[Haskell-cafe] Rewrite thunk action rule?
I have a program with this data structure:
data Element = Element {
elementOrigin :: V,
elementSubs :: [Element]
}
and this important bit of code that operates on it:
transform :: T - Element - Element
transform t e = Element {
elementOrigin = tmulv t (elementOrigin e),
elementSubs = map (transform t) (elementSubs e)
}
Where V is a vertex and T is a matrix transformation. The following is true:
transform a (transform b e) == transform (a * b) e
I have read about rewrite rules, such would efficiently rewrite the obvious
transformations. However, given that the program will be applying *many*
transformations to very deep and wide Element trees, and applying those
transformations at many levels, I don't see how the optimizer would be able to
handle all cases, for instance a thunk getting left over from perhaps
evaluation prior to some IO function.
FWIW here's an example tree-builder I'm using to test with:
mkElems 0 _ = Element {
elementOrigin = V 0 0,
elementSubs = []
}
mkElems depth width = Element {
elementOrigin = V 0 0,
elementSubs = replicate width $ transform (rotation (pi /
(fromIntegral width))) $ transform (translation $ V 1 1) $ mkElems (depth - 1)
width
}
with depth = width = 5
If I could somehow arrange for the transform function to detect when it
is being applied to a unevaluated thunk, and then modify the thunk in
place, that would basically be the behavior I need. Any suggestions?
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Re: [Haskell-cafe] Trouble with FFI on Windows2000...
Serge LE HUITOUZE wrote: I do the following: dlltool -d cproj1.def -l libcproj1.a ghc --make testFFI_2.hs -optl-lcproj1 -optl-L. This seems fine, since it produces a testFFI_2.exe. However, executing it, I get a MSWindows error box with a message that looks like (approximate translation): DLL (null) not found on specified path At first, I didn't have the LIBRARY directive in the .def file, so I thought that was the reason for the (null) appearing in the message. But adding said directive didn't change anything... dlltool -d cproj1.def -l libcproj1.a -D cproj1.dll ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Line noise
On Tuesday 23 September 2008 02:27:17 Brian Hurt wrote: On Sun, 21 Sep 2008, wren ng thornton wrote: Even with functionalists ---of the OCaml and SML ilk--- this use of spaces can be confusing if noone explains that function application binds tighter than all operators. Bwuh? Ocaml programmers certainly know that application binds tighter than operators. And as: let f x y = ... in f a b is more efficient (in Ocaml) than: let f (x, y) = ... in f (a, b) (Ocaml doesn't optimize away the tuple allocation)... That is incorrect. OCaml does optimize away that tuple: both forms compile to the same 2-argument function. OCaml does not optimize away this tuple: let a, b = 1, 2 So, when efficiency is important, you write: let a = 1 and b = 2 -- Dr Jon Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/?e ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal Install Links to Source from Haddock Docs
the answer: not cabal install, just cabal. thart...@thartman-laptop:~/haskellInstalls/smallInstalls/pureMD5-0.2.3 thart...@thartman-laptop:~/haskellInstalls/smallInstalls/pureMD5-0.2.3cabal --help | grep -i doc haddock Generate Haddock HTML documentation. thart...@thartman-laptop:~/haskellInstalls/smallInstalls/pureMD5-0.2.3cabal haddock --help | grep -i link --hyperlink-source Hyperlink the documentation to the source code thart...@thartman-laptop:~/haskellInstalls/smallInstalls/pureMD5-0.2.3cabal haddock --hyperlink-source 2008/12/21 R Hayes rfha...@reillyhayes.com: Is there a way I can get Haddock Docs WITH links to source (local) from modules installed with cabal install xxx? Getting the docs themselves is pretty easy by changing either ~/.cabal/config or using --enable-documentation. Automatically generating the source (colourised or not) and integrated links eludes me. -r ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Rewrite thunk action rule?
2008/12/21 Peter Todd p...@petertodd.org If I could somehow arrange for the transform function to detect when it is being applied to a unevaluated thunk, and then modify the thunk in place, that would basically be the behavior I need. Any suggestions? That is exactly what is already happening. Perhaps you want what you think is happening: if a value *is* evaluated, you want to apply the transformation right then instead of making a thunk. By the way, this is very operational thinking for Haskell. Haskell tries quite hard to abstract away operational thinking, so thinking on this level will be difficult and more work than you should be doing to write a program. May I ask why you want this behavior? Have you just tested it and observed that it is running too slowly and you are trying to speed it up? Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Windows vs. Linux x64
On Friday 12 December 2008 13:57:44 Simon Marlow wrote: - it means recompiling *everything*. It's a complete new way, so you have to make the decision to do this once and for all, or build all your libraries + RTS twice. In JITed languages they can make the choice at runtime, which makes it much easier. Is anyone developing a JIT Haskell compiler? The approach has many important practical benefits and tools like LLVM are a joy to use... -- Dr Jon Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/?e ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [Haskell] ANN: Hoogle with more libraries
Hi Bob, 1. Searching using a package name that isn't all lower case results in nothing (e.g. (a - b) - f a - f b +InfixApplicative gives no results, while (a - b) - f a - f b +infixapplicative gives 2). Yes, if you do +InfixApplicative it assumes you mean only in the module InfixApplicative, not the package. Module is upper case, package starts with lowercase. 2. Searching with the +package syntax seems to remove all other possible results. Perhaps it would be nice to show results from the default library set below. Add +default to search the default too. If you get the package name wrong (i.e. specify a package that hoogle can't see), it would be nice for it to report something like google does -- maybe you meant xyz. Definately! The whole area needs an overhall. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Yampa vs. Reactive
Hi Tom, In reactive, one doesn't. All behaviors and events have the same absolute 0 value for time. Right. I believe the possibility of starting behaviors later is quite important. And from what Conal wrote in a related mail, I take it that this is recognized, and that this capability is something that is being considered for reactive? Best, /Henrik -- Henrik Nilsson School of Computer Science The University of Nottingham n...@cs.nott.ac.uk This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Logos of Other Languages
Paulo Tanimoto wrote: Another idea: something in the form of an Ouroboros. Is that already taken for a programming language? http://en.wikipedia.org/wiki/Ouroboros Something like this? http://www.haskell.org/sitewiki/images/f/fd/Ouroborous-oval.png Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Comparing on multiple criteria
Hello all, Data.Ord has a handy function called comparing, and its documentation shows an example of its use. But what if you want to sort a list of values based on multiple criteria? It turns out there is a neat way to do this: compareTuple = mconcat [comparing fst, comparing snd] The default Monoid instances for Ordering and functions work exactly as required here. (Thanks to vixey in #haskell for the hint to look at monoids!) To reverse the order of a criterion or a set of criteria, flip can be used: compareTuple' = mconcat [comparing fst, flip $ comparing snd] I think it would be really neat if these two use cases were also described in comparing's documentation. Who is the right person to ask this of? Thanks in advance, Martijn. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] forkIO on multicore
So this benchmark is primarily a stress test of the parallel garbage collector since it is GC that is taking 75-80% of the time. Note that the mutator elapsed time goes down slightly with 2 cores compared to 1 however the GC elapsed time goes up slightly. Thanks Duncan, Jake et al. I'm more familiar with MPI and OpenMP for parallelism; it seems I've got a lot more thinking to do when it comes to Haskell. I'll look at some more tutorials, and then most likely Data Parallel Haskell. Cheers, Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparing on multiple criteria
On Dec 21, 2008, at 8:52 AM, Martijn van Steenbergen wrote: Hello all, Data.Ord has a handy function called comparing, and its documentation shows an example of its use. But what if you want to sort a list of values based on multiple criteria? It turns out there is a neat way to do this: compareTuple = mconcat [comparing fst, comparing snd] The default Monoid instances for Ordering and functions work exactly as required here. (Thanks to vixey in #haskell for the hint to look at monoids!) Indeed, this is great to know. I can't help but notice that there is no documentation of any kind at all for the Monoid instance of Ordering; how were we supposed to know this behavior existed in the first place, except by hunting down the source code for the instance declaration? -Jan-Willem Maessen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparing on multiple criteria
On Sun, Dec 21, 2008 at 9:20 AM, Jan-Willem Maessen jmaes...@alum.mit.eduwrote: Indeed, this is great to know. I can't help but notice that there is no documentation of any kind at all for the Monoid instance of Ordering; how were we supposed to know this behavior existed in the first place, except by hunting down the source code for the instance declaration? It seems we have no good way to associate documentation with instances. Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Is this related to monomorphism restriction?
