On 09/29/13 08:20, Edward Kmett wrote:
I don't know that it belongs in the standard libraries, but there
could definitely be a package for something similar.
ConstraintKinds are a pretty hefty extension to throw at it, and the
signature written there prevents it from being used on ByteString,
On 09/13/13 01:51, Michael Snoyman wrote:
On Fri, Sep 13, 2013 at 5:38 AM, Mario Blažević blama...@acanac.net
mailto:blama...@acanac.net wrote:
On 09/11/13 19:37, John Lato wrote:
3. I'm not entirely sure that the length* functions belong
here. I
understand why
On 09/13/13 02:28, Michael Snoyman wrote:
On Fri, Sep 13, 2013 at 9:18 AM, Mario Blažević blama...@acanac.net
mailto:blama...@acanac.net wrote:
On 09/13/13 01:51, Michael Snoyman wrote:
On Fri, Sep 13, 2013 at 5:38 AM, Mario Blažević
blama...@acanac.net
On 09/11/13 19:37, John Lato wrote:
I didn't see this message and replied privately to Michael earlier, so
I'm replicating my comments here.
1. Sooner or later I expect you'll want something like this:
class LooseMap c el el' where
lMap :: (el - el') - c el - c el'
It covers the case of
On 09/02/13 06:53, Nicolas Trangez wrote:
# Redirected to haskell-cafe
On Sun, 2013-09-01 at 14:58 +0400, Artyom Kazak wrote:
Would this be an appropriate place to propose adding mapM_ (and then
possibly mapM) to bytestring library?
Was it suggested before? If yes, why was it rejected?
This
On 13-08-22 04:04 PM, Petr Pudlák wrote:
Or, if there are no such definitions, where would be a good place to add
them?
If they are to be added to the base libraries, the Data.Monoid module
would be my choice.
I did wish I had the AppMonoid instance on several occasions, when
using
See also this thread from two years ago:
http://www.haskell.org/pipermail/haskell-cafe/2011-June/091294.html
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The new package monoid-subclasses [1] exports a number of classes
that sit between monoids and groups: ReductiveMonoid,
CancellativeMonoid, GCDMonoid, MonoidNull, and FactorialMonoid among
others. The package also comes with class instances for all applicable
data types from base, vector,
On 13-03-11 10:52 PM, Michael Orlitzky wrote:
On 03/11/2013 11:48 AM, Brent Yorgey wrote:
So I'd like to do it again this time around, and am looking for
particular projects I can suggest to them. Do you have an open-source
project with a few well-specified tasks that a relative beginner (see
On 13-01-26 05:28 AM, Erik de Castro Lopo wrote:
Thiago Negri wrote:
Do you need advice on what? I didn't understand your last phrase.
Well I have data from two sources, stdin and the calculation
thread. If I was doing this in C, I'd probably use a pipe for the
calculation data and then do
On 12-09-26 08:07 PM, wren ng thornton wrote:
On 9/25/12 1:57 PM, Sjoerd Visscher wrote:
Maybe we could make a literal [a,b,c] turn into
unpack [a,b,c]#
where
[a,b,c]#
is a statically-allocated vector?
I'm kinda surprised this isn't already being done. Just doing this seems
like it'd
On 12-09-18 07:37 PM, Richard O'Keefe wrote:
On 19/09/2012, at 1:43 AM, Stefan Monnier wrote:
The problem with that is that some people DO end some headings with
a full stop; for them your special syntax is not natural.
Markdown/ReST is already using the no syntax idea (e.g. compared to
On 12-08-15 02:54 PM, Daniel Hlynskyi wrote:
Hello Cafe.
Consider code, that takes input from handle until special substring
matched:
matchInf a res s | a `isPrefixOf` s = reverse res
matchInf a res (c:cs) = matchInf a (c:res) cs
hTakeWhileNotFound str hdl = hGetContents
On 12-05-22 09:55 AM, Benjamin Ylvisaker wrote:
Has anyone ever worked on implementing something like this in Haskell?
http://www.cs.hmc.edu/~stone/papers/ocm-unpublished.pdf
The outline of the idea:
- Concurrent programming is really hard with the popular frameworks
today.
- For most
On 12-04-07 05:35 PM, Myles C. Maxfield wrote:
So here are my questions:
...
