cygdrive/h/download/hdirect-0.19/lib' make: *** [lib] Error 2 I have this setting in config.mk: HC=ghc TARGETPLATFORM=cygwin32 Any clue? Cheers, Petter Egesund Norway ########################################### This message has been scanned by F-Secure Anti-Virus for Microsoft Exchange. For more information, connect to http://www.F-Secure.com/

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