Why isn't the last line of this code allowed? f :: (TestClass a) = a - Integer f = const 1 a = (f,f) g = fst a The only thing I can think about is monomorphism restriction, but it's allowed (...) (...) The reason is that a has type a :: (TestClass a, TestClass b) = (a,b) and then when we take 'fst' of this value (as in g) we get g :: (TestClass a, TestClass b) = a which is an ambiguous type, (...) Is there some version (i.e., set of extensions) of Haskell where this would be allowed? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Rewrite thunk action rule?
On Sun, Dec 21, 2008 at 02:56:06AM -0700, Luke Palmer wrote:
2008/12/21 Peter Todd p...@petertodd.org
If I could somehow arrange for the transform function to detect when it
is being applied to a unevaluated thunk, and then modify the thunk in
place, that would basically be the behavior I need. Any suggestions?
That is exactly what is already happening. Perhaps you want what you think
is happening: if a value *is* evaluated, you want to apply the
transformation right then instead of making a thunk.
Not quite. If I have a thunk, at the low level somewhere it must refer
to the transform function, the transform matrix, and the element that is
to be transformed. If I apply another transform to that unevaluated
thunk, my understanding is that haskell will represent it as such:
thunk transform Ta (thunk transform Tb e)
When I want the following:
thunk transform (Ta * Tb) e
This alternate definition of the Element structure might make more
sense:
data Element = Element {
elementOrigin :: V,
elementSubs :: [Element]
}
| ElementThunk T Element
transform :: T - Element - Element
transform t (ElementThunk t2 e) = ElementThunk (tmul t t2) e
transform t e = ElementThunk t e
transform t e = Element {
elementOrigin = tmulv t (elementOrigin e),
elementSubs = map (transform t) (elementSubs e)
}
This gives a behavior close to what I want, applying a transform to an
element results in a thunk, and subsequent transforms simply modify
the thunk, the problem is that I don't see a way to implicitly coerce an
ElementThunk into an Element on demand for all the other code in the
program that expects elements. (such as the elementOrigin function)
By the way, this is very operational thinking for Haskell. Haskell tries
quite hard to abstract away operational thinking, so thinking on this level
will be difficult and more work than you should be doing to write a program.
Yes, but this part of the program is library code, that will be used by
a whole pile of other stuff, so if I can get the right behavior
magically the rest of the program will be a lot easier to write.
FWIW this is EDA software, those elements refer to elements of a
printed circuit board layout, and the transform operations correspond to
stuff like moving a chip on the board. The representation of a simple IC
would consist of something like an element, with a bunch of sub-elements
for each pin, all of which have geometry data.
May I ask why you want this behavior? Have you just tested it and observed
that it is running too slowly and you are trying to speed it up?
I've written a previous version of this program in Python actually,
where I explicitly modeled the lazy evaluation behavior that I wanted.
It all worked great, but the overall speed was still quite slow. I was
hoping that Haskell, built around lazy evaluation already, would be a
better fit.
That, and in any case, other aspects of the program that I've re-written
in Haskell saw about a 5-1 redunction in code length... :)
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Re: [Haskell-cafe] Rewrite thunk action rule?
On Sun, Dec 21, 2008 at 10:27 AM, Peter Todd p...@petertodd.org wrote:
data Element = Element {
elementOrigin :: V,
elementSubs :: [Element]
}
| ElementThunk T Element
transform :: T - Element - Element
transform t (ElementThunk t2 e) = ElementThunk (tmul t t2) e
transform t e = ElementThunk t e
transform t e = Element {
elementOrigin = tmulv t (elementOrigin e),
elementSubs = map (transform t) (elementSubs e)
}
This gives a behavior close to what I want, applying a transform to an
element results in a thunk, and subsequent transforms simply modify
the thunk, the problem is that I don't see a way to implicitly coerce an
ElementThunk into an Element on demand for all the other code in the
program that expects elements. (such as the elementOrigin function)
Oh! Okay, studying your code a bit, I think I finally understand what
you're trying to do. Tell me if I'm wrong. You have a list of elements es
and a composition of transforms t1,t2,t3, and instead of applying t1, t2,
and t3 to each element, you want to collapse them together into a single
matrix and apply that matrix to each element.
This is definitely a modeling level thing to do; you don't need to go
anywhere near rewrite rules or thinking about internal representations or
anything like that. A bit of old fashioned abstraction should do the trick.
Your Thunk representation is not that bad. I can't really weigh the
trade-offs for you. Keep the data type abstract and only allow access
through functions (like elementOrigin). Then I don't see the problem with
redefining elementOrigin as:
elementOrigin (Element v subs) = v
elementOrigin (ElementThunk t e) = tmulv t (elementOrigin e)
Keep the number of operations which need to know the representation
(constructors) of Element as small as you can.
Another possibility is this:
data Element = Element
{ elementOrigin :: V
, elementSubs :: [(T,Element)]
}
Where, of course, the transform for each sub-element is relative.
Overall I think your thunk solution is a very nice trade-off. (Minor
rhetorical note: I would probably name your ElementThunk constructor
Transform or ElementTransform instead)
Hmm, you have an invariant that the pattern ElementThunk t (ElementThunk t
e) never occurs. It would be good style to encode this:
data PrimElement = PrimElement { elementOrigin :: V, elementSubs ::
[Element] }
data Element = Element (Maybe T) PrimElement
That Maybe bugs me. You could factor that out into the T type with a
special optimization for the identity transform. Hmm, then the
[(T,Element)] encoding and this one are identical. Fun. :-)
Short answer: *abstract data type!*
Luke
By the way, this is very operational thinking for Haskell. Haskell tries
quite hard to abstract away operational thinking, so thinking on this
level
will be difficult and more work than you should be doing to write a
program.
Yes, but this part of the program is library code, that will be used by
a whole pile of other stuff, so if I can get the right behavior
magically the rest of the program will be a lot easier to write.
FWIW this is EDA software, those elements refer to elements of a
printed circuit board layout, and the transform operations correspond to
stuff like moving a chip on the board. The representation of a simple IC
would consist of something like an element, with a bunch of sub-elements
for each pin, all of which have geometry data.
May I ask why you want this behavior? Have you just tested it and
observed
that it is running too slowly and you are trying to speed it up?
I've written a previous version of this program in Python actually,
where I explicitly modeled the lazy evaluation behavior that I wanted.
