Re: [Haskell-cafe] Re: excercise - a completely lazy sorting algorithm
Interesting. Can you make the definition of quicksort non-recursive, too? Perhaps with help of a bootstrapping combinator like the one implicit in the approach I have given earlier? treeSort = bootstrap partitionOnMedian bootstrap f = Fix . helper . f where helper = fmap (Fix . helper . f) partitionOnMedian :: forall a. (Ord a) = (S.Seq a) - BTreeRaw a (S.Seq a) Extra points if you can give 'bootstrap' or an equivalent in terms of existing Haskell combinators. Matthias. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: excercise - a completely lazy sorting algorithm
Matthias Görgens wrote:
Interesting. Can you make the definition of quicksort non-recursive,
too? Perhaps with help of a bootstrapping combinator like the one
implicit in the approach I have given earlier?
treeSort = bootstrap partitionOnMedian
bootstrap f = Fix . helper . f
where helper = fmap (Fix . helper . f)
partitionOnMedian :: forall a. (Ord a) = (S.Seq a) - BTreeRaw a (S.Seq a)
Extra points if you can give 'bootstrap' or an equivalent in terms of
existing Haskell combinators.
Sure, no problem.
Of course, some part of algorithm has to be recursive, but this can be
outsourced to a general recursion scheme, like the hylomorphism
hylo :: Functor f = (a - f a) - (f b - b) - (a - b)
hylo f g = g . fmap (hylo f g) . f
This scheme is a combination of the anamorphism which builds the tree of
recursive calls
data Fix f = In { out :: f (Fix f) }
ana :: Functor f = (a - f a) - a - Fix f
ana f = In . fmap (ana f) . f
and a catamorphism which combines the results
cata :: Functor f = (f b - b) - Fix f - b
cata g = g . fmap (cata g) . out
so we could also write
hylo f g = cata g . ana f
For quicksort, the call tree is the fixed point of the functor
type Size= Int
data Q a b = Empty | Merge Size a b b
instance Functor (Q a) where
fmap f (Merge n x b b') = Merge n x (f b) (f b')
fmap f Empty= Empty
The algorithm
quicksort = hylo partition merge
proceeds in the two well-known phases: first, the input list is
partitioned into two parts separated by a pivot
partition [] = Empty
partition (x:xs) = Merge (length xs + 1) x ls xs
where
ls = filter (= x) xs
rs = filter ( x) xs
and then the sorted results are merged
merge Empty = []
merge (Merge _ x a b) = a ++ [x] ++ b
The random access tree implementation can be obtained by using a
different merge function. In particular, the quicksort from my
previous post was parametrized on merge (with a slightly different way
to indicate the list lengths); any function of type
(Size - a - b - b - b) - b - c
is equivalent to a function of type
(Q a b - b) - c
Incidentally, the random access tree *is* the call tree for quicksort,
so we'd have
merge = In
and we can shorten the whole thing to
quicksort = ana partition
which is essentially what you coded.
To read about hylo f g = cata g . ana f with quicksort as example
again in a slightly different light, see also the following blog post by
Ulisses Costa
http://ulissesaraujo.wordpress.com/2009/04/09/hylomorphisms-in-haskell/
Regards,
apfelmus
--
http://apfelmus.nfshost.com
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Re: [Haskell-cafe] ANN: hsparql, a SPARQL query generator/DSL and client
Excerpts from Jeff Wheeler's message of Thu Jul 09 00:27:51 +0200 2009: I'm excited to announce the first version of hsparql. HSparql makes it easy to query SPARQL-compliant servers using a relatively intuitive DSL and very simple client. I've looked at your DSL and it looks really neat. While reading I was wondering if GADTs could help having an even nicer query language. -- Nicolas Pouillard http://nicolaspouillard.fr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: excercise - a completely lazy sorting algorithm
Thanks. I heard about the hylo-, ana- and catamorphisms before, but never explicitly used them. Time to get started. And yet another question: One can get the median in deterministic linear time. For quicksort choosing the median as pivot keeps the O(n log n) average running time and brings down the expected worst case, too. Do you know of a (natural) way to combine selecting the median and doing the quicksort, so that you don't compare unnecessarily? The way to de-randomize quickselect is to calculate medians of medians. I.e. solve the problem for smaller instances first. I suspect if we follow this strategy with the reified quicksort call-trees, the de-randomized quicksort will look a lot like mergesort. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Where can I get GHC for Solaris?
On Jul 8, 2009, at 03:32 , John Ky wrote: | /export/home/a-m/joky/ghc-6.8.2/utils/ghc-pkg/ghc-pkg.bin --global-conf /export/home/a-m/joky/.tools/ghc-6.8.2/lib/ghc-6.8.2/ package.conf update - --force ld.so.1: ghc-pkg.bin: fatal: libm.so.2: version `SUNW_1.2' not found (required by file /export/home/a-m/joky/ghc-6.8.2/utils/ghc-pkg/ghc-pkg.bin) ld.so.1: ghc-pkg.bin: fatal: libm.so.2: open failed: No such file or directory gmake isn't the problem here. The problem was that the binary was built on a system with the C99 patches installed (ghc pretty much requires them) but there aren't that many Solaris 9 systems with the C99 patches and the patches themselves seem to be impossible to find. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Hayoo! beta 0.4
Timo B. Hübel wrote: Visit Hayoo! here: http://holumbus.fh-wedel.de/hayoo Additionally, we have again updated the search index. It contains all packages from Hackage as well as gtk2hs as of 06.07.2009, a total of 111.946 function and type definitions. Is it possible that coverage has decreased in some areas? I am pretty sure that a week ago or so I could use Hayoo to find sumP :: Num a = [:a:] - a from GHC.PArr. Now, that result does not turn up anymore. Ciao, Janis. -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:vo...@tcs.inf.tu-dresden.de ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: darcs 2.3 beta 2
