On 19.12.2011 19:29, Henning Thielemann wrote:
Shortest and most obfuscating solution I found is:
import Data.Ord (comparing)
import Control.Applicative ((<$))
compareLength :: [a] -> [a] -> Ordering
compareLength = comparing (()<$)
comparingLength = comparing void
It's two character short
On 01.12.2011 23:47, dokondr wrote:
To be precise, $0 always contains the path to the program called. You
are right, this path will change depending on location from which the
program was called. So $0 is OK for my case, while current directory is
unrelated.
Actually it contains whatever was pa
On 07.09.2011 00:56, Brandon Allbery wrote:
2011/9/6 Poprádi Árpád mailto:popradi_ar...@freemail.hu>>
updateData1 :: X -> MonadicEnv()
updateData1 d = do; env <- get; put env {data1 = d}
> updateData1 d = modify (\r -> r {data1 = d})
But there is, sadly, no eta-reduced version of rec
On 02.08.2011 08:16, Sebastian Fischer wrote:
Data.Foldable also provides the monoidal fold function foldMap. It is
left unspecified whether the elements are accumulated leftwards,
rightwards or in some other way, which is possible because the combining
function is required to be associative. Doe
> Any examples for hangups of 'smartEq' are greatly appreciated, I couldn't
> produce any so far.
>
Following sequences will hang smartEq. They are both infinite and aperiodic.
smartEq (fromList primes) (fromList primes)
smartEq (fromList pidigits) (fromList pidigits)
___
On Fri, Jul 1, 2011 at 12:54 PM, Eugene Kirpichov wrote:
> Alexey, your definition of "mean" does not look like "liftS2 (/) sum
> length" - you have to manually "fuse" these computations.
>
Well it was fused for numerical stability
> I'm asking for a formalism that does this fusion automatically
On Fri, Jul 1, 2011 at 12:21 PM, Eugene Kirpichov wrote:
> I meant the average of the whole list - given a sumS and lengthS ("S"
> for "Stream"), write meanS as something like liftS2 (/) sumS lengthS.
>
> Or is that possible with lazy lists too?
>
Sure you can. Sum, length and mean could be calcul
On 22.06.2011 00:32, pipoca wrote:
On Jun 21, 4:15 pm, Alexander Solla wrote:
The problem is that a sum type must "name" the different types, or else it
can't give access to them. How is a function supposed to know if a value
blah :: A :+: B
is an A or a B? It seems possible that it could f
On 11.06.2011 02:02, Dmitri O.Kondratiev wrote:
I am looking for platform-independent library to generate simple
histograms in png format.
Does such thing exist?
You may give chart[1,2] a try if dependency on cairo is acceptable.
It can generate PNG among other options.
[1] http://hackage.has
forever a = a>> forever a
doesn't tie to itself without optimisations, so my guess is that it gets
expanded when you run/eval/execState it in ghci, building the thunk
a>> a>> a>> a>> ...
If you define
forever' a = let a' = a>> a' in a'
the variant using forever' runs in constant spac
On 09.06.2011 20:09, Yves Parès wrote:
Is it not:
> noLeak :: State Int ()
> noLeak = do
> a <- get
*>* *let a' = (a + 1)
> a' `seq` put a'*
> noLeak
??
Indeed. Now I understand. It didn't work for me earlier because of
different behavior of 'forever' in ghci and compiled code.
T
Hello café!
This mail is literate haskell
I have some difficulties with understanding how bang patterns and seq
works.
> {-# LANGUAGE BangPatterns #-}
> import Control.Monad
> import Control.Monad.Trans.State.Strict
>
> leak :: State Int ()
> leak = do
> a <- get
> put (a+1)
> leak
This
On 30.05.2011 14:45, Henning Thielemann wrote:
Alexey Khudyakov schrieb:
On 30.05.2011 12:26, Bas van Dijk wrote:
How about 'checkers' by Conal Elliott:
http://hackage.haskell.org/package/checkers
We really need better search on hackage than C-f in browser. I didn't
find them
On 30.05.2011 12:26, Bas van Dijk wrote:
On 30 May 2011 00:14, Alexey Khudyakov wrote:
It always puzzled me why there are no packages for for testing general
type classes laws. (Monoid laws, monad laws etc). It looks like ideal
case for quickcheck and smallcheck.
