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GHC and Panther (Mac OS X 10.3)
by Thomas Davie 20 Nov '03

20 Nov '03

Hi, I've just upgraded to OS X 10.3 and have been having some problems with ghc. I'm using ghc 5.04.3 because it is compatible with hat - I'm doing a uni project on hat at the moment, so it's critical that it works. When I attempt to build hmake using ghc I get a whole load of errors like these: ghc -DUSE_READLINE=1 -L/sw/lib/ -lreadline -I/sw/include -package lang -c -o /Users/tatd100/Documents/Work/Project/Tools/hmake-3.08/targets/powerpc- Darwin7/obj/hmake/QSort.o QSort.hs slow-fast dropthrough not mangled _sAi_entry: addi r0,r22,12 cmplw cr7,r0,r23 ble- cr7,L11 lis r2,ha16(L_MainCapability$non_lazy_ptr) lwz r2,lo16(L_MainCapability$non_lazy_ptr)(r2) lwz r29,12(r2) b L12 L11: lwz r15,0(r22) lwz r16,4(r22) lwz r17,8(r22) addi r22,r22,12 lis r2,ha16(L_sAi_fast3$non_lazy_ptr) lwz r29,lo16(L_sAi_fast3$non_lazy_ptr)(r2) L12: mtctr r29 bctr .align 2 .section __TEXT,__text,regular,pure_instructions Which eventually drop down to one error that kills the whole process: ghc -DUSE_READLINE=1 -L/sw/lib/ -lreadline -I/sw/include -package lang -c -cpp -o /Users/tatd100/Documents/Work/Project/Tools/hmake-3.08/targets/powerpc- Darwin7/obj/hmake/Compat.o Compat.hs Compat.hs:1: parse error on input `#' make[1]: *** [/Users/tatd100/Documents/Work/Project/Tools/hmake-3.08/targets/ powerpc-Darwin7/obj/hmake/Compat.o] Error 1 make: *** [targets/powerpc-Darwin7/hmake-ghc] Error 2 I'm guessing that there's some binary compatibility issues here... Could it be panther using gcc3.3? Thanks Bob

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Functional Code Generation
by Brandon Michael Moore 20 Nov '03

20 Nov '03

I think I remeber seeing a paper about techniques for writing code generators in Haskell targeting stack based bytecodes that encoded bytecode sequences in a way that the typechecker could give you some sanity guarantees, and then talked a bit about using dynamic programming for optimizing bytecode sequences. I haven't turned up anything searching Google and CiteSeer (though I don't really know good words to search for), so I'm hoping someone here remembers. A friend of mine is implementing a Scheme -> OCaml bytecode compiler for a class and I think some of the ideas from that paper would help, whatever they were. Thanks Brandon

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Aggressive inlining
by Blue Steel 19 Nov '03

19 Nov '03

I'm working on a parlor trick. I would like to solve a 3-SAT problem at compile time, so that the executable is super fast. Consider --------------------------------------------------- formula (x1,x2,x3) = (x1 || x2) && x3 tf = [True, False] assignments = [(x1,x2,x3)|x1<-tf,x2<-tf,x3<-tf] solutions = filter formula assignments main = do print solutions --------------------------------------------------- Theoretically, a compiler could optimize this to --------------------------------------------------- main = do print [(True,True,True),...] --------------------------------------------------- Is this actually possible in GHC? I've played with inline pragmas and looked at -ddump-..., but I haven't made much progress. Of course, the goal is to replace "formula" with a formula that takes a 30-tuple instead of a triple and really let GHC crank. Thanks for any help. __________________________________ Do you Yahoo!? Protect your identity with Yahoo! Mail AddressGuard http://antispam.yahoo.com/whatsnewfree

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Re: Haskell Server Pages
by Niklas Broberg 19 Nov '03

19 Nov '03

I am part of a project working on an implementation of an HSP system, very much inspired by the paper you mention by Eric Meijer and Daan Leijen. It is our goal to make a complete HSP system with a model for HTML in Haskell, a pre-processor, and a runtime system/plugins for various web servers. The ETA is set to May -04, until then you can follow our progress at http://www.dtek.chalmers.se/~d00nibro/hsp/ There is a simple version of a pre-processor available from our Download page, but use it at your own risk ;) /Niklas _________________________________________________________________ MSN 8 with e-mail virus protection service: 2 months FREE* http://join.msn.com/?page=features/virus