Hello! Two weeks passed and it is about time to release darcs 2.3 beta 2 (it's already a day late, sorry about that). As with beta 1, there is only a single installation package for this release of darcs: cabalised source. (Please note that the final version with also come with the legacy autoconf-based buildsystem, for the last time.) You can either download a tarball from http://repos.mornfall.net/darcs/darcs-2.2.98.2.tar.gz and build manually (see the build instructions in README inside the tarball), or, alternatively, you can use cabal-install to obtain a copy (the beta release is now available on Hackage): $ cabal update $ cabal install darcs-beta This, if successful, will give you a darcs binary in `~/.cabal/bin` -- you should probably add that to your PATH. What's new since beta 1 --- There are basically two relatively intrusive changes since beta 1. First, I have added index upgrade functionality to hashed-storage and this is now used by darcs, so that any bad or incompatible indexes are recreated transparently by darcs. Moreover, the index format is now architecture-independent, meaning that repositories shared across multiple architectures should not suffer from excessive index rebuilding. Second, Ganesh has done further work on his gzip CRC correction code. There is a very slight risk of regressions, so if you have around any repositories with broken CRCs in them, please test this functionality. Moreover, there is now an option to limit the repair to current repository, avoiding changes in related branches or caches. Trent, Thorkil and Eric have done cleanup work and a number of minor fixes for this release, improving overall quality and polish. One bug in the new indexing code has been found and reported by Eric and Guillaume independently, and is fixed in hashed-storage 0.3.4 (which required by this beta). You can track the release plan and progress at our wiki: http://wiki.darcs.net/development. The question of GHC 6.8 --- Using GHC 6.10.3 or newer is *strongly recommended*. You may compile darcs with GHC 6.8, but there are several caveats. If you are using 6.8.2 or older, please disable mmap support (pass -f-mmap to cabal install or runghc Setup configure below). Note that the GHC 6.8.2 that ships with Debian Lenny is not affected and it should be safe to keep mmap enabled. It is also recommended to disable use of Hackage zlib when compiling with GHC 6.8.2 (including the Debian Lenny version): pass -f-zlib to cabal. When using zlib, we have seen occasional crashes with error messages like openBinaryFile: file locked -- this is a known GHC 6.8.2 bug (and is fixed in GHC 6.8.3). Last, if you are using a 64-bit system, darcs may hang when you exit a pager when compiled with GHC older than 6.10.3. Although this is harmless, it is quite inconvenient. Overall, the status of GHC 6.8 is semi-supported: for many cases, things will work just fine, especially if you take a little extra caution with compilation flags. Yours, Petr. -- Petr Ročkai | http://web.mornfall.net A physicist is an atom's way of knowing about atoms. (George Wald) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Laziness enhances composability: an example
Hi, I'm wondering what a good example of why laziness enhances composability would be. I'm specifically looking for something that can't implemented in Python with iterators (at least not elegantly), but can actually be implemented in Haskell. Thanks, Cristiano ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness enhances composability: an example
Hello, A wonderful, and practical example, is the techniques in this modular lazy search paper: http://web.cecs.pdx.edu/~apt/jfp01.ps They build simple solvers, like backtracking, backjumping, etc. and then compose them together like: bt . bj The techniques are very much based on laziness. - jeremy At Thu, 9 Jul 2009 14:55:09 +0200, Cristiano Paris wrote: [1 multipart/alternative (7bit)] [1.1 text/plain; ISO-8859-1 (7bit)] Hi, I'm wondering what a good example of why laziness enhances composability would be. I'm specifically looking for something that can't implemented in Python with iterators (at least not elegantly), but can actually be implemented in Haskell. Thanks, Cristiano [1.2 text/html; ISO-8859-1 (quoted-printable)] [2 text/plain; us-ascii (7bit)] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness enhances composability: an example
On 9 Jul 2009, at 14:55, Cristiano Paris wrote: Hi, I'm wondering what a good example of why laziness enhances composability would be. I'm specifically looking for something that can't implemented in Python with iterators (at least not elegantly), but can actually be implemented in Haskell. Pretty much anything that uses tying the knot is very difficult to implement in a non-lazy language without a lot of indirection. Bob ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness enhances composability: an example
Thank you for your suggestions! C. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Alternative IO
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance Alternative IO where
empty = undefined
x | y = handle (\ (_ :: SomeException) - y) x
This would allow to write IO code which failsafes to a value if the previous
computation failed, i.e.:
*Main Control.Applicative undefined | print Hello
Hello
*Main Control.Applicative print Hello | undefined
Hello
It seems a neat way to catch exception in some scenarios. What do you think?
Why is not Alternative IO defined in Control.Applicative?
Thanks,
Cristiano
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Re: [Haskell-cafe] Laziness enhances composability: an example
Hello Cristiano, Thursday, July 9, 2009, 4:55:09 PM, you wrote: the best known example is chessmate implementation in Wadler's why functional programming matter but i don't know much about Python iterators, so can't say what is difference. may be its' only simplicity since lazy lists is looks like and processed just as lists while generators in any other language is separate data structure Hi, I'm wondering what a good example of why laziness enhances composability would be. I'm specifically looking for something that can't implemented in Python with iterators (at least not elegantly), but can actually be implemented in Haskell. Thanks, Cristiano -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Leaner Haskell.org frontpage
Hi, i find the current www.haskell.org frontpage quite overwhelming. Compare it for example with the home pages of other programming languages : http://caml.inria.fr/ http://factorcode.org/ http://sbcl.sourceforge.net/ http://www.ruby-lang.org/en/ http://www.falconpl.org/ Here is my sketch of a leaner, more structured Haskell front page: http://www.haskell.org/haskellwiki/User:Lenny222/Haskell Comments? Bye, Lenny ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Alternative IO
On Thu, 9 Jul 2009, Cristiano Paris wrote:
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance Alternative IO where
empty = undefined
x | y = handle (\ (_ :: SomeException) - y) x
This would allow to write IO code which failsafes to a value if the previous
computation failed, i.e.:
*Main Control.Applicative undefined | print Hello
Hello
*Main Control.Applicative print Hello | undefined
Hello
It seems a neat way to catch exception in some scenarios. What do you think?
Why is not Alternative IO defined in Control.Applicative?
I just say, what I always say. :-) 'error' denotes a programming error and
catching it is a hack, sometimes needed but less often than you think.
