[Haskell-cafe] Re: Set Operations In Haskell's Type System
On May 6, 4:30 am, Bartek Ćwikłowski paczesi...@gmail.com wrote: hello, 2010/5/6 John Creighton johns2...@gmail.com: a isa d if their exists a b and c such that the following conditions hold: a isa subset of b, b isa c c is a subset of d This definition doesn't make sense - it's recursive, but there's no base case, unless this is some kind of co-recursion. Are you sure that subset isn't what you really want? With subset you can already ask questions such as is tabby cat an animal?. If so, my code (from hpaste) already has this (iirc isDescendentOf ). When I succeed in implementing it I'll show you the result. Anyway, some perspective (perhaps), I once asked, what is the difference between a subset and an element of a set: http://www.n-n-a.com/science/about33342-0-asc-0.html It sounds like a strange question but is a cat a subset of noun? Cat is relay just a word or a label, we could be referring to the word Cat, The set of all Cats or a particular cat. If by Nouns we mean physical things then the set of cats is a subset of the set of things that are nouns. However, if by noun we mean a type of word, then cat is not a type or word but noun is a type of word. From the perspective of programing the latter observation seems more useful. It involves some context in that we wish to treat word types and instances of those word types differently rather then trying to fit them into some homogeneous hierarchy. For instance if we are building grammar parsing rules then we probably only care what type or word or phrase something is and any hierarchical relationship beyond that are not relevant to the context of parsing. Now if our goal is only to parse then perhaps their is a better approach but object oriented programing has shown how subclass polymorphism adds some level of abstraction and helps to make code more generic. Haskel's type system allows for even more generic approaches. To summarize, I have chosen to define isa as a relationship between hierarchies, while subset/superset are our standard heiercrical view of the world (e.g. animal kingdom). Now with regards to my definition, let's go further. Let's create an equivalence between a noun phrase of length one and a Noun. http://en.wikipedia.org/wiki/Noun_phrase while we may wish to view the noun as primitive, with regards to meaning the phrase narrows the scope of the noun. For instance big cat, means that cat can no longer refer to all cats but the cats must be big. Now if we want to know if big cat is a noun, it is enough to know that, big cat is a subset of cat, cat is a common noun, and common noun is a subset of noun. (I'm aware some may object to big cat being a noun but big cat is a thing and a noun is a thing). This keeps us from directly having to program a direct relationship between big cat and noun. One of the goals of AI is to minimize what we have to tell our system in order to solve a problem. This is referred to as the A to I ratio. Generic programing has this characteristic in that our code is widely applicable. The isa rule above makes code more generic in that we are now able to write functions four nouns which will apply to say big cat with out even having to tell our program that big cat is a noun, rather it can directly infer it from the rules we supplied. -- note 1) Okay I'm aware some will argue my definitions here and if it helps I could choose new words, the only question really is, is the relationship isa which I described a useful abstraction. I think it is and weather it is or not would of course depend on if it reduces the amount of code that needs to be written and it produces the correct results. We could create other relationships which embody what other people think a useful isa function should do and they could be used either in parallel with my relationship or with a completely different approach. I cannot say weather such alternative relationships will be more or less useful. note2 ) For the purpose of the above I guess we can define Noun to be a noun phrase of length one (we can choose a different word if someone prefers to call this instead of a noun.), note 3) Anyway, with regards to the above I am using subset with regards to scope (the number of _ something can refer to) and isa with regards to type of scope. So noun says the scope refers to a person place or thing and then, the noun (or noun phrase) limits the scope of these things that the phrase/noun can refer to. This is perhaps not the standard English/linguistic usage and I am sure their are many reasonable objections to the above on semantic grounds. I am not interested in a debate on semantics but will listen to suggestions for alternative terms/definitions. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Dynamic CSV Parsing - Parsec