It all worked great, but the overall speed was still quite slow. I was
hoping that Haskell, built around lazy evaluation already, would be a
better fit.
That, and in any case, other aspects of the program that I've re-written
in Haskell saw about a 5-1 redunction in code length... :)
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[Haskell-cafe] Removing/Uninstalling cabal packages ?
Hi, I have been doing a few experiments with cabal packages lately and I wish to uninstall these to return to a cleaner package base. However, there doesn't seem to be a cabal uninstall command and reading the documentation at http://www.haskell.org/ghc/docs/latest/html/Cabal/index.html does not tell much about how to do that manually. Note that what I wish to do is both delete the installed files and the cabal database so that the uninstalled packages does not show anymore when running cabal list --installed. Would anyone know how to do that ? Thanks in advance. Regards, Laurent -- Laurent Giroud m...@niaow.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: bytestring-trie 0.1.0
Thanks for working on this! A nice efficient bytestring-trie is the sort of data structure we should have had in Haskell for some time now, and I'm sure I'll be giving it a great deal of use. Regards, Sterl. On Dec 20, 2008, at 1:06 AM, wren ng thornton wrote: -- Announcing: bytestring-trie 0.1.0 (beta) An efficient finite map from (byte)strings to values. The implementation is based on big-endian patricia trees, like Data.IntMap. We first trie on the Word8 elements of a Data.ByteString, sharing string prefixes where possible, and then trie on the big-endian bit representation of those elements. Patricia trees have efficient algorithms for union and other merging operations, but they're also quick for lookups and insertions. -- Future Extensions * I've done spot checking to make sure it works, but haven't constructed an extensive test suite. Does anyone know of a good data set already out there for testing corner cases? I'm sure other dictionary writers have come up with one. * A Word8 is much smaller than the architecture's natural Word size. Therefore it'd be more efficient for the trie on bits to read off a whole Word at a time. This work is in progress, but I need help from people with 64-bit and big-endian machines in order to verify the code works on those architectures. * Using ByteStrings allows for trieing on any packed byte representation of a value, but they're not Strings. Integration with Data.ByteString.Char8, utf8-string, and utf8-light should happen. * The current implementation also only accepts strict ByteStrings. When chopping up strings to share prefixes we share the smaller string. For very long strings when many deletions are expected, this can still hold onto more memory than necessary. Accepting lazy ByteStrings or adding heuristics for when to copy prefixes instead of sharing will fix this. -- Links Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/ bytestring-trie Darcs: http://code.haskell.org/~wren/bytestring-trie/ Haddock (Darcs version): http://code.haskell.org/~wren/bytestring-trie/dist/doc/html/ bytestring-trie/ -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Time for a new logo?
On 2008 Dec 17, at 8:42, Darrin Thompson wrote: X monad could have a variant of this logo too. X= (That's how I originally thought of it, just was too lazy to post it anywhere. Sorry about that.) Or just a lambda with an extra contrasting stroke to make an X (λ' very roughly, if you have the right font). -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Logos of Other Languages
what about such a variation? something between an ouroborob, a lambda and a mermaid... By the way: I mixed up something: My note, that the orouboros was used as a logo for Heinz von Försters second order cybernetics, was not correct. The correct note should have been: Heinz von Förster, the later founder of the second order cybernetics, invented the ouroboros as a logo for the american society for cybernetics. http://www.asc-cybernetics.org/ daniel Paulo Tanimoto wrote: Another idea: something in the form of an Ouroboros. Is that already taken for a programming language? http://en.wikipedia.org/wiki/Ouroboros Something like this? http://www.haskell.org/sitewiki/images/f/fd/Ouroborous-oval.png Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe inline: lambda-ouroboros.JPG___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Is this related to monomorphism restriction?
You have a few options.
In Haskell98 (no extensions):
a () = (f,f)
g () = fst (a ())
-- alternatively
g x = fst (a ()) x
Here you make it explicit that a and g are functions; the
monomorphism restriction is there to stop things that look like values
(and therefore you expect to only get evaluated once) from being
functions (which get evaluated every time they are used).
Alternatively, you are allowed to tell the compiler This value should
be polymorphic with a type signature:
a :: TestClass a = (a - Integer, a - Integer)
a = (f,f)
g :: TestClass a = a - Integer
g = fst a
The non-haskell98 solution:
{-# LANGUAGE NoMonomorphismRestriction #-}
But beware that it is really there to protect you; code that uses g
will compile to something very similar to the first operation I
showed, re-evaluating fst a and doing dictionary selection at every
use of g.
-- ryan
On Sun, Dec 21, 2008 at 9:21 AM, Maurício briqueabra...@yahoo.com wrote:
Why isn't the last line of this code allowed?
f :: (TestClass a) = a - Integer
f = const 1
a = (f,f)
g = fst a
The only thing I can think about is monomorphism
restriction, but it's allowed (...)
(...) The reason is that a has type
a :: (TestClass a, TestClass b) = (a,b)
and then when we take 'fst' of this value (as in g) we get
g :: (TestClass a, TestClass b) = a
which is an ambiguous type, (...)
Is there some version (i.e., set of extensions) of
Haskell where this would be allowed?
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Re: [Haskell-cafe] Re: Time for a new logo?
BTW, in Russian the character X (pronounced a bit like English H) is the first letter in Haskell. On 21 Dec 2008, at 21:48, Brandon S. Allbery KF8NH wrote: On 2008 Dec 17, at 8:42, Darrin Thompson wrote: X monad could have a variant of this logo too. X= (That's how I originally thought of it, just was too lazy to post it anywhere. Sorry about that.) Or just a lambda with an extra contrasting stroke to make an X (λ' very roughly, if you have the right font). -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Data.List.Split
I am pleased to announce the release of Data.List.Split, which provides a wide range of strategies and a unified combinator framework for splitting lists with respect to some sort of delimiter. It strives to be flexible yet simple. If you've ever wished there was a simple 'split' function you could grab from Data.List, this is the package for you---no matter which of the seventeen* slightly different ways to split a list you actually need! Just use one of the prepackaged splitting strategies, or build your own with the combinator library. Get it from Hackage: cabal install split http://hackage.haskell.org/cgi-bin/hackage-scripts/package/split Get the source: darcs get http://code.haskell.org/~byorgey/code/split Get excited: http://byorgey.wordpress.com/2008/12/21/datalistsplit/ -Brent * Actual number may vary. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Is this related to monomorphism restriction?
Hello, You can work around the monomorphism restriction with extensions but to fix the ambiguity in your program that Reiner pointed out you'll have to change the program to specify how you'd like to instantiate a. here are all the types once again: f :: (TestClass a) = a - Integer f = const 1 a :: (TestClass a, TestClass b) = (a - Integer, b - Integer) a = (f,f) g :: (TestClass a, TestClass b) = a - Integer -- ambiguous g = fst a Note that the type of 'g' to the right of '=' does not mention 'b'. This means that the type of 'g' is ambiguos because the type checker does not know how to pick a type for 'b'. To fix that, you could: 1. Give 'a' a less general type, for example: a :: (TestClass a) = (a - Integer, a - Integer) 2. Write a type signature on the use of 'a': g :: TestClass a = a - Integer g = fst (a :: (a - Integer, a - Integer)) Here we are using another GHC extension called scoped type variables to associate the a in the type signature of g with the a in the type annotation for the value a. Hope that this helps, Iavor On Sun, Dec 21, 2008 at 9:21 AM, Maurício briqueabra...@yahoo.com wrote: Why isn't the last line of this code allowed? f :: (TestClass a) = a - Integer f = const 1 a = (f,f) g = fst a The only thing I can think about is monomorphism restriction, but it's allowed (...) (...) The reason is that a has type a :: (TestClass a, TestClass b) = (a,b) and then when we take 'fst' of this value (as in g) we get g :: (TestClass a, TestClass b) = a which is an ambiguous type, (...) Is there some version (i.e., set of extensions) of Haskell where this would be allowed? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Removing/Uninstalling cabal packages ?