For exceptions one must use 'throw'. Thus, you may e.g. define
empty = throw ...___
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Re: [Haskell-cafe] Alternative IO
On Thu, Jul 9, 2009 at 3:42 PM, Edward Kmett ekm...@gmail.com wrote: Hrmm. This should probably be made consistent with the MonadPlus instance for IO, so empty = ioError (userError mzero) I agree. Of course, that was only a first attempt :) Cristiano ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness enhances composability: an example
On Thu, Jul 9, 2009 at 3:42 PM, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello Cristiano, Thursday, July 9, 2009, 4:55:09 PM, you wrote: the best known example is chessmate implementation in Wadler's why functional programming matter but i don't know much about Python iterators, so can't say what is difference. may be its' only simplicity since lazy lists is looks like and processed just as lists while generators in any other language is separate data structure Thanks. In fact, I was stuck trying to find an example which couldn't be written using Python's iterators. The only difference coming up to my mind was that Haskell's lists are a more natural way to express a program relying on laziness. That was the reason why added the clause at least not elegantly in my first post. Cristiano ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
2009/7/9 hask...@kudling.de: Hi, i find the current www.haskell.org frontpage quite overwhelming. Compare it for example with the home pages of other programming languages : http://caml.inria.fr/ http://factorcode.org/ http://sbcl.sourceforge.net/ http://www.ruby-lang.org/en/ http://www.falconpl.org/ Here is my sketch of a leaner, more structured Haskell front page: http://www.haskell.org/haskellwiki/User:Lenny222/Haskell Comments? My favorite in all these is haskell.org :) I find it very to the point and not overwhelming at all : it's easy to glance over it and find quickly what I want. In fact, the homepage reflects well the language and its community: effective, useful, healthy and joyful. Cheers, Thu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness enhances composability: an example
Bulat Ziganshin wrote: Hello Cristiano, Thursday, July 9, 2009, 4:55:09 PM, you wrote: the best known example is chessmate implementation in Wadler's why functional programming matter Aeh, ... Wadler's - Hughes' -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:vo...@tcs.inf.tu-dresden.de ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Removing polymorphism from type classes (viz. Functor)
Well, you're going to wind up with a lot of cases where you really want a quantified context, even with just your Functor definition, but in that same spirit you can build an 'Applicative-like' instance as well. type family Arg f :: * type instance Arg [a - b] = [a] type family Result f :: * type instance Result [a - b] = [b] class Pointed f = Applicative f where (*) :: f - Arg f - Result f instance Applicative [a - b] where fs * xs = do f - fs; map f The thing is these definitions are very hard to actually use. I have a similar construction for Foldable/Traversable-like containers in the 'monoids' package as Data.Generator that you might want to look at for ideas. -Edward Kmett On Tue, Jul 7, 2009 at 7:03 PM, George Pollard por...@porg.es wrote: Ok, so I have a small idea I'm trying to work on; call it a Prelude-rewrite if you want. For this I want to be able to have the hierarchy Functor → Applicative → Monad. For Functor, I would like to be able to implement it for a wider variety of types, as there are types which have aren't polymorphic which would also benefit from having an instance. My running example for this set of types is ByteString; the module contains the method: map ∷ (Word8 → Word8) → ByteString → ByteString However, we cannot use this for Functor because ByteString isn't polymorphic. To get around this, I devised the following: Introduce a type family which represents ‘points’ inside the type: type family Point f ∷ ★ For ByteString we have: type instance Point ByteString = Word8 For a polymorphic example (lists) we have: type instance Point [a] = a Now Functor becomes: class SimpleFunctor f where fmap ∷ (Point f → Point f) → (f → f) However, this doesn't allow for the existence of functions with the type (a → b). I need to introduce another type into the class: class Functor f g where fmap ∷ (Point f → Point g) → (f → g) But having two types isn't very nice (for one thing we can't introduce a fundep because for lists as it fails one of the coverage conditions), so introduce another type family to represent types which can be produced by giving a free variable: type Subst f a ∷ ★ type Subst [a] b = [b] type Subst ByteString b = ByteString class Functor f where fmap ∷ (Point f → Point (Subst f a)) → (f → Subst f a) I'm not sure how much of a hack this is, or if there is a better way. It seems to be OK... Now I want to implement Applicative. It would make sense to have ‘return’ be split out into a separate class, because this can be restricted in a similar way to Functor: class Pointed f where return ∷ Point f → f instance Pointed [a] where return x = [x] instance Pointed ByteString where return = BS.singleton Now, I want to be able to restrict Applicative to things which have [Pointed f, and forall a b. Point f ~ (a → b)]. At the moment I can't figure this out because I believe it would require something like the ‘quantified contexts’ proposal: class (Pointed f, ∀ a b. Point f ~ (a → b)) ⇒ Applicative f where ... I could have something like: class (Pointed f, Point f ~ (a → b)) ⇒ Applicative f a b where apply ∷ f → Subst f a → Subst f b This is still not very nice, because it requires two more type variables in the class, and the non-type-families version is far more straightforward... in fact, it makes sense for the Applicative class to have a polymorphic type because it must be able to have ‘return’ applied to arbitrary functions (remember [fmap f xs ≡ return f `apply` xs]). So back to: class Applicative f where apply ∷ f (a → b) → f a → f b But then ‘return’ cannot be added via a superclass restriction to Pointed! I seem to have painted myself into a corner. Does anyone see a better way to go about this? Thanks, - George ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Alternative IO
Hrmm. This should probably be made consistent with the MonadPlus instance
for IO, so
empty = ioError (userError mzero)
Otherwse, I'm surprised this isn't already in the standard library.
I'd suggest submitting it to librar...@.
-Edward Kmett
On Thu, Jul 9, 2009 at 9:27 AM, Cristiano Paris
cristiano.pa...@gmail.comwrote:
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance Alternative IO where
empty = undefined
x | y = handle (\ (_ :: SomeException) - y) x
This would allow to write IO code which failsafes to a value if the
previous computation failed, i.e.:
*Main Control.Applicative undefined | print Hello
Hello
*Main Control.Applicative print Hello | undefined
Hello
It seems a neat way to catch exception in some scenarios. What do you
think? Why is not Alternative IO defined in Control.Applicative?
Thanks,
Cristiano
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Re: [Haskell-cafe] Alternative IO
To be honest -- that seems rather nice. Can has in Hackage?
Bob
On 9 Jul 2009, at 15:27, Cristiano Paris wrote:
As a joke, I wrote an instance of Alternative for IO actions:
{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Control.Applicative
import Control.Exception
instance Alternative IO where
empty = undefined
x | y = handle (\ (_ :: SomeException) - y) x
This would allow to write IO code which failsafes to a value if the
previous computation failed, i.e.:
*Main Control.Applicative undefined | print Hello
Hello
*Main Control.Applicative print Hello | undefined
Hello
It seems a neat way to catch exception in some scenarios. What do
you think? Why is not Alternative IO defined in Control.Applicative?
