On 3/5/09, Ryan Ingram ryani.s...@gmail.com wrote:
...
Here is the problem with your update:
tree = Fork (Leaf 1) (Leaf 2)
ztree = initZ tree
test = fromJust $ do
z1 - moveLeft ztree
let z2 = update z1 3
z3 - moveUp z2
z4 - moveLeft z3
this z4
I'd expect test to equal
Don Stewart ha scritto:
manlio_perillo:
Hi.
After some work I have managed to implement two simple programs that
parse the Netflix Prize data set.
For details about the Netflix Prize, there was a post by Kenneth Hoste
some time ago.
I have cabalized the program, and made available
Cristiano Paris wrote:
Ryan Ingram wrote:
...
Here is the problem with your update:
tree = Fork (Leaf 1) (Leaf 2)
ztree = initZ tree
test = fromJust $ do
z1 - moveLeft ztree
let z2 = update z1 3
z3 - moveUp z2
z4 - moveLeft z3
this z4
I'd expect test to equal 3, but I
Anish Muttreja ha scritto:
[...]
How about this. Is there a reason why I can't
replace the variables b and c in the type signature of mapReduce with with (IO b')
and (IO c'). b and c can be any types.
mapReduce :: Strategy (IO b')-- evaluation strategy for mapping
- (a - IO
On Thu, Mar 5, 2009 at 11:21 AM, Heinrich Apfelmus
apfel...@quantentunnel.de wrote:
...
Such self-reference is usually called tying the knot, see also
http://www.haskell.org/haskellwiki/Tying_the_Knot
I didn't know. Would you call this Tying the knot as well?
Bulat Ziganshin ha scritto:
Hello Manlio,
Tuesday, March 3, 2009, 5:35:33 PM, you wrote:
There are 100,000,000 ratings, so I create 100,000,000 arrays containing
only one element.
every array needs ~30 bytes - it's a minimal memory block ghc can
alloc for variable-sized objects. multiple
On Thursday 05 March 2009 09:45:51 Magicloud Magiclouds wrote:
I am confused. Code like this works in other WM, except xmonad.
You code does not set _NET_WM_STRUT property. And because of that xmonad
doesn't treat it specifically. You can inspect you window properties using
`xprop' utility.
Hi Gwern,
I get String/Data.Binary issues too. My suggestion would be to change
your strings to ByteString's, serisalise, and then do the reverse
conversion when reading. Interestingly, a String and a ByteString have
identical Data.Binary reps, but in my experiments converting,
including the cost
Ha. There's even a wiki page on the paradoxes of set theory
http://en.wikipedia.org/wiki/Paradoxes_of_set_theory
If I recall correctly, a math professor once told me that it is not yet
proven if the cardinality of the power set of the natural numbers is larger
or smaller or equal than the
Am Donnerstag, 5. März 2009 13:09 schrieb Peter Verswyvelen:
Ha. There's even a wiki page on the paradoxes of set theory
http://en.wikipedia.org/wiki/Paradoxes_of_set_theory
If I recall correctly, a math professor once told me that it is not yet
proven if the cardinality of the power set of
I wrote a solution to this problem, but it appears to return incorrect
results. There's a pastebin of the code at
http://hpaste.org/fastcgi/hpaste.fcgi/view?id=2121 and a picture of the
inputs, outputs, and expected results graphed at
http://img510.imageshack.us/img510/9971/resultsg.jpg
I'm
Lennart Augustsson wrote:
I don't see any breaking of referential transparence in your code.
Every time you do an IO operation the result is basically
non-deterministic since you are talking to the outside world.
You're assuming the IO has some kind of semantics that Haskell makes
no promises
On Wed, Mar 04, 2009 at 10:59:53PM -0500, Brandon S. Allbery KF8NH wrote:
On 2009 Mar 4, at 21:40, Magicloud Magiclouds wrote:
Could someone give me a sample or something I could learn from? Thanks.
