On Mon, May 16, 2011 at 10:47 PM, Gregory Guthrie wrote:
> Below is the install result. It does claim that "You must install OpenCV
> (development packages) prior to installing this package."
> I don't' see any Haskell /cabal opencv package, so am not sure what this
> means one has to do.
The e
Below is the install result. It does claim that "You must install OpenCV
(development packages) prior to installing this package."
I don't' see any Haskell /cabal opencv package, so am not sure what this means
one has to do.
I am not familiar enough with the Haskell install and make environment
Oh, in case the code would be helpful.. ;)
import Data.Set (toList, fromList, intersection, size)
import Data.List ((\\))
import System.Random (randomRIO)
import Data.Word (Word32)
import Graphics.UI.SDL as SDL
main = do
SDL.init [InitVideo, InitTimer, InitEventthread]
w <- setVideoMode 1440
Greetings Haskellers,
I'm relatively new to the language and I'm writing a basic game of life
simulation to try out the SDL bindings. The program updates the window with
the next generation of cells each time you press 'n', and the problem I'm
finding is that every so often the window stops upda
On Mon, May 16, 2011 at 8:40 PM, Gracjan Polak wrote:
> result <- runErrorT $ do
> lift $ print "was here"
> fail "msg"
>
> (result = Left "msg")
>
> after a while the print statement may be removed:
>
> result <- runErrorT $ do
> fail "msg"
>
> (result = Left "msg")
That seems pr
At Mon, 16 May 2011 22:31:14 +0100,
Simon Marlow wrote:
>
> Good example - so it looks like we don't get full sequential consistency
> on x86 (actually I'd been thinking only about write ordering and
> forgetting that reads could be reordered around writes).
>
> But that's bad because it means
Daniel Fischer googlemail.com> writes:
>
> On Monday 16 May 2011 23:41:44, Gracjan Polak wrote:
> > Thanks Daniel, Yves and Edward for explanation. Two things come to my
> > mind now.
> >
> > 1. It should be unified.
>
> The (Either e) Monad instance was recently changed after people have long
On Tuesday 17 May 2011 00:22:02, Alexey Khudyakov wrote:
> 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 se
On 16/05/2011, at 7:39 PM, Ketil Malde wrote:
> I'm not intimately familiar with IEEE 754, but in any case we'd be in
> good company: R typically lets you select to sort NaNs as greater or
> less than any other values, and sorts non-NaN values correctly also in
> the presence of NaNs, I think.
>
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 Monday 16 May 2011 23:41:44, Gracjan Polak wrote:
> Thanks Daniel, Yves and Edward for explanation. Two things come to my
> mind now.
>
> 1. It should be unified.
The (Either e) Monad instance was recently changed after people have long
complained that there shouldn't be an (Error e) constrai
On Mon, May 16, 2011 at 4:41 PM, Gracjan Polak wrote:
>
> Thanks Daniel, Yves and Edward for explanation. Two things come to my mind
> now.
>
> 1. It should be unified. Why? Because conceptually:
>
> runIdentity (runErrorT (fail "msg")) :: Either String Int
> Left "msg"
>
> and
>
> fail "msg" ::
Thanks Daniel, Yves and Edward for explanation. Two things come to my mind now.
1. It should be unified. Why? Because conceptually:
runIdentity (runErrorT (fail "msg")) :: Either String Int
Left "msg"
and
fail "msg" :: Either String Int
*** Exception: msg
Should be the same as Identity monad
On 16/05/11 20:31, dm-list-haskell-c...@scs.stanford.edu wrote:
At Mon, 16 May 2011 10:56:02 +0100,
Simon Marlow wrote:
Yes, it's not actually documented as far as I know, and we should fix
that. But if you think about it, sequential consistency is really the
only sensible policy: suppose one
On Monday 16 May 2011 23:05:22, Yves Parès wrote:
> Probably because in the instance of Monad Either, fail has not been
> overloaded, and still has its default implementation:
> fail = error
Right. It used to be different in mtl-1.*, when there was an
instance Error e => Monad (Either e) where
On Monday 16 May 2011 22:26:18, I wrote:
> On Monday 16 May 2011 20:49:35, austin seipp wrote:
> > As you can see, with the foldr definition, GHC is able to fuse the
> > iteration of the input list with the generation of the result - note
> > the 'GHC.Base.++' call with the first argument being a l
I suspect it is because the "fail" method for the 'Either' monad
instance makes use of Haskell's error function, since the instance is
defined generally and there is no way to override it for (Either
String a).