Thanks,
Cristiano
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Re: [Haskell-cafe] Leaner Haskell.org frontpage
Hello haskell, Thursday, July 9, 2009, 5:54:16 PM, you wrote: i find the current www.haskell.org frontpage quite overwhelming. it's rather frequent topic here :) Here is my sketch of a leaner, more structured Haskell front page: http://www.haskell.org/haskellwiki/User:Lenny222/Haskell i like your design. i believe that homepage is used primarily by first-time users and here they will find all they need to understand haskell and start to use it -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] iteratee enumHandle
I'm testing iteratee. This is the possible bug I've found import Data.Iteratee.IO import Data.Iteratee.Base import Data.Iteratee.Char import System.IO import Control.Exception main = do h - openFile mamma23 ReadWriteMode hPutStrLn h ciao hSeek h AbsoluteSeek 0 l - (enumHandle h stream2list :: IO (Iteratee IO String)) = run print $ assert (l == ciao) () assertion failed This aside, I'd like to know if there is a way to use parsec library to make an Iteratee, so if it's possible to make parsec spit out a continuation on EOF, or maybe as in delcont language to capture it. thanks paolino ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] About return type
_ Messenger安全保护中心，免费修复系统漏洞，保护Messenger安全！ http://im.live.cn/safe/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
I find it very to the point and not overwhelming at all : it's easy to glance over it and find quickly what I want. Thanks for your feedback. Most people feel overwhelmed when confronted with more than 7+-2 items: http://www.smashingmagazine.com/2007/10/09/30-usability-issues-to-be-aware-of/ On the current Haskell frontpage there are over 60 links competing for attention. I am not sure whether we should design interfaces solely with few people having exceptional abilities in mind. This could be understood as a statement about who Haskell is made for in itself. Bye, Lenny ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] About the return type
I have trouble in returning a list of Figures. I want return a type of m (Maybe [Figure IO]), but the type of dv_findFigure is :: a - Point - s (Maybe (Figure s)). How can change the code below to get a s (Maybe [Figure s])? Thank you in advance! dv_findFigure :: a - Point - s (Maybe (Figures)) fig_contains :: fig - Point - m Bool anc :: Point do fs - dv_getSelFigs dv fs' - filterM (`fig_contains` anc) fs f - case fs' of [] - dv_findFigure dv anc fig : _ - return $ Just fig case f of Just f' - tool_dragtrack self f' Nothing - dv_clearSel dv tool_areatrack self Couldn't match expected type `Figure m' against inferred type `[Figure IO]' Expected type: m (Maybe (Figure m)) Inferred type: m (Maybe [Figure IO]) In the expression: return $ Just fs In a case alternative: fig : _ - return $ Just fs ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
hask...@kudling.de wrote: Most people feel overwhelmed when confronted with more than 7+-2 items: http://www.smashingmagazine.com/2007/10/09/30-usability-issues-to-be-aware-of/ This refers to the number of items/things people can remember in their short-time memory. This has nothing to do with the maximum number of menu items you should use. There is of course a limit, but there is no reason to limit it to 7+-2. Cheers, -- Jochem Berndsen | joc...@functor.nl GPG: 0xE6FABFAB ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
2009/7/9 hask...@kudling.de: I find it very to the point and not overwhelming at all : it's easy to glance over it and find quickly what I want. Thanks for your feedback. Most people feel overwhelmed when confronted with more than 7+-2 items: http://www.smashingmagazine.com/2007/10/09/30-usability-issues-to-be-aware-of/ On the current Haskell frontpage there are over 60 links competing for attention. I am not sure whether we should design interfaces solely with few people having exceptional abilities in mind. This could be understood as a statement about who Haskell is made for in itself. Well, I guess there is room for personnal preference... But I don't find correct to say 60 links competing for attention. You forget to mention the section titles and the separation in two columns. You could have said more than 600 words competing for attention... I can understand people find it overwhelming, but only *at first sight*. I would make the comparison with a table of content for a book. I've seen book providing a chapters at a glance part, just before the real table of content. Glancing a few pages to see the chapter names (that is not paying attention to the sections and subsections) is not very more complicated. For the hompage we're talking about, glancing is even simpler since everything is on the same page and you can scroll it quite easily. I'm not sure hiding a level of the hierarchy of information behind a few clicks make things easier. Please don't be upset by my opinion, it's just that; I've no will to enforce it to anybody :) Cheers, Thu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
I've seen book providing a chapters at a glance part, just before the real table of content. Such an inverted pyramid is exactly the consequence Nielson draw from the F shape pattern (http://www.useit.com/alertbox/reading_pattern.html). And that's my critque: i don't see the most important things there are to be sayed about Haskell in the top left corner. For the hompage we're talking about, glancing is even simpler since everything is on the same page and you can scroll it quite easily. I don't agree that everything on one page makes comprehension easier. I'm not sure hiding a level of the hierarchy of information behind a few clicks make things easier. That depends on which task we are talking about: - getting an overview of all available information, or - finding exactly what you are looking for I think we should optimize for the latter, where What is Haskell? being the most improtant question. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
I never said we should only expose 7 links. Take for example the task Find out more about this Haskell i heared about. You would need to scan the right half of the front page and you need to scan the left part of the page. There you need to scan About, it could be explained under Why use Haskell? or Language definition or Haskell in 5 steps or Learning Haskell or Wiki articles or Blog articles and news. Where should i look? I have to scan a lot of text, i have to keep a lot of options in mind and for my taste the load is too much. Be my limit 7 or 20 links. hask...@kudling.de wrote: Most people feel overwhelmed when confronted with more than 7+-2 items: http://www.smashingmagazine.com/2007/10/09/30-usability-issues-to-be-aware-of/ This refers to the number of items/things people can remember in their short-time memory. This has nothing to do with the maximum number of menu items you should use. There is of course a limit, but there is no reason to limit it to 7+-2. Cheers, -- Jochem Berndsen | joc...@functor.nl GPG: 0xE6FABFAB ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
Are there any kind of hard statistics and analytics that we can base this discussion upon? There is always room for improvement, but stumbling around in the dark making blind guesses may not be the best way to go. Although I personally feel that Lenny's proposed page is an improvement, statistics could tell us what actual people actually use the site for. I don't see any tracking code in the page source. Maybe the site admins could install Google Analytics? It's free, easy to install and use, and very informative. (Or some other usage tracker; I merely suggested GA because I use it and know that it works well.) Thomas On Thu, Jul 9, 2009 at 17:53, hask...@kudling.de wrote: I never said we should only expose 7 links. Take for example the task Find out more about this Haskell i heared about. You would need to scan the right half of the front page and you need to scan the left part of the page. There you need to scan About, it could be explained under Why use Haskell? or Language definition or Haskell in 5 steps or Learning Haskell or Wiki articles or Blog articles and news. Where should i look? I have to scan a lot of text, i have to keep a lot of options in mind and for my taste the load is too much. Be my limit 7 or 20 links. hask...@kudling.de wrote: Most people feel overwhelmed when confronted with more than 7+-2 items: http://www.smashingmagazine.com/2007/10/09/30-usability-issues-to-be-aware-of/ This refers to the number of items/things people can remember in their short-time memory. This has nothing to do with the maximum number of menu items you should use. There is of course a limit, but there is no reason to limit it to 7+-2. Cheers, -- Jochem Berndsen | joc...@functor.nl GPG: 0xE6FABFAB ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
ttencate: Are there any kind of hard statistics and analytics that we can base this discussion upon? There is always room for improvement, but stumbling around in the dark making blind guesses may not be the best way to go. Although I personally feel that Lenny's proposed page is an improvement, statistics could tell us what actual people actually use the site for. FWIW, the current layout is actually based on previous analysis of Popular Pages a few years ago, so that we have O(1) access to key resources. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: hsparql, a SPARQL query generator/DSL and client