Hi Günther, A simple method is to parameterize a parse function by something you parsed previously. For the example you gave, I would try something like this: import ParseToken cellContent = do ... -- parses the contents of a cell cvsParser = do headings - sepBy identifier semi cs - count (length headings - 1) (do c - cellContent; semi; return c) c - cellContent return (cs ++ [c]) Of course, you can put the last two lines into a separate function that is parameterized with the list of headings found. (Instead of these lines, I would also define an abstraction function sepByCount p n sep that parses n occurrences of p, each separated by sep.) Best regards, Bernd Am 07.05.2010 00:40, schrieb Günther Schmidt: Hello, I'm trying to build a CSV parser that can dynamically assemble a parser from the values of the first line. As the most simple example the parse of the first line would return a parser with which subsequent lines would then be parsed. This parser would, for instance, only parse lines with the exact number of columns as found in the first line. Where I eventually want to go is a bit more complicated than this, but for now I'd be grateful for suggestions on how to go about the simple case. Best regards 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] darcs to mercurial migration
On Thu, 06 May 2010 01:08:08 +0200, Günther Schmidt gue.schm...@web.de wrote: Hello, I'm switching from darcs to mercurial with some of my projects. I'd like to retain as much of the history as possible, what tools are there available for this? I recommend you darcs-fast-export and then use the/a mercurial fast-import. http://vmiklos.hu/project/darcs-fast-export/ Regards, -- Nicolas Pouillard http://nicolaspouillard.fr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Mirror repository for gtk2hs
Hi all, Because code.haskell.org is unstable recently, and many gtk2hs users can't get code from http://code.haskell.org/gtk2hs So i build a mirror repository at http://patch-tag.com/r/AndyStewart/gtk2hs-sync-mirror/home You can access this mirror repository when code.haskell.org down. This mirror repository synchronous http://code.haskell.org/gtk2hs Hourly. Because mirror repository just read-only, please send any patches to gtk2hs main repository (http://code.haskell.org/gtk2hs) I need thanks Thomas Hartman (the administor of patch-tag.com), i can't build this mirror repository if haven't his help. Thanks Thomas! Enjoy, everybody! -- Andy ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Database connection pool
On Fri, May 7, 2010 at 1:02 AM, Bas van Dijk v.dijk@gmail.com wrote:
On Thu, May 6, 2010 at 11:54 PM, Bas van Dijk v.dijk@gmail.com
wrote:
On Thu, May 6, 2010 at 7:48 PM, Bas van Dijk v.dijk@gmail.com
wrote:
On Thu, May 6, 2010 at 3:24 PM, Michael Snoyman mich...@snoyman.com
wrote:
On Thu, May 6, 2010 at 9:13 AM, Bryan O'Sullivan b...@serpentine.com
wrote:
On Wed, May 5, 2010 at 10:51 PM, Michael Snoyman mich...@snoyman.com
wrote:
* When a connection is released, is goes to the end of the pool, so
connections get used evenly (not sure if this actually matters in
practice).
In practice, you're better off letting idle connections stay that way,
because then your DB server can close connections and free up
resources. In
other words, when you're done with a connection, put it at the front
of the
reuse queue, not the back.
You'll also want to handle the possibility that a connection that you
grab
from the pool has been closed by the server. Many connection pooling
implementations I've seen get this wrong in subtle or expensive ways.
Thanks for the feedback. I've gone ahead and implemented a simple
resource
pool module. Since I need it to work with monad transformer stacks,
I've
built it on top of MonadCatchIO-transformers. I've put the code up in a
gist
on github[1]. I would appreciate if anyone could review this,
especially to
make sure the exception handling code is correct. block and unblock in
particular concern me.
Thanks,
Michael
[1] http://gist.github.com/392078
I also have a suggestion for your design. (Note however that I don't
have much experience with resource pools.)
In your current design a Pool has a fixed maximum number of opened
resources. I can imagine situations where the maximum number of opened
resources can change dynamically. For example due to plugging in (or
out) a new blade server at run-time which will increase (or decrease)
the maximum number of resources that can be handled.
So what about changing:
createPool :: IO a - Int - IO (Pool a)
to:
createPool :: IO (Maybe a) - IO (Pool a)
so, instead of statically storing the maximum number of opened
resources (Int), the resource creation function will decide itself
when it has created enough (Maybe a).