3. Are there any parsers that support streaming semantics and being
used as a monad transformer? This would require rewriting my whole
program to use this new parser, but if that's what I have to do, then
so be it.
On 12-03-11 09:09 AM, Paolo Capriotti wrote:
The Category law would be broken, though:
unawait x id == yield x !== unawait x
How did you get this equation? It's not even well-typed:
unawait :: a - Pipe a b m ()
yield :: b - Pipe a b m ()
You're right, it's completely wrong. I was
On 12-03-11 12:39 PM, Chris Smith wrote:
On Sun, Mar 11, 2012 at 10:30 AM, Mario Blaževićblama...@acanac.net wrote:
(p1 unawait x) p2 = (p1 p2)* unawait x -- this one
tripped me up
I don't think this could reasonably hold. For example, you'd expect
that for any p, idP p == idP
On 12-03-11 01:36 PM, Chris Smith wrote:
On Sun, Mar 11, 2012 at 11:22 AM, Mario Blaževićblama...@acanac.net wrote:
No, idP does terminate once it consumes its input. Your idP p first
reproduces the complete input, and then runs p with empty input.
This is just not true. idP consumes
On 12-03-10 05:16 AM, Paolo Capriotti wrote:
On Sat, Mar 10, 2012 at 4:21 AM, Mario Blaževićblama...@acanac.net wrote:
I like your design, it seems to strike a good balance between elegance
and practicality. The only thing missing for the latter is a deeper support
for chunking. Of course,
On 12-03-10 05:19 PM, Twan van Laarhoven wrote:
On 2012-03-10 11:16, Paolo Capriotti wrote:
Another issue is how to deal with unconsumed input. For that, there is
a ChunkPipe type (in pipes-extra) with a specialized monad instance
that threads unconsumed input along. You can see an example of
On 12-03-10 09:05 PM, Twan van Laarhoven wrote:
On 2012-03-11 00:09, Mario Blažević wrote:
On 12-03-10 05:19 PM, Twan van Laarhoven wrote:
-- | Pass some unconsumed input back upstream.
-- The next @await@ will return this input without blocking.
unawait :: Monad m = a - Pipe a b m
On 12-03-09 07:36 PM, Paolo Capriotti wrote:
I'm pleased to announce the release of version 0.0.1 of pipes-core, a
library for efficient, safe and compositional IO, similar in scope to
iteratees and conduits.
I like your design, it seems to strike a good balance between
elegance and
On 12-02-13 10:12 AM, Roel van Dijk wrote:
Hello,
I have a program which I believe can benefit from concurrency. But I
am wondering if the mechanisms I need already exist somewhere on
Hackage.
You can try monad-coroutine. Here is an incomplete transcription of
your code:
import
On 12-01-28 06:56 AM, Felipe Almeida Lessa wrote:
On Sat, Jan 28, 2012 at 9:40 AM, Yves Parèsyves.pa...@gmail.com wrote:
I think there is still no consensus on which iteratee library is the one
to use. There are at least iteratee, enumerator, iterIO, conduit, and
pipes. The reusability of your
On 11-09-05 10:42 AM, Sjoerd Visscher wrote:
This way these laws hold for non-empty lists:
maximumBy f xs = last (sortBy f xs)
minimumBy f xs = head (sortBy f xs)
That's not a bad justification for the way implementation works,
even if it's not the original reason behind it. I think
I was recently surprised to discover that the maximum and maximumBy
functions always return the *last* maximum, while minimum and minimumBy
return the *first* minimum in the list. The following GHCi session
demonstrates this:
$ ghci
GHCi, version 7.2.1: http://www.haskell.org/ghc/ :? for
For anybody interested in programming languages or markup languages,
there is an open job position for a junior developer at Stilo
(http://www.stilo.com/). Haskell is currently used only for prototyping,
but there are plans to begin some major development in Haskell within a
year.
The job
On 11-06-20 10:45 AM, Richard Senington wrote:
Hi all,
I have recently become interested in Dataflow programming and how it
related to functional languages.
I am wondering if the community has any advice on reading matter or
other directions to look at.
So far I have been looking through
On 11-06-09 04:14 PM, Alexander V Vershilov wrote:
Hello.