On Thu, Jul 9, 2009 at 4:34 AM, Nicolas Pouillardnicolas.pouill...@gmail.com wrote: I've looked at your DSL and it looks really neat. While reading I was wondering if GADTs could help having an even nicer query language. To be honest, I really only know the name GADT, I don't really know anything about them. I guess I have a good excuse to go learn them, though, now. :) Jeff Wheeler ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
2009/7/9 Don Stewart d...@galois.com: ttencate: Are there any kind of hard statistics and analytics that we can base this discussion upon? There is always room for improvement, but stumbling around in the dark making blind guesses may not be the best way to go. Although I personally feel that Lenny's proposed page is an improvement, statistics could tell us what actual people actually use the site for. FWIW, the current layout is actually based on previous analysis of Popular Pages a few years ago, so that we have O(1) access to key resources. Wonderful ! Do you mean that if we put every links from haddock on the homepage, we'd have O(1) access to any piece of documentation ? haskell.org is the neatest data structure of functional programming ! Thu ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
I think it would be best if the page were targeted towards newcomers, and not as a jump point for resources. Such a jump page is useful, but not as a homepage. Perhaps haskell.org/linkswould be a better place for such a thing. As an aside, in the current homepage, the Haskell description is outweighed by the link menu on the left. IMO the reader's eyes should move from the title, to the description, then either down or left. Currently my attention is split evenly between the link menu and the title/description, which results in confusion. On Thu, Jul 9, 2009 at 12:33 PM, Don Stewart d...@galois.com wrote: ttencate: Are there any kind of hard statistics and analytics that we can base this discussion upon? There is always room for improvement, but stumbling around in the dark making blind guesses may not be the best way to go. Although I personally feel that Lenny's proposed page is an improvement, statistics could tell us what actual people actually use the site for. FWIW, the current layout is actually based on previous analysis of Popular Pages a few years ago, so that we have O(1) access to key resources. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge. - Daniel J. Boorstin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
ttencate: On Thu, Jul 9, 2009 at 18:33, Don Stewartd...@galois.com wrote: ttencate: Are there any kind of hard statistics and analytics that we can base this discussion upon? There is always room for improvement, but stumbling around in the dark making blind guesses may not be the best way to go. Although I personally feel that Lenny's proposed page is an improvement, statistics could tell us what actual people actually use the site for. Thanks Don, I should have thought of that. It's a start! No matter what we decide, I'd like to advocate for maintaining the RSS feed of Hackage uploads on the front page -- this is what makes the page seem alive and active, and was introduced in response to John Hughes complaining the page was always out of date. (Similar to the Arch Linux package updates: http://www.archlinux.org/) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Leaner Haskell.org frontpage
Hello Don, Thursday, July 9, 2009, 8:33:17 PM, you wrote: FWIW, the current layout is actually based on previous analysis of Popular Pages a few years ago, so that we have O(1) access to key resources. yes, and it means that page is optimized for regular Haskell users what is proposed, though, is to optimize it for newcomers so they will find their way to Haskell so first we need to decide what category of users homepage should be optimized for. who can set up poll? -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
By the way, the most valuable pixels, right at the top of the page, are wasted on wiki stuff. Compare http://www.haskell.org/ with, for example, http://www.ruby-lang.org/ http://python.org/ If, like the consensus seems to be, the page should be made more friendly to beginners (who are unlikely to want to contribute to the wiki right away), then this should be moved elsewhere, or at the very least made smaller and less obtrusive. Thomas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
bulat.ziganshin: Hello Don, Thursday, July 9, 2009, 8:33:17 PM, you wrote: FWIW, the current layout is actually based on previous analysis of Popular Pages a few years ago, so that we have O(1) access to key resources. yes, and it means that page is optimized for regular Haskell users what is proposed, though, is to optimize it for newcomers so they will find their way to Haskell so first we need to decide what category of users homepage should be optimized for. who can set up poll? Perhaps a newbie page can be designed separately first, and hosted concurrently. Then we can offer both: Newbies: http://haskell.org Everything regular users need at fingertips http://dashboard.haskell.org/ A newbie porthole is a great idea. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Leaner Haskell.org frontpage
Hello Don, Thursday, July 9, 2009, 8:58:48 PM, you wrote: Newbies: http://haskell.org Everything regular users need at fingertips http://dashboard.haskell.org/ yes, my vision is that newbies will go to homepage, from google search or by typing haskell.org. we cannot expect that they will search for some special newbie page while amateurs have more chances to know about their special page. actually, we probably need to provide link to O(1) page at homepage. btw, it's rather close to sitemap page provided at some sites -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
On Thu, Jul 9, 2009 at 10:00 AM, Thomas ten Cate ttenc...@gmail.com wrote: By the way, the most valuable pixels, right at the top of the page, are wasted on wiki stuff. Compare http://www.haskell.org/ with, for example, http://www.ruby-lang.org/ http://python.org/ The thing I like the most from the ruby page is the top box of content where it starts describing ruby with a Read more... link adjacent to a code snippet. Because I doubt anyone will agree on *the one* best code snippet to show people, I think there should/could be a pool of fun snippets and loading the page picks one at random. I have no idea if the wiki engine supports this. I also like the strip of links at the top with things like, Download, Community, and so on. Something I think the Haskell page does much better than the other two, is the listing of events and hackage updates. Both of those sections feel inviting to me. It makes me curious and I want to explore. The python page looks at least as cluttered as the haskell page. Neither the haskell page or the python page have the same look and feel of the ruby page. I think the shaded/gradient backgrounds actually add a lot to the visual experience. I also like that the boxes have a different bg color for the box title and the box contents. I also like the use of icons on the ruby page. The Download Ruby link/box with the download icon is very inviting. I just want to download it, even if I'm not going to use ruby! Perhaps we could have a contest similar to the logo contest but for homepage asthetics redesign. I think the content on the haskell page is great, but the visual style of the presentation could be improved considerably. If, like the consensus seems to be, the page should be made more friendly to beginners (who are unlikely to want to contribute to the wiki right away), then this should be moved elsewhere, or at the very least made smaller and less obtrusive. Optimizing for newcomers seems wise. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness enhances composability: an example
On Thursday 09 July 2009, Cristiano Paris wrote: Thanks. In fact, I was stuck trying to find an example which couldn't be written using Python's iterators. The only difference coming up to my mind was that Haskell's lists are a more natural way to express a program relying on laziness. That was the reason why added the clause at least not elegantly in my first post. Hi, I recently tried writing some code to simulate a certain protocol in Python. I thought I'll go the smart way and rely on the Python yield construct to do a CPS transformation of my code. While this worked to a certain extent, composability was a problem, because any sub-procedure which used yield (and thus was an iterator) required being called in a rather inelegant way. Thanks! Marcin Kosiba signature.asc Description: This is a digitally signed message part. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] c2hs confusion with a simple function
The c2hs documentation at
http://www.cse.unsw.edu.au/~chak/haskell/c2hs/docu/implementing.html#id314947
gives me an example to follow for this case:
{#fun notebook_query_tab_label_packing as ^
`(NotebookClass nb, WidgetClass cld)' =
{notebook `nb',
widget `cld' ,
alloca- `Bool' peekBool*,
alloca- `Bool' peekBool*,
alloca- `PackType' peekEnum*} - `()'#}
so I took the original C binding:
void SHPGetInfo(SHPHandle, int*, int*, double*, double*)
And wrote a c2hs binding:
{#fun SHPGetInfo as getInfo
{ fromSHPHandle `SHPHandle'
, alloca- `Int'
, alloca- `Int'
, alloca- `Double'
, alloca- `Double'
} - `()' #}
The error I get:
Internal.chs:85:2:
Couldn't match expected type `Int'
against inferred type `(Ptr b - IO c) - IO c'
Expected type: IO (Int, Int, Double, Double)
Inferred type: IO
((Ptr b - IO c) - IO c,
(Ptr b1 - IO c1) - IO c1,
(Ptr b2 - IO c2) - IO c2,
(Ptr b3 - IO c3) - IO c3)
In the expression:
alloca $ \ a2' - alloca $ \ a3' - alloca $ \ a4' - ...
In the expression:
let a1' = fromSHPHandle a1
in alloca $ \ a2' - alloca $ \ a3' - alloca $ ...
I've tried ending it with withCIntConv and withCFloatConv to no avail.