On Sun, Dec 21, 2008 at 12:12 PM, Laurent Giroud m...@niaow.com wrote: I have been doing a few experiments with cabal packages lately and I wish to uninstall these to return to a cleaner package base. However, there doesn't seem to be a cabal uninstall command and reading the documentation at http://www.haskell.org/ghc/docs/latest/html/Cabal/index.html does not tell much about how to do that manually. I think you want 'ghc-pkg list' and 'ghc-pkg unregister'. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Is this related to monomorphism restriction?
2008/12/21 Iavor Diatchki iavor.diatc...@gmail.com g :: TestClass a = a - Integer g = fst (a :: (a - Integer, a - Integer)) Which I believe needs to be written: g :: forall a. TestClass a = a - Integer g = fst (a :: (a - Integer, a - Integer)) Here we are using another GHC extension called scoped type variables to associate the a in the type signature of g with the a in the type annotation for the value a. Hope that this helps, Iavor On Sun, Dec 21, 2008 at 9:21 AM, Maurício briqueabra...@yahoo.com wrote: Why isn't the last line of this code allowed? f :: (TestClass a) = a - Integer f = const 1 a = (f,f) g = fst a The only thing I can think about is monomorphism restriction, but it's allowed (...) (...) The reason is that a has type a :: (TestClass a, TestClass b) = (a,b) and then when we take 'fst' of this value (as in g) we get g :: (TestClass a, TestClass b) = a which is an ambiguous type, (...) Is there some version (i.e., set of extensions) of Haskell where this would be allowed? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] The Haskell re-branding exercise
A call has gone out for a new logo for Haskell. Candidates (including a couple of mine) are accumulating here. There has also been a long thread on the Haskell Cafe mailing list. I've lived through a couple of corporate rebranding exercises in my time, and I've read about some others. They follow a pattern: Management decide that the organisation needs a makeover to change public perception. A new corporate "look and feel" is part of this, and a new logo is therefore required. The rest of the makeover may be deep or shallow; that doesn't affect the rest of this story. The new branding is released with as much fanfare as possible. Press releases are released. Staff are given briefings about the significance of the whole exercise and the bold new future that it symbolises. The staff universally agree that the new logo is not a patch on the old one. The old one was a much loved friend; it stood for something; people have spent years working for it. The new one is obviously a piece of cheap gimcrackery munged up by an overpaid consultancy hired by senior managers who mistake image for substance. A ten year-old with an Etch-a-Sketch could have done better. Over time the new logo blends in and becomes part of the scenery. Years pass. Go to stage 1 and repeat. This suggests that the current effort to find a new logo for Haskell needs to go back to the basics. Its no good expecting consensus on one of the suggestions because there are too many options and everyone has their favourite. Nothing will attract a majority of the community. Furthermore I think that (just like programmers everywhere) we have dived into development before deciding what the requirements are. This is reflected in the mailing list discussion, where two broad positions seem to be emerging. On one side we have what I think of as the "Vulcans". This group sees Haskell as abstract and difficult, and believes that the logo should reflect these qualities. They want mathematical symbols to dominate the design. On the other side we have the "Warm Fuzzies". They want Haskell to be perceived as accessible and welcoming, and so want a logo featuring something warm and friendly. A paradox of the Haskell world is that, while the language is Vulcan, the community around it is dominated by Warm Fuzziness. Clearly the two are not mutually exclusive. A rebranding exercise needs to start with a short list of adjectives that the brand is to represent, and I think that the Haskell community needs to decide this before it fires up Inkscape. To that end, here are a sample of adjectives in alphabetical order: abstract, academic, accessible, accurate, adventurous, business-like, communal, complicated, dangerous, different, easy, exciting, familiar, friendly, fun, fuzzy, hard, interesting, inventive, precise, productive, profitable, reliable, revolutionary, safe, simple, strange, supportive, warm, welcoming. What are the top three adjectives we want to project? Once we have decided that, we can write a brief for the Haskell logo. Note that the selected adjectives need not be related. In fact they may be partly contradictory. I've already noted that the language is Vulcan whereas the community is Warm and Friendly. So they might reasonably be the three adjectives (though I wouldn't take "Vulcan" too literally). The challenge will then be for the graphical work to project these qualities, even if they seem incompatible. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: intimidating terminology (was: Re: [Haskell-cafe] Time for a new logo?)
On 2008 Dec 19, at 4:13, Lennart Augustsson wrote: When accurate names for Haskell concepts already exist we should use them (as we have tried in the past). There has been too much invention of misleading terminology in computing already. If some people can't handle things having the right names, well, maybe they should try another language. (What would happen if we used the new name principle, e.g., in cooking? Oh, cinnamon is a difficult name, I'll call it tangy spice instead.) Cinnamon's already got an accuracy problem anyway: what most people in the US call cinnamon is actually cassia. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
Wonderful, Paul. Could you add your list of adjectives to the wiki page. Note that the initial deadline was Dec 31, after which time we can filter out dupes and narrow down the logos to about 5 or so different directions to have a vote on. Anything you can do to help direct or improve quality is welcome! -- Don paul: A [1]call has gone out for a new logo for Haskell. Candidates (including a [2]couple of [3]mine) are accumulating [4]here. There has also been a long thread on the Haskell Cafe mailing list. I've lived through a couple of corporate rebranding exercises in my time, and I've read about some others. They follow a pattern: 1. Management decide that the organisation needs a makeover to change public perception. A new corporate look and feel is part of this, and a new logo is therefore required. The rest of the makeover may be deep or shallow; that doesn't affect the rest of this story. 2. The new branding is released with as much fanfare as possible. Press releases are released. Staff are given briefings about the significance of the whole exercise and the bold new future that it symbolises. 3. The staff universally agree that the new logo is not a patch on the old one. The old one was a much loved friend; it stood for something; people have spent years working for it. The new one is obviously a piece of cheap gimcrackery munged up by an overpaid consultancy hired by senior managers who mistake image for substance. A ten year-old with an Etch-a-Sketch could have done better. 4. Over time the new logo blends in and becomes part of the scenery. Years pass. Go to stage 1 and repeat. This suggests that the current effort to find a new logo for Haskell needs to go back to the basics. Its no good expecting consensus on one of the suggestions because there are too many options and everyone has their favourite. Nothing will attract a majority of the community. Furthermore I think that (just like programmers everywhere) we have dived into development before deciding what the requirements are. This is reflected in the mailing list discussion, where two broad positions seem to be emerging. * On one side we have what I think of as the Vulcans. This group sees Haskell as abstract and difficult, and believes that the logo should reflect these qualities. They want mathematical symbols to dominate the design. * On the other side we have the Warm Fuzzies. They want Haskell to be perceived as accessible and welcoming, and so want a logo featuring something warm and friendly. A paradox of the Haskell world is that, while the language is Vulcan, the community around it is dominated by Warm Fuzziness. Clearly the two are not mutually exclusive. A rebranding exercise needs to start with a short list of adjectives that the brand is to represent, and I think that the Haskell community needs to decide this before it fires up Inkscape. To that end, here are a sample of adjectives in alphabetical order: abstract, academic, accessible, accurate, adventurous, business-like, communal, complicated, dangerous, different, easy, exciting, familiar, friendly, fun, fuzzy, hard, interesting, inventive, precise, productive, profitable, reliable, revolutionary, safe, simple, strange, supportive, warm, welcoming. What are the top three adjectives we want to project? Once we have decided that, we can write a brief for the Haskell logo. Note that the selected adjectives need not be related. In fact they may be partly contradictory. I've already noted that the language is Vulcan whereas the community is Warm and Friendly. So they might reasonably be the three adjectives (though I wouldn't take Vulcan too literally). The challenge will then be for the graphical work to project these qualities, even if they seem incompatible. References Visible links 1. http://www.haskell.org/pipermail/haskell-cafe/2008-December/051836.html 2. http://www.haskell.org/haskellwiki/Image:Haskell-logo-revolution.png 3. http://www.haskell.org/sitewiki/images/f/fd/Ouroborous-oval.png 4. http://www.haskell.org/haskellwiki/Haskell_logos/New_logo_ideas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] GHC libraries documentation and links to source files