I'm writing a small tcp server with that can handle connections and
answer by rules writen in a small script that can be interpreted by server.
For this purpose I've written an interpreter that has type
ErrorT MyError (StateT
On 11-06-03 06:00 AM, Yitzchak Gale wrote:
Mario Blažević wrote:
I don't know if this helps, but the incremental-parser library has
exactly the combinator you're looking for.
Wow, that is a beautiful implementation of a general parser
library. So much simpler than Parsec. Thanks
On Thu, Jun 2, 2011 at 10:02 AM, Yitzchak Gale g...@sefer.org wrote:
I often find while using attoparsec and attoparsec-text that I need to
match a number of text parsers consecutively and concatenate the
result. By text parser I mean Parser ByteString for attoparsec and
Parser Text for
On 11-05-30 05:05 AM, Alexey Khudyakov wrote:
On 30.05.2011 12:26, Bas van Dijk wrote:
On 30 May 2011 00:14, Alexey Khudyakovalexey.sklad...@gmail.com 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
On 11-05-25 08:52 AM, Johan Tibell wrote:
On Wed, May 25, 2011 at 2:01 PM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com wrote:
With my wl-pprint-text package, Jason Dagit suggested to me on
#haskell that it would make sense to make such a pretty-printer be
class-based so that the same API
On 11-05-06 11:15 AM, Alex Mason wrote:
Hi All,
I really love the look of this package, but if this is going be *the* iteratee
package, I would absolutely love to see it fix some of the biggest mistakes in
the other iteratee packages, soecifically naming. A change in naming for the
terms
On 11-05-06 09:58 PM, dm-list-haskell-c...@scs.stanford.edu wrote:
At Fri, 06 May 2011 21:27:21 -0400,
Mario Blažević wrote:
I'd been thinking about using the terms Source and Sink, but Source is
very overloaded, and SinkSource doesn't exactly roll off the tongue
or evoke a particularly helpful
On 11-03-30 05:29 PM, Mathijs Kwik wrote:
Hi all,
I'm playing around a bit with arrows (more specifically, something
like a CPS style streamprocessor as described in Generalising Monads
to Arrows by John Hughes).
I had struggled with the same problem a year ago, and I concluded it
was
On 11-03-26 12:27 AM, Steven Shaw wrote:
Hi Mario,
I wondered if you had an application in mind for your incremental
parser library in Haskell? A little while ago I was following the
development of an open source text editor for Mac OS X called
Kod[.app]. They were wanting an incremental
On 11-03-26 04:33 PM, John A. De Goes wrote:
I noticed this problem some time ago. Beyond just breaking monadic
associativity, there are many other issues with standard definitions
of iteratees:
1. It does not make sense in general to bind with an iteratee that
has already consumed
Packages monad-parallel [1], monad-coroutine [2] and SCC [3] have been
upgraded on Hackage to version 0.7.
The monad-parallel library defines two Monad subclasses,
MonadParallel and MonadFork, that enable some monadic computations to be
executed in parallel and their results combined. The
On Sun, Mar 20, 2011 at 10:50 AM, Christopher Done chrisd...@googlemail.com
wrote:
On 20 March 2011 15:05, Pieter Laeremans pie...@laeremans.org wrote:
Hi all,
The MIME package that can be found on hackage, uses String as input.
Would i be considered better if there would be a version
The first version of incremental-parser has been released on Hackage
[1]. It's yet another parser combinator
library, providing the usual set of Applicative and Monad combinators. Apart
from this, it has three twists that make it
unique.
First, the parser is incremental. That means it can
This seems very interesting. One question:
The MonadPlus and the Alternative instance differ: the former's mplus
combinator equals the asymmetric | choice.
Why?
Good question. Basically, I see MonadPlus as a union of Monad and
Alternative. The class should not exist at all. But as
exist in two
forms, the lazy one and the greedy one, and the only difference is the
underlying choice combinator, (|) vs. (|).
I'm not aware of any other parsing library taking this road, though, and
there must be a good reason. I'll try and see.
2011/3/22 Mario Blažević mblaze...@stilo.com
I've tried to send the verification e-mail from trac.haskell.org to three
different e-mail accounts in the last 24 hours. None arrived.