The original c2hs file is attached. I'm sure there are many more
problems, but this is the one I'm working on at the moemnt...
-- Jeff
Internal.chs
Description: Binary data
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Re: [Haskell-cafe] Laziness enhances composability: an example
On Thursday 09 July 2009, you wrote: 2009/7/9 Marcin Kosiba marcin.kos...@gmail.com: I thought I'll go the smart way and rely on the Python yield construct to do a CPS transformation of my code. While this worked to a certain extent, composability was a problem, because any sub-procedure which used yield (and thus was an iterator) required being called in a rather inelegant way. i confess to not understanding the inelegance. can you provide an example where an iterator inside CPS requires special support? Hi, To illustrate what I meant I'm attaching two examples. In example_1.py I've written code the way I think would be elegant (but it doesn't work). In example_2.py I've written code so that it works, but it isn't elegant. I know I'm abusing Python iterators here. Also, I'm not sure the way to compose iterators shown in example_2.py is the only option. Actually I'd love to see a better solution, because it would remove a lot of bloat from my code ;) Thanks! Marcin Kosiba example_1.py Description: application/python example_2.py Description: application/python signature.asc Description: This is a digitally signed message part. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
On Thu, Jul 9, 2009 at 3:11 PM, Derek Elkins derek.a.elk...@gmail.comwrote: On Thu, Jul 9, 2009 at 12:31 PM, Jason Dagitda...@codersbase.com wrote: On Thu, Jul 9, 2009 at 10:00 AM, Thomas ten Cate ttenc...@gmail.com wrote: By the way, the most valuable pixels, right at the top of the page, are wasted on wiki stuff. Compare http://www.haskell.org/ with, for example, http://www.ruby-lang.org/ http://python.org/ The thing I like the most from the ruby page is the top box of content where it starts describing ruby with a Read more... link adjacent to a code snippet. Because I doubt anyone will agree on *the one* best code snippet to show people, I think there should/could be a pool of fun snippets and loading the page picks one at random. I have no idea if the wiki engine supports this. I also like the strip of links at the top with things like, Download, Community, and so on. Something I think the Haskell page does much better than the other two, is the listing of events and hackage updates. Both of those sections feel inviting to me. It makes me curious and I want to explore. The python page looks at least as cluttered as the haskell page. Neither the haskell page or the python page have the same look and feel of the ruby page. I think the shaded/gradient backgrounds actually add a lot to the visual experience. I also like that the boxes have a different bg color for the box title and the box contents. I also like the use of icons on the ruby page. The Download Ruby link/box with the download icon is very inviting. I just want to download it, even if I'm not going to use ruby! Perhaps we could have a contest similar to the logo contest but for homepage asthetics redesign. I think the content on the haskell page is great, but the visual style of the presentation could be improved considerably. If, like the consensus seems to be, the page should be made more friendly to beginners (who are unlikely to want to contribute to the wiki right away), then this should be moved elsewhere, or at the very least made smaller and less obtrusive. Optimizing for newcomers seems wise. Jason This is what I see when visiting the Ruby page: DoS vulnerability in BigDecimal That's true. And I never said we want to copy the ruby community :) In fact, I'd prefer to not be associated with them given the community's blatant unprofessionalism and sexism (cf. CouchDB presentation at a semi-recent ruby conference). I do think their page has more visual appeal though. So other than pointing out the DoS, did you have feedback? Thanks, Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
IMO, causing a segfault in the interpreter is more than just a DOS vulnerability :) On Thu, Jul 9, 2009 at 6:11 PM, Derek Elkins derek.a.elk...@gmail.comwrote: On Thu, Jul 9, 2009 at 12:31 PM, Jason Dagitda...@codersbase.com wrote: On Thu, Jul 9, 2009 at 10:00 AM, Thomas ten Cate ttenc...@gmail.com wrote: By the way, the most valuable pixels, right at the top of the page, are wasted on wiki stuff. Compare http://www.haskell.org/ with, for example, http://www.ruby-lang.org/ http://python.org/ The thing I like the most from the ruby page is the top box of content where it starts describing ruby with a Read more... link adjacent to a code snippet. Because I doubt anyone will agree on *the one* best code snippet to show people, I think there should/could be a pool of fun snippets and loading the page picks one at random. I have no idea if the wiki engine supports this. I also like the strip of links at the top with things like, Download, Community, and so on. Something I think the Haskell page does much better than the other two, is the listing of events and hackage updates. Both of those sections feel inviting to me. It makes me curious and I want to explore. The python page looks at least as cluttered as the haskell page. Neither the haskell page or the python page have the same look and feel of the ruby page. I think the shaded/gradient backgrounds actually add a lot to the visual experience. I also like that the boxes have a different bg color for the box title and the box contents. I also like the use of icons on the ruby page. The Download Ruby link/box with the download icon is very inviting. I just want to download it, even if I'm not going to use ruby! Perhaps we could have a contest similar to the logo contest but for homepage asthetics redesign. I think the content on the haskell page is great, but the visual style of the presentation could be improved considerably. If, like the consensus seems to be, the page should be made more friendly to beginners (who are unlikely to want to contribute to the wiki right away), then this should be moved elsewhere, or at the very least made smaller and less obtrusive. Optimizing for newcomers seems wise. Jason This is what I see when visiting the Ruby page: DoS vulnerability in BigDecimal ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge. - Daniel J. Boorstin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
On Thu, Jul 9, 2009 at 12:31 PM, Jason Dagitda...@codersbase.com wrote: On Thu, Jul 9, 2009 at 10:00 AM, Thomas ten Cate ttenc...@gmail.com wrote: By the way, the most valuable pixels, right at the top of the page, are wasted on wiki stuff. Compare http://www.haskell.org/ with, for example, http://www.ruby-lang.org/ http://python.org/ The thing I like the most from the ruby page is the top box of content where it starts describing ruby with a Read more... link adjacent to a code snippet. Because I doubt anyone will agree on *the one* best code snippet to show people, I think there should/could be a pool of fun snippets and loading the page picks one at random. I have no idea if the wiki engine supports this. I also like the strip of links at the top with things like, Download, Community, and so on. Something I think the Haskell page does much better than the other two, is the listing of events and hackage updates. Both of those sections feel inviting to me. It makes me curious and I want to explore. The python page looks at least as cluttered as the haskell page. Neither the haskell page or the python page have the same look and feel of the ruby page. I think the shaded/gradient backgrounds actually add a lot to the visual experience. I also like that the boxes have a different bg color for the box title and the box contents. I also like the use of icons on the ruby page. The Download Ruby link/box with the download icon is very inviting. I just want to download it, even if I'm not going to use ruby! Perhaps we could have a contest similar to the logo contest but for homepage asthetics redesign. I think the content on the haskell page is great, but the visual style of the presentation could be improved considerably. If, like the consensus seems to be, the page should be made more friendly to beginners (who are unlikely to want to contribute to the wiki right away), then this should be moved elsewhere, or at the very least made smaller and less obtrusive. Optimizing for newcomers seems wise. Jason This is what I see when visiting the Ruby page: DoS vulnerability in BigDecimal ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