Regards,
Bas
How about something like this:
{-# LANGUAGE NoImplicitPrelude #-} -- (I like to be explicit)
module Pool (Pool, new, withPool) where
import Data.Function ( ($), (.) )
import Data.Maybe ( Maybe(Nothing,Just), maybe )
import Data.Functor( ($) )
import Control.Monad ( return, (=), (), (=), fail,
join, liftM )
import Control.Monad.STM ( atomically )
import Control.Concurrent.STM.TVar ( TVar, newTVarIO, readTVar, writeTVar
)
import Control.Monad.CatchIO ( MonadCatchIO, block, finally )
import Control.Monad.IO.Class ( liftIO )
newtype Pool r = Pool (TVar [r])
new :: MonadCatchIO m = m (Pool r)
new = liftIO $ Pool $ newTVarIO []
withPool :: MonadCatchIO m = Pool r - m (Maybe r) - (r - m a) - m
(Maybe a)
withPool (Pool tv) mk f = block $ join $ liftIO $ atomically $ do
rrs - readTVar tv
case rrs of
[] - return $ mk = maybe (return Nothing) with
r:rs - writeTVar tv rs return (with r)
where
with r = liftM Just (f r)
`finally`
liftIO (atomically $ writeTVar tv . (r:) = readTVar
tv)
Note that I don't store the resource creation action (m (Maybe r))
inside the pool. It's just passed as an argument to withPool.
Regards,
Bas
Note that it's probably better to pass the resource creation action as
the first argument to withPool:
withPool :: MonadCatchIO m = m (Maybe r) - Pool r - (r - m a) - m
(Maybe a)
This way it's easier to create specialized withPool functions by
partially applying a specific resource creation action to withPool as
in:
withDBConsPool :: MonadCatchIO m = Pool DBCon - (DBCon - m a) - m
(Maybe a)
withDBConsPool = withPool connectWithDB
Regards,
Bas
Bas,
Thank you for all the very thorough comments. If I'm understanding
correctly, there are two categories of suggestion:
1) Make the resource exhaustion mechanism more extensible.
2) Avoid wormholes
Please tell me if I've missed something.
Regarding (1), I think your approach is definitely better for complex pools;
however, for the usually case, I think it would present a more difficult API
for users. I could definitely imagine wrapping an easier-to-use interface
around your final example.
Regarding (2), I was not aware of it, thank you for updating me on the
issue.
So, here's my idea of how to wrap your Pool module to provide a simple
Re: [Haskell-cafe] ANNOUNCE: gt-tools-0.1.4
On Fri, May 7, 2010 at 4:12 AM, Felipe Lessa felipe.le...@gmail.com wrote: On Thu, May 06, 2010 at 09:30:50PM +0300, Sergei Trofimovich wrote: /me wonders if Miss lambdabot might like to have such functionality. What do you think? Do the terms of use of Google Translate allow it? I can't remember, but they try to block it. However, there is a public API. --Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [Long, probably not-beginners anymore] Parallel folds and folds as arrows (was: Re: [Haskell-beginners] Re: When, if ever, does Haskell calculate once?)
On Friday 07 May 2010 03:15:19, Maciej Piechotka wrote:
On Thu, 2010-05-06 at 23:46 +0200, Daniel Fischer wrote:
Share.share :: GHC.Types.Int
GblId
[Str: DmdType]
Share.share =
case GHC.List.$wlen @ GHC.Integer.Type.Integer Share.share_a 0
of ww_amc { __DEFAULT -
GHC.Types.I# (GHC.Prim.+# ww_amc ww_amc)
}
Hmm. What's the name of this form and how to get it?
It's GHC's intermediate language, named Core. It's sort of a slimmed down
Haskell.
You can get it by
a) compiling with the -ddump-simpl flag
(e.g. ghc -O2 -ddump-simpl --make prog prog.core
If you don't redirect, it's spat out to stdout, better to have it in a file
for reading. Also, it's easier to read with syntax-highlighting, plain
Haskell-highlighting already goes a long way.)
b) using Don Stewart's ghc-core (http://hackage.haskell.org/package/ghc-
core), e.g. ghc.core -f html -- -O2 Source.hs Source.html
Looking at the core, you can see what GHC really makes from your code.
No.
cFoldl' f g (b0,c0) xs0 = lgo b0 c0 xs0
where
lgo b c [] = (b,c)
lgo !b !c (x:xs) = lgo (f b x) (g c x) xs
Ok. Fixed (I tried fast rewrite from foldr')
Doesn't matter when compiled with optimisations (produces nearly identical
core), but without optimisations the original constructs a new pair in each
step.
However, I inadvertently swapped the clauses of lgo (could also be fixed by
putting the bang patterns in the first clause). That didn't matter as long
as both accumulating functions were lengthFold, but it makes a big
difference when one is (+).
64-bit system? I get
64 bit, GHC 6.12.2.