Hi. I have noted that recent versions of the GHC libraries documentation, no longer have links to the source code. What is the reason? I find it very useful. Thanks Manlio Perillo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
2008/12/21 Paul Johnson p...@cogito.org.uk This suggests that the current effort to find a new logo for Haskell needs to go back to the basics. Its no good expecting consensus on one of the suggestions because there are too many options and everyone has their favourite. Nothing will attract a majority of the community. I agree with this, which I why I would propose using Condorcet-voting. Personally I find the current logo horrendous. I think it's ugly and intimidating at the same time. I don't really care too much which one of the proposals should win, just so long as I can weed out some of the ones I really hate. Condorcet voting will pick a good compromise, where someone like me could just put all the acceptable ones at shared #1, and all the ones I dislike at #2., and someone with stronger opinions could flesh it out some more. The point being that the least disliked logo wins out. Maybe nobody will be happy, but hopefully most people won't be deeply unhappy with it. It would be a shame if there's lots of votes that are spread out over a large group of fairly similar logos that are good, and then a crappy one wins out with 6% of the vote because there weren't any others like it so the votes for that style weren't spread out over multiple entries. Wikipedia: http://en.wikipedia.org/wiki/Condorcet_voting -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
Would you be willing to set up a little online voting system (or do you know of one) so we can implement this? Assume there'll be 10 candidates. -- Don sylvan: 2008/12/21 Paul Johnson [1]p...@cogito.org.uk This suggests that the current effort to find a new logo for Haskell needs to go back to the basics. Its no good expecting consensus on one of the suggestions because there are too many options and everyone has their favourite. Nothing will attract a majority of the community. I agree with this, which I why I would propose using Condorcet-voting. Personally I find the current logo horrendous. I think it's ugly and intimidating at the same time. I don't really care too much which one of the proposals should win, just so long as I can weed out some of the ones I really hate. Condorcet voting will pick a good compromise, where someone like me could just put all the acceptable ones at shared #1, and all the ones I dislike at #2., and someone with stronger opinions could flesh it out some more. The point being that the least disliked logo wins out. Maybe nobody will be happy, but hopefully most people won't be deeply unhappy with it. It would be a shame if there's lots of votes that are spread out over a large group of fairly similar logos that are good, and then a crappy one wins out with 6% of the vote because there weren't any others like it so the votes for that style weren't spread out over multiple entries. Wikipedia: [2]http://en.wikipedia.org/wiki/Condorcet_voting -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862 References Visible links 1. mailto:p...@cogito.org.uk 2. http://en.wikipedia.org/wiki/Condorcet_voting ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
I am very shortly travelling abroad for several weeks and will not have (reliable access to) a computer, but isn't this a task for one of the haskell web-apps people (HSP, HAppS, Turbinado, etc.) to show us once and for all why *their* library is better than the competition? :-) On Sun, Dec 21, 2008 at 9:23 PM, Don Stewart d...@galois.com wrote: Would you be willing to set up a little online voting system (or do you know of one) so we can implement this? Assume there'll be 10 candidates. -- Don sylvan: 2008/12/21 Paul Johnson [1]p...@cogito.org.uk This suggests that the current effort to find a new logo for Haskell needs to go back to the basics. Its no good expecting consensus on one of the suggestions because there are too many options and everyone has their favourite. Nothing will attract a majority of the community. I agree with this, which I why I would propose using Condorcet-voting. Personally I find the current logo horrendous. I think it's ugly and intimidating at the same time. I don't really care too much which one of the proposals should win, just so long as I can weed out some of the ones I really hate. Condorcet voting will pick a good compromise, where someone like me could just put all the acceptable ones at shared #1, and all the ones I dislike at #2., and someone with stronger opinions could flesh it out some more. The point being that the least disliked logo wins out. Maybe nobody will be happy, but hopefully most people won't be deeply unhappy with it. It would be a shame if there's lots of votes that are spread out over a large group of fairly similar logos that are good, and then a crappy one wins out with 6% of the vote because there weren't any others like it so the votes for that style weren't spread out over multiple entries. Wikipedia: [2]http://en.wikipedia.org/wiki/Condorcet_voting -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862 References Visible links 1. mailto:p...@cogito.org.uk 2. http://en.wikipedia.org/wiki/Condorcet_voting ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Sebastian Sylvan +44(0)7857-300802 UIN: 44640862 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
On Sun, Dec 21, 2008 at 01:23:33PM -0800, Don Stewart wrote: Would you be willing to set up a little online voting system (or do you know of one) so we can implement this? Assume there'll be 10 candidates. What about www.doodle.com? Ciao, Kili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
kili: On Sun, Dec 21, 2008 at 01:23:33PM -0800, Don Stewart wrote: Would you be willing to set up a little online voting system (or do you know of one) so we can implement this? Assume there'll be 10 candidates. What about www.doodle.com? That looks like it might be an option, embedded in a page with the 10 candidates. Thanks! Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Threads with high CPU usage
Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. What can I do? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Threads with high CPU usage
On 2008 Dec 21, at 16:47, Don Stewart wrote: redcom: The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. How are you compiling this code (-O -threaded ?) and what does the forkIO'd thread do? Does it allocate? Sounds to me like it's making FFI calls to a database library. I smell bound threads, especially if the UI also makes FFI calls. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC libraries documentation and links to source files
Hello Manilo and Haskell-cafe, On Sun, Dec 21, 2008 at 4:07 PM, Manlio Perillo manlio_peri...@libero.itwrote: Hi. I have noted that recent versions of the GHC libraries documentation, no longer have links to the source code. What is the reason? I find it very useful. I would like to suggest that all Haskell libraries generate documentation with view source links. Like Manilo, I also find it very useful. Thank you. __ Donnie Jones ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Threads with high CPU usage