On Thu, Jul 9, 2009 at 5:17 PM, Jason Dagitda...@codersbase.com wrote: On Thu, Jul 9, 2009 at 3:11 PM, Derek Elkins derek.a.elk...@gmail.com wrote: On Thu, Jul 9, 2009 at 12:31 PM, Jason Dagitda...@codersbase.com wrote: On Thu, Jul 9, 2009 at 10:00 AM, Thomas ten Cate ttenc...@gmail.com wrote: By the way, the most valuable pixels, right at the top of the page, are wasted on wiki stuff. Compare http://www.haskell.org/ with, for example, http://www.ruby-lang.org/ http://python.org/ The thing I like the most from the ruby page is the top box of content where it starts describing ruby with a Read more... link adjacent to a code snippet. Because I doubt anyone will agree on *the one* best code snippet to show people, I think there should/could be a pool of fun snippets and loading the page picks one at random. I have no idea if the wiki engine supports this. I also like the strip of links at the top with things like, Download, Community, and so on. Something I think the Haskell page does much better than the other two, is the listing of events and hackage updates. Both of those sections feel inviting to me. It makes me curious and I want to explore. The python page looks at least as cluttered as the haskell page. Neither the haskell page or the python page have the same look and feel of the ruby page. I think the shaded/gradient backgrounds actually add a lot to the visual experience. I also like that the boxes have a different bg color for the box title and the box contents. I also like the use of icons on the ruby page. The Download Ruby link/box with the download icon is very inviting. I just want to download it, even if I'm not going to use ruby! Perhaps we could have a contest similar to the logo contest but for homepage asthetics redesign. I think the content on the haskell page is great, but the visual style of the presentation could be improved considerably. If, like the consensus seems to be, the page should be made more friendly to beginners (who are unlikely to want to contribute to the wiki right away), then this should be moved elsewhere, or at the very least made smaller and less obtrusive. Optimizing for newcomers seems wise. Jason This is what I see when visiting the Ruby page: DoS vulnerability in BigDecimal That's true. And I never said we want to copy the ruby community :) In fact, I'd prefer to not be associated with them given the community's blatant unprofessionalism and sexism (cf. CouchDB presentation at a semi-recent ruby conference). I do think their page has more visual appeal though. So other than pointing out the DoS, did you have feedback? I admit it; you caught me. I'm not a newbie and I don't use the front page terribly often, but I do like most of the links that are on it. The Ruby page is certainly prettier, but the layout of the Haskell page is fine in my opinion; the difference is mainly eye-candy. On another topic, I know people have expressed that they have liked the fact that the entire Haskell site is a wiki; this expressing openness and community involvement. I personally don't find the Haskell front page too cluttered and I think most of issue in that vein could be resolved by simply making sure the most important/newbie-oriented links are above the fold and appropriately emphasized/categorized as is partially done already. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell used for data analysis - OLAP?
Hi, I've developed this commercial app in Haskell with all of the business logic coded in SQL with the help of haskelldb. Some of the intermediate results (of queries) I had to manifest in extra tables because the initial query was expensive, the intermediate result would be the source data of other queries and queries can't themselves be indexed for further efficient querying. Since the amount of data could become rather large, in-memory processing wasn't an option and I thus chose SQL (Sqlite). The solution works, but still I'm not quite happy about it, since I consider the tables that hold intermediate results fixes. I understand that the financial industry employs Haskell to analyse large data set under complex schemes. I wonder what techniques are employed for that, do they use Haskell to create some sort of OLAPish tools? Do they use Haskell to run complex queries against SQL data warehouses? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
I like the Haskell page the way it is. The O'Caml web page, is, by comparison, infuriatingly unhelpful. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] iteratee enumHandle
Hi Paolino. What's happening is reading [Char] uses the Storable instance for Char which is 32-bit. Thus, you get gibberish. The below does what you want, by reading Word8s and converting them. import Control.Exception import Data.Char import Data.Iteratee.IO import Data.Iteratee.Base import Data.Word import System.IO main :: IO () main = do h - openFile mamma23 ReadWriteMode hPutStr h ciao hSeek h AbsoluteSeek 0 l - enumHandle h readString = run print $ assert (l == ciao) () -- This is declared on its own so I can give a type signature without making -- any of the above lines unmanageably long. readString :: IterateeG [] Word8 IO String readString = joinI $ mapStream (chr . fromIntegral) stream2list This only works for ASCII, of course. Someone should write some enumerators for the other encodings. Regards, Echo Nolan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Leaner Haskell.org frontpage
On Thu, Jul 9, 2009 at 6:12 PM, Derek Elkinsderek.a.elk...@gmail.com wrote: I'm not a newbie and I don't use the front page terribly often, but I do like most of the links that are on it. The Ruby page is certainly prettier, but the layout of the Haskell page is fine in my opinion; the difference is mainly eye-candy. On another topic, I know people have expressed that they have liked the fact that the entire Haskell site is a wiki; this expressing openness and community involvement. I personally don't find the Haskell front page too cluttered and I think most of issue in that vein could be resolved by simply making sure the most important/newbie-oriented links are above the fold and appropriately emphasized/categorized as is partially done already. I strongly feel that the homepage should be made more newbie friendly, and I think the Ruby page has done this well, disregarding the news section. I suspect most people who like the Ruby page see the Ruby is... section as especially effective at introducing the language, and the random snippet is a simple way to show off a bit of code before they dive into a tutorial. Furthermore, the Download link is useful, but since GHC can be complicated (and varies by platform), we probably want to include pretty well thought-out instructions behind the link if we include a similar feature. I also quite like the Participate box on the Ruby page, which is very inviting. Regarding the current Haskell homepage, I feel the events are given far too high a place on the homepage. Almost no newbies will be interested in these, and most experienced users will know of the events via the mailing lists. The headlines below that deserve significantly more attention, and perhaps should be updated with greater frequency (and dated, and have RSS). The updated package list is fine, I think. The navigation is a bit tricky, in my opinion. To a beginner (that doesn't know what GHC is), the two download links may be confusing, although I suspect most would correctly assume that Download Haskell was correct option. The Find A Library is a good link, but the Search that follows it is awkward. There are three large search choices for beginners: 1) the search at the top, which confusingly has two submit buttons (with ambiguous differences to a beginner); 2) the Search link near the top of the navigation (which links to an almost empty page that might as well be included at the link's location); and 3) the Search link underneath the About header, which doesn't seem to belong at all. Jeff Wheeler (Sorry, sent this to just Derek at first.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: AC-Vector, AC-Colour and AC-EasyRaster-GTK
