September 2010 - Haskell-Cafe

When I change the cabal file to say preference: base >= 4
by caseyh＠istar.ca 29 Sep '10

29 Sep '10

When I change the cabal file to say preference: base >= 4 I still get, "you are using base 3.0 which is deprecated." When I change the overall cabal profile, the error message still comes up. It seems like some other part of the install process is controlling the base version, besides the *.cabal and cabal profile file.

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ICFP2010 contest results?
by Ryan Ingram 29 Sep '10

29 Sep '10

I saw the winner was announced. Is there a highscore table? We were in the top 5, I want to see how well we did. -- ryan

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Re: [Haskell-cafe] Retargeting Haskell compiler to embedded/hardware
by Atze Dijkstra 29 Sep '10

29 Sep '10

Hi Tom, The Utrecht Haskell Compiler (UHC) is internally organized as a set of compilers, for which you can configure the aspects you want. It is relatively easy to extract such a particular combination and use it as a starting point. Or you might install UHC itself and use the installed libraries, which include abstract syntax, parser, etc. There is some variation depending on what you need, so check out http://www.cs.uu.nl/wiki/UHC for initial reading, and let me know whether you need more info. regards, On 29 Sep, 2010, at 16:49 , S. Doaitse Swierstra wrote: > > > Begin forwarded message: > >> From: Tom Hawkins <tomahawkins(a)gmail.com> >> Date: 29 september 2010 03:58:11 GMT+02:00 >> To: haskell-cafe <haskell-cafe(a)haskell.org> >> Subject: [Haskell-cafe] Retargeting Haskell compiler to embedded/hardware >> >> A few years ago I attempted to build a Haskell hardware compiler >> (Haskell -> Verilog) based on the Yhc frontent. At the time I was >> trying to overcome several problems [1] with implementing a hardware >> description language as a light eDSL, which convinced me a proper >> compiler may be a better approach. Yhc was recommended as a good >> starting point since it had a simpler IR compared with GHC -- at least >> at the time. >> >> I am considering restarting this effort, but this time to target hard >> realtime embedded code. What is the recommended compiler to start >> from? I need an IR that is post type checking with as much desugaring >> as possible, and a code base that is relatively easy to splice and >> build. >> >> My other requirement is not to be bound to IO () for 'main'. The top >> level will be a monad, but with different semantics than IO. I would >> also like to reuse the standard library, with exception to the values >> related to IO. >> >> What are my options? >> >> Thanks. >> >> -Tom >> >> [1] Lack of observable sharing; function definitions, case >> expressions, ADTs disappear at compile time; etc. >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe > - Atze - Atze Dijkstra, Department of Information and Computing Sciences. /|\ Utrecht University, PO Box 80089, 3508 TB Utrecht, Netherlands. / | \ Tel.: +31-30-2534118/1454 | WWW : http://www.cs.uu.nl/~atze . /--| \ Fax : +31-30-2513971 .... | Email: atze(a)cs.uu.nl ............ / |___\

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Re: [Haskell-cafe] Help to create a function to calculate a n element moving average ??
by S. Doaitse Swierstra 29 Sep '10

29 Sep '10

On 29 sep 2010, at 00:58, ok(a)cs.otago.ac.nz wrote: >> Avoiding repeated additions: >> >> movingAverage :: Int -> [Float] -> [Float] >> movingAverage n l = runSums (sum . take n $l) l (drop n l) >> where n' = fromIntegral n >> runSums sum (h:hs) (t:ts) = sum / n' : runSums (sum-h+t) hs ts >> runSums _ _ [] = [] >> >> Doaitse > > I very very carefully avoided doing any such thing in my example code. > For each output result, my code does two additions and one division. > Yours does one addition, one subtraction, and one division, for the > required case n = 3. The way I formulated it, each calculation is > independent. The way you've formulated it, the error in one > calculation accumulates into the next. NOT a good idea. If this an issue then: module MovingAverage where movingAverage :: [Float] -> [Float] movingAverage (x:y:l) = movingAverage' x y l where movingAverage' x y (z:zs) = (x+y+z)/3:movingAverage' y z zs movingAverage' _ _ _ = [] movingAverage _ = [] has far fewer pattern matches, Doaitse > >

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Help to create a function to calculate a n element moving average ??
by rgowka1 29 Sep '10

29 Sep '10

Type signature would be Int -> [Double] -> [(Double,Double)] Any thoughts or ideas on how to calculate a n-element moving average of a list of Doubles? Let's say [1..10]::[Double] what is the function to calculate the average of the 3 elements? [(1,0),(2,0),(3,2),(4,3)....] :: [(Double,Double)] (1,0) the average is zero as the length is less than 3 (2,0) the average is zero as the length is less than 3 (3,2) the average is (1+2+3)/3 = 2 (4,3) the average is (2+3+4)/3 = 9 ......

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can't find in hayoo
by Roderick Ford 29 Sep '10

29 Sep '10

I need the trick to get from ByteString -> [GHC.Word.Word8] and Hayoo is not helping. Super simple I expected. I haven't even tried to compile it yet. I am just trying to read in the bytes and encode with base64: import Codec.Binary.Base64 import Data.ByteString import System.Directory import System.Environment main :: do args <- getArgs bFileExist <- System.Directory.doesFileExist (args !! 0) let bytedata = --ByteString -> [GHC.Word.Word8] if bFileExist then putStrLn $ Codec.Binary.Base64.encode bytedata else putStrlLn ("File does not exist: " ++ (args !! 0)) return ()

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Candlestick charts
by rgowka1 29 Sep '10

29 Sep '10

Hi - What are the libraries to use in Haskell to generate a stock candlestick chart like http://stockcharts.com/h-sc/ui?s=SPY&p=D&b=5&g=5&id=p05007254056 I will use Finance-Quote-Yahoo to get the quote data from Yahoo. thanks for all your help.

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ANN: collada-output-0.1
by Tillmann Vogt 29 Sep '10

29 Sep '10

A new graphics library: http://hackage.haskell.org/package/collada-output Most of the graphics libraries on hackage use OpenGL to visualize 3d objects. With this library you now have the choice to use an external tool for visualization and enjoy the flexibility of a standard format for 3d data exchange. I.e. one could generate a raytraced animation or load the objects in a game engine. I think that the generation of 3d objects can be much more powerful and elegant than in other languages. Since this library can be an output for some other libraries on hackage, I would agree to various changes to achieve composability of libraries. Cheers, Tillmann

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Announce: lhae-0.0.3
by Alexander Bau 29 Sep '10

29 Sep '10

lhae[1] is a spreadsheet program. It features a simple formula language and some basic statistical methods, like descriptive statistics and pivot tables. 0.0.2 -> 0.0.3: --------------- Improvements: - Right click menu at columns/row headers and cells - Insert rows/columns between exisiting rows/columns - Boolean values - New functions: ==,/=,<,<=,>,>=,not - If-then-else expressions - New constants: true,false,pi - Filtering of columns/rows - Relative references - Copy formulas into multiple cells Fixed bugs: - Import from csv files - Table updates when deleting/inserting rows/columns - When closing tables: no more "Want to save?" queries on already saved tables [1] http://hackage.haskell.org/package/lhae

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Web application framework comparison?
by Dave Hinton 29 Sep '10

29 Sep '10

There are 179 packages in the Web category on Hackage. It am finding it difficult, as someone who is not familiar with any of the Haskell web application frameworks on Hackage (and there seem to be at least 9), to determine which are good quality, which do things I would like a web framework to do for me, and which insist on doing things I would rather do myself. Is there a page comparing the major frameworks somewhere? I've been unable to find one via Google.

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