- Haskell-Cafe - Haskell.org

ANN: bytestring-trie 0.2.2 (major bugfix)
by wren ng thornton 11 Jun '10

11 Jun '10

-------------------------------------------- -- bytestring-trie 0.2.2 (major bugfix) -------------------------------------------- Another release for efficient finite maps from (byte)strings to values. This version corrects a major bug affecting all users who merge tries. -------------------------------------------- -- Changes (since 0.1.4) -------------------------------------------- * Corrected a major bug in mergeBy which caused conflicting values to be merged in the wrong order. Since this is a core function, all other merging-based functions are affected as well (e.g., unionR, unionL,...). The bug was filed by Gregory Crosswhite (thanks!). * added Data.Trie.Convenience.fromListWith --- A variant of 'fromListR' that takes a function for combining values on conflict. * generalized the type of toListBy * removed KeyString and KeyElem aliases * documentation tweaks -------------------------------------------- -- Future work -------------------------------------------- * Worked on explicit definitions for foldl and foldr, as opposed to the default definitions given by Foldable using Endo. The suggested definitions are around 3x faster than the old definitions, however the order of folding is different than foldrWithKey (which seems to have the correct order). These definitions are not currently being used, but perhaps the future will see faster folding functions for Tries. -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/bytestring-trie Darcs: http://community.haskell.org/~wren/bytestring-trie/ Haddock (Darcs version): http://community.haskell.org/~wren/bytestring-trie/dist/doc/html/bytestring… -- Live well, ~wren

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QuickCheck 2
by wren ng thornton 10 Jun '10

10 Jun '10

Since GHC 6.12 ships with QC2 it looks like it's finally time to get around to converting some old testing scripts. Unfortunately, one of the things I couldn't figure out last time I looked (and hence why I haven't switched) is how to reconfigure the configuration parameters to the driver function. Is there a porting guide anywhere, or how else can I adjust the configuration parameters (in particular, the configMaxTest and configMaxFail parameters)? -- Live well, ~wren

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Re: [Haskell-cafe] Problems with threading?
by Isaac Gouy 10 Jun '10

10 Jun '10

--- On Thu, 6/10/10, Louis Wasserman <wasserman.louis(a)gmail.com> wrote: > Date: Thursday, June 10, 2010, 1:32 AM > Yeah, Control.Parallel would be nice to have. Heck, ideally I could get > the whole Haskell Platform, which would be a reasonable comparison to > the huge Java and C++ libraries accessible to those languages. > Out of curiosity, though, Haskell's thread-ring implementation just > tumbled down the rankings http://shootout.alioth.debian.org > /u64q/program.php?test=threadring&lang=ghc&id=3. Previously, it'd been > doing most of its work on a single core, now it's spread out. Any ideas > for fixin' it? (I'm going to to try using forkOnIO.) There are 4 sets of "rankings" so - http://shootout.alioth.debian.org/u64/program.php?test=threadring&lang=ghc&… I have been wondering what approach is recommended when one part of a program would be a lot faster with -threaded but other parts of the program would be a lot faster without -threaded. I can see that the C++ and Fortran and ... programmers would just wrap part of their program source code with a pragma.

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Re: [Haskell-cafe] Problems with threading?
by Isaac Gouy 10 Jun '10

10 Jun '10

--- On Thu, 6/10/10, Louis Wasserman <wasserman.louis(a)gmail.com> wrote: > Date: Thursday, June 10, 2010, 11:25 AM > > There are 4 sets of "rankings" so - > > http://shootout.alioth.debian.org/u64/program.php?test=threadring&lang=ghc&… > Yes, but Haskell used to be doing much better specifically on the u64q, > which was why I was surprised. I tend not to believe "used to be doing much better" comments until I'm shown the numbers ;-)

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Haskell logo
by Andrew Coppin 10 Jun '10

10 Jun '10

I just visited haskell.org and noticed that the old logo is back. Anybody know when/why this happened?

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Contacting Planet Haskell
by Jason Dagit 10 Jun '10

10 Jun '10

Hello, I recently tried to send an email to the planet Haskell admins. The webpage says to use planet(a)community.haskell.org. The mail was undelivered after several days and the daemon gave up trying to deliver it. My sending did overlap with the haskell.org downtown but I don't think that should have been a problem because: 1) It looks like it retried after haskell.org was back up 2) I'm pretty sure community is a different host than haskell.org 3) Shouldn't a backup mx handle this? Thanks, Jason

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Removing alternate items from a list
by R J 10 Jun '10

10 Jun '10

What's the cleanest definition for a function f :: [a] -> [a] that takes a list and returns the same list, with alternate items removed? e.g., f [0, 1, 2, 3, 4, 5] = [1,3,5]? _________________________________________________________________ The New Busy is not the old busy. Search, chat and e-mail from your inbox. http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:…

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A Finally Tagless Pi Calculus
by Edward Kmett 10 Jun '10