How about 'checker
Hello
It always puzzled me why there are no packages for for testing general
type classes laws. (Monoid laws, monad laws etc). It looks like ideal
case for quickcheck and smallcheck.
I'm glad to present package quickcheck-properties[1]. It containt set
of generic properties for semiroups, monoid
On 16.05.2011 22:51, Casey McCann wrote:
How so? Equality on floating point values other than NaN works just
fine and behaves as expected. It's just that they violate all sorts of
algebraic laws when arithmetic is involved so sequences of operations
that should be equivalent aren't, in ways that
On 03.05.2011 00:43, Antoine Latter wrote:
On Mon, May 2, 2011 at 3:01 PM, Alexey Khudyakov
wrote:
Hello everyone!
Haskell have nice automatically derivable Show type class. It's quite useful
for debugging with one exception. String representation of even moderately
large value is compl
Hello everyone!
Haskell have nice automatically derivable Show type class. It's quite
useful for debugging with one exception. String representation of even
moderately large value is completely unreadable (example below).
My question is there any tool for reformatting result of show so it
co
> Speaking of that Double instance... both data-binary and cereal use
> decodeFloat and encodeFloat which mean they suffer from the same
> problems as realToFrac, namely that -0 becomes 0 and NaN becomes
> -Infinity (I'm not sure why the latter happens since the decoded
> values differ... must be a
On 09.02.2011 23:16, Cristiano Paris wrote:
On Wed, Feb 9, 2011 at 19:33, Alexey Khudyakov
wrote:
...
If Private is not exported one cannot add instances to PRead.
Nice trick. I would have thought of hiding the classes PRead and
PWrite but I'm not sure if it could break the code
On 09.02.2011 20:15, Cristiano Paris wrote:
Now the problem.
I would like to enforce permissions not at the role level, but at the
permissions level. Let's say that I want to leave "unseal" unchanged,
I'd like to "construct" a p-value for unseal "combining" functions
checking for single permissi
On 09.02.2011 20:57, Chris Smith wrote:
On Wed, 2011-02-09 at 18:15 +0100, Cristiano Paris wrote:
I've a type problem that I cannot solve and, before I keep banging my
head against an unbreakable wall, I'd like to discuss it with the
list.
If I'm understanding your high-level goals correctly,
On 07.02.2011 00:37, Johan Tibell wrote:
Also there is a container-classes package which provide set of type class
for containers.
I'd like to avoid MPTC and fundeps if possible.
I think haskell2010's type system is just not expressive enough to
create interface generic enough. It's not possi
On 06.02.2011 23:29, Johan Tibell wrote:
On Sun, Feb 6, 2011 at 8:48 PM, Andrew Coppin
wrote:
In particular, I get strange looks from people in the OOP community when I
say I'm using a language that doesn't have any abstractions at all for
dealing polymorphically with containers. In general, i
We already know that there are noncommutative modules/vectorspaces of
interest (e.g., modules over quaternions and modules over graph paths),
why not support them from the beginning? It seems like you're going out
of your way to exclude things that would be trivial to include. This is
exactly wh
On 05.11.2010 14:08, Mitar wrote:
So I know I can move some hard-coded combination into a function. But
I would like to cover all combinations and tell with arguments which
combination I want.
I'm not sure what do you exactly want. But what about applicative
functors? They offer nice notation
On Wed, Oct 27, 2010 at 2:53 AM, wren ng thornton wrote:
> On 10/26/10 8:51 AM, Alexey Khudyakov wrote:
>>
>> On 24.10.2010 03:38, wren ng thornton wrote:
>>>
>>> I don't care much about the name of the class, I'd just like support for
>>>
On Sat, Oct 30, 2010 at 2:07 PM, Henning Thielemann
wrote:
> wren ng thornton schrieb:
>> On 10/22/10 8:46 AM, Alexey Khudyakov wrote:
>>> Hello everyone!