Hi Günter Günther Schmidt wrote: Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. It could be the database library, as it may use unsafe foreign calls. Unsafe foreign calls blocks all other threads, even if you compile with the -threaded option. See http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Concurrent.html#4 . I cannot claim to know how all Haskell database libraries are implemented, but at least some of them use unsafe foreign calls. So which database library is you using? What can I do? If the problem has to do with unsafe foreign calls, then you can implement the database calls in a separate process. Not the easiest options, but I can think of no other. Günther /Mads Lindstrøm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Threads with high CPU usage
Hi Mads, I'm using HDBC with sqlite3 Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Threads with high CPU usage
Would forkOS instead of forkIO help in this case? On Sun, Dec 21, 2008 at 11:16 PM, Mads Lindstrøm mads_lindstr...@yahoo.dkwrote: Hi Günter Günther Schmidt wrote: Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. It could be the database library, as it may use unsafe foreign calls. Unsafe foreign calls blocks all other threads, even if you compile with the -threaded option. See http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Concurrent.html#4. I cannot claim to know how all Haskell database libraries are implemented, but at least some of them use unsafe foreign calls. So which database library is you using? What can I do? If the problem has to do with unsafe foreign calls, then you can implement the database calls in a separate process. Not the easiest options, but I can think of no other. Günther /Mads Lindstrøm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Threads with high CPU usage
Hi Peter, Peter Verswyvelen wrote: Would forkOS instead of forkIO help in this case? No, according to http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Concurrent.html#v%3AforkOS : Using forkOS instead of forkIO makes no difference at all to the scheduling behaviour of the Haskell runtime system. It is a common misconception that you need to use forkOS instead of forkIO to avoid blocking all the Haskell threads when making a foreign call; this isn't the case. To allow foreign calls to be made without blocking all the Haskell threads (with GHC), it is only necessary to use the -threaded option when linking your program, and to make sure the foreign import is not marked unsafe. /Mads On Sun, Dec 21, 2008 at 11:16 PM, Mads Lindstrøm mads_lindstr...@yahoo.dk wrote: Hi Günter Günther Schmidt wrote: Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. It could be the database library, as it may use unsafe foreign calls. Unsafe foreign calls blocks all other threads, even if you compile with the -threaded option. See http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Concurrent.html#4 . I cannot claim to know how all Haskell database libraries are implemented, but at least some of them use unsafe foreign calls. So which database library is you using? What can I do? If the problem has to do with unsafe foreign calls, then you can implement the database calls in a separate process. Not the easiest options, but I can think of no other. Günther /Mads Lindstrøm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Threads with high CPU usage
Hi Günther, Hi Mads, I'm using HDBC with sqlite3 Looking at http://software.complete.org/software/repositories/entry/hdbc-sqlite3/Database/HDBC/Sqlite3/Connection.hs and http://software.complete.org/software/repositories/entry/hdbc-sqlite3/Database/HDBC/Sqlite3/Statement.hsc you can see that HDBC-sqlite's foreign calls are indeed marked unsafe. /Mads Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Threads with high CPU usage
redcom: Hi Mads, I just noticed that too. I had been wondering why this problem does not occur with the sample app from RWH eventhough I was employing the same technics as they did. It just occured to me that all the DB interactions in their app are fairly short and thus the problem never becomes apparent. Thanks everyone, I was going crazy here, couldn't figure out what I was doing wrong. Would anyone happen to know of a safe alternative to HDBC? Modify the 'unsafe' inports to be 'safe'? I don't think HDBC is going to call back in, so should be fine. John? That said, we use Takusen or sqlite3 at work, without troubles. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Threads with high CPU usage
Hi Mads, I just noticed that too. I had been wondering why this problem does not occur with the sample app from RWH eventhough I was employing the same technics as they did. It just occured to me that all the DB interactions in their app are fairly short and thus the problem never becomes apparent. Thanks everyone, I was going crazy here, couldn't figure out what I was doing wrong. Would anyone happen to know of a safe alternative to HDBC? Günther Am 21.12.2008, 23:39 Uhr, schrieb Mads Lindstrøm mads_lindstr...@yahoo.dk: Hi Günther, Hi Mads, I'm using HDBC with sqlite3 Looking at http://software.complete.org/software/repositories/entry/hdbc-sqlite3/Database/HDBC/Sqlite3/Connection.hs and http://software.complete.org/software/repositories/entry/hdbc-sqlite3/Database/HDBC/Sqlite3/Statement.hsc you can see that HDBC-sqlite's foreign calls are indeed marked unsafe. /Mads Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Threads with high CPU usage
Hi Don, Modify the 'unsafe' inports to be 'safe'? I don't think HDBC is going to call back in, so should be fine. John? Sorry, total noob here, could you be more specific? Günther That said, we use Takusen or sqlite3 at work, without troubles. I might also check into that. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Comparing on multiple criteria
On Sun, Dec 21, 2008 at 11:20 AM, Jan-Willem Maessen jmaes...@alum.mit.edu wrote: On Dec 21, 2008, at 8:52 AM, Martijn van Steenbergen wrote: Hello all, Data.Ord has a handy function called comparing, and its documentation shows an example of its use. But what if you want to sort a list of values based on multiple criteria? It turns out there is a neat way to do this: compareTuple = mconcat [comparing fst, comparing snd] The default Monoid instances for Ordering and functions work exactly as required here. (Thanks to vixey in #haskell for the hint to look at monoids!) Indeed, this is great to know. I can't help but notice that there is no documentation of any kind at all for the Monoid instance of Ordering; how were we supposed to know this behavior existed in the first place, except by hunting down the source code for the instance declaration? This is a great example of why it's a bad idea to introduce new functionality with a Monoid instance. Even if you know the instance exists, mappend is so general that it's difficult or impossible to predict what it will do at a given type. There should be an explicit function for combining Ordering values lexicographically, with a note in the documentation saying that it's the basis of the Monoid instance. -- Dave Menendez d...@zednenem.com http://www.eyrie.org/~zednenem/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Trouble with the ST monad
Hello, I'm trying to write a function that would take an STArray and and shuffle its elements. I'm having trouble with the ST monad, though, and couldn't find out how fix this issue. The problem happens when I use runST to extract the shuffled array from the ST monad. I'm getting the following error: Inferred type is less polymorphic than expected Quantified type variable `s' is mentioned in the environment: a :: STArray s Int a The full code is at http://hpaste.org/13240#a1 Any help would be appreciated. Thanks, Andre ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The Haskell re-branding exercise
G'day all. Quoting Sebastian Sylvan syl...@student.chalmers.se: Personally I find the current logo horrendous. I think it's ugly and intimidating at the same time. I don't really care too much which one of the proposals should win, just so long as I can weed out some of the ones I really hate. I guess this is one difference between the Haskell rebranding exercise and other corporate rebranding exercises: Nobody especially likes the current logo. (Disclaimer: It would be fair to say that there are some who don't hate it as much as Sebastian, but nobody really likes it.) Cheers, Andrew Bromage ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Trouble with the ST monad