(xmobar is open source, you could look through its source)
xmobar is not open source. xmobar
Whenever I'm looking for a bug in Haskell code, I find it helpful to start
by seeing if I can simplify the code any first. In this case, there are a
couple of things I notice:
- validPointsOf is just a filter. It would be easier to write valid ::
MyDirection - Bool and then validPointsOf =
On 5 Mar 2009, at 13:29, Daniel Fischer wrote:
In standard NBG set theory, it is easy to prove that card(P(N)) ==
card(R).
No, it is an axiom: Cohen showed in 1963 (mentioned in Mendelson,
Introduction to Mathematical Logic) that the continuum hypothesis
(CH) is independent of
Am Donnerstag, 5. März 2009 13:40 schrieb Rob Crowther:
I wrote a solution to this problem, but it appears to return incorrect
results. There's a pastebin of the code at
http://hpaste.org/fastcgi/hpaste.fcgi/view?id=2121 and a picture of the
inputs, outputs, and expected results graphed at
Am Donnerstag, 5. März 2009 14:58 schrieb Hans Aberg:
On 5 Mar 2009, at 13:29, Daniel Fischer wrote:
In standard NBG set theory, it is easy to prove that card(P(N)) ==
card(R).
No, it is an axiom: Cohen showed in 1963 (mentioned in Mendelson,
Introduction to Mathematical Logic) that the
2009/3/5 Hans Aberg hab...@math.su.se:
GHC says that for any set x, there are no cardinalities between card x and
No it doesn't.
It says there is a syntax error in my code.
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Am Donnerstag, 5. März 2009 15:12 schrieb Daniel Fischer:
Yes, but the continuum hypothesis is 2^Aleph_0 == Aleph_1, which is quite
something different from 2^Aleph_0 == card(R).
You can show the latter easily with the Cantor-Bernstein theorem,
independent of CH or AC.
Just to flesh this up
On 5 Mar 2009, at 15:12, Daniel Fischer wrote:
No, it is an axiom: Cohen showed in 1963 (mentioned in Mendelson,
Introduction to Mathematical Logic) that the continuum hypothesis
(CH) is independent of NBG+(AC)+(Axiom of Restriction), where AC is
the axiom of choice.
Yes, but the continuum
Hi.
I'm still having problems with the uvector package.
I have an IntMap (UArr xxx) data type, and I want to serialize it to
disk, in binary format.
I'm using the uvector package from
http://patch-tag.com/repo/pumpkin-uvector/home
The problem is with missing instance declarations, for
You're assuming that IO operations have semantics.
From the Haskell program's point of view, and when reasoning about
Haskell programs (not their interaction with the world) you should
assume that every IO operation returns a random result.
The way Oleg's program behaves does not break RT under
On 5 Mar 2009, at 15:23, Daniel Fischer wrote:
Just to flesh this up a bit:
let f : P(N) - R be given by f(M) = sum [2*3^(-k) | k - M ]
f is easily seen to be injective.
define g : (0,1) - P(N) by
let x = sum [a_k*2^(-k) | k in N (\{0}), a_k in {0,1}, infinitely
many a_k =
1]
and then g(x)
On Thu, 2009-03-05 at 13:08 +, Simon Marlow wrote:
Lennart Augustsson wrote:
I don't see any breaking of referential transparence in your code.
Every time you do an IO operation the result is basically
non-deterministic since you are talking to the outside world.
