February 2012 - Haskell-Cafe

Adding Html formatting to formlets
by Alberto G. Corona 03 Feb '12

03 Feb '12

I came across the idea that is easy to define additional operators to Text.FormLets for adding custom HTML formatting. Had anyone tried that? For example to enclose the Prod formulary in a Table using Text.XHtml tags. I defined additional operators <<< and <++ for enclosing and prepending Html to a formLet, respectively: >data Prod= Prod{pname :: String, pprice :: Int} >getProd= table <<< ( > Prod <$> tr <<< (td << "enter the name" <++ td <<< getString (pname <$> mp)) > <*> tr <<< (td << "enter the price" <++ td <<< getInt ( pprice <$> mp))) even: >p << "paragraph" <++ getProd ++> (more Html stuff) is possible or even it is possible an operator <+> > getProd <+> someOtherStuff to return Either Prod OtherStuff I did it in my own version of FormLets. So It is too heavy to put here a running example. It is part of a package that I will upload soon to hackage. This also may work for embedding formLets in other haskell HTML formats besides Text.XHtml.

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Fwd: Contributing to http-conduit
by Chris Wong 03 Feb '12

03 Feb '12

Sorry, accidentally clicked "Reply" rather than "Reply to all". Here's the message I sent: ---------- Forwarded message ---------- From: Chris Wong <chrisyco+haskell-cafe(a)gmail.com> Date: Fri, Feb 3, 2012 at 7:44 PM Subject: Re: [Haskell-cafe] Contributing to http-conduit To: "Myles C. Maxfield" <myles.maxfield(a)gmail.com> On Fri, Feb 3, 2012 at 5:32 PM, Myles C. Maxfield <myles.maxfield(a)gmail.com> wrote: > I propose making an entirely unrelated package, public-suffix-list, with a > module Network.PublicSuffixList, which will expose this function, as well as > functions about parsing the list itself. Thoughts? I'll volunteer to write this module, but I'm not sure whether to read it in at run time, or generate the module containing the data in advance. The latter seems less error-prone -- no messing around with file paths or IO. Chris

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ANN: combinatorics
by wren ng thornton 03 Feb '12

03 Feb '12

-------------------------------------------- -- combinatorics 0.1.0 -------------------------------------------- The combinatorics package offers efficient *exact* computation of common combinatorial functions like the binomial coefficients and factorial. (For fast *approximations*, see the math-functions package instead.) -------------------------------------------- -- Long Description -------------------------------------------- * Math.Combinatorics.Primes: provides the prime numbers via Runciman's lazy wheel sieve algorithm. Provided here since efficient algorithms for combinatorial functions often require prime numbers. The current version memoizes the primes as an infinite list CAF, which could lead to memory leaks in long-running programs with irregular access to large primes. I'm looking into a GHC patch to allow resetting individual CAFs from within compiled programs so that you can explicitly decide when to un-memoize the primes. (In GHCi when you reload a module all the CAFs are reset. However, there's no way to access this feature from within compiled programs as yet.) * Math.Combinatorics.Binomial: offers a fast computation of the binomial coefficients based on the prime factorization of the result. As it turns out, it's easier to compute the prime factorization of the answer than it is to compute the answer directly! And you don't even need the factorial function to do so. Albeit, with a fast factorial function, the naive definition of binomial coefficients gives this algorithm a run for its money. * Math.Combinatorics.Factorial: offers a fast computation of factorial numbers. As Peter Luschny comments[1], the factorial function is often shown as a classic example of recursive functions, like addition of Peano numbers, however that naive way of computing factorials is extremely inefficient and does a disservice to those learning about recursion. The current implementation uses the split-recursive algorithm which is more than sufficient for casual use. I'm working on implementing the parallel prime-swing algorithm, which should be a bit faster still. [1] http://www.luschny.de/math/factorial/FastFactorialFunctions.htm -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/combinatorics Darcs: http://community.haskell.org/~wren/combinatorics Haddock (Darcs version): http://community.haskell.org/~wren/combinatorics/dist/doc/html/combinatorics -- Live well, ~wren

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cabal-install package precedence with --extra-lib-dirs
by Scott Lawrence 02 Feb '12

02 Feb '12

When running cabal install with --extra-lib-dirs=./lib, if a package is found both in ~/.cabal/lib and ./lib, cabal seems to favor the ~/.cabal/lib one. Is there some way to specify the correct precedence to use? -- Scott Lawrence

