All,
I have a simple Haskell P2P library that I've been playing with in
simulations of 20 to 600 nodes. To run the simulation there is a
Haskell thread (forkIO) for every node in the system, one that starts
up all the nodes and prints the info (so prints aren't mangled), and
one that acts as the
[...] unsafe [PerformIO ...] looks safer to me.
Hmmm
Stefan
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I have thought about applications of patch theory like this as well.
I could imagine applying it to the undo stack in GIMP. Allowing you
to undo things on different layers. I think one of the things you
Don't know about the GIMP, but in Emacs, you can select a region of text
and undo just
Hi Dan,
I was wondering whether anyone had any suggestions on a good way to
generate repetitive code with associated types and kind annotations.
I'd like to use TH but as far as I understand, it doesn't support this
yet (I think associated types are in HEAD but not kinds),
I implemented type
Una Merge does real-time merging and has per user undo. And it can do
lots of stuff that seems darcs-like, though I don't know enough about
darcs to say for sure (e.g. moving a user's own edits after other
edits).
http://www.n-brain.net/una_merge.html
Regards,
John A. De Goes
But testing for something being evaluated has to be in the IO monad,
or else you're going to break the semantics.
On Fri, May 8, 2009 at 4:14 PM, Don Stewart d...@galois.com wrote:
Andy Gill has been advocating programmatic access to the 'is evaluated'
status bit for years now. 'seq' becomes
Neil Mitchell wrote:
[...]
Which is a shame, having Bits on Bool seems entirely logical, having
Num a superclass of Bits seems a little less clear.
There are two default implementations in Bits
bit i = 1 `shiftL` i
x `testBit` i = (x .. bit i) /= 0
which rely on Num
On Fri, May 8, 2009 at 2:37 PM, Andrew Coppin
andrewcop...@btinternet.comwrote:
John Lask wrote:
on the other hand a function to release pool memory to the OS down to the
current active level should (I hope) be easily implementable, and quickly
incorporated into application where required,
Hi
I guess I should write the skeleton of the code I want to generate,
get HSE to parse it, and then replace the parts I want to change of
the AST with what I need? Is there a nicer way (TH-like?) to get the
modified AST into GHC than prettyprinting the AST again and asking GHC
to compile
Hi Jason,
Hi Neil,
A bit off-topic, but your post reminded me: Does HLint currently help the
user find space leaks? For example, does it recommend strict folds instead
of lazy folds? I looked at the FAQ but this was not listed. I don't really
know how feasible this is.
It spots when you
Hi Doaitse
Doaitse Swierstra wrote:
Dear Rouan,
on
http://www.cs.uu.nl/wiki/HUT/WebHome
you will find a collection of tools which may help you to construct
a
compiler. As an example you will find a Tiger compiler constructed
with the uulib tools and the uuagc attribute grammar
Thomas
You can build your own scheduler very easily using what is already
there.
As with any simulation the two things that you need to capture are
dependency and resource contention. Haskell does both the dependency
stuff beautifully and the resource contention. Using STM you can even
get
Could anyone look at this segment of code; it's not compiling wondering if
anyone could correct me as to why. Thanks
Code:
-- Film as datatype
type Title = String
type Director = String
type Year = Int
type Fan = String
data Film = Film Title Director Year [Fan]
-- List of films
properly, the slight variation is actually a good test). What I would
like to know is are there any plans for GHC to incorporate
user-definable scheduler?
What exactly is it that you want from a user-definable scheduler? Do
you want co-operative scheduling in your program, or do you want
At Sat, 9 May 2009 04:54:13 -0700 (PDT),
applebiz89 wrote:
Could anyone look at this segment of code; it's not compiling wondering if
anyone could correct me as to why. Thanks
There is a ton of things wrong with that code.