You're assuming the
Am Donnerstag, 5. März 2009 16:55 schrieb Hans Aberg:
On 5 Mar 2009, at 15:23, Daniel Fischer wrote:
Just to flesh this up a bit:
let f : P(N) - R be given by f(M) = sum [2*3^(-k) | k - M ]
f is easily seen to be injective.
define g : (0,1) - P(N) by
let x = sum [a_k*2^(-k) | k in N
On Thu, Mar 5, 2009 at 2:08 PM, Simon Marlow marlo...@gmail.com wrote:
So the argument is something like: we can think of the result of a call to
unsafeInterleaveIO as having been chosen at the time we called
unsafeInterleaveIO, rather than when its result is actually evaluated. This
is on
On 5 Mar 2009, at 17:06, Daniel Fischer wrote:
Cantor-Bernstein doesn't require choice (may be different for
intuitionists).
http://en.wikipedia.org/wiki/Cantor-Bernstein_theorem
Yes, that is right, Mendelson says that. - I find it hard to figure
out when it is used, as it is so
Hi Manlio,
I'm not sure the whole list wants to hear about bugs in my
modifications to an alpha library! :-)
But basically, I haven't added a Binary instance for productions like
that yet. This isn't trivial, but shouldn't be hard. Otherwise, using
the unsafe serialization functions I provide in
On Thu, Mar 5, 2009 at 7:08 AM, Simon Marlow marlo...@gmail.com wrote:
So the argument is something like: we can think of the result of a call to
unsafeInterleaveIO as having been chosen at the time we called
unsafeInterleaveIO, rather than when its result is actually evaluated. This
is on
On 2009 Mar 5, at 8:21, Andrea Rossato wrote:
On Wed, Mar 04, 2009 at 10:59:53PM -0500, Brandon S. Allbery KF8NH
wrote:
On 2009 Mar 4, at 21:40, Magicloud Magiclouds wrote:
Could someone give me a sample or something I could learn from?
Thanks.
(xmobar is open source, you could look
On Wed, Mar 4, 2009 at 5:03 PM, FFT fft1...@gmail.com wrote:
Are MPI bindings still the best way of using Haskell on Beowulf
clusters? It's my feeling that the bindings stagnated, or are they
just very mature?
What's the story with distributed memory multiprocessing? Are Haskell
programmers
On Tue, Mar 03, 2009 at 07:27:35AM -1000, Tim Newsham wrote:
How about this. Is there a reason why I can't
replace the variables b and c in the type signature of mapReduce with with
(IO b')
and (IO c'). b and c can be any types.
mapReduce :: Strategy (IO b')-- evaluation strategy for
I've been working on a little project, and one of the things I need to
do is dynamically compile and import a Haskell Source file containing
filtering definitions. I've written a small monad called Filter which is
simply:
type Filter a = Reader (Config, Email) a
To encompass all the email
I am looking for a way to test if a file is empty.
Something like isFileEmpty along the lines of
System.Directory.doesFileExist?
A function that wraps stat would also serve the purpose.
I get the feeling that someone must have felt the need for this before
me, but Google search not yield
Am Donnerstag, 5. März 2009 19:48 schrieb Joseph Fredette:
getFilterMain :: Deliverable a = FilePath - Interpreter (Filter
a)
getFilterMain fMainLoc =
do
loadModules [fMainLoc]; setTopLevelModules [(takeWhile
(/='.') fMainLoc)]
fMain - (interpret
Am Donnerstag, 5. März 2009 19:56 schrieb Anish Muttreja:
I am looking for a way to test if a file is empty.
Something like isFileEmpty along the lines of
System.Directory.doesFileExist?
If you're on a *nixy OS,
System.Posix.Files
getFileStatus, fileSize ...
dunno if Windows has similar
On Thu, 05 Mar 2009 19:56:42 +0100, Anish Muttreja
anishmuttr...@gmail.com wrote:
I am looking for a way to test if a file is empty.
Something like isFileEmpty along the lines of
System.Directory.doesFileExist?
A function that wraps stat would also serve the purpose.
I get the feeling that
On Thu, Mar 05, 2009 at 08:15:03PM +0100, Daniel Fischer wrote:
Am Donnerstag, 5. März 2009 19:56 schrieb Anish Muttreja:
I am looking for a way to test if a file is empty.
Something like isFileEmpty along the lines of
System.Directory.doesFileExist?