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Re: [Haskell-cafe] strict version of Haskell - does it exist?
by Marc Weber 02 Feb '12

02 Feb '12

> jsonLines :: C.Resource m => C.Conduit B.ByteString m Value > jsonLines = C.sequenceSink () $ do > val <- CA.sinkParser json' > CB.dropWhile isSpace_w8 > return $ C.Emit () [val] Adding a \state -> (the way Felipe Lessa told me) make is work and it runs in about 20sec and that although some conduit overhead is likely to take place. omitting my custom data type using bytestrings operating on Value of Aeson reduces running time to 16secs. PHP/C++ still wins: less than 12secs. Now I can imagine again that even a desktop multi core system is faster than a single threaded C application. Thanks for your help. Maybe I can setup profiling again to understand why its still taking little bit more time. Marc Weber

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ANN: test-framework-doctest 0.2 (now works also with test-framework 0.5)
by Sakari Jokinen 02 Feb '12

02 Feb '12

test-framework-doctest provides integration between doctest-haskell and test-framework.. See http://hackage.haskell.org/package/test-framework-doctest for details. Big thanks to Simon Hengel who did all the real work in making the library work with test-framework 0.5 cheers Sakari

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zlib 0.5.3.2 broken?
by Michael Snoyman 02 Feb '12

02 Feb '12

Hi all, I've received a number of reports of a broken zlib 0.5.3.2 (and experienced it myself). Is this a generally known issue? As a temporary workaround, I've released a new version of zlib-bindings that has an upper bound on zlib to avoid 0.5.3.2 (and later). Once a new patched version is released, I'll release an updated version of zlib-bindings to remove that overly restrictive upper bound. Michael

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PhD studentship in Nottingham (closing date 10th February)
by Graham Hutton 02 Feb '12

02 Feb '12

Dear all, I am currently advertising a PhD Studentship in Functional Programming at the University of Nottingham in the UK: http://www.nottingham.ac.uk/jobs/currentvacancies/ref/SCI1088 The closing date is *** Friday 10th February 2012 ***. If you would like to apply, please follow the instructions in the advert, rather than clicking on "apply online". Many thanks, Graham Hutton -- Prof Graham Hutton Functional Programming Lab School of Computer Science University of Nottingham, UK http://www.cs.nott.ac.uk/~gmh This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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ANN: NubFinder : Mining Opinions on the Web
by dokondr 02 Feb '12

02 Feb '12

Hello, I am pleased to announce NubFinder research project. Goal: develop technology to search and analyze user opinions on the Web. NubFinder and NubTrend are research prototypes trying first to accomplish a more 'simple' task - classification of emotions in Twitter messages, and then approach opinion mining. NubFinder project site: https://sites.google.com/site/nubfinder NubFinder discussion group: http://groups.google.com/group/nubfinder Thanks for your interest in NubFinder Research! -- All the best, Dmitri O. Kondratiev "This is what keeps me going: discovery" dokondr(a)gmail.com http://sites.google.com/site/dokondr/welcome

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ANN: hledger 0.17
by Simon Michael 02 Feb '12

02 Feb '12

Happy new year all. hledger and hledger-web 0.17 are released. Not quite as planned, this release mainly fixes bugs and updates dependencies. Also the hledger-vty and hledger-chart packages have been demoted to "unmaintained extras" for now to save time. hledger is a library, command-line tool, and web app for reporting on financial transactions stored in a text file. It is a haskell port and friendly fork of John Wiegley's Ledger. Home: http://hledger.org To install: cabal update, then cabal install hledger (or cabal-install hledger-web). If you have any trouble, please let me know, or watch the mail list/bug tracker for updates. (Ready to run binaries are provided on request to project donors, a great way to support the project - see http://hledger.org/DOWNLOAD.html.) Release notes for 0.17: * support HP 2011.4.0.0 * support and require cmdargs 0.9 * allow non-threaded builds, supporting more debian architectures * parsing: give a clearer error when journal file path contains ~ * parsing: -B/--cost now ignores P historical prices, like ledger * parsing: inferred amounts now use the cost commodity if known, like ledger (#69) * balance: report differently-priced lots in an account as a single amount, like ledger * web: support and require yesod >= 0.9.4 * web: use the main aeson package again * web: fix a regression with dollar signs in hamlet templates * web: add form allowed blank account names (#81) * chart, vty: hledger-chart and hledger-vty demoted to non-maintained extras for now Best, -Simon

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