Note that I'm not trying to create a new account, I'm trying to verify my
e-mail address in order to edit the Wiki pages of my projects.
Can anybody else
I've sent an e-mail to Haskell Café this morning about my troubles
with Trac confirmation e-mails. The e-mail must have reached the server,
because it showed up in the mailing list archive:
http://www.haskell.org/pipermail/haskell-cafe/2011-March/090311.html
This other archive,
of the module, class and its single
method, and what instances to declare inside the module.
-Edward
On Fri, Dec 24, 2010 at 4:51 AM, Stephen Tetley
stephen.tet...@gmail.comwrote:
On 24 December 2010 02:16, Mario Blažević mblaze...@stilo.com wrote:
To turn the proof obligation around, what could
(Foldable f, Pointed f) = Sequence f
or whatever.
On Fri, Dec 24, 2010 at 4:51 AM, Stephen Tetley stephen.tet...@gmail.comwrote:
On 24 December 2010 02:16, Mario Blažević mblaze...@stilo.com wrote:
To turn the proof obligation around, what could possibly be the downside
of
adding a puny
Why are Cofunctor and Comonad classes not a part of the base library?
I recently defined a data type (Control.Cofunctor.Ticker in
monad-coroutine on Hackage) that happens to be a co-functor, or
contra-functor if you prefer. In other words, it can implement the
following function:
cofmap ::
On Thu, Dec 23, 2010 at 5:25 PM, Stephen Tetley stephen.tet...@gmail.comwrote:
On 23 December 2010 21:43, Mario Blažević mblaze...@stilo.com wrote:
Why are Cofunctor and Comonad classes not a part of the base library?
[SNIP]
Later on I found that this question has been raised before
On Thu, Dec 23, 2010 at 11:25 PM, Tony Morris tonymor...@gmail.com wrote:
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
...regardless of the utility of a contravariant functor type-class, I
strongly advocate for calling it Contrafunctor and not Cofunctor. I
have seen numerous examples of
On 10-11-14 07:36 PM, Jiansen He wrote:
Hi cafe,
I wounder if it is possible to tell a haskell system that two
computations with side effects could be executed concurrently.
Here is an affected example:
Suppose two people want to compare their age, but do not want to leak
their personal
Packages monad-coroutine and SCC have been upgraded to version 0.6 on
Hackage.
The monad-coroutine package exports a generic monad transformer
Coroutine: Functor s = MonadTrans (Coroutine s). A
Coroutine-transformed monad can suspend at any point, returning its
resumption wrapped in the
The newly released coroutine-enumerator package can be used as a bridge
between the enumerator and monad-coroutine packages. It provides two-way
conversion functions between an Iteratee and an Await-suspending coroutine,
and also between an Enumerator and a Yield-suspending coroutine.
As a little
I had the exact same problem in my regional-pointers package in the
withArray function:
withArray ∷ (Storable α, MonadCatchIO pr)
⇒ [α]
→ (∀ s. RegionalPtr α (RegionT s pr) → RegionT s pr β)
→ pr β
I had to replace the original:
withArray vals =
Before uploading a new version of my project on Hackage, I decided to
future-proof it against GHC 7.0. I ran into several compile errors caused by
the changes in let generalization, but these were easy to fix by adding
extra type annotations. But then I ran into another problem that I can't
Yves Parès wrote:
It helps me understand better, but would you have some simple code that
would do that ?
You can look at the definition of the coroutine monad transformer in
the monad-coroutine package as well:
http://hackage.haskell.org/package/monad-coroutine
The heart of
Patrick LeBoutillier wrote:
...
Basically I'm looking for a bit of feedback/info:
- Does anyone know if there are already similar projets out there?
You've already got some references, you can also look at
http://hackage.haskell.org/package/scc which includes a shell language.
- Does
There are three new packages on Hackage:
- monad-parallel 0.5
(http://hackage.haskell.org/package/monad-parallel)
- monad-coroutine 0.5
(http://hackage.haskell.org/package/monad-coroutine)
- Streaming Component Combinators 0.5
(http://hackage.haskell.org/package/scc)
The
Victor Nazarov wrote:
Hello,
I've been writing some GUI application with Gtk2hs. It's an
interpreter for lambda-calculus and combinatory logic, it's GPL and if
you interested I can share it with cafe.