% ghc -V
The Glorious Glasgow Haskell Compilation System, version 6.12.2
% file a.out
a.out: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically
linked (uses shared libs), for GNU/Linux 2.6.9, not stripped
And that is strange, because I get the same figures for that one as
for the first (times differ by a few hundredths of a second).
Fixed or non-fixed version?
Is that a difference between 32-bit code generator and 64-bit or
between GHC versions (6.12.2 here, but 6.10.3 gives roughly the same
results)?
Hmm. Compiler and platform matches. Unless you use some other 64-bit
platform - not x86-64 ;)
No, I have a 32-bit system (I got almost exactly half the allocation
figures you got, so I suspected your Ints [and small Integers] were twice
as large as mine).
main =
print $! uncurry (+) (cFoldl' lengthFold lengthFold
(0, 0) [1..size])
And that gives the same figures as the other two (plus/minus 0.05s).
All are compiled with optimizations.
All compiled with -O2.
Hmm. Difference between -O1 and -O2
No, they produce identical core for these.
Fixed versions and with sum (and -O2):
main = let a = [1..size]
l = length a + sum a
in print $! l
Lot's of memory(Over 3 GiB). I voluntarily killed process
Yes, of course.
main = print $! length [1..size] + sum [1..size]
Lot's of memory(Over 3 GiB). I voluntarily killed process.
So far as being inplace.
Yes. Actually, with optimisations turned on, GHC *does* share the list
[1 .. size]. Oops.
It's not shared with -O0 unless you give it a name.
main = print $! uncurry (+) (cFoldl' lengthFold (+) (0, 0) [1..size])
50015000
16,889,753,976 bytes allocated in the heap
3,356,480 bytes copied during GC
1,976 bytes maximum residency (1 sample(s))
28,200 bytes maximum slop
1 MB total memory in use (0 MB lost due to fragmentation)
Generation 0: 32216 collections, 0 parallel, 0.29s, 0.38s
elapsed
Generation 1: 1 collections, 0 parallel, 0.00s, 0.00s
elapsed
INIT time0.00s ( 0.00s elapsed)
MUT time 14.89s ( 15.12s elapsed)
GCtime0.29s ( 0.38s elapsed)
EXIT time0.00s ( 0.00s elapsed)
Total time 15.18s ( 15.50s elapsed)
%GC time 1.9% (2.4% elapsed)
Alloc rate1,134,094,110 bytes per MUT second
Productivity 98.1% of total user, 96.1% of total elapsed
./a.out +RTS -s 15.18s user 0.11s system 98% cpu 15.503 total
With the really fixed cFoldl' (overflows of course):
./lsCFoldl +RTS -s
1087459712
4,015,621,900 bytes allocated in the heap
126,564 bytes copied during GC
1,460 bytes maximum residency (1 sample(s))
29,892 bytes maximum slop
1 MB total memory in use (0 MB lost due to fragmentation)
Generation 0: 7659 collections, 0 parallel, 0.07s, 0.05s elapsed
Generation 1: 1 collections, 0 parallel, 0.00s, 0.00s elapsed
INIT time0.00s ( 0.00s elapsed)
MUT time1.50s ( 1.54s elapsed)
GCtime0.07s ( 0.05s elapsed)
EXIT time
[Haskell-cafe] Re: [Long, probably not-beginners anymore] Parallel folds and folds as arrows (was: Re: [Haskell-beginners] Re: When, if ever, does Haskell calculate once?)