If you're on a *nixy OS,
Avoid unpack!
ndmitchell:
Hi Gwern,
I get String/Data.Binary issues too. My suggestion would be to change
your strings to ByteString's, serisalise, and then do the reverse
conversion when reading. Interestingly, a String and a ByteString have
identical Data.Binary reps, but in my
manlio_perillo:
Hi.
I'm still having problems with the uvector package.
I have an IntMap (UArr xxx) data type, and I want to serialize it to
disk, in binary format.
I'm using the uvector package from
http://patch-tag.com/repo/pumpkin-uvector/home
The problem is with missing
On Thu, Mar 05, 2009 at 12:50:20PM -0500, Brandon S. Allbery KF8NH wrote:
On 2009 Mar 5, at 8:21, Andrea Rossato wrote:
xmobar is not open source. xmobar is FREE software!
I don't do fundamentalist religion...
qualifying as fundamentalism the avoidance of cheap marketing
strategies is just a
Avoid massive reductions in runtime while maintaining the same API?
I did move to using ByteString's internally for those bits later on,
but reading String's from Data.Binary with a ByteString+unpack went
much more quickly than reading String's
On Thu, Mar 5, 2009 at 7:35 PM, Don Stewart
Hi
I am on Linux. BTW, Hoogle does not seem to know about
System.Posix.Files, though it did point me to System.IO.FileSize
which would also have served the purpose.
To build the Hoogle libraries I need to build the packages. I run
Windows not Linux, so its a bit difficult to index
This doesn't seem to do it, same type error... Maybe I need to use some
kind of witness type -- to inform the compiler
of the type of a @ runtime?
Daniel Fischer wrote:
Am Donnerstag, 5. März 2009 19:48 schrieb Joseph Fredette:
getFilterMain :: Deliverable a = FilePath - Interpreter
getFileStatus, fileSize ...
Great, thanks.
BTW, Hoogle does not seem to know about
System.Posix.Files, though it did point me to System.IO.FileSize
which would also have served the purpose.
Yep, this was discussed in a Hoogle and Network.Socket thread I
started last week. There is a wiki
So, by using the Haskell interpreter, you're using the
not-very-well-supported dynamically-typed subset of Haskell. You can
tell this from the type signature of interpret:
interpret :: Typeable a = String - a - Interpreter a
as :: Typeable a = a
as = undefined
(from
Luke Palmer lrpal...@gmail.com wrote:
I don't think set theory is trivial in the least. I think it is
complicated, convoluted, often anti-intuitive and nonconstructive.
Waaagh!
I mean trivial in the mathematical sense, as in how far away from the
axioms you are. The other kind of
To wrap up:
While formalising, there is always a tradeoff between complexity of
the theory you're using and the complexity of it being applied to some
specific topic. Category theory hits a very, very sweet spot there.
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So, I tried both of those things, both each alone and together. No dice.
Same error, so I reverted back to the
original. :(
However, I was, after some random type signature insertions, able to
convert the problem into a different one, via:
getFilterMain :: Deliverable a = FilePath -
Hi there!
It's been quiet for a while around the 'new logo' competition, but
here is how it is going to work:
The list with options can be found here (for now): http://community.haskell.org/~eelco/poll.html
Notice that some (very) similar logos are grouped as one option
(thanks to Ian
On Wed, 4 Mar 2009, John Lato wrote:
John A. De Goes schrieb:
Elsewhere, laziness can be a real boon, so I don't understand your
question, Why have laziness in Haskell at all?
As I have written, many libaries process their data lazily (or could be
changed to do so without altering their
Eelco Lempsink ee...@lempsink.nl wrote:
The poll won't be public, but every subscriber to Haskell-Cafe
will get a (private) voting ballot by email.
What about us gmane users?
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for copyright history. All rights reserved.
eelco:
Hi there!
It's been quiet for a while around the 'new logo' competition, but here
is how it is going to work:
The list with options can be found here (for now):
http://community.haskell.org/~eelco/poll.html Notice that some (very)
similar logos are grouped as one option (thanks
In this chat server implementation
http://www.haskell.org/haskellwiki/Implement_a_chat_server
forkIO is used with fix as in:
reader - forkIO $
http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v:.
fix $ http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v:.