Max Rabkin wrote: On Sat, Jul 4, 2009 at 8:38 PM, Andrew Coppinandrewcoppin at btinternet.com wrote: A few reasons: 1. I never knew it existed. ;-) A good reason. However, it's good to do a quick search over Hackage before uploading (or before writing) so you know what's out there. Also, if you hadn't used an AC- prefix, you'd have had a name collision. Is there a particular reason why you want your name in the package name rather than just the author field? I find it amazing that you independently chose to spell colour with a `u'. It makes me feel better about my choice. 2. It's mind-blowingly complex. Colour *is* complex. Which is why I'm so glad Russell O'Connor did all the hard work for me :) Well, no, because now I'm going to have to spend a few hours trying to find out what CIE is before I can even use that library. I think really it's just aimed at a different problem. It looks like it's trying to specify actual real-world colours. [It's news to me that this isn't fundamentally impossible...] I'm only trying to specify colours on a computer screen. And as we all know, computer screens aren't calibrated in any way, and the same RGB value looks different on each display. But then, I'm only trying to write a fractal generator, so CIE specifications are somewhat overkill here. ;-) You can use by lib without worrying about the CIE. You can use my library without ever importing or using the word CIE. However, the CIE stuff is there for those who need it. Perhaps I (maybe with some help) need to make a tutorial on the haskell wiki to try to make it less intimidating. 3. It doesn't appear to provide arithmetic over colours. It provides darken, blend and addition (though addition is called mappend rather than (+)). signum, abs and fromInteger don't make a huge amount of sense for colours. Yeah, I implemented signum and so forth for colours and vectors, but they're not particularly meaningful... [Insert remark here about Haskell's numeric class hierachy.] So mappend gives you colour addition [with the perplexing comments about gamut, presumably some kind of small mammal?], but there's no subtraction? No multiplication? No linear blending? Linear blending is done by the affineCombo function. I think the darken function will do what you mean by multiplication Colour subtraction can be done by adding (using mappend) a colour that has been darkend by a factor of (-1). I don't believe there is any demand for a colour subtraction fuction, so I don't have a name for it. I suppose these sorts of questions can be put nicely into a short tutorial on the wiki. 4. It's parameterised over the component type; my library is hard-coded to specific types for speed. My feeling would be to trust the specializer until it lets me down. Has it let you down in the past? Heh, my colour library includes a custom floor implementation that talks to the GHC primops directly because calling floor is too slow... [In case that sounds like idle talk, I had a program go from 10 seconds to less than 1 second just by using this function. There's a few tickets about it on the GHC Trac.] Certainly speed is an issue that I haven't tackled yet since I don't know too much about how to optimized Haskell code. I was thinking of sprinkling in some SPECIALIZE pragmas and maybe adding some RULES to make operations more effecient. For example we could have a rule to rewrite floor to some sort of GHC specific fast floor function. (Although that rule probably deserves to be in some sort of more general location). Any help in this direction would be appricated (perferably while keeping things as portable as possible). This all being said, the major problem my code solves is doing blending in a linear colour space. This necessarily make converting to non-linear sRGB for output much slower. So for people who want speed over proper blending, then probably AC-Colour is the package they need to reach for. Essentially the two packages do fill different niches! BTW, the EasyRaster package looks useful. I haven't looked at EasyRaster yet, but I got excited when I saw it announced. :) -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
Ignoring the rest of the thread, but jumping in here... hask...@kudling.de wrote: For the hompage we're talking about, glancing is even simpler since everything is on the same page and you can scroll it quite easily. I don't agree that everything on one page makes comprehension easier. I'm not sure hiding a level of the hierarchy of information behind a few clicks make things easier. That depends on which task we are talking about: - getting an overview of all available information, or - finding exactly what you are looking for I agree with minh thu. For the newcomer to the Haskell community the big question is not what is Haskell? but rather I've heard of this Haskell thing, how do I get started? and I've tinkered with this Haskell thing, where do I get more? The biggest thing I dislike about the alternative pages mentioned by the OP is that they fail in this task. Many of those pages are entirely unhelpful on where to go and/or are filled with administrative nonsense only the compiler developers would care about. Those that aren't are so so polished that there's no content left, or if there is it can't be easily discerned from all the other polish (e.g. the Ruby site. *I* know the content there is meaningful, but the presentation has a very corporate who-gives-a-damn flavor to it which dissuades actually reading the page). Certainly changes could be made (e.g. the verbiage of the description paragraph, moving the language choice to the top, minimizing the realestate devoted to the top bar, simplifying the many redundant search boxes/links,...) but I think by and large the page is very good as a portal for new users as well as for experienced community members looking for That One Thing Whatsitcalled. Hiding the TOC content behind links is a sure way to keep people from finding it and reading it. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
Rick R wrote: As an aside, in the current homepage, the Haskell description is outweighed by the link menu on the left. IMO the reader's eyes should move from the title, to the description, then either down or left. Currently my attention is split evenly between the link menu and the title/description, which results in confusion. This would be (partially) fixed by reducing the whitespace between the title and the description. Our eyes are attracted to whitespaces, so this is one of the key areas that makes or breaks a design. As it stands the description is stranded and has nothing to lead one into it; whereas the sidebar is taller, in bold, in highlight color,... -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
Don Stewart wrote: ttencate: On Thu, Jul 9, 2009 at 18:33, Don Stewartd...@galois.com wrote: ttencate: Are there any kind of hard statistics and analytics that we can base this discussion upon? There is always room for improvement, but stumbling around in the dark making blind guesses may not be the best way to go. Although I personally feel that Lenny's proposed page is an improvement, statistics could tell us what actual people actually use the site for. Thanks Don, I should have thought of that. It's a start! No matter what we decide, I'd like to advocate for maintaining the RSS feed of Hackage uploads on the front page -- this is what makes the page seem alive and active, and was introduced in response to John Hughes complaining the page was always out of date. (Similar to the Arch Linux package updates: http://www.archlinux.org/) +1. I also like the events listing, since community events tend to be one of the hardest things to get a single concrete listing of. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Colour tutorial (Was: AC-Vector, AC-Colour and AC-EasyRaster-GTK)
On Thu, 9 Jul 2009, rocon...@theorem.ca wrote: You can use by lib without worrying about the CIE. You can use my library without ever importing or using the word CIE. However, the CIE stuff is there for those who need it. Perhaps I (maybe with some help) need to make a tutorial on the haskell wiki to try to make it less intimidating. Okay, I threw together a quick introduction at http://www.haskell.org/haskellwiki/Colour. Any changes, comments, corrections, and addtions are welcome. It's a wiki! The word CIE does occur at all in the document. -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Leaner Haskell.org frontpage
Jeff Wheeler wrote: I suspect most people who like the Ruby page see the Ruby is... section as especially effective at introducing the language, and the random snippet is a simple way to show off a bit of code before they dive into a tutorial. I'll agree that that part is slick. The rest of it I dislike. In particular the whole right column is indicative of link hell where they couldn't just decide on a single way to make links: there's the download button which is different (fine), there're the first two boxes (also fine), there's the third box which is like the first two but has a whole bunch of extraneous text, there's a bullet listing of top projects which looks entirely different, there's a random RSS link which looks different again, and then it flows into the old-posts segment of the main body which is different again, and then we get to the footer links which mirror the header (this one is fine), and then i18n links are different again and relegated to a footnote (which isn't very inviting to non-English natives),... Whereas haskell.org is much more consistent in picking a single style and running with it. There are some things that could be tweaked (why is GHC in bold? can we remove the extra leading line between indented link groups and their heading link?) but it gives a much more coherent and well designed image. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
