Welcome to issue 210 of the HWN, a newsletter covering developments in
the Haskell community. This release covers the week of November 27 to
December 3, 2011.
You can find the HTML version at:
http://contemplatecode.blogspot.com/2011/12/haskell-weekly-news-issue-210.html
Announcements
Heinric
On Wed, Dec 7, 2011 at 23:24, Alexej Segeda
wrote:
> case s of
>(s == reverse s)-> putStrLn (s ++ " is a
> palindrome")
>otherwise -> putStrLn (s ++ " is not a
> palindrome")
>
case does pattern matching, not Boolean expression
Hi!
A couple of months ago, I wrote an exam in an introductory Haskell course and
failed, all because of an assignment that I was convinced would work, but for
some reason, it didn't. The assignment was to write a function that would take
a line, then determine whether it's a palindrome or not
On Wed, Dec 7, 2011 at 20:35, Jason Dagit wrote:
> > They *do* terminate; a zombie is a dead process waiting for its parent to
> > reap it with waitForProcess. There's also some POSIX stuff you can do to
> > have them auto-reaped, but doing that correctly and portably is somewhat
> > painful.
>
On Wed, Dec 7, 2011 at 7:19 AM, Brandon Allbery wrote:
> On Wed, Dec 7, 2011 at 06:47, Dan Rosén wrote:
>>
>> I'm using Haskell to run a lot of instances of an Automated Thorem Prover,
>> eprover. I have pasted a smaller version of my program at
>> http://hpaste.org/54954. It runs eprover sequent
Thank you very much for your answers.
Felipe's suggestion to use waitForProcess after terminateProcess did the
trick. No more zombies around :)
Best regards,
Dan Rosén
On Wed, Dec 7, 2011 at 4:39 PM, Donn Cave wrote:
> Quoth Felipe Almeida Lessa ,
> > On Wed, Dec 7, 2011 at 1:19 PM, Brandon Al
Henrik Nilsson writes:
>> Just like chatter and chattee, employer and employee, there is an
>> iterator (usually as part of an enumerator/ee) and an iteratee.
> Thanks for the attempt to explain. But I, at least, remain mystified,
> and I agree with Douglas that the terminology is confusing.
FW
On Wed, Dec 7, 2011 at 5:48 AM, Dmitry Kulagin wrote:
> I am still pretty new in Haskell, but this problem annoys me already.
>
> If I define certain monad as a type synonym:
>
> type StateA a = StateT SomeState SomeMonad a
>
> Then I can't declare new monad based on the synonym:
>
> type St
Hi Ertugrul,
> Coroutines actually capture this kind of composition (where some code
> interrupts itself to hand control over to some other code) very well.
> Perhaps it would be better to use terms from that abstraction instead.
> In fact, iteratees are a special case of coroutines.
That would
On Wed, Dec 7, 2011 at 1:07 PM, Dmitry Kulagin wrote:
>> For short, type synonyms work for mere aliases, but not for full-fledged>
>> type-level non-inductive functions.> And sometimes we intuitively want to
>> use them as such.
> Thank you, Yves! It is now more clear for me.
>
> Still, it seems
Henrik Nilsson wrote:
> > Just like chatter and chattee, employer and employee, there is an
> > iterator (usually as part of an enumerator/ee) and an iteratee.
>
> Thanks for the attempt to explain. But I, at least, remain mystified,
> and I agree with Douglas that the terminology is confusing.
>
Quoth Felipe Almeida Lessa ,
> On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery wrote:
>> They *do* terminate; a zombie is a dead process waiting for its parent to
>> reap it with waitForProcess. There's also some POSIX stuff you can do to
>> have them auto-reaped, but doing that correctly and por
On Wed, Dec 7, 2011 at 10:27, Felipe Almeida Lessa
wrote:
> On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery
> wrote:
> > They *do* terminate; a zombie is a dead process waiting for its parent to
> > reap it with waitForProcess. There's also some POSIX stuff you can do to
> > have them auto-reape
On Wed, Dec 7, 2011 at 1:19 PM, Brandon Allbery wrote:
> They *do* terminate; a zombie is a dead process waiting for its parent to
> reap it with waitForProcess. There's also some POSIX stuff you can do to
> have them auto-reaped, but doing that correctly and portably is somewhat
> painful.