>>>
>>> It's well known that Num & Co type classes are not adequate for vectors
>>> (I
On 24.10.2010 03:38, wren ng thornton wrote:
On 10/23/10 4:53 PM, Alexey Khudyakov wrote:
On 23.10.2010 05:11, wren ng thornton wrote:
I'd rather see,
class Additive v where -- or AdditiveMonoid, if preferred
zeroV :: v
(^+^) :: v -> v -> v
class Additive v => AdditiveGroup v
On 24.10.2010 01:19, Daniel Peebles wrote:
Just out of curiosity, why do you (and many others I've seen with
similar proposals) talk about additive monoids? are they somehow
fundamentally different from multiplicative monoids? Or is it just a
matter of notation? When I was playing with building a
On 23.10.2010 05:11, wren ng thornton wrote:
On 10/22/10 8:46 AM, Alexey Khudyakov wrote:
Hello everyone!
It's well known that Num & Co type classes are not adequate for vectors
(I don't mean arrays). I have an idea how to address this problem.
Conal Elliott wrote very ni
Hello everyone!
It's well known that Num & Co type classes are not adequate for vectors
(I don't mean arrays). I have an idea how to address this problem.
Conal Elliott wrote very nice set of type classes for vectors.
(Definition below). I used them for some time and quite pleased. Code is
c
On 07.09.2010 20:51, Henning Thielemann wrote:
This solution looks very ugly to me. Catching 'error's is debugging, but
parser failure is kind of exception handling. I guess, the errors you
want to catch are caused by non-supported fail method, right? Can't you
use a monad transformer like explic
On 05.09.2010 22:02, Don Stewart wrote:
For strict, checked binary parsing, use the cereal package. For lazy
binary parsing with async errors, use binary.
Unfortunately cereal is too slow. I got ~5x slowdown with cereal and had
to patch binary in order to incorporated error handling (essentiall
On 22.08.2010 21:23, Yves Parès wrote:
In fact the encoding problem is more general.
When I simply do 'readFile "bar/fooé"', then I'm told:
*** Exception: bar/fooé: openFile: does not exist (No such file or
directory)
How am I supposed to read files whose names contains non-ASCII characters?
(I
On 21.08.2010 01:38, Lars Petersen wrote:
* Float and Double are serialised big-endian according to binary-ieee754
I'd like to point out that binary-ieee754 is dead slow[1] and not usable
when one cares about performance. IMHO lack of ways to serialize
floating point data in IEEE754 format is
On 05.08.2010 13:35, Henning Thielemann wrote:
On Wed, 4 Aug 2010, John Meacham wrote:
The numeric classes are sort of messed up when it comes to non integral
values. (not that they are perfect for other things) for instance,
realToFrac doesn't preserve NaN or Infinity,
Why should realToFrac
On 03.08.2010 21:25, Andrew Coppin wrote:
Now suppose that instead of a container type with an associated element
type, what we want is several pairs of types having a one-to-one
relationship, and we want to be able to traverse that relationship in
either direction. What's the best way to do that
On Fri, 30 Jul 2010 15:20:55 -0700
John Meacham wrote:
> > > type family Add n m :: *
> > >
> > > type instance Add Zero Zero = Zero
> > > type instance Add Zero (SuccessorTo n) = SuccessorTo n
> > > type instance Add (SuccessorTo n) m= SuccessorTo (Add n m)
> >
> > Standard packag
monad. Moreover it Monad in this
example could be replaced with Functor or other type class
I wonder could this function be written without resorting to concrete
monad
--
Alexey Khudyakov
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ly good but "one size doesn't fit all" rule does apply here.