10 Jun '10

Keegan McAllister gave a very nice talk at Boston Haskell last night about "First Class Concurrency". His slides are available online at http://t0rch.org/ His final few slides covered the Pi calculus: http://en.wikipedia.org/wiki/Pi_calculus I took a few minutes over lunch to dash out a finally tagless version of the pi calculus interpreter presented by Keegan, since the topic of how much nicer it would look in HOAS came up during the meeting. For more information on finally tagless encodings, see: http://www.cs.rutgers.edu/~ccshan/tagless/jfp.pdf<http://www.cs.rutgers.edu/%7Eccshan/tagless/jfp.pdf> Of course, Keegan went farther and defined an encoding of the lambda calculus into the pi calculus, but I leave that as an exercise for the reader. ;) -Edward Kmett > {-# LANGUAGE Rank2Types, TypeFamilies, FlexibleInstances #-} > module Pi where > import Control.Applicative > import Control.Concurrent A finally tagless encoding of the Pi calculus. Symantics is a portmanteau of Syntax and Semantics. > class Symantics p where > type Name p :: * > new :: (Name p -> p) -> p > out :: Name p -> Name p -> p -> p > (|||) :: p -> p -> p > inn :: Name p -> (Name p -> p) -> p > rep :: p -> p > nil :: p > embed :: IO () -> p Type level fixed points > newtype Nu f = Nu { nu :: f (Nu f) } > fork :: IO () -> IO () > fork a = forkIO a >> return () > forever :: IO a -> IO a > forever p = p >> forever p Executable semantics > instance Symantics (IO ()) where > type Name (IO ()) = Nu Chan > new f = Nu <$> newChan >>= f > a ||| b = forkIO a >> fork b > inn (Nu x) f = readChan x >>= fork . f > out (Nu x) y b = writeChan x y >> b > rep = forever > nil = return () > embed = id A closed pi calculus term > newtype Pi = Pi { runPi :: forall a. Symantics a => a } > run :: Pi -> IO () > run (Pi a) = a > example = Pi (new $ \z -> (new $ \x -> out x z nil > ||| (inn x $ \y -> out y x $ inn x $ \ y -> nil)) > ||| inn z (\v -> out v v nil)) A pretty printer for the pi calculus > newtype Pretty = Pretty { runPretty :: [String] -> Int -> ShowS } > > instance Symantics Pretty where > type Name Pretty = String > new f = Pretty $ \(v:vs) n -> > showParen (n > 10) $ > showString "nu " . showString v . showString ". " . > runPretty (f v) vs 10 > out x y b = Pretty $ \vs n -> > showParen (n > 10) $ > showString x . showChar '<' . showString y . showString ">. " . > runPretty b vs 10 > inn x f = Pretty $ \(v:vs) n -> > showParen (n > 10) $ > showString x . showChar '(' . showString v . showString "). " . > runPretty (f v) vs 10 > p ||| q = Pretty $ \vs n -> > showParen (n > 4) $ > runPretty p vs 5 . > showString " | " . > runPretty q vs 4 > rep p = Pretty $ \vs n -> > showParen (n > 10) $ > showString "!" . > runPretty p vs 10 > nil = Pretty $ \_ _ -> showChar '0' > embed io = Pretty $ \_ _ -> showString "{IO}" > instance Show Pi where > showsPrec n (Pi p) = runPretty p vars n > where > vars = fmap return vs ++ > [i : show j | j <- [1..], i <- vs] where > vs = ['a'..'z'] Pi> example nu a. (nu b. (b<a>. 0 | b(c). c<b>. b(d). 0) | a(b). b<b>. 0)

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Re: [Haskell-cafe] Removing alternate items from a list
by John Lato 10 Jun '10

10 Jun '10

> From: Markus L?ll <markus.l2ll(a)gmail.com> > > So out of curiosity i took the definitions given in this thread, and > tried to run timing-tests. > Here's what I ran: >> ghc -prof -auto-all -o Test Test.h >> Test +RTS -p > and then looked in the Test.prof file. I think this is a poor approach for timing tests, for two reasons: 1) -O or -O2. Reporting performance results from non-optimized builds is often highly misleading. 2) -auto-all inhibits performance of code, sometimes significantly. You'd be better off using a non-profiling build and criterion. Plus criterion does the statistics for you and warns about possibly invalid samples. John

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Execution call graph pruning
by C K Kashyap 10 Jun '10

10 Jun '10

Hi, I have a call grah which contains information of the edges in the following format caller callee count (time spent by the caller) =================================== foo bar 10 100 xxx yyy 20 10 zzz yyy 10 10 (I used pintool pintool.org to generate this call graph) Now, the problem is that the graph is huge and it take a long to render using 'dot' or use any visualizing tool. Even if they render, it's too cluttered to be useful. I wanted to prune the graph in such a way that I'd have only the edges corresponding to the top 10% of the time consumers. What would be a good way to do such a thing? Has anyone written some utility that I could use? -- Regards, Kashyap

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