On Thu, 2009-03-05 at 15:36 -0800, Daryoush Mehrtash wrote:
In this chat server implementation
http://www.haskell.org/haskellwiki/Implement_a_chat_server
forkIO is used with fix as in:
reader - forkIO $ fix $ \loop - do
(nr', line) - readChan chan'
when (nr /= nr') $
On Thu, 2009-03-05 at 16:12 -0800, Jonathan Cast wrote:
On Thu, 2009-03-05 at 15:36 -0800, Daryoush Mehrtash wrote:
In this chat server implementation
http://www.haskell.org/haskellwiki/Implement_a_chat_server
forkIO is used with fix as in:
reader - forkIO $ fix $ \loop - do
Hi
I've downloaded Hackmain from patch-tag, but I'm getting a different
error. The error I get is:
Hackmain.hs:63:10:
No instance for (Data.Typeable.Typeable2
Control.Monad.Reader.Reader)
arising from a use of `interpret' at Hackmain.hs:63:10-67
Hint
On Thu, 2009-03-05 at 23:52 +0100, Henning Thielemann wrote:
On Wed, 4 Mar 2009, John Lato wrote:
John A. De Goes schrieb:
Elsewhere, laziness can be a real boon, so I don't understand your
question, Why have laziness in Haskell at all?
As I have written, many libaries process their
Hi David,
I'm working on a Haskell library for interacting with emacs org files. For
those that do not know, an org file is a structured outline style file that
has nested headings, text, tables and other elements.
Great! Sounds like fun. :)
Now, this all works as expected (files are
Oh, crap- I must have never pushed the latest patches, I did put the
typeable instances in all the appropriate places. And provided a (maybe
incorrect? Though I'm fairly sure that shouldn't affect the bug I'm
having now) Typeable implementation for Reader, but I still get this
ambiguous type.
Quoth Jonathan Cast jonathancc...@fastmail.fm:
You can certainly use let:
reader - forkIO $ let loop = do
(nr', line) - readChan chan'
when (nr /= nr') $ hPutStrLn hdl line
loop
in loop
But the version with fix is clearer (at least to people who have fix in
their
On Thu, Mar 5, 2009 at 6:27 PM, Donn Cave d...@avvanta.com wrote:
Quoth Jonathan Cast jonathancc...@fastmail.fm:
You can certainly use let:
reader - forkIO $ let loop = do
(nr', line) - readChan chan'
when (nr /= nr') $ hPutStrLn hdl line
loop
in loop
I can calculate non-nested list comprehensions without a problem, but am unable
to calculate nested comprehensions involving, for example, the generation of a
list of pairs where the first and separate elements are drawn from two separate
lists, as in:
[(a, b) | a - [1..3], b - [1..2]]
Keep in mind this is a *lexical* rewrite. In the generator rule x and e
are not independent: x is a pattern (which introduces a bind variable)
and e is an expression (with free variables, one of which may be bound by x)
After one application of the generator rule, we get (using a lambda
Ok, so I've pulled the latest version and the error I get now is:
Hackmain.hs:70:43:
Ambiguous type variable `a' in the constraint:
`Deliverable a'
arising from a use of `getFilterMainStuff' at Hackmain.hs:
70:43-60
Probable fix: add a type signature that fixes these type
On 2009 Mar 5, at 8:08, Simon Marlow wrote:
So the argument is something like: we can think of the result of a
call to unsafeInterleaveIO as having been chosen at the time we
called unsafeInterleaveIO, rather than when its result is actually
evaluated. This is on dodgy ground, IMO: either
Well thanks to everyone that has replied so far - I've had an interesting time
trying out different ideas.
Firstly, for Neil Mitchell's suggestions regarding uniplate:
I read through both uniplate and scrap your boilerplate libraries (found the
second after reading about uniplate). For whatever
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