- Haskell-Cafe - Haskell.org

serious defect in system-uuid
by Jason Dusek 02 Dec '08

02 Dec '08

I discovered that my UUID type causes a <<loop>> when tested for equality. Anyone who is using `system-uuid`, please upgrade to version 1.0.2. -- _jsn

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System.IO.UTF8 Problem
by Ben George 02 Dec '08

02 Dec '08

Hi, so I've been working with System.IO.UTF8 trying to get it to render Japanese characters correctly. Using just IO I've gotten it to output the correct unicode values, however, replacing the IO.putStrLn commands with System.IO.UTF8 yielded some strange errors. I went through the program and replaced the System.IO.UTF8 putStrLn and hGetLine commands with their "normal" IO counterparts, however, simply having the "import System.IO.UTF8" line at the beginning of the file causes an error during compilation. $ghc file.hs compilation IS NOT required byteindex.o: In function `sKE_info': (.text+0x8bf): undefined reference to `__stginit_utf8zmstringzm0zi3zi3_SystemziIOziUTF8_' collect2: ld returned 1 exit status Below is the output of ghc -v. I am running Ubuntu 7.10 gutsy. I have been getting the same error whether GHC was compiled from binaries or source. Currently I am running GHC (version 6.8.3) compiled from source. $ ghc -v file.hs Glasgow Haskell Compiler, Version 6.8.3, for Haskell 98, stage 2 booted by GHC version 6.8.3 Using package config file: /usr/local/lib/ghc-6.8.3/package.conf wired-in package base mapped to base-3.0.2.0 wired-in package rts mapped to rts-1.0 wired-in package haskell98 mapped to haskell98-1.0.1.0 wired-in package template-haskell mapped to template-haskell-2.2.0.0 wired-in package ndp not found. Hsc static flags: -static Created temporary directory: /tmp/ghc6586_0 *** Checking old interface for main:Main: compilation IS NOT required *** Touching object file: touch byteindex.o *** Linker: gcc -v -o a.out -DDONT_WANT_WIN32_DLL_SUPPORT byteindex.o -L/usr/local/lib/ghc-6.8.3/lib/haskell98-1.0.1.0 -L/usr/local/lib/ghc-6.8.3/lib/array-0.1.0.0 -L/usr/local/lib/ghc-6.8.3/lib/process-1.0.0.1 -L/usr/local/lib/ghc-6.8.3/lib/unix-2.3.0.1 -L/usr/local/lib/ghc-6.8.3/lib/random-1.0.0.0 -L/usr/local/lib/ghc-6.8.3/lib/directory-1.0.0.1 -L/usr/local/lib/ghc-6.8.3/lib/filepath-1.1.0.0 -L/usr/local/lib/ghc-6.8.3/lib/old-time-1.0.0.0 -L/usr/local/lib/ghc-6.8.3/lib/old-locale-1.0.0.0 -L/usr/local/lib/ghc-6.8.3/lib/base-3.0.2.0 -L/usr/local/lib/ghc-6.8.3 -lHShaskell98-1.0.1.0 -lHSarray-0.1.0.0 -lHSprocess-1.0.0.1 -lHSunix-2.3.0.1 -lutil -ldl -lHSrandom-1.0.0.0 -lHSdirectory-1.0.0.1 -lHSfilepath-1.1.0.0 -lHSold-time-1.0.0.0 -lHSold-locale-1.0.0.0 -lHSbase-3.0.2.0 -lHSrts -lm -lgmp -ldl -lrt -u base_GHCziBase_Izh_static_info -u base_GHCziBase_Czh_static_info -u base_GHCziFloat_Fzh_static_info -u base_GHCziFloat_Dzh_static_info -u base_GHCziPtr_Ptr_static_info -u base_GHCziWord_Wzh_static_info -u base_GHCziInt_I8zh_static_info -u base_GHCziInt_I16zh_static_info -u base_GHCziInt_I32zh_static_info -u base_GHCziInt_I64zh_static_info -u base_GHCziWord_W8zh_static_info -u base_GHCziWord_W16zh_static_info -u base_GHCziWord_W32zh_static_info -u base_GHCziWord_W64zh_static_info -u base_GHCziStable_StablePtr_static_info -u base_GHCziBase_Izh_con_info -u base_GHCziBase_Czh_con_info -u base_GHCziFloat_Fzh_con_info -u base_GHCziFloat_Dzh_con_info -u base_GHCziPtr_Ptr_con_info -u base_GHCziPtr_FunPtr_con_info -u base_GHCziStable_StablePtr_con_info -u base_GHCziBase_False_closure -u base_GHCziBase_True_closure -u base_GHCziPack_unpackCString_closure -u base_GHCziIOBase_stackOverflow_closure -u base_GHCziIOBase_heapOverflow_closure -u