On May 16, 2011, Gracjan Polak wrote:
> Control.Monad.Error Prelude> runErrorT (fail
Probably because in the instance of Monad Either, fail has not been
overloaded, and still has its default implementation:
fail = error
Whereas runErrorT explicitely catches the exception.
2011/5/16 Gracjan Polak
>
> Hi all,
>
> A why question: Why:
>
> Control.Monad.Error Prelude> runErrorT (fa
Hi all,
A why question: Why:
Control.Monad.Error Prelude> runErrorT (fail "msg") :: IO (Either String Int)
Left "msg"
but
Control.Monad.Error Prelude> (fail "msg") :: (Either String Int)
*** Exception: msg
?
--
Gracjan
___
Haskell-Cafe mailing
On Monday 16 May 2011 20:49:35, austin seipp wrote:
> As you can see, with the foldr definition, GHC is able to fuse the
> iteration of the input list with the generation of the result - note
> the 'GHC.Base.++' call with the first argument being a list from
> [x..x*2], and the second list to appen
You're both right indeed - I didn't look for the definition of
concatMap in GHC.List.
I thought it could be some behavior with the new inliner, so I defined
concatMap in terms of foldr, put it in a seperate module, and then
included it and used it in my test:
Concatmap2.hs:
module Concatmap2 (con
At Tue, 17 May 2011 02:18:55 +1000,
Bernie Pope wrote:
>
> http://augustss.blogspot.com/2011/04/
> ugly-memoization-heres-problem-that-i.html
>
> He says that "There's no guarantee about readIORef and writeIORef when doing
> multi-threading.". But I was wondering if that was true, and if it were
On Monday 16 May 2011 20:49:35, austin seipp wrote:
> Looking at the Core for an utterly trivial example (test x = concatMap
> k x where k i = [i..i*2]), the foldr definition seems to cause a
> little extra optimization rules to fire, but the result seems pretty
> big. The definition using concatMa
At Mon, 16 May 2011 10:56:02 +0100,
Simon Marlow wrote:
>
> Yes, it's not actually documented as far as I know, and we should fix
> that. But if you think about it, sequential consistency is really the
> only sensible policy: suppose one processor creates a heap object and
> writes a reference
On Mon, May 16, 2011 at 3:49 PM, austin seipp wrote:
> I don't know why GHC doesn't have this rule by default, though. We can
> at least rig it with a RULES pragma, however:
>
> $ cat concatmap.hs
> module Main where
>
> {-# RULES
> "concatMap/foldr" forall x k. concatMap k x = foldr ((++) . k) []
Looking at the Core for an utterly trivial example (test x = concatMap
k x where k i = [i..i*2]), the foldr definition seems to cause a
little extra optimization rules to fire, but the result seems pretty
big. The definition using concatMap results in core like this:
main_go2 =
\ (ds_aqV :: [Int
On Mon, May 16, 2011 at 3:39 AM, Ketil Malde wrote:
> I'm not intimately familiar with IEEE 754, but in any case we'd be in
> good company: R typically lets you select to sort NaNs as greater or
> less than any other values, and sorts non-NaN values correctly also in
> the presence of NaNs, I thin
Николай Кудасов wrote:
Problem becomes much more complex when I want to add function calls into
my language. Type class CallArgs has an instance CallArgs (IO a)
(CodeGenFunction r (Value a)), which can't be given as a constraint in
typed AST because of free variable r. For a long time I have h
On Mon, May 16, 2011 at 8:37 AM, Gregory Guthrie wrote:
> I wanted to look into using Haskell for an introductory Image Processing
> class, but the main package used for such things (OpenCV) does not appear to
> be available for windows systems.
>
> Is there some other good option for image proc
On 16/05/2011 10:07 AM, Michael Vanier wrote:
Usually in monad tutorials, the >>= operator for the list monad is
defined as:
m >>= k = concat (map k m) -- or concatMap k m
but in the GHC sources it's defined as:
m >>= k = foldr ((++) . k) [] m
As far as I can tell, this definition is equivale
You might want to read the Repa tutorial:
http://www.haskell.org/haskellwiki/Numeric_Haskell:_A_Repa_Tutorial
e.g.
fromList (Z :. (3::Int)) [1,2,3]
2011/5/16 Grigory Sarnitskiy :
>> There's fromIArray and fromList [1]. Does that answer your question?
>
> Huh, yes, thank you! But still
> There's fromIArray and fromList [1]. Does that answer your question?