But
Hi,
Ertugrul wrote:
> Just like chatter and chattee, employer and employee, there is an
> iterator (usually as part of an enumerator/ee) and an iteratee.
Thanks for the attempt to explain. But I, at least, remain mystified,
and I agree with Douglas that the terminology is confusing.
Usually, t
On Wed, Dec 7, 2011 at 06:47, Dan Rosén wrote:
> I'm using Haskell to run a lot of instances of an Automated Thorem Prover,
> eprover. I have pasted a smaller version of my program at
> http://hpaste.org/54954. It runs eprover sequentially on all input files,
> with a timeout of 100ms. Unfortunat
Douglas McClean wrote:
> I love iteratees as a paradigm for IO, but I am having trouble
> developing a relationship with the names. Could someone explain their
> origin?
>
> It seems like if iteratees consume things, enumerators produce them,
> andenumeratees do both that names like Sink, Source,
The Programming Languages Group of Ghent University invites applicants
for a PhD position. This position centers around the modular treatment
of side-effects in purely functional programs and models. It is part
of the project "Modular handling of effects in purely functional
programs and models" un
Quick suggestion: did you try using waitForProcess just after terminateProcess?
Cheers,
--
Felipe.
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> For short, type synonyms work for mere aliases, but not for full-fledged>
> type-level non-inductive functions.> And sometimes we intuitively want to use
> them as such.
Thank you, Yves! It is now more clear for me.
Still, it seems that ability to use partially applied type synonyms would be
v
Ah, maybe Dan could tell us if it works only with GHC 7.
Dmitry, I had your problem many times. The last time was when I saw you
could define the ContT monad in terms of Cont (the opposite is done in the
mtl).
It leads to a simpler code, but you are stucked when trying to define ContT
as an instan
Hi Haskell-Cafe,
I'm using Haskell to run a lot of instances of an Automated Thorem Prover,
eprover. I have pasted a smaller version of my program at
http://hpaste.org/54954. It runs eprover sequentially on all input files,
with a timeout of 100ms. Unfortunately, it leaves a lot of zombie processe
> Dmitry, does your code work with LiberalTypeSynonyms extention activated?
No, the same error:
Type synonym `StateA' should have 1 argument, but has been given 0
But I have GHC 6.12.3
Dmitry
2011/12/7 Yves Parès :
> This is impossible:
> in the definition of 'StateT s m a', m must be a monad and
This is impossible:
in the definition of 'StateT s m a', m must be a monad and then have the *
-> * kind.
So you cannot pass (StateA a), because it has simply the * kind.
Dmitry, does your code work with LiberalTypeSynonyms extention activated?
2011/12/7 Øystein Kolsrud
> You should be able to
> You should be able to write something like this:
>
> type StateB a b = StateT SomeOtherState (StateA a) b
Thank you for reply, but this variant actually does not compile:
StateA and (StateA a) have different kinds.
Dmitry
>
> Best regards, Øystein Kolsrud
>
>
> On Wed, Dec 7, 2011 at 11:48 AM,
You should be able to write something like this:
type StateB a b = StateT SomeOtherState (StateA a) b
Best regards, Øystein Kolsrud
On Wed, Dec 7, 2011 at 11:48 AM, Dmitry Kulagin wrote:
> Hi Dan,
>
> I am still pretty new in Haskell, but this problem annoys me already.
>
> If I define certain
Hi Dan,
I am still pretty new in Haskell, but this problem annoys me already.
If I define certain monad as a type synonym:
type StateA a = StateT SomeState SomeMonad a
Then I can't declare new monad based on the synonym:
type StateB a = StateT SomeOtherState StateA a
The only way I kn
Dear List,
I have a point misunderstood!
I am using second generation strategies of Haskell to parallelize some
number of algorithms in Haskell.
The missing point here is that:
In some cases, neither of created sparks are converted into OS threads,
but parallelization happens surprisingly, wh
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