Your package couldn't be used to represent big numbers. Little real
work has been done on this so it's reasonable to expect progress or
even some breakthough.
Maybe some generic intef
Hello
I'm wondering is there any haskellers in CERN? Given quality
and usability of software there must be people looking for
better alternatives.
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On Fri, Jul 23, 2010 at 4:04 PM, Daniel Díaz wrote:
> Hi,
>
> I uploaded a package, named HaTeX, to Hackage, but it gets a build failure:
>
> Any idea?
Cabal file has BOM in the beginning. Maybe it make parser choke...
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On Sat, Jul 3, 2010 at 10:54 PM, Alexey Khudyakov
wrote:
> On Sat, Jul 3, 2010 at 8:57 PM, braver wrote:
>> I dump results of a computation as a Data.Trie of [(Int,Float)]. It
>> contains about 5 million entries, with the lists of 35 or less pairs
>> each. It takes 8
On Sat, Jul 3, 2010 at 8:57 PM, braver wrote:
> I dump results of a computation as a Data.Trie of [(Int,Float)]. It
> contains about 5 million entries, with the lists of 35 or less pairs
> each. It takes 8 minutes to load with Data.Binary and lookup a single
> key. What can take so long? If I
On Mon, Jun 28, 2010 at 7:02 PM, Jake McArthur wrote:
> On Sun, Jun 27, 2010 at 4:44 PM, Alexey Khudyakov
> wrote:
>> Dependent types would be nice but there isn't anything usable out there.
>> Newtype wrapper parametrized by type level number works fine so far.
>>
On Mon, Jun 28, 2010 at 12:00 AM, Alexander Solla wrote:
>
> On Jun 27, 2010, at 12:29 PM, Alexey Khudyakov wrote:
>
>> This is of course faster but what I really want is vectors with length
>> parametrized by type. This way I can write generic code. Uniform
>> repres
On Sun, 27 Jun 2010 19:55:21 +1000
Roman Leshchinskiy wrote:
> On 25/06/2010, at 06:41, Alexey Khudyakov wrote:
>
> > Then constructor like one below arise naturally. And I don't know how to
> > write
> > them properly. It's possible to use fromList but
have both automatic
decoding of file names and working with file names with incorrect
encoding.
--
Alexey Khudyakov
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On Fri, 25 Jun 2010 18:30:06 -0300
Felipe Lessa wrote:
> On Fri, Jun 25, 2010 at 12:41:48AM +0400, Alexey Khudyakov wrote:
> > Then constructor like one below arise naturally. And I don't know how to
> > write
> > them properly. It's possible to use
On Sat, 26 Jun 2010 10:14:50 -0300
Felipe Lessa wrote:
> On Sat, Jun 26, 2010 at 05:01:06PM +0400, Bulat Ziganshin wrote:
> > but what you propose cannot be used in Windows at all! while current
> > FilePath still works on Unix, with manual filenames en/decoding
>
> Now we got back on topic! :)
>
Hello, cafe
I have question about vector package.
Currently I'm playing with data types which are isomorphic to vectors of fixed
length. Think about vector in N-dimensional space, list of parameters to
function R^n → R, set of measurements with uncertainties, etc. They have
different semantics bu
On Thu, 17 Jun 2010 13:45:16 -0400
cas...@istar.ca wrote:
> :)
>
Objection!
http://hackage.haskell.org/package/BASIC
A simplified version of the original BASIC embedded in Haskell.
--
Alexey Khudyakov
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On Fri, Jun 4, 2010 at 8:31 PM, Alexey Khudyakov
wrote:
> Here is code I use to work around this issue:
>
Forgot to mention. This code checks for end of input. Your data is
infinite so you simplify
definition if you like
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On Fri, Jun 4, 2010 at 8:02 PM, Pete Chown <1...@234.cx> wrote:
> I've been trying to get in touch with the maintainers of the Binary package,
> to report an issue. When I emailed the addresses given on Hackage, I got an
> automated response saying I had used an address that was no longer current.