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Partially ordered collections (revisited)
by Graham Klyne 19 Nov '03

19 Nov '03

I've taken the suggestions made by Tom and Robert and combined them into a new module with some supporting functions and test cases. A copy is attached, in case it's of use to anyone. #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact

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Haskell Server Pages
by "Grigory Makeev 19 Nov '03

19 Nov '03

Hello, I'm interested in writing a personal home-page in a functional way, and i'm in need of some clues. Is there any resource, devoted exactly to the functional approaches to the web programming and web design? I've seen a WASH project, but i'm not really saticefied with the way pages look there. What i trully need is something like Haskell Server Pages system, from Erik Meijer's "Haskell Server Pages. Functional programming and the Battle for the Middle Tier" paper, but i haven't found any implementation of that. I'm not very good at either web programming, or Haskell, i'm just a fan of it, and there's no way i can implement that myself. Is anyone writing currently something like table = <table border="1"> <% mkRows cells%></table> Can anyone provide me with some links? Best regards, Grigory

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Haskell Server Pages
by "Grigory Makeev 19 Nov '03

19 Nov '03

Hello, I'm interested in writing a personal home-page in a functional way, and i'm in need of some clues. Is there any resource, devoted exactly to the functional approaches to the web programming and web design? I've seen a WASH project, but i'm not really saticefied with the way pages look there. What i trully need is something like Haskell Server Pages system, from Erik Meijer's "Haskell Server Pages. Functional programming and the Battle for the Middle Tier" paper, but i haven't found any implementation of that. I'm not very good at either web programming, or Haskell, i'm just a fan of it, and there's no way i can implement that myself. Is anyone writing currently something like table = <table border="1"> <% mkRows cells%></table> Can anyone provide me with some links? Best regards, Grigory

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oh, i'm sorry for doubling a message
by "Grigory Makeev 19 Nov '03

19 Nov '03

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There is flexible exception handling in Haskell?
by 7253146＠informatica.alumnos.uma.es 18 Nov '03

18 Nov '03

Hi all. I am porting to Haskell a small zlib-based library for .zip files (I have not seen any released package for it, although it should very useful). The matters come when I try to address exceptional conditions: all the library functions return a integer code with OK/SOMEERROR meaning. The most natural way to carry the exceptional situations should be raise IO exceptions, but here comes the problem: how can I define new Exception codes, instead of raising userError all the time? I think it makes sense for a library to raise specialized exceptions, instead of userErrors. There is such a mechanism? Can someone help? Thanks. --------------------------------------------- Este mensaje lo ha enviado un Alumno de la Universidad de Malaga. http://www.alumnos.uma.es/

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Subsumption in partially ordered sets
by Graham Klyne 18 Nov '03

