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"In several chapters there is a penetrating conceptual analysis of the matter at hand, on which a superstructure of code is erected."
by KC 21 May '11

21 May '11

Interesting comment on the book "The Fun of Programming" in JOOP. "In several chapters there is a penetrating conceptual analysis of the matter at hand, on which a superstructure of code is erected." -- -- Regards, KC

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Is there a place where we can have a discussion on the merits of various GUI's & various graphics? And then vote?
by KC 20 May '11

20 May '11

:) -- -- Regards, KC

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。就qhyrdvefhvfgyvvr，fhfxuhxxyvvhvvvvvghvvvvvrvvvvvvvvevx。
by andrew 20 May '11

20 May '11

466

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Reverse Show instance
by Andrew Coppin 20 May '11

20 May '11

Cannot deduce (Show x) from context (Show (x, y)). Cannot deduce (Show y) from context (Show (x, y)). Um... seriously? From Prelude, we have Show x, Show y => Show (x, y) So clearly it works in the forward direction. But apparently not in the reverse direction. Is this a bug or a feature? (I.e., is there some obscure possibility I haven't thought of which means that doing the reverse inference would be incorrect?)

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Trying to return a map from State monad
by michael rice 19 May '11

19 May '11

I'm not sure what's going on BELOW. Was working with mapAccumL earlier and decided to move over to State monad for more control. :m + Data.Map:m + Data.ListPrelude Data.List Data.Map> let f key new old = new ++ oldPrelude Data.List Data.Map> let moby2 = "Moby Dick is a great book. Moby Dick was a white whale."Prelude Data.List Data.Map> fst $ mapAccumL (\ (m,p) w -> ((insertWithKey' f p [w] m, (snd p, w)),"")) (singleton ("\n", "\n") [], ("\n","\n")) (words moby2)(fromList [(("\n","\n"),["Moby"]),(("\n","Moby"),["Dick"]),(("Dick","is"),["a"]),(("Dick","was"),["a"]),(("Moby","Dick"),["was","is"]),(("a","great"),["book."]),(("a","white"),["whale."]),(("book.","Moby"),["Dick"]),(("great","book."),["Moby"]),(("is","a"),["great"]),(("was","a"),["white"])],("white","whale.")) Michael BELOW=========================== import Control.Monad.Stateimport Data.Map type Prefix = (String,String)type GeneratorState = (Map Prefix [String],Prefix,[String]) non_word = "\n" f key new old = new ++ old buildMap :: GeneratorState (Map Prefix [String]) buildMap = do (mp,(pfx1,pfx2),all@(w1:words)) <- get if (Prelude.null all) then {- No more words. Return final map (adding non_word for prefix). -} return (insertWithKey' f (pfx1,pfx2) [non_word] mp) else {- Add word to map at prefix. Continue. -} put (insertWithKey' f (pfx1,pfx2) [w1] mp, (pfx2,w1), words) buildMap ========================== Prelude> :l markov3.hs[1 of 1] Compiling Main ( markov3.hs, interpreted ) markov3.hs:11:12: `GeneratorState' is applied to too many type arguments In the type signature for `buildMap': buildMap :: GeneratorState (Map Prefix [String])Failed, modules loaded: none.

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where is it appropriate to write library-related suggestions?
by Nicholas Tung 19 May '11

19 May '11

Hi all, I am curious if there is an avenue to make suggestions / comments about libraries? For example, "proc" in System.Process conflicts with the Arrows notation "proc", yielding confusing error messages. thanks, Nicholas — https://ntung.com — CS and Mathematics major @ UC Berkeley

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For Euler 25; What is the first term in the Fibonacci sequence to contain 1000 digits?; the following seems to work.
by KC 19 May '11

19 May '11

For Euler 25; What is the first term in the Fibonacci sequence to contain 1000 digits?; the following seems to work. -- For number of digits being 5 or more. fibNdigits :: Int -> Int fibNdigits nDigits = floor (((fromIntegral nDigits) - 1.0) / (logBase 10 phi)) + 2 where sq5 = sqrt 5 :: Double phi = (1 + sq5) / 2 -- -- Regards, KC

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Status of Haskell + Mac + GUIs & graphics
by Dummy 19 May '11

19 May '11

Hi, i am really happy about this lively discussion around Haskell (Mac) GUIs. I might hint to two other options: 1) Eclipse's SWT wraps the native platform's toolkits quite sucessfully. The platform-dependent bindings are mostly automatically generated, afaik. Some time ago i summarized my thoughts about extending SWT's infrastructure/code for Haskell here: http://www.reddit.com/r/haskell_proposals/comments/9w7nk/adjust_the_swt_bin… 2) Ruby's Shoes provides simple native wrappers as i've pointed out on Reddit: http://www.reddit.com/r/haskell/comments/he8pl/status_of_haskell_mac_guis_g… Bye, Lenny