On Friday 07 May 2010 16:15:41, Daniel Fischer wrote: b) using Don Stewart's ghc-core (http://hackage.haskell.org/package/ghc- core), e.g. ghc.core -f html -- -O2 Source.hs Source.html And of course, the html backend of ghc-core was removed with version 0.5 :( If you want html output, $ cabal install --constraint=hscolour == 1.13 ghc-core-0.4.3 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] accents
Hello, i'm still struggling with ghci and accents. Prelude é \233 I've installed GHC 6.12.1, which gave me a better result: Prelude putStrLn é é but still: Prelude é \233 I'm trying to search a file with french words with Regex, but i stumble on accents: *Main findRegexFile abnégation [] *Main findRegexFile abn.gation [abn\218gation,abn\218gations] I don't know the encoding of my file, how to deduce it? What is the encoding used by ghci? Unicode? Its seems not be the same since the représentation for é is not the same (\233 and \218). How to have accented characters in ghci? Can't find any ressources on the net. Cheers, Corentin PS: please let me know is you can't see the accented characters in this email, i'll send you another version with pictures. On 3/24/10, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: Dupont Corentin corentin.dup...@gmail.com writes: a - readFile list.txt head $ lines a abn\233gation putStrLn displays a strange character for the é. That is the escaped form of é. You have several options: 1) Use the utf8-string package for I/O 2) Use the text package for I/O (and set an encoding) 3) GHC 6.12.1 uses the system's locale for encoding; as such if your system normally lets you see accented characters then putStrLn, etc. will print them out. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Type system game (was: Nomic game in Haskell)
Hello, I think your type should be: type Board a b c d e f g h i = Either (Three a b c) (Either (Three d e f) (Either (Three g h i) (Either (Three a d g) (Either (Three b e h) (Either (Three c f i) (Either (Three a e i) (Three c e g))) as far as i can understand, it seems thats it's mandatory for Player 1 to play in a,b,c to win? So victory should go to player 2? Cheers, Corentin On 4/16/10, Dan Piponi dpip...@gmail.com wrote: On Thu, Apr 15, 2010 at 4:58 PM, Ashley Yakeley ash...@semantic.org wrote: type Board a b c d e f g h i = Either (Three a b c) (Either (Three d e f) (Either (Three g h i) (Either (Three a d g) (Either (Three b e h) (Either (Three c f i) (Either (Three a e i) (Either (Three c e g) ))) In the service of readability we could also define: data X = X data O Though the victory conditions aren't precisely the usual ones. -- Dan ___ 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] accents
On Friday 07 May 2010 17:05:08, Dupont Corentin wrote:
Hello,
i'm still struggling with ghci and accents.
Prelude é
\233
That uses the Show instance of Char, which escapes all characters greater
than '\127' ('\DEL'), so that's no problem, jut inconvenient.
I've installed GHC 6.12.1, which gave me a better result:
Prelude putStrLn é
é
putStrLn doesn't escape printable characters.
but still:
Prelude é
\233
That's interpreted as
print é
which is
putStrLn (show é)
, hence escaped.
I'm trying to search a file with french words with Regex, but i
stumble on accents:
*Main findRegexFile abnégation
[]
*Main findRegexFile abn.gation
[abn\218gation,abn\218gations]
Okay, your file seems to have a weird encoding.
Prelude putStrLn [toEnum 218]
Ú
I don't know the encoding of my file, how to deduce it?
What is the encoding used by ghci? Unicode?
I think it uses the system locale and defaults to utf-8 if it can't
determine the locale.
Its seems not be the same since the représentation for é is not the
same (\233 and \218).
How to have accented characters in ghci? Can't find any ressources on
the net.
Cheers,
Corentin
PS: please let me know is you can't see the accented characters in
this email, i'll send you another version with pictures.
On 3/24/10, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote:
Dupont Corentin corentin.dup...@gmail.com writes:
a - readFile list.txt
head $ lines a
abn\233gation
putStrLn displays a strange character for the é.
That is the escaped form of é. You have several options:
1) Use the utf8-string package for I/O
2) Use the text package for I/O (and set an encoding)
3) GHC 6.12.1 uses the system's locale for encoding; as such if your
system normally lets you see accented characters then putStrLn,
etc. will print them out.
