December 2010 - Haskell-Cafe

ANN: Digestive functors 0.0.2.0
by Jasper Van der Jeugt 10 Dec '10

10 Dec '10

Hello all, I'm very glad to announce the 0.0.2.0 release of the digestive functors library. The library provides a general API to input consumption, and is an upgrade of formlets. I've written an announcing blogpost and tutorial with more information here: http://jaspervdj.be/posts/2010-12-09-digestive-functors-0.0.2.html You can get it on hackage here: http://hackage.haskell.org/package/digestive-functors As always, all feedback is welcome. Kindest regards, Jasper Van der Jeugt

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Haskell and javascript
by jean-christophe mincke 10 Dec '10

10 Dec '10

Hello, I have just discovered WebSharp, a .Net product for web development that allows you to write client code in F# and have it translated into javascript. Does anyone know about somethig similar in Haskell? Thank you Regards J-C

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haskell flickr bindings: "invalid signature" when uploading
by Dougal Stanton 10 Dec '10

10 Dec '10

I've mailed the maintainer of the flickr api package but thought I would see if other people had this experience too. Google doesn't reveal many people using this package as far as I can tell. In short, authentication works fine but uploading images fails with this message. This happens with the included examples/Uploader.hs as well as my own code. toRequest: POST request contains 1 files; unable to represent as query string Defaulting to multiform/form-data instead Flickr error: Code: 96 Type: Flickr API error Details: Invalid signature I haven't had a chance to dive deeper into this yet, but any advice gratefully received. Cheers, D -- Dougal Stanton dougal(a)dougalstanton.net // http://www.dougalstanton.net

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Setting runtime memory limits on GHC programs to avoid thrashing
by John D. Ramsdell 10 Dec '10

10 Dec '10

Enclosed is a simple script that sets GHCRTS and provides a reasonable memory limit on systems that have /proc/meminfo. By default, the GHC runtime will grow to a size that can cause thrashing. John

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Missing Functor instances in GHC 7?
by Sebastian Fischer 10 Dec '10

10 Dec '10

Hello, according to http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Monad.ht… Control.Monad exports 20 Functor instance declarations in base-4.3.0.0. However: bash# ghc-pkg list | grep base base-4.3.0.0 bash# ghci --version The Glorious Glasgow Haskell Compilation System, version 7.0.1 bash# ghci Prelude> import Control.Monad Prelude Control.Monad> :i Functor class Functor f where fmap :: (a -> b) -> f a -> f b (GHC.Base.<$) :: a -> f b -> f a -- Defined in GHC.Base instance Functor Maybe -- Defined in Data.Maybe instance Functor [] -- Defined in GHC.Base instance Functor IO -- Defined in GHC.Base There are only 3 instances instead of 20. Importing Control.Applicative gives 3 more instances but for example the instance for ((->) r) is still missing. Is my installation broken? Or has anybody similar problems finding Functor instances in GHC 7? Sebastian

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ANNOUNCE: mime-mail 0.1.0
by Michael Snoyman 09 Dec '10

09 Dec '10

Hi all (again), I'm happy to announce the second major release of the mime-mail[1] package. mime-mail is a package providing support for rendering multipart emails. This new release introduces: * A partHeaders record, allowing you to place arbitrary headers on individual parts of a message. This is especially useful for ContentID * Support for quoted-printable. There are two new Encoding constructors added: QuotedPrintableText and QuotedPrintableBinary. They differ in how they treat newline characters: the latter outputs CRs and LFs in an escaped form, while the former strips all CRs and outputs LFs as the ASCII codes for "\r\n". * Support for encoded-word for header values. This is a completely transparent change: now if you use non-ASCII characters in your header values, mime-mail will automatically encode appropriately. Enjoy! Michael [1] http://hackage.haskell.org/package/mime-mail

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Re: [Haskell-cafe] [Haskell] ANNOUNCE: genprog-0.1
by Alberto G. Corona 09 Dec '10