The problem is that you are trying to return a mutable array out of an ST computation. This lets the mutability of the computation escape. That's what the s type variable is for; without it, runST is just unsafePerformIO. To solve your problem, you need to eliminate any references to the state from the output of runST. I suggest looking into the function freezeSTArray: From http://haskell.org/ghc/docs/latest/html/libraries/base/GHC-Arr.html#v:freezeSTArray freezeSTArray :: Ix i = STArray s i e - ST s (Array i e) (See my annotation at http://hpaste.org/13240#a2) This allows you to remove any reference to the state from the array computation. Alternatively, if you want this to be part of a larger mutable computation, you can return the result in ST; this is what the version of shuffle you have in the paste does. -- ryan On Sun, Dec 21, 2008 at 4:14 PM, Andre Nathan an...@digirati.com.br wrote: Hello, I'm trying to write a function that would take an STArray and and shuffle its elements. I'm having trouble with the ST monad, though, and couldn't find out how fix this issue. The problem happens when I use runST to extract the shuffled array from the ST monad. I'm getting the following error: Inferred type is less polymorphic than expected Quantified type variable `s' is mentioned in the environment: a :: STArray s Int a The full code is at http://hpaste.org/13240#a1 Any help would be appreciated. Thanks, Andre ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Records and associated types
Am Donnerstag, 11. Dezember 2008 22:04 schrieb Taru Karttunen: Hello What is the correct way to transform code that uses record selection with TypeEq (like HList) to associated types? Hello Taru, you might want to look at http://www.mail-archive.com/glasgow-haskell-users%40haskell.org/msg12788.html and its follow-ups. Best wishes, Wolfgang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Threads with high CPU usage
Tried running the program with +RTS -Nn where n = 2 or more? that should use more OS threads On Sun, Dec 21, 2008 at 10:43 PM, Günther Schmidt red...@fedoms.com wrote: Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. What can I do? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] A hell of a question
I just want to say Hello to let you know that there are some serious entities watching you besides monads and FBI:-) There has been a hell of a discussion recently about logos, languages and religion and I want to add to this. First let me disassociate Haskell from Taoism which to may taste has left us in an unhealthy climate. It suffices to say that Taoism is a school of clever trics and cute aphorisms but without the slightest attempt to explain or generalize let alone produce an abstract idea or a system. That is why its wisdom is non transferable in spite of majority of humans desending from it. Haskell on the contrary is a minority school that implements abstract ideas for problem solving in the most transferable way to date, so that other languages look into it for their share. But don't worry, thay will choke becouse it is them who practice Taoizm. Playing too many tricks will eventually trick them, even if some are powerful enough to brainwash dicent professors to preach interoperability or the like. Every viable complexity needs a single underlying concept to survive, including you and the universe. Microsoft and the like excluding;-) Haskell has all that: consistency, transparency and self-contained concept. However Haskell is also somehow asynchronic with the Bible as it is condemned to perpetual purity only to be saved from it via monads, which according to Spinoza are arranged by God in a perfect order which ascends to God, the supreme monad!!!. Thus we can look at Haskell's purity as a kind of harmless attempt to play God by means of incapsulating the world only to ignor it. This could somehow put it in the same boat with the devil. They both prefer your brain to Turing machin:-) I would leave with the eternal question what the hell Haskell is? and with my Santa Close emphasising Haskell's purity and my simplicity. Here: http://haskell.org/sitewiki/images/7/79/WCF.Andrzej.Jaworski.gif Have fun, -Andrzej Jaworski ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Trouble with the ST monad
On Sun, 2008-12-21 at 16:47 -0800, Ryan Ingram wrote: The problem is that you are trying to return a mutable array out of an ST computation. This lets the mutability of the computation escape. That's what the s type variable is for; without it, runST is just unsafePerformIO. Thanks! If only I knew that was the problem... It wouldn't have costed me the whole afternoon :P Is there any difference between using freeze/thaw from Data.Array.MArray versus freezeSTArray/thawSTArray from GHC.Arr? Best, Andre ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Threads with high CPU usage
redcom: Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a mainIteration in there. How are you compiling this code (-O -threaded ?) and what does the forkIO'd thread do? Does it allocate? Would increasing the runtime scheduling ticks help? (Perhaps , if the UI is mostly sleeping). -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Pattern combinators
I'd love to see a copy of this go up on hackage for experimentation. Would
you care to upload your code, or send it to me so I can upload it?
On Sun, Dec 21, 2008 at 12:37 AM, David Menendez d...@zednenem.com wrote:
On Sat, Dec 20, 2008 at 9:34 PM, Jacques Carette care...@mcmaster.ca
wrote:
Andrew Wagner wrote:
Wadler posted a blog entry the other day about a paper on
pattern-matching
in Haskell (http://wadler.blogspot.com/). I've taken a first stab at
turning
it into actual code for hackage (http://hpaste.org/13215). There are
two
commented-out definitions that don't type-check, though, and the types
are
too wild for me to grok. Anybody have any suggestions for 1.) How to fix
it
and/or 2.) How to use data/type/newtype to simplify the types and make
it
more manageable? Thanks!
Both errors are because you are using any instead of any'; you might
wish to put
import Prelude hiding any
at the top of your code, just to avoid such confusion.
Example 14 also uses (.-.) where it should use (..), and it either
needs some more parentheses or some precedence declarations for the
operators.
To make the types more readable (but not necessarily more manageable), I
have made some changes to my version of this code.
One oddity in the paper is the type of the failure continuations, ()
- ans. I'm guessing that's left over from an earlier phase of
development. In my own transcription of the library, I eliminated the
() parameter without apparent loss of functionality.
I think I've managed to work out the structure of the types, which can
mostly be expressed in modern Haskell.
The matching part of the patterns have this general form:
type PMatch vec vec' ans = (vec - ans) - (() - ans) - vec' - ans
where vec and vec' are the list of argument types before and after the
subpattern match, and ans is the final answer. (In my code, I just use
ans instead of () - ans for the failure continuation.)
This gets us:
nil :: PMatch vec vec ans
one :: a - PMatch (a,vec) vec ans
(#) :: PMatch vec vec' ans - PMatch vec' vec'' ans - PMatch vec vec''
ans
fail :: PMatch vec vec' ans
catch :: PMatch vec vec' ans - PMatch vec vec' ans - PMatch vec vec' ans
These types are less general than the ones Haskell would infer, but
they do not appear to lose any functionality.
The currying part of the pattern is less easy to analyze. I've been
able to use type families to relate the curried and uncurried form of
the function types, but I'm working with GHC 6.8, so it's possible
this won't work with the more modern implementations.
Given the list of argument types and the answer type, generate a
curried function type:
type family Curry vec ans
type instance Curry () ans = ans
type instance Curry (a,vec) ans = a - Curry vec ans
zero, succ zero, and so forth take a function in curried form and
transform it into a function that takes a nested tuple:
type CurryDigit vec ans = Curry vec ans - vec - ans
zero :: CurryDigit () ans
succ zero :: CurryDigit (a,()) ans
succ :: CurryDigit vec ans - CurryDigit (a,vec) ans
succ . succ :: CurryDigit vec ans - CurryDigit (a,(b,vec)) ans
So the currying part of the pattern will have the form:
type PCurry vec vec' ans = CurryDigit vec' ans - CurryDigit vec ans
So a pattern has the type,
type Pattern a vec vec' ans = (PCurry vec vec' ans, a - PMatch
vec vec' ans)
where a is the value being examined, vec and vec' are the list of
unbound argument types before and after the match, and ans is the
result.
var :: Pattern a (a,vec) vec ans
cst :: (Eq a) = a - Pattern a vec vec ans
pair :: Pattern a vec vec' ans - Pattern b vec' vec'' ans -
Pattern (a,b) vec vec'' ans
Coming from the other side, match takes a value and a case statement
and produces a result:
type Case a ans = a - (() - ans) - ans -- or just a - ans -
ans in my code
match :: a - Case a ans - ans
(|||) combines case statements:
(|||) :: Case a ans - Case a ans - Case a ans
and (-) creates them from a pattern and a curried function,
(-) :: Pattern a vec () ans - Curry vec ans - Case a ans
Note that (-) requires the pattern to leave no unbound variables
after matching.
Given the way everything is polymorphic in ans, it may be possible to
hide it, but I haven't tried yet.