18 Nov '03

I have a need for an algorithm to perform "subsumption" on partially ordered sets of values. That is, given a selection of values from a partially ordered set, remove all values from the collection that are less than some other member of the collection. Below is some code I have written, which works, but I'm not sure that it's especially efficient or elegant. Are there any published Haskell libraries that contain something like this? #g -- (The implementation here is based on values of type (Eq a) => [Maybe a], where the partial ordering is defined by function 'pcompare'. Function dropSubsumed (and helpers) is the subsumption calculation. testds1, testds2, testds3, testds4, testds5 are test cases, and all should be True.) [[ -- Type for result of partial order comparison (PNR is no-relationship) data PartOrdering = PLT | PEQ | PGT | PNR deriving (Eq, Show) -- Drop tuples from the supplied list that are subsumed by -- more specific ones. -- dropSubsumed :: (Eq a) => [[Maybe a]] -> [[Maybe a]] dropSubsumed [] = [] dropSubsumed [a] = [a] dropSubsumed (a1:as) = dropSubsumed1 a1 as dropSubsumed1 a1 [] = [a1] dropSubsumed1 a1 (a2:a2s) = case pcompare a1 a2 of PEQ -> dropSubsumed1 a1 a2s PGT -> dropSubsumed1 a1 a2s PLT -> dropSubsumed1 a2 a2s PNR -> dropSubsumed2 [] a1 $ dropSubsumed1 a2 a2s -- Merge new head element into list from which subsumed elements -- have already been removed. The extra (first) parameter is used -- to construct a result in which the order of remaining elements -- is preserved with respect to the original list. dropSubsumed2 a1s a [] = a : revConcat a1s [] dropSubsumed2 a1s a ar@(a2:a2s) = case pcompare a a2 of PEQ -> a : revConcat a1s a2s PGT -> a : revConcat a1s a2s PLT -> revConcat a1s ar PNR -> dropSubsumed2 (a2:a1s) a a2s revConcat :: [a] -> [a] -> [a] revConcat [] a2s = a2s revConcat (a1:a1s) a2s = revConcat a1s (a1:a2s) -- Perform subsumption calculation between a pair of tuples -- A tuple with more information subsumes a one with less but -- consistent information. -- pcompare :: (Eq a) => [Maybe a] -> [Maybe a] -> PartOrdering pcompare a1s a2s = pcompare1 a1s a2s PEQ pcompare1 [] [] po = po pcompare1 (Just _:a1s) (Nothing:a2s) po = if (po == PEQ) || (po==PGT) then pcompare1 a1s a2s PGT else PNR pcompare1 (Nothing:a1s) (Just _:a2s) po = if (po == PEQ) || (po==PLT) then pcompare1 a1s a2s PLT else PNR pcompare1 (a1:a1s) (a2:a2s) po = if a1 == a2 then pcompare1 a1s a2s po else PNR pcompare1 _ _ _ = PNR testds1 = ds1a == ds1b ds1a = dropSubsumed [ [Just 'a',Just 'b',Just 'c'] , [Just 'a',Just 'b',Nothing ] , [Just 'a',Nothing ,Just 'c'] , [Just 'a',Nothing ,Nothing ] , [Nothing ,Just 'b',Just 'c'] , [Nothing ,Just 'b',Nothing ] , [Nothing ,Nothing ,Just 'c'] , [Nothing ,Nothing ,Nothing ] ] ds1b = [ [Just 'a',Just 'b',Just 'c'] ] testds2 = ds2a == ds2b ds2a = dropSubsumed [ [Just 'a',Just 'b',Nothing ] , [Just 'a',Nothing ,Just 'c'] , [Just 'a',Nothing ,Nothing ] , [Nothing ,Just 'b',Just 'c'] , [Nothing ,Just 'b',Nothing ] , [Nothing ,Nothing ,Just 'c'] , [Nothing ,Nothing ,Nothing ] ] ds2b = [ [Just 'a',Just 'b',Nothing ] , [Just 'a',Nothing ,Just 'c'] , [Nothing ,Just 'b',Just 'c'] ] testds3 = ds3a == ds3b ds3a = dropSubsumed [ [Just "a1",Just "b1",Just "c1"] , [Just "a2",Just "b2",Nothing ] , [Just "a3",Nothing ,Just "c3"] , [Just "a4",Nothing ,Nothing ] , [Nothing ,Just "b5",Just "c5"] , [Nothing ,Just "b6",Nothing ] , [Nothing ,Nothing ,Just "c7"] , [Nothing ,Nothing ,Nothing ] ] ds3b = [ [Just "a1",Just "b1",Just "c1"] , [Just "a2",Just "b2",Nothing ] , [Just "a3",Nothing ,Just "c3"] , [Just "a4",Nothing ,Nothing ] , [Nothing ,Just "b5",Just "c5"] , [Nothing ,Just "b6",Nothing ] , [Nothing ,Nothing ,Just "c7"] ] testds4 = ds4a == ds4b ds4a = dropSubsumed [ [Just 1, Just 1 ] , [Just 2, Nothing] , [Nothing,Just 3 ] , [Nothing,Nothing] ] ds4b = [ [Just 1, Just 1 ] , [Just 2, Nothing] , [Nothing,Just 3 ] ] -- Check handling of equal values testds5 = ds5a == ds5b ds5a = dropSubsumed [ [Just 1, Just 1 ] , [Just 2, Nothing] , [Nothing,Just 3 ] , [Nothing,Nothing] , [Just 1, Just 1 ] , [Just 2, Nothing] , [Nothing,Just 3 ] ] ds5b = [ [Just 1, Just 1 ] , [Just 2, Nothing] , [Nothing,Just 3 ] ] ]]

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