February 2008 - Haskell-Cafe

ANNOUNCE: parameterized-data 0.1 - Parameterized data library implementing lightweight dependent types
by Alfonso Acosta 28 Feb '08

28 Feb '08

This library provides an implementation of parameterized types using type-level computations to implement the type parameters and emulate dependent types. Right now only fixed-sized vectors are provided (based on Oleg's "Number-parameterized types" [1] and Frederik Eaton's Vectro library [2]) HackageDB page: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/parameterized-da… Darcs repository: http://code.haskell.org/parameterized-data/ Again, big thanks to Oleg and Wolfgang for their help and suggestions. [1] http://okmij.org/ftp/Haskell/number-parameterized-types.html [2] http://ofb.net/~frederik/vectro/

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Re: [Haskell-cafe] Bay Area talk tomorrow, on concurrent/parallel Haskell
by PR Stanley 28 Feb '08

28 Feb '08

At 13:23 28/02/2008, you wrote: >Hello, > >I wish I could be there, but I'm in Kentucky. ;) >It would be great if someone could have this talk recorded and >posted on youtube, or something similar. > >Thank you. >Now, there's an idea which could be extended to all Haskell related >gatherings. >__ >Donnie > >On 2/27/08, Bryan O'Sullivan ><<mailto:bos@serpentine.com>bos(a)serpentine.com> wrote: >Satnam Singh of Microsoft Research will be speaking about concurrent >and parallel programming at Stanford tomorrow. > >Details here: > ><http://www.realworldhaskell.org/blog/2008/02/28/stanford-haskell-talk-2008-…>http://www.realworldhaskell.org/blog/2008/02/28/stanford-haskell-talk-2008-… > > <b >_______________________________________________ >Haskell-Cafe mailing list ><mailto:Haskell-Cafe@haskell.org>Haskell-Cafe(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell-cafe > > >_______________________________________________ >Haskell-Cafe mailing list >Haskell-Cafe(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell-cafe

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Bay Area talk tomorrow, on concurrent/parallel Haskell
by Bryan O'Sullivan 28 Feb '08

28 Feb '08

Satnam Singh of Microsoft Research will be speaking about concurrent and parallel programming at Stanford tomorrow. Details here: http://www.realworldhaskell.org/blog/2008/02/28/stanford-haskell-talk-2008-… <b

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Rendering TTF fonts in Haskell and OpenGL
by Jefferson Heard 28 Feb '08

28 Feb '08

In C and in Java, I can use truetype fonts in Haskell using select libraries, and I'd like to be able to do the same in Haskell. Are there any portable libraries out there for loading fonts into OpenGL geometry for Haskell? I can use the vector fonts from GLUT is absolutely neccessary, but I'd like something that looks a little more professional. Are there any suggestions? -- Jeff -- I try to take things like a crow; war and chaos don't always ruin a picnic, they just mean you have to be careful what you swallow. -- Jessica Edwards

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ANNOUNCE: type-level 0.1: Haskell type-level programming library
by Alfonso Acosta 27 Feb '08

27 Feb '08

The goal of the "Type-level" library is to standardize and extend the features offered by the multiple (and heterogeneous) type-level programming implementations already around. To date, type-level Booleans and arbitrary sized Naturals are supported. I implemented a few things I didn't see in any other type-level programming libraries: * Numerals use decimal representation to make error reports friendlier. * Type-level numerals can be intuitively typed in different bases (although everything is internally represented in base 10) by using aliases: D16 represents the type-level decimal 16 B1010 represents the type-level binary 1010 076 represents the type-level octal 76 HFF represents the type-level hexadecimal FF * All basic arithmetic operations are supported (including logarithm and exponentiation in any base) * The library provides reification of Naturals and Booleans (from value-level to type-level) . To get the code: HackageDB page (including haddock documentation): http://hackage.haskell.org/cgi-bin/hackage-scripts/package/type-level-0.1 Darcs repository: http://code.haskell.org/type-level/ Big Thanks to Oleg and Wolfgang for their suggestions and contributions. Actually, most of the implementation of Naturals is based on Oleg's "Binary Type Arithmetic" http://okmij.org/ftp/Haskell/types.html#binary-arithm

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Haskell Jobs
by Tom Hawkins 27 Feb '08

27 Feb '08

Hi, We have an opening for a software engineer, with the potential for a lot of Haskell development. Our group at Eaton (http://www.eaton.com/) develops real-time control software for vehicle and machinery applications. This position is specifically for the design and verification of hydraulic hybrid vehicle systems. Think Toyota Prius, but with a accumulator and hydraulic pump instead of a battery and an electric motor. That, and these vehicles can weight over 30,000 pounds. The primary tasks would include vehicle software design, system verification with simulation and possibly formal analysis, telemetry development for remote diagnostics, and tool development to further automate our design flows. Currently we use Haskell for our in-house data analysis tools, and some vehicles run code partially generated by a Haskell DSL. We hope to expand our use of Haskell, especially for simulation regression suites -- maybe QuickCheck in combination with a system modeling and verification DSL. If interested, send a resume. Thanks! -Tom