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Re: [Haskell-cafe] darcs to mercurial migration
On Fri, May 7, 2010 at 2:29 AM, Nicolas Pouillard nicolas.pouill...@gmail.com wrote: On Thu, 06 May 2010 01:08:08 +0200, Günther Schmidt gue.schm...@web.de wrote: Hello, I'm switching from darcs to mercurial with some of my projects. I'd like to retain as much of the history as possible, what tools are there available for this? I recommend you darcs-fast-export and then use the/a mercurial fast-import. http://vmiklos.hu/project/darcs-fast-export/ Does this tool use libdarcs to read the darcs repository data and metadata? I see the claim that it is correct on the page you linked to: Correct darcs-fast-export produces correct results in any extreme cases. It has been tested with a collection of large darcs repos (called big-zoohttp://code.haskell.org/darcs/big-zoo/). And several testcases under the t/ directory. The correctness argument is solely based on testing of the conversion on repositories? If so, how can it remain correct when darcs changes the format or semantics of its data? Tailor on the other hand, invokes the various vcs directly and transfers the diffs between the repositories. This seems inherently safer to me. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANNOUNCE: network-protocol-xmpp 0.3
On Mon, 3 May 2010 07:43:25 -0700 John Millikin jmilli...@gmail.com wrote: My library, network-protocol-xmpp[2], is an implementation of most of RFC 3920 and a bit of RFC 3921. It supports opening client-to-server and component-to-server sessions, which is useful for implementing XMPP-based clients. This library's interface is very simple: clients may start a session with 'runClient' or 'runComponent', send and receive stanzas, and resume stored sessions. Later, I intend to add additional modules to support features such as MUC or file transmission, but for now I'd like to make sure the core library works. There's an example XMPP client, echo.hs[3], in the Darcs repository. Hi, John and Stephan! It's very nice to see such thing on hackage. I'm planning to write some long hanging notification robots at work using your library, so I have some questions and comments: 1. gsasl hackage package did not build for me against libgsasl-0.2.28. It did not define _MAJOR _MINOR macros, So I had to update up to libgsasl-1.4 which worked fine. Is there way to put constraints to pkgconfig-depends to .cabal file? 2. Just running echo.hs example causes it to be closed on timeout from server side (we use OpenFire and idle timeout there is 6 minutes). So my question is rore about library design abilities: can you inject ping stanzas (on expired timeout) messages into that example too? Thanks! -- Sergei signature.asc Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: test-framework 0.3.0
I'm pleased to announce the release of version 0.3 of test-framework (http://hackage.haskell.org/package/test-framework-0.3.0). This package provides a nice test runner for HUnit, QuickCheck 1 and QuickCheck 2 tests. To see a detailed example of the runner in action, please check out our website at http://batterseapower.github.com/test-framework The highlights of this release are: * Thanks to the contributions of Rogan Creswick at Galois, you can now get JUnit XML output from the test runner using the --jxml=FILENAME option * There is a new command line option (--plain), which tells the test runner to avoid using any ANSI features - this can be handy if you are (for example) viewing test output in Emacs Cheers, Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] {-# LANGUAGE DeriveApplicative #-} ?
Hi, If you think you can write an algorithm for deriving Applicative, I'd welcome you to try adding it to Derive: http://community.haskell.org/~ndm/derive The Functor/Foldable/Traversable derivations all started out in Derive, got tested/implemented/refined there, then moved to GHC later. I think that's a reasonable path with any Applicative derivation. Thanks, Neil On Thu, May 6, 2010 at 11:53 AM, Ben Millwood hask...@benmachine.co.uk wrote: On Thu, May 6, 2010 at 8:55 AM, Pavel Perikov peri...@gmail.com wrote: Hi, list!. Now in 6.12.1 we have DeriveFunctor, DeriveFoldable and DeriveTraversable. This greatly simplifies the reuse structure style of programming. Some structure (not just _data_ structure) got captured in ADT and can be reused for various purposes. Wouldn't it be nice to have the ability to derive Applicative as well? It shouldn't be more difficult than deriving Functor but will provide exciting possibilities. Just think about liftA2. The difference is that there is at most one law-abiding instance of Functor for each type, whereas there are in principle multiple possible instances for Applicative for a type. E.g. the following: instance Applicative [] where pure x = [x] fs * xs = concatMap (\f - map f xs) fs instance Applicative [] where pure = repeat (f:fs) * (x:xs) = f x : fs * xs _ * _ = [] are both law-abiding instances (although only one has a corresponding law-abiding Monad, I believe). Which should GHC choose? It's worth noting, though, that there are other derivable classes that don't have a single implementation. It's a question of trading off complexity of the compiler versus saved effort in code versus additional clarity in code, I think. ___ 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] Would it be evil to add deriving Typeable to newtype Q?
Hi Leonel,
You might want to try Derive
(http://community.haskell.org/~ndm/derive) if DrIFT doesn't work for
you. They do roughly the same jobs, but Derive has more output formats
(it can be spliced in as Template Haskell, generate #include files,
output text etc) more derivations (but not quite overlapping -
although both have Typeable), and is fully cabal-friendly on all
platforms.
Thanks, Neil
On Thu, May 6, 2010 at 3:42 PM, Leonel Fonseca leone...@gmail.com wrote:
Hey, the hint provided by Ben worked like a charm.
I've also tried Ivan suggestions both on my windows and linux installations.
DrIFT-cabalized couldn't install at all at windows since I don't use MinGW.
So, I ghc'ed --make DrIFT.