base_GHCziIOBase_NonTermination_closure -u base_GHCziIOBase_BlockedOnDeadMVar_closure -u base_GHCziIOBase_BlockedIndefinitely_closure -u base_GHCziIOBase_Deadlock_closure -u base_GHCziIOBase_NestedAtomically_closure -u base_GHCziWeak_runFinalizzerBatch_closure -u base_GHCziConc_ensureIOManagerIsRunning_closure Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.1.3 --program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr --enable-checking=release i486-linux-gnu Thread model: posix gcc version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2) /usr/lib/gcc/i486-linux-gnu/4.1.3/collect2 --eh-frame-hdr -m elf_i386 --hash-style=both -dynamic-linker /lib/ld-linux.so.2 -o a.out -u base_GHCziBase_Izh_static_info -u base_GHCziBase_Czh_static_info -u base_GHCziFloat_Fzh_static_info -u base_GHCziFloat_Dzh_static_info -u base_GHCziPtr_Ptr_static_info -u base_GHCziWord_Wzh_static_info -u base_GHCziInt_I8zh_static_info -u base_GHCziInt_I16zh_static_info -u base_GHCziInt_I32zh_static_info -u base_GHCziInt_I64zh_static_info -u base_GHCziWord_W8zh_static_info -u base_GHCziWord_W16zh_static_info -u base_GHCziWord_W32zh_static_info -u base_GHCziWord_W64zh_static_info -u base_GHCziStable_StablePtr_static_info -u base_GHCziBase_Izh_con_info -u base_GHCziBase_Czh_con_info -u base_GHCziFloat_Fzh_con_info -u base_GHCziFloat_Dzh_con_info -u base_GHCziPtr_Ptr_con_info -u base_GHCziPtr_FunPtr_con_info -u base_GHCziStable_StablePtr_con_info -u base_GHCziBase_False_closure -u base_GHCziBase_True_closure -u base_GHCziPack_unpackCString_closure -u base_GHCziIOBase_stackOverflow_closure -u base_GHCziIOBase_heapOverflow_closure -u base_GHCziIOBase_NonTermination_closure -u base_GHCziIOBase_BlockedOnDeadMVar_closure -u base_GHCziIOBase_BlockedIndefinitely_closure -u base_GHCziIOBase_Deadlock_closure -u base_GHCziIOBase_NestedAtomically_closure -u base_GHCziWeak_runFinalizzerBatch_closure -u base_GHCziConc_ensureIOManagerIsRunning_closure /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/crt1.o /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/crti.o /usr/lib/gcc/i486-linux-gnu/4.1.3/crtbegin.o -L/usr/local/lib/ghc-6.8.3/lib/haskell98-1.0.1.0 -L/usr/local/lib/ghc-6.8.3/lib/array-0.1.0.0 -L/usr/local/lib/ghc-6.8.3/lib/process-1.0.0.1 -L/usr/local/lib/ghc-6.8.3/lib/unix-2.3.0.1 -L/usr/local/lib/ghc-6.8.3/lib/random-1.0.0.0 -L/usr/local/lib/ghc-6.8.3/lib/directory-1.0.0.1 -L/usr/local/lib/ghc-6.8.3/lib/filepath-1.1.0.0 -L/usr/local/lib/ghc-6.8.3/lib/old-time-1.0.0.0 -L/usr/local/lib/ghc-6.8.3/lib/old-locale-1.0.0.0 -L/usr/local/lib/ghc-6.8.3/lib/base-3.0.2.0 -L/usr/local/lib/ghc-6.8.3 -L/usr/lib/gcc/i486-linux-gnu/4.1.3 -L/usr/lib/gcc/i486-linux-gnu/4.1.3 -L/usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib -L/lib/../lib -L/usr/lib/../lib byteindex.o -lHShaskell98-1.0.1.0 -lHSarray-0.1.0.0 -lHSprocess-1.0.0.1 -lHSunix-2.3.0.1 -lutil -ldl -lHSrandom-1.0.0.0 -lHSdirectory-1.0.0.1 -lHSfilepath-1.1.0.0 -lHSold-time-1.0.0.0 -lHSold-locale-1.0.0.0 -lHSbase-3.0.2.0 -lHSrts -lm -lgmp -ldl -lrt -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/i486-linux-gnu/4.1.3/crtend.o /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/crtn.o byteindex.o: In function `sKE_info': (.text+0x8bf): undefined reference to `__stginit_utf8zmstringzm0zi3zi3_SystemziIOziUTF8_' collect2: ld returned 1 exit status *** Deleting temp files: Deleting: /tmp/ghc6586_0/ghc6586_0.s Warning: deleting non-existent /tmp/ghc6586_0/ghc6586_0.s *** Deleting temp dirs: Deleting: /tmp/ghc6586_0 Any help would be greatly appreciated. -- Ben George blgeorge(a)fastmail.fm -- http://www.fastmail.fm - The way an email service should be