The problem is that the GUI code has become very ugly and I'm tempted
to rewrite it totally.
Stupid question: Is it related to Arrows?
Not really. You might say it's more general than arrows, because
the streaming components are not restricted to a single input and
single output type. On the other hand, they are all specific to stream
processing, much like Fudgets and Yampa
On Sun 17/01/10 4:47 PM , Twan van Laarhoven twa...@gmail.com sent:
The Arrow class is too big, it includes too many things and it should be
split up. This is yet another example. You can get some of the benefits of
standard classes by making Transducer an instance of
Henning Thielemann wrote:
Mario Blažević schrieb:
Version 0.4 of Streaming Component Combinators, or SCC for short, has
been released on Hackage. Get it at
http://hackage.haskell.org/package/scc
There isn't much new high-level functionality compared to the
previous version
I can't test it right now, but wouldn't the
following do the job in the Identity monad?
forkExec :: Identity a - Identity (Identity a)
forkExec k = let result = runIdentity k
in result `par` return (Identity result)
Since Identity is a newtype, would that be
I recommend using -ddump-simpl, as it produces more readable output.
Actually, I can't see any effect of that pragma in the
core files whatsoever, but it certainly has effect on
run time.
How about diffing the whole core output (and using -ddump-simpl). If
there's a performance
On Fri 22/05/09 10:51 AM , John Lato jwl...@gmail.com sent:
Hi Mario,
It looks like the parallelize function is getting inlined when it's in
the same file, but not when it's in a separate file.
Adding a {-# INLINE parallelize #-} pragma to the module with
parallelize recovers all the
You could probably see exactly what's happening in
more detail by going through the Core output.
Thank you, this advice helped. The Core output indicates
that function `test' evaluates the arguments to
`parallelize' before it calls it. In other words, the
call to `parallelize' is optimized
On Sat 23/05/09 4:15 PM , Alexander Dunlap alexander.dun...@gmail.com sent:
Does anybody know of a pragma or another way to make a
function *non-strict* even if it does always evaluate its
argument? In other words, is there a way to
selectively disable the strictness optimization?
On Sat 23/05/09 2:51 PM , Duncan Coutts duncan.cou...@worc.ox.ac.uk sent:
On Sat, 2009-05-23 at 13:31 -0400, Mario Blažević wrote:
...
So the function is not strict, and I don't understand
why GHC should evaluate the arguments before the call.
Right, it's lazy in the first and strict
I'll cut to the chase. The short program below works perfectly: when I compile
it
with -O2 -threaded and run with +RTS -N2 command-line options, I get a nearly
50%
real-time improvement:
$ time ./primes-test +RTS -N2
5001
real0m9.307s
user0m16.581s
sys 0m0.200s
However, if I move
I think that
http://www.haskell.org/pipermail/haskell-cafe/2008-April/041461.html
may be relevant. It's a design decision.
Thanks for the link. I've read through the thread, but rather than try to
figure out if it's the same issue and whether it's a design decision or a
historical
I have, for a change, a relatively simple problem with type classes. Can
somebody explain to me, or point me to an explanation of the behaviour I see?
Here is a short and useless example:
{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-}
import Data.Maybe
class Container x y
I'll take a swing at this one:
instance Container (Maybe x) [x] where
wrapper = isNothing
. . .
That isn't a sensible definition of 'wrapper', but I believe without
trying to compile it is completely legal. Which wrapper do you use?
You /don't/ have a different matching Container
Hello. I'm trying to apply the nested regions (as in Lightweight Monadic
Regions by Oleg Kiselyov and Chung-chieh Shan) design pattern, if that's the
proper term. I was hoping to gain a bit more type safety in this little library
I'm working on -- Streaming Component Combinators, available on
I forgot the subject, sorry for reposting...
I'm trying to apply the nested regions (as in Lightweight Monadic Regions by
Oleg Kiselyov and Chung-chieh Shan) design pattern, if that's the proper term,
in hope to gain a bit more type safety in this little library I'm working on
(Streaming
Hello. I have a question about parallel computation in Haskell. After
browsing the GHC library documentation, I was left with impression that there
are two separate mechanisms for expressing concurrency: Control.Parallel.par
for pure computations and Control.Concurrent.forkIO for
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