I have attached a version that at least compiles, but there are
Hi
applebiz89 wrote:
Could anyone look at this segment of code; it's not compiling wondering if
anyone could correct me as to why. Thanks
Code:
-- Film as datatype
type Title = String
type Director = String
type Year = Int
type Fan = String
data Film = Film Title Director Year [Fan]
On May 8, 2009, at 16:31 , Sittampalam, Ganesh wrote:
Brandon S. Allbery KF8NH wrote:
Unless it catches exceptions itself (which strikes me as a bad idea;
it becomes a trivial way to ignore exceptions, leading to bad
programming practices) either they're handled inside the _|_ (in
which case it
On Thu, 2009-05-07 at 18:13 -0500, Vasili I. Galchin wrote:
sorry should read With Haskell Platform
1) Can we still publish/push up packages to Hackage? E.g. now I am
trying to get Graham Lyle's Swish (semantic web package) cabalized.
2) Will Hackage go away?
Hackage and the
On Wed, 2009-05-06 at 19:37 -0500, Vasili I. Galchin wrote:
are them some CLI switches I can enable in order to better determine
what parse error is??
The problem is that we're using a parser that has no support for
producing parse errors (Text.ParserCombinators.ReadP). The only reason
we're
On Tue, 2009-05-05 at 22:39 -0500, Vasili I. Galchin wrote:
Hello,
I have forgotten the runhaskell CLI parameters ... sigh. In
particular I want to a local build of a set of of package:
runhaskell Setup.hs configure --user???
I just did a runhaskell -? which didn't tell me
On Sat, May 9, 2009 at 6:28 AM, Neil Brown nc...@kent.ac.uk wrote:
properly, the slight variation is actually a good test). What I would
like to know is are there any plans for GHC to incorporate
user-definable scheduler?
What exactly is it that you want from a user-definable scheduler? Do
Why doesn't this work?
Michael
data Maybe a = Nothing | Just a
instance Monad Maybe where
return = Just
fail = Nothing
Nothing = f = Nothing
(Just x) = f = f x
instance MonadPlus Maybe where
mzero = Nothing
Nothing
Brandon S. Allbery KF8NH wrote:
On May 8, 2009, at 16:31 , Sittampalam, Ganesh wrote:
Brandon S. Allbery KF8NH wrote:
Unless it catches exceptions itself (which strikes me as a bad idea;
it becomes a trivial way to ignore exceptions, leading to bad
programming practices) either they're
Because you're looking for:
Just 3 = return . (+1)
or more simply
Just 3 = Just . (+1)
or more generally:
return 3 = return . (+1)
The second argument of (=) is supposed to be of type (Monad m = a
- m b) but (+1) ishe of type (Num a = a - a). Wre is the monad in
that?
Thomas
On Sat, May 9,
applebiz89 wrote:
becomeFan :: Title - fanName - [Film] - [Film]
becomeFan _ _ [] = []
becomeFan Title fanName ((Film Title Director Year fan):xs)
| filmName == title = (Film Title Director Year fanName:fan) : xs
| otherwise = (Film Title Director Year fan) : becomeFan Title fanName
I think you're looking for fmap/liftM here. The type of = is:
(=) :: (Monad m) = m a - (a - m b) - m b
so it's trying to make your function (1+) return m b, which in this
case should be a Maybe. Clearly, (1+) doesn't return a Maybe, so it
breaks. Another options is to do return . (1+) to lift
On Sat, 9 May 2009, michael rice wrote:
Prelude Just 3 = (1+)
fmap (1+) (Just 3)
or
Just 3 = return . (1+)
or, with consistent order of functions
return . (1+) = Just 3
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Hi,
(1+) :: Num a = a - a
For the bind operator, you need something of type a - Maybe b on the
RHS, not simply a - a. You want one of these instead:
fmap (1+) (Just 3)
liftM (1+) (Just 3)
Alternatively, you may find it useful to define something like:
(*) = flip liftM
so that you can
On May 9, 2009, at 15:31 , michael rice wrote:
Prelude Just 3 = (1+)
interactive:1:0:
No instance for (Num (Maybe b))
arising from a use of `it' at interactive:1:0-14
Possible fix: add an instance declaration for (Num (Maybe b))
In the first argument of `print', namely `it'
michael rice wrote:
Prelude Just 3 = (1+)
Let's check the types.