The principal weakness of these pattern-matching combinators is that
there
is no support for algebraic types, i.e. things like
data Tree a = Leaf | Branch (Tree a) (Tree a)
I can see how to use Typeable to deal with that, but is there a simpler
way?
You can define the patterns manually:
leaf = (id, \v - case v of { Leaf - nil; _ - fail })
branch p q = (curry_p . curry_q, \v - case v of { Branch l r -
match_p l # match_q r; _ - fail})
where
(curry_p, match_p) = p
(curry_q, match_q) = q
I assume generating these would be pretty straightforward to automate
with Template
[Haskell-cafe] Can I build and install GHC 6.10.1 without previous installed ghc
Hi All, I have our own Linux distribution installed in my server. it is based on RedHat 9.0. Because it is the server, I can not update it to any other linux distribution Here is my situation, I have no machine with any version of ghc installed. This is what I did % wget http://haskell.org/ghc/dist/6.10.1/ghc-6.10.1-src.tar.bz2 % wget http://haskell.org/ghc/dist/6.10.1/ghc-6.10.1-src-extralibs.tar.bz2 % tar -jxf ghc-6.10.1-src-extralibs.tar.bz2 %tar -jxvf ghc-6.10.1-src.tar.bz2 % cd ghc-6.10.1 % sh boot grep: packages: No such file or directory Booting . Booting libraries/base Booting libraries/directory /usr/share/aclocal/libgcrypt.m4:23: warning: underquoted definition of AM_PATH_LIBGCRYPT run info '(automake)Extending aclocal' or see http://sources.redhat.com/automake/automake.html#Extending-aclocal /usr/share/aclocal/ao.m4:9: warning: underquoted definition of XIPH_PATH_AO Booting libraries/editline Booting libraries/network Booting libraries/old-time Booting libraries/process Booting libraries/regex-posix Booting libraries/time Booting libraries/unix % ./configure checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking target system type... x86_64-unknown-linux-gnu Canonicalised to: x86_64-unknown-linux checking for ghc... no checking for ghc-pkg matching ... no checking for ghc-pkg... no checking whether ghc has editline package... no checking for nhc... no checking for nhc98... no checking for hbc... no checking for ld... /usr/local/bin/ld configure: error: GHC is required unless bootstrapping from .hc files. I know http://hackage.haskell.org/trac/ghc/wiki/Building/Prerequisites said that GHC 6.6 is required to build and install the GHC 6.10.1 So I try to follow the instructions http://hackage.haskell.org/trac/ghc/wiki/Building/Porting. Because I don't have any ghc installed in any machine. I have to use the Porting GHC to a new platform %./configure --enable-hc-boot --enable-hc-boot-unregisterised checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking target system type... x86_64-unknown-linux-gnu Canonicalised to: x86_64-unknown-linux checking for ghc... no checking for ghc-pkg matching ... no checking for ghc-pkg... no checking whether ghc has editline package... no checking for nhc... no checking for nhc98... no checking for hbc... no checking for ld... /usr/local/bin/ld checking for path to top of build tree... ./configure: line 2733: -v0: command not found ./configure: line 2737: utils/pwd/pwd: No such file or directory configure: error: cannot determine current directory I think it is because the utils/pwd/pwd.hs is not compiled and linked into the ``pwd''. So I create a bash version of pwd #!/bin/bash pwd And m make it executeble, chmod +x utils/pwd/pwd Then I try to run the ./configure --enable-hc-boot --enable-hc-boot-unregisterised again %./configure --enable-hc-boot --enable-hc-boot-unregisterised again %cd includes %make %cd .. Finnally, I found I still need ghc is intalled on the host machine. %perl --version This is perl, v5.8.5 built for x86_64-linux-thread-multi Copyright 1987-2004, Larry Wall Perl may be copied only under the terms of either the Artistic License or the GNU General Public License, which may be found in the Perl 5 source kit. Complete documentation for Perl, including FAQ lists, should be found on this system using `man perl' or `perldoc perl'. If you have access to the Internet, point your browser at http://www.perl.com/, the Perl Home Page. %gcc --version gcc (GCC) 4.1.2 Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. %make --version GNU Make 3.80 Copyright (C) 2002 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. %autoconf --version autoconf (GNU Autoconf) 2.59 Written by David J. MacKenzie and Akim Demaille. Copyright (C) 2003 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. %automake --version automake (GNU automake) 1.9.2 Written by Tom Tromey tro...@redhat.com. Copyright 2004 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. %sed --version GNU sed version 4.1.2 Copyright (C) 2003 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, to the extent permitted by law. %diff --version diff (GNU
Re: [Haskell-cafe] Can I build and install GHC 6.10.1 without previous installed ghc
chunye.wang: Hi All, I have our own Linux distribution installed in my server. it is based on RedHat 9.0. Because it is the server, I can not update it to any other linux distribution Here is my situation, I have no machine with any version of ghc installed. Please use a basic linux binary. http://haskell.org/ghc/download_ghc_6_10_1.html#x86linux Such as Linux (x86) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Can I build and install GHC 6.10.1 without previous installed ghc
Hi Don, I tried to install the ghc 6.8.0 last year but failed for some reason. Now I decide to do it again, because I'd like to try some examples in Real World Haskell Now I remember why I try to install it from source code, because the binary version has the following problem. %./configure checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking target system type... x86_64-unknown-linux-gnu Which we'll further canonicalise into: x86_64-unknown-linux checking for path to top of build tree... pwd: timer_create: Invalid argument configure: error: cannot determine current directory I know my linux distribution is a private modified version, which is based on RedHat 9.0 I guess it is pretty old version. I also installed many other software from source code. I guess ``timer_create '' is failed because of library confliction. Best Regards Chunye Wang chunye.w...@nsn.com -Original Message- From: ext Don Stewart [mailto:d...@galois.com] Sent: Monday, December 22, 2008 11:31 AM To: Wang, Chunye (NSN - CN/Beijing) Cc: Haskell-Cafe@haskell.org; glasgow-haskell-us...@haskell.org Subject: Re: [Haskell-cafe] Can I build and install GHC 6.10.1 without previous installed ghc chunye.wang: Hi All, I have our own Linux distribution installed in my server. it is based on RedHat 9.0. Because it is the server, I can not update it to any other linux distribution Here is my situation, I have no machine with any version of ghc installed. Please use a basic linux binary. http://haskell.org/ghc/download_ghc_6_10_1.html#x86linux Such as Linux (x86) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: llvm-0.4.0.1
We have now released version 0.4.0.1 of the Haskell LLVM bindings. (This release that is quite incompatible with the old 0.0.2 release.) LLVM is a virtual machine and the bindings allow you to generate code for this virtual machine. This code can then be executed by a JIT or written to a file for further processing by the LLVM tools. The LLVM bindings has two layers. You can either use the low level bindings that is just the same as the C bindings for the LLVM. This level is quite unsafe as there is very little type checking. The recommended way is a high level binding (somewhat less complete) which eliminates many errors by leveraging the Haskell type system. A simple example, generating code for a function that adds two numbers and then calling it from Haskell: import Data.Int import LLVM.Core import LLVM.ExecutionEngine cgplus :: CodeGenModule (Function (Int32 - Int32 - IO Int32)) cgplus = createFunction InternalLinkage $ \ x y - do r - add x y ret r main = do ioplus - simpleFunction cgplus let plus = unsafePurify ioplus print $ plus 20 22 Enjoy! Bryan O'Sullivan Lennart Augustsson ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