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ANNOUNCE: hsparklines 0.1.0 - A sparklines implementation in Haskell
by Hitesh Jasani 27 Feb '08

27 Feb '08

Sparklines are small, word sized graphs that can be interspersed with text to provide context and enhance communication. There are implementations in many languages and even some web services that will generate them on the fly. I was looking for a Haskell solution and finding none, wrote my own. * http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hsparklines-0.1.0 * http://www.jasani.org/2008/02/initial-release-of-hsparklines-010.html On a side note, while writing my blog entry I decided to generate a sparkline for the number of uploads to hackage. If it's any indication, the Haskell community is growing by leaps and bounds. - Hitesh

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where is module System.Posix.Types?
by Galchin Vasili 27 Feb '08

27 Feb '08

Hello, I don't see the types modules in with the other modules in the Posix pacakage, ?? Thanks, Vasya

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Just a quick question
by Imam Tashdid ul Alam 27 Feb '08

27 Feb '08

A few days back, I *think* I stumbled upon the statement "the interaction between GADTs and functional dependencies is not yet well understood". Then I glossed over it. Now that I have (finally) started understanding what GADTs are meant to do, I am somewhat terrified. Did I read that one correctly? Or was it "... between GADTs and *typeclasses*..."? Was it? Gah. That would be disastrous. ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs

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Re: [Haskell-cafe] fast integer base-2 log function?
by Jens Blanck 27 Feb '08

27 Feb '08

> {-# LANGUAGE MagicHash #-} > import GHC.Exts > import Data.Bits > > -- experiment with using a LUT here (hint: FFI + static arrays in C) > ilog2i0, ilog2i1, ilog2i2, ilog2i3, ilog2i4 :: Int -> Int -> Int > ilog2i0 k x | x .&. 0xFFFF0000 /= 0 = ilog2i1 (k + 16) (x `shiftR` 16) > | otherwise = ilog2i1 k x > ilog2i1 k x | x .&. 0xFF00 /= 0 = ilog2i2 (k + 8) (x `shiftR` 8) > | otherwise = ilog2i2 k x > ilog2i2 k x | x .&. 0xF0 /= 0 = ilog2i3 (k + 4) (x `shiftR` 4) > | otherwise = ilog2i3 k x > ilog2i3 k x | x .&. 0xC /= 0 = ilog2i4 (k + 2) (x `shiftR` 2) > | otherwise = ilog2i4 k x > ilog2i4 k x | x .&. 0x2 /= 0 = k + 1 + (x `shiftR` 1) > | otherwise = k + x > > log2i :: Integer -> Int -- actually returns bit length, and returns > garbage on negatives, but do you care? > log2i (J# len adr) = ilog2i0 0 (I# (indexIntArray# adr (len -# 1#))) + I# > (32# *# (len -# 1#)) > log2i (S# sml) = ilog2i0 0 (I# sml) > > I tried the above but I got wrong results on 2^31..2^32-1 because in the additions in ilog2i4, the number x was -1 because of sign extension performed by the shifts all the way (thanks for the ghci debugger). (So, yes, I do care somewhat about garbage on negatives :) I modified to the following hoping also to use both on 32 and 64 bit machines. Have I shot myself in the foot anyway? For example, is there a guarantee that the most significant limb is non-zero? Is there any possibility of this or some related function being added to Data.Bits? {-# LANGUAGE MagicHash #-} import GHC.Exts import Data.Bits limbSize = bitSize (0 :: Int) ilog2 k x = case limbSize of 64 -> ilog2i0 k (fromIntegral x) 32 -> ilog2i1 k (fromIntegral x) _ -> undefined -- experiment with using a LUT here (hint: FFI + static arrays in C) ilog2i0, ilog2i1, ilog2i2, ilog2i3, ilog2i4, ilog2i5 :: Int -> Word -> Int ilog2i0 k x | x .&. 0xFFFFFFFF00000000 /= 0 = ilog2i1 (k + 32) (x `shiftR` 32) | otherwise = ilog2i1 k x ilog2i1 k x | x .&. 0xFFFF0000 /= 0 = ilog2i2 (k + 16) (x `shiftR` 16) | otherwise = ilog2i2 k x ilog2i2 k x | x .&. 0xFF00 /= 0 = ilog2i3 (k + 8) (x `shiftR` 8) | otherwise = ilog2i3 k x ilog2i3 k x | x .&. 0xF0 /= 0 = ilog2i4 (k + 4) (x `shiftR` 4) | otherwise = ilog2i4 k x ilog2i4 k x | x .&. 0xC /= 0 = ilog2i5 (k + 2) (x `shiftR` 2) | otherwise = ilog2i5 k x ilog2i5 k x | x .&. 0x2 /= 0 = k + 1 + fromIntegral (x `shiftR` 1) | otherwise = k + fromIntegral x log2i :: Integer -> Int -- actually returns bit length log2i (J# len adr) = ilog2 0 (I# (indexIntArray# adr (len -# 1#))) + I# (32# *# (len -# 1#)) log2i (S# sml) = ilog2 0 (I# sml)

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