Huh, yes, thank you! But still I don't get it. Neither
arr1 = fromList 3 [1,2,3] :: Array DIM1 Int
nor
arr1 = fromList (1,3) [1,2,3] :: Array DIM1 Int
works
___
Haskell-Cafe mai
On Mon, May 16, 2011 at 1:33 PM, Grigory Sarnitskiy wrote:
> Hello!
>
> I'm probing CUDA with Haskell, accelerate package to be exact. Sound stupid,
> but I couldn't find how to actually construct an array, for example Vector
> Float.
>
> There is quite a number of examples provided with the pac
Hello!
I'm probing CUDA with Haskell, accelerate package to be exact. Sound stupid,
but I couldn't find how to actually construct an array, for example Vector
Float.
There is quite a number of examples provided with the package, but they seem
not simple enough for me just to start.
__
On 16 May 2011 19:56, Simon Marlow wrote:
> On 13/05/2011 21:12, Bernie Pope wrote:
>
Could you please point me to more information about the sequential
>> consistency of IORefs? I was looking for something about this recently
>> but couldn't find it. I don't see anything in the Haddock for Data.
On Mon, May 16, 2011 at 8:10 AM, Robert Clausecker wrote:
> I found out, that GHC implements typeclasses as an extra argument, a
> record that stores all functions of the typeclass. So I was wondering,
> is there a way (apart from using newtype) to pass a custom record as the
> typeclass record, t
Robert Clausecker wrote:
> I found out, that GHC implements typeclasses as an extra argument, a
> record that stores all functions of the typeclass. So I was wondering,
> is there a way (apart from using newtype) to pass a custom record as
> the typeclass record, to modify the behavior of the typ
I wanted to look into using Haskell for an introductory Image Processing class,
but the main package used for such things (OpenCV) does not appear to be
available for windows systems.
Is there some other good option for image processing in Haskell, or has anyone
ported openCV to a windows Leksa
Hello!
I found out, that GHC implements typeclasses as an extra argument, a
record that stores all functions of the typeclass. So I was wondering,
is there a way (apart from using newtype) to pass a custom record as the
typeclass record, to modify the behavior of the typeclass? I thought
about som
Ahh, never mind... I just realized there's no way to relate the `info`
in the instance to the `info` in the class definition.
Alright, I'll keep trying to make this work. Sorry for the noise!
/ Emil
2011-05-16 12:19, Emil Axelsson skrev:
Hello!
At the end of this message is a program with a
Hello!
At the end of this message is a program with a simple expression type,
and a class `ToExpr` that generalizes expressions to arbitrary Haskell
types. Every node in `Expr` is annotated with some abstract information.
The program raises the following type error:
test.hs:13:5:
Couldn'
On 13/05/2011 21:12, Bernie Pope wrote:
On 13 May 2011 19:06, Simon Marlow mailto:marlo...@gmail.com>> wrote:
As far as memory consistency goes, we claim to provide sequential
consistency for IORef and IOArray operations, but not for peeks and
pokes.
Hi Simon,
Could you please poi
On 16 May 2011 19:07, Michael Vanier wrote:
> Usually in monad tutorials, the >>= operator for the list monad is defined
> as:
>
> m >>= k = concat (map k m) -- or concatMap k m
>
> but in the GHC sources it's defined as:
>
> m >>= k = foldr ((++) . k) [] m
>
> As far as I can tell, this
On Monday 16 May 2011 11:07:15, Michael Vanier wrote:
> Usually in monad tutorials, the >>= operator for the list monad is
> defined as:
>
> m >>= k = concat (map k m) -- or concatMap k m
>
> but in the GHC sources it's defined as:
>
> m >>= k = foldr ((++) . k) [] m
>
> As far as I c
Usually in monad tutorials, the >>= operator for the list monad is
defined as:
m >>= k = concat (map k m) -- or concatMap k m
but in the GHC sources it's defined as:
m >>= k = foldr ((++) . k) [] m
As far as I can tell, this definition is equivalent to the previous one
(correct me
A few people have mentioned that the flattening process is easier to
understand from example diagrams. Now it's possible to generate those
diagrams automatically:
http://www.cs.berkeley.edu/~megacz/garrows/flattening.examples/
- a
___
Haskell-Ca
Casey McCann writes:
> It would improve things in the sense of giving well-behaved instances
> for Eq and Ord, yes. It would not improve things in the sense that it
> would violate the IEEE floating point spec.
I'm not intimately familiar with IEEE 754, but in any case we'd be in
good company: R
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