Prelude :t (=)
(=) :: (Monad m) = m a - (a - m b) - m b
Prelude :t Just 3
Just 3 :: (Num t) = Maybe t
Prelude :t (1 +)
(1 +) :: (Num a) = a - a
Renaming the variables in the type of (1 +) gives:
(1 +) :: (Num
Hi,
Haskell expects the function with type (a - m b) in the right side of
(=),
but you put there function with type (a - a):
try:
:t (Just 3 =)
(Just 3 =) :: (Num a) = (a - Maybe b) - Maybe b
and:
:t (1+)
(1+) :: (Num a) = a - a
You should put (1+) into Maybe monad, just do return.(1+), so
On Sat, May 9, 2009 at 12:31 PM, michael rice nowg...@yahoo.com wrote:
Why doesn't this work?
Michael
data Maybe a = Nothing | Just a
instance Monad Maybe where
return = Just
fail = Nothing
Nothing = f = Nothing
(Just x) = f = f x
Hey Michael,
If you would look at the type of =, it would give
(=) :: (Monad m) = m a - (a - m b) - m b
and specifically in your case:
(=) :: Maybe a - (a - Maybe b) - Maybe b
You are applying Just 3 as first argument, which is correct, but then supply
a partially applied function (1+) which
Types.
(=) :: Monad m = m a - (a - m b) - m b
(1+) :: Num a = a - a
So, the typechecker deduces that 1) a is the same as m b, and 2)
a (and m b, therefore) must be of class Num
Now,
Just 3 :: Num t = Maybe t
and the typechecker learns from that that m a must be the same as
Maybe t,
Excerpts from michael rice's message of Sat May 09 14:31:20 -0500 2009:
Why doesn't this work?
Michael
data Maybe a = Nothing | Just a
instance Monad Maybe where
return = Just
fail = Nothing
Nothing = f = Nothing
(Just x) = f = f
Am Samstag 09 Mai 2009 21:31:20 schrieb michael rice:
Why doesn't this work?
Michael
[mich...@localhost ~]$ ghci
GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base
On 10 May 2009, at 00:30, Brandon S. Allbery KF8NH wrote:
On May 9, 2009, at 15:31 , michael rice wrote:
Prelude Just 3 = (1+)
That (a - m b) in the middle is what's failing to typecheck. The
error is a bit obtuse because ghci is trying hard to find a way to
do what you want, so it
On May 9, 2009, at 18:03 , Miguel Mitrofanov wrote:
On 10 May 2009, at 00:30, Brandon S. Allbery KF8NH wrote:
On May 9, 2009, at 15:31 , michael rice wrote:
Prelude Just 3 = (1+)
That (a - m b) in the middle is what's failing to typecheck. The
error is a bit obtuse because ghci is trying
On May 9, 2009, at 18:16 , Brandon S. Allbery KF8NH wrote:
That's the only way I can get the error he got; if it uses Maybe as
the monad then why is the Maybe on the *inside* in the error
message? Clearly it bound m to something else, and ((-) r) is the
only other one I can think of
Thanks .. very interesting on the cabal parsers. I somehow got around my
problem ... forgot how though.
Vasili
On Sat, May 9, 2009 at 10:48 AM, Duncan Coutts
duncan.cou...@worc.ox.ac.ukwrote:
On Wed, 2009-05-06 at 19:37 -0500, Vasili I. Galchin wrote:
are them some CLI switches I can enable
... There have been 12 replies to this question, all of which say the
same thing. I'm glad we're so happy to help, but does
Just 3 = return . (+1)
Need to be explained by 12 different people?
fmap (trying to++) $ Just help -- :D
Cory
Why doesn't this work?
Michael
[mich...@localhost ~]$
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