2009/12/4 Roman Salmin :
> On Fri, Dec 04, 2009 at 01:43:42PM +, Matthias Görgens wrote:
>> > _So my strong opinion that solution is only DSL not EDSL_
>>
>> Why do you think they will learn your DSL, if they don't learn any
>> other language?
> I didn't said that they didn't learn any langua
On Fri, Nov 27, 2009 at 10:36 PM, Mark Lentczner wrote:
> I'm in the same quandary:
>
> Data.Binary from the binary package has no error handling
> Data.Serialize from the cereal package uses only strict ByteString
>
> I was going to add error handling to Binary as a weekend project (it isn't
> t
Hello
Is there any plans to add error handling for binary? When it comes to
binary parsing most awkward part is error handling
I presume answer will be like "there are some vague plans but no one
to implement them" so the second question how could it be done?
Naive implementation of error handl
On Sun, Nov 15, 2009 at 8:59 PM, Don Stewart wrote:
> alexey.skladnoy:
>> I found that perfomace of indexU is very poor and it is not fast O(1)
>> operation which is very surprising. Here is some benchmarcking I've
>> done. Everything compiled with -O2
>
> You're using the streamed version when it
On Sun, Nov 15, 2009 at 5:50 PM, Felipe Lessa wrote:
> On Sun, Nov 15, 2009 at 03:00:34PM +0300, Alexey Khudyakov wrote:
>> Naive implementation using lists and index lookup.
>> 2.15 second for 200*200 array
>> > sliceXlist :: Int -> UArr Double -> [UArr Dou
Hello
This post meant to be literate haskell.
I found that perfomace of indexU is very poor and it is not fast O(1)
operation which is very surprising. Here is some benchmarcking I've
done. Everything compiled with -O2
Code below converts square 2D array to list of 1D arrays. Summation of
array
> Yes. We decided that having the Get monad as a lazy state monad just
> doesn't make sense. It makes this one use case work, but causes more
> problems generally. Certainly we need to be able to do lazy binary
> deserialisation too, but our feeling is that it should be more explicit
> and integrat
On Wed, Sep 23, 2009 at 11:19 PM, Daniel Peebles wrote:
> I believe this is a bug that was introduced in 6.10.2 (it definitely
> worked in 6.10.1) that has since been fixed in HEAD. This newtype
> deriving issue also prevents the uvector testsuite from running at the
> moment.
>
Yes. It works in 6
On Mon, Jun 29, 2009 at 12:58 PM, Ketil Malde wrote:
>
> Hi,
>
> A bit off-topic, but this is the café, after all...
>
> Like many here, I run XMonad as my window manager on top of Linux.
> On - at least my brand of - Linux, networking is generally handled by
> NetworkManager, which really needs it
> I have so far only tested it with ghc 6.8.3 on MacOS 10.3.9 (powerPC),
> but I know of no reason why it wouldn't work with other versions and
> OSs.
>
It breaks on Linux (and all unices) because name of file in tarball is
'rungekutta.hs' not
'RungeKutta.hs' as required. In other words: god blame
>
> This upsets me. We need to get on with doing this properly. The
> System.IO.UTF8 module is a useful interim workaround but we're not using
> it properly most of the time.
>
> ... skipped ...
>
> The right thing to do is to make Prelude.putStrLn do the right thing. We
> had a long discussion on
>
> That really ought to work. Is the file encoded in UTF-8 (rather than,
> eg. latin-1)?
>
This should pretend to work. Simple print functions garble unicode characters.
For example :
> putStrLn "Ну и где этот ваш хвалёный уникод?"
prints following output
C 8 345 MB>B 20H E20;Q=K9 C=8:>4?
Not
st of data (possibly millions of elements) and it will traverse
input data for each histogram.
It seems that I need to use mutable array and/or ST monad or something else.
Sadly both of them are tricky and difficult to understand. So good examples or
any other ideas greatly appreciated.
--
Alexey
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