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bug in time libs?
by Jason Dusek 02 Dec '08

02 Dec '08

I'm on 6.10.1, using the libs provided with the binary of GHC for Mac OS X. I was fooling around with the time package in GHCi and something seems to be off. I have included a transcript. If I take a time diff, then the seconds are positive when the picos are negative and vice versa. -- _jsn |...transcript...| Prelude System.Time> :m + System.Time Prelude System.Time> t0 <- System.Time.getClockTime Prelude System.Time> t1 <- System.Time.getClockTime Prelude System.Time> diffClockTimes t0 t1 TimeDiff { tdYear = 0 , tdMonth = 0 , tdDay = 0 , tdHour = 0 , tdMin = 0 , tdSec = -7 , tdPicosec = 238846000000 } Prelude System.Time> diffClockTimes t1 t0 TimeDiff { tdYear = 0 , tdMonth = 0 , tdDay = 0 , tdHour = 0 , tdMin = 0 , tdSec = 7 , tdPicosec = -238846000000 }

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Re: Binary Trees missing on hackage
by Andrew Wagner 02 Dec '08

02 Dec '08

The reasons I've always heard for this is that 1.) It's so easy to define a tree and 2.) There are tons of different variations of trees and what you can do with them. Not that I 100% agree, just what I've always heard. On Mon, Dec 1, 2008 at 6:09 AM, Christian Maeder <Christian.Maeder(a)dfki.de>wrote: > Hi, > > I was surprised that I could not find a "classical" binary tree data > structure on hackage, mainly for teaching purposes, like: > > data BinTree a = Nil | Node (BinTree a) a (BinTree a) > > with a couple of utility functions and instances (i.e. in-order traversal). > > Surely, one may argue, that such a tree can always be defined on the fly > when needed, but nobody would argue so for lists or tuples. (Although > I've rarely seen someone redefining lists, it is quite common to > introduce user-defined products or enumerations.) > > There are rose trees in Data.Tree and many other variants of trees are > conceivable, ie. > > data Boom a = Leaf a | Node (Boom a) (Boom a) > > or a kind of combination: > > data BinLeafTree a b = > Leaf b > | Node (BinLeafTree a b) a (BinLeafTree a b) > > I don't know, why I find the above BinTree most important. I'm not even > sure if such a tree could be re-used for Search- or AVL-trees that need > strict fields with redundant size or height counters for efficiency > reasons. > > In any case I would find such a data type at least as useful as > http://hackage.haskell.org/cgi-bin/hackage-scripts/package/OneTuple > > Who would supply and maintain such a package? Or did I simply not search > hard enough? > > Cheers Christian > > P.S. I took the (non-empty) "Boom" from the Boom-Hierarchy described in > "An Exploration of the Bird-Meertens Formalism" by Roland Backhouse > 1988, Groningen > > _______________________________________________ > Libraries mailing list > Libraries(a)haskell.org > http://www.haskell.org/mailman/listinfo/libraries >

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Can anybody give me some advice on this?
by Georgel Calin 02 Dec '08

02 Dec '08

Hello everybody, I have a piece of code that gives me headaches for some time now. Simply put, I would like to know which is the best way to overpass a "Couldn't match expected type * against inferred type *"-error and an "Occurs check: cannot construct the infinite type:"-error in the following situation: {-# OPTIONS -fglasgow-exts #-} > module Simple where > import Text.ParserCombinators.Parsec > > data HData a = O | C a deriving (Eq,Ord,Show) > data IN l = IN Int (HData l) deriving (Eq,Ord,Show) > data CH l = CH Char (HData l) deriving (Eq,Ord,Show) > -- data type is well-defined: > sample = C(IN 0 (C(CH 'a' (C(IN 1 (C(CH 'b' (C(IN 2 O))))))))) > > embeddedParser types = do string "end"; spaces; return O > {- > <|> do let h = head types > let t = tail types > case h of > 1 -> do aux <- pInt > rest <- embeddedParser $t++[h] > return $ C (IN aux rest) > 2 -> do aux <- pCh > rest <- embeddedParser $t++[h] > return $ C (CH aux rest) > _ -> error "unallowed type" > -} > pInt = do n <- fmap read $ many1 digit; return $ fromInteger n > pCh = do c <- letter; return $ c > simple = embeddedParser [1,2] > > -- the above result from sample I would like to get by running > -- parseTest simple "0a1b2end" > The way I see it, the defined datatype works but I am a bit clueless about how to modify the parser to accept things of the type (e.g.): HData (IN (CH (IN (CH (IN a))))) (and in general of any finite type embedded like this). Thanks in advance for your help, George