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Haskell Weekly News: Issue 182
by Daniel Santa Cruz 19 May '11

19 May '11

Welcome to issue 180 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of May 8 to 14, 2011. Announcements Eric Kow released the second edition of Parallel Haskell Digest [http://goo.gl/OXGIw] Don Stewart sent in a proposal from the Haskell.org committee to incorporate Haskell.org [http://goo.gl/X1j8i] Lazycat Manatee has released a new version of Manatee [http://goo.gl/vVTgy] Quotes of the Week * Richard O'Keefe: [On iterators and generators] This being Haskell, I'm expecting to see Cogenerator... * luqui: Haskell is a DSL for writing monad tutorials. * mattmight: Coq is a tool for turning ordinary programs into POPL papers. * kmc: most CS courses will teach you four kinds of Java * geheimdienst: haskell makes hard things easy and easy things a strong lax monoidal endofunctor ... * spoolio: Haskell programmers know the cost of nothing, the type of everything, and might know the value of a few things later. * catamorphism: FP is related to FP in the same way that UML is related to OOP. * geheimdienst: * geheimdienst will from now on use a function carpeTiem aliased to getCurrentTime * edwardk: [on data-accessor] However, its choice of internal representation makes me throw up in my mouth a little bit Top Reddit Stories * Fancy function graphs! Domain: pnyf.inf.elte.hu, Score: 47, Comments: 21 On Reddit: http://goo.gl/ibZO1 Original: http://goo.gl/24hQ6 * Online SVG figures with Haskell Domain: self.haskell, Score: 46, Comments: 11 On Reddit: http://goo.gl/jgxk4 * Erlang-in-Haskell: an implementation of an Erlang-like distributed computing framework for Haskell Domain: hackage.haskell.org, Score: 41, Comments: 2 On Reddit: http://goo.gl/yMMRG Original: http://goo.gl/eq6s3 * Why Eager Languages Don't Have Products and Lazy Languages Don't Have Sums Domain: james-iry.blogspot.com, Score: 38, Comments: 35 On Reddit: http://goo.gl/ngpNe Original: http://goo.gl/2O6yq * Introducing JsonGrammar Domain: martijn.van.steenbergen.nl, Score: 34, Comments: 2 On Reddit: http://goo.gl/wiGI9 Original: http://goo.gl/ns20k * The reasons I don't write all my code in Haskell Domain: codeflow.wordpress.com, Score: 33, Comments: 34 On Reddit: http://goo.gl/HMZ8c Original: http://goo.gl/hyuSa * Experimental GHC with GHCJS built in and Cabal support for JavaScript files Domain: article.gmane.org, Score: 30, Comments: 3 On Reddit: http://goo.gl/8zzZT Original: http://goo.gl/MQMvN * Two fun bits of Haskell teaching news Domain: serpentine.com.nyud.net, Score: 28, Comments: 3 On Reddit: http://goo.gl/JQUtF Original: http://goo.gl/mYz1q * Themes on Streams Domain: byorgey.wordpress.com, Score: 26, Comments: 1 On Reddit: http://goo.gl/ywP1K Original: http://goo.gl/ywPnl * CmdArgs - Fighting the GHC Optimiser Domain: neilmitchell.blogspot.com, Score: 20, Comments: 15 On Reddit: http://goo.gl/0WThF Original: http://goo.gl/CgCgz Top StackOverflow Questions * Safe execution of untrusted Haskell code votes: 19, answers: 2 http://goo.gl/9eHuc * When do I use ByteString and when do I not? votes: 16, answers: 2 http://goo.gl/vVQig * Why can I not make String an instance of a typeclass? votes: 14, answers: 3 http://goo.gl/Pn8DS * Android application in haskell votes: 11, answers: 1 http://goo.gl/UfnA1 * What are the most important abstractions in Haskell? Monads? Applicatives? votes: 9, answers: 3 http://goo.gl/RaXVQ About the Haskell Weekly News To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. Until next time, Daniel Santa Cruz

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ANNOUNCE: levmar-1.0
by Bas van Dijk 18 May '11

18 May '11

Dear all, I released levmar-1.0, an implementation of the Levenberg-Marquardt minimization algorithm that can be used for least squares, curve fitting and nonlinear programming. The most important change in this release is the use of vectors and matrices from the hmatrix package (which uses the high performance vector package). An application at work became 25 times faster when switching to the new levmar! I'm not sure this major speedup can be entirely attributed to the switch from lists to vectors. I also switched the FFI types from CDouble to Double in the internal bindings-levmar package. This made the expensive realToFrac conversions from CDouble to Double unnecessary which I believe had a big impact. API Documentation: http://hackage.haskell.org/package/levmar-1.0 I also switched the repository from darcs to git and hosted it on github: https://github.com/basvandijk/levmar/ Regards, Bas

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