09 Dec '10

Hi ;) 2010/12/8 Mitar <mmitar(a)gmail.com> > Hi! > > On Wed, Dec 8, 2010 at 3:39 PM, Alberto G. Corona <agocorona(a)gmail.com> > wrote: > > DNK? I think you mean DNA. > > Sorry. In my native language it is DNK. ;-) > > > the genotype program that develips the fenotype is much more smooth and > > granular than a computer program. A chante un a gen does not make you to > > have a extra bone. It can make you to have your hand slighltly longer. or > > shorter. > > Because we are using very small programs. A change of one constant in > a Linux kernel would also be a very small change in general. Maybe > some esoteric device would not function anymore, but this is it. Of > course there would be also changes which would make whole kernel > dysfunctional. > > Of course there are smooth zones in the fitness landscape of any code. what is necessary is to direct the process by avoiding absurd replacements (mutations that goes straight to dead zones) and rules for changing from a smooth to another smooth area once the local maximum is not satisfactory. Or to detect them as early as possible (that is, rules again). That is what I mentioned before. > > In fact there are metalevels of selection that discard abrupt changes. > For > > example, when females ovulate there are a strong selection where > thounsands > > of candidate cell ovules are tested and discarded. This is one of the > > reasons why anomalous mutations are scarce. > > I doubt that. Aren't female eggs made while she is still a fetus? And > they do not divide anymore later on? > This selection of candidate eggs happens each month within each ovulation period. It is mentioned in this superb conference series by Yale university. It is a very good introduction. I don´t remember the exact chapter. sorry: http://www.youtube.com/watch?v=VjgHd6HKtvE Moreover, the genetic code has evolved to evolve. For many reasons. Neither Haskell nor any conventional language has. One of the safety measures of the genetic code is protectin itself against undesired mutations. This is something vital for life. Cancer is one consequence. but another consequences are more deadly: If a mother spend nine months to produce an unfit child this is a dead end for the mother´s genome line. For this reason, undesired mutations, specially in reproductive cells are either repaired or discarded. This selection is more strong in females than in males (for investment reasons) . The rate of mutations in living beings is equal to the theorical optimum for procariots and eucariouts. This is another examople of how finely tuned the DNA has evolved for evolution. The molecular bonds are strong enough just to permit the right rate of mutation . But the DNA i´m sure, has much more secrets to learn and discover. So in conclusion there are much details to learn and to implement to have sucessful general genetic algorithms for genetic programming. But the research promises a lot of fun.

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Operator #
by c8h10n4o2 09 Dec '10

09 Dec '10

What does # mean in this code ? (from Data.List) findIndices p ls = loop 0# ls where loop _ [] = [] loop n (x:xs) | p x = I# n : loop (n +# 1#) xs | otherwise = loop (n +# 1#) xs -- View this message in context: http://haskell.1045720.n5.nabble.com/Operator-tp3299360p3299360.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Re: [Haskell-cafe] A home-brew iteration-alike library: some extension quiestions
by Permjacov Evgeniy 09 Dec '10

09 Dec '10

-------- Original Message -------- Subject: Re: [Haskell-cafe] A home-brew iteration-alike library: some extension quiestions Date: Thu, 09 Dec 2010 23:07:49 +0300 From: Permjacov Evgeniy <permeakra(a)gmail.com> To: Antoine Latter <aslatter(a)gmail.com> On 12/09/2010 10:54 PM, Antoine Latter wrote: > I only have some surface level questions/comments - > > What existing packages is this similar to? How is it different from > any previous work in the area? > Main idea was taken from Iteratees invented by Oleg Kiselev (there are two packages on hackage implementing this ideas: data-iteraties and enumerator packages) The difference is, that I wished haskell-2010 compilant package for left-foldable streams, including support for easy builing, transcoding, merging and folding of streams relying on do-notation (see Data.Iteration.Unicode.* for examples of transcoding streams: it is quite clean and easily understandable) and ability to specify easily monadic actions in stream processors. > Also, likes looks like you don't need the 'Monad m' constraint on your > various Monad and Functor instances in Data.Iteration.Types, which I > think is one of the nicest properties of the continuation-based > approach to something like this. Errgh. That may be true, but I did not consider non-monadic context at all, so I enforced this constrain mindlessly > It's a mater of taste which way to go, but I prefer importing modules > qualified rather than have type-suffixes on functions - so I would > rather use 'I.next' and 'A.next' instead of 'nextI' and 'nextA'. But > reasonable people can disagree on this. > > Take care, > Antoine Thanks! > On Thu, Dec 9, 2010 at 1:42 PM, Permjacov Evgeniy <permeakra(a)gmail.com> wrote: >> Hi. I Wrote a simple iteration library. It was not intensively tested, >> so it MAY contatin bugs, but it is very unlikely. The library is >> currently on github: https://github.com/permeakra/iteration >> >> I'm not ready to upload it to hackage, as some testing and extension is >> really needed. However, I'd like to know about possible flaws. >> >> Current goal is addition of byte-stream (de)compression and IO functions >> extenstion. After this package will be cabalized and uploaded to >> hackage. So, while design is not frozen yet, I'm interested in criticism -)/ >> >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >>

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Re: [Haskell-cafe] ANN: hledger 0.13
by Simon Michael 09 Dec '10

09 Dec '10

On Dec 9, 2010, at 7:34 AM, Peter Simons wrote: > I can tell it's doing more harm than good. The situation right now is > that it's impossible to install hledger on ArchLinux -- not because Why ? I haven't yet heard why depending on the higher process version is a problem.

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