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'#' in literate haskell
by John MacFarlane 01 Dec '08

01 Dec '08

Can anyone explain why ghc does not treat the following as a valid literate haskell program? --------- test.lhs ---- # This is a test > foo = reverse . words ------------------------ When I try to load this in ghci (or compile it using ghc), I get: test.lhs:1:2: lexical error at character 'T' It seems that the problem is the '#' character in the first column. Replacing it with something else, or moving it to the right one space, solves the problem. The following literate haskell program, from http://notvincenz.blogspot.com/2008/01/literate-haskell-and-c.html, also fails to load for me, for the same reason (the leading '#' in line 8). ---- literate-haskell-and-c.lhs --- /* c and lhs file > > module Foo where > main = print "Haskell" > */ #include int main() { printf("C\n"); return 0; } ------------------------------------ I've reproduced this with ghc 6.10.1 and ghc 6.8.3 (linux binaries from haskell.org) and with ghc 6.8.2 (Ubuntu intrepid). Interestingly, hugs (September 2006 version) has no trouble with test.lhs. I haven't tried ghc 6.6. I care about this because I'd like to use markdown conventions to format the comment parts of literate haskell programs. Markdown supports atx-style headers, which begin with strings of '#' characters starting in the first column. I know that some people use markdown with literate haskell, so there must be something basic here that I'm missing! John

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Re: The Knight's Tour: solutions please
by Diego Echeverri 01 Dec '08

01 Dec '08

>>I've created a wiki page, >>http://haskell.org/haskellwiki/The_Knights_Tour >>I note the LogicT version is the shortest so far. >>-- Don Probably noob question. I was looking into the first solution in the page and tried to replace sortOn f = map snd . sortBy (comparing fst) . map (f &&& id) for sortOn' f = sortBy (comparing fst) The first one was much faster? Why? Thanks! Diego

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Scala job in Boston writing quantitative finance software
by Paul Chiusano 01 Dec '08

01 Dec '08

Hi folks, The company I work for, ClariFI (http://clarifi.com/) is looking to hire developers with a strong background in functional programming to do a mixture of Scala and Java programming. It's fine if you don't happen to know Scala but are strong in Haskell - we are looking for people who really "get" FP and who we could turn loose designing and implementing clean, functional code in Scala once up to speed with the language. You'd also work on extending existing Scala modules and integrating the library code you write with application code written in Java. For more info, check out our official job posting: http://www.clarifi.com/About-ClariFI-Careers.php#SoftwareEngineer Some background on us: ClariFI is a small company (about 15 developers) that specializes in software for quantitative investment management. Our chief product, ModelStation, is used by portfolio managers for handling all stages of the quant process: building and backtesting of factors, portfolio optimization, simulation of trading strategies, performance and risk attribution, overall data management (including organizing huge amounts of time series data pulled from a diverse set of raw sources), and lots more. We don't expect you to have a background in finance but you should be willing and able to learn a lot once you start. This position is in our Boston office, so you must live or be willing to relocate here in order to be considered. If you're interested, send an email to myself or my boss, Scott McFarland (smcfarland(a)clarifi.com) along with your resume. Also, feel free to contact either of us if you just have questions about the position. Cheers, Paul

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Parallel alpha-beta search
by Colin Paul Adams 01 Dec '08

01 Dec '08

Has anyone ever attempted this in Haskell? If so, what sort of speed-up have you had (with which algorithm)? -- Colin Adams Preston Lancashire

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howto tuple fold to do n-ary cross product?
by Larry Evans 01 Dec '08

01 Dec '08

http://www.muitovar.com/monad/moncow.xhtml#list contains a cross function which calculates the cross product of two lists. That attached does the same but then used cross on 3 lists. Naturally, I thought use of fold could generalize that to n lists; however, I'm getting error: {-- cut here Compilation started at Sun Nov 23 13:15:24 make runghc -XMultiParamTypeClasses -XFunctionalDependencies -XFlexibleInstances cross.hs cross.hs:23:30: Occurs check: cannot construct the infinite type: a = (a, a) Expected type: [a] -> [a] -> [a] Inferred type: [a] -> [a] -> [(a, a)] In the first argument of `Data.Foldable.foldl1', namely `cross' In the first argument of `print', namely `(Data.Foldable.foldl1 cross (list2, list3, list1))' make: *** [run] Error 1 }-- cut here How do I apply fold to cross and n lists, for n>=0? TIA. -regards, Larry

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