Both, windows and linux, refused to complete work with this error:
drift: can't find module Control/Monad
Thank you.
{-# LANGUAGE DeriveDataTypeable, StandaloneDeriving #-}
import Data.Typeable
import Language.Haskell.TH
deriving instance Typeable1 Q
--
Leonel Fonseca.
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[Haskell-cafe] Re: ANNOUNCE: network-protocol-xmpp 0.3
On Fri, May 7, 2010 at 10:09, Sergei Trofimovich sly...@gmail.com wrote: 1. gsasl hackage package did not build for me against libgsasl-0.2.28. It did not define _MAJOR _MINOR macros, So I had to update up to libgsasl-1.4 which worked fine. Is there way to put constraints to pkgconfig-depends to .cabal file? Hm -- I didn't realize anybody was using pre-release GNU SASL libraries. I've updated the gsasl Cabal file to depend on version 1.1 or higher of the C library (which should be sufficient). 2. Just running echo.hs example causes it to be closed on timeout from server side (we use OpenFire and idle timeout there is 6 minutes). So my question is rore about library design abilities: can you inject ping stanzas (on expired timeout) messages into that example too? Added to the example -- it now uses a thread to send ping stanzas every 60 seconds. You'll want to install n-p-xmpp 0.3.1 , which adds locking around the bodies of 'putStanza' and 'getStanza' -- this allows multiple threads to safely write to the session. Also: if there's anything else that you'd like to have added to the library, please feel free to ask! I don't do much fancy stuff with XMPP, so I don't know which XEP's would be the most useful to implement. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANN: test-framework 0.3.0
On 5/7/10 10:49 AM, Max Bolingbroke wrote: * There is a new command line option (--plain), which tells the test runner to avoid using any ANSI features - this can be handy if you are (for example) viewing test output in Emacs Thanks! I'll use that in the next release of shelltestrunner. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Would it be evil to add deriving Typeable to newtype Q?
Neil Mitchell ndmitch...@gmail.com writes: You might want to try Derive (http://community.haskell.org/~ndm/derive) if DrIFT doesn't work for you. They do roughly the same jobs, but Derive has more output formats (it can be spliced in as Template Haskell, generate #include files, output text etc) more derivations (but not quite overlapping - although both have Typeable), and is fully cabal-friendly on all platforms. I take it you haven't had the legal problems that DrIFT had when it used to be called Derive? http://www.dcs.gla.ac.uk/~nww/Derive/History.html -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
Yes, I wonder why mtl is not updated so as to remove this restriction. 2010/5/1 John Millikin jmilli...@gmail.com You might want to make a local version of ErrorT in your library, to avoid the silly 'Error' class restriction. This is pretty easy; just copy it from the 'transformers' or 'mtl' package. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC 6.12 on OS X 10.5
On Mon, Dec 28, 2009 at 9:03 AM, Aaron Tomb at...@galois.com wrote: On Dec 22, 2009, at 9:36 PM, wren ng thornton wrote: Aaron Tomb wrote: I've come across the issue with iconv, as well. The problem seems to be that some versions of iconv define iconv_open and some related functions as macros (that then call libiconv_open, etc.), and some versions of iconv have exported functions for everything. In particular, the iconv bundled with OS X (1.11) defines iconv_open, but the iconv installed with MacPorts (1.13) does not. The binary package for GHC 6.12.1 seems to have been compiled on a system without MacPorts, and therefore references iconv_open (etc.) from the Apple-distributed version of the library. If you set up an installation of GHC 6.12 on OS X (I've only tried 10.5) with no references to /opt/local/lib, everything works fine. If you include /opt/local/lib in the extra-lib-dirs field of your .cabal/config file, it tries to link with the MacPorts version and fails with undefined references. Is this a problem with *versions* of iconv, or with branches/forks? If it's versions, then it seems like migrating to =1.13 would be good for everyone. If it's just branches, do you know whether this afflicts Fink users as well as MacPorts users, or should I be the guinea pig to test that? It's a problem with versions. I checked that the official iconv repository does indeed make the change between 1.11 and 1.13 that causes the problem. The issue is that OS X includes an old version. So migrating to =1.13 means convincing Apple to upgrade what they include with the system. If we can accomplish that, I'd be thrilled. But it hasn't happened yet as of 10.6. Fink comes with 1.12. I'm not sure whether 1.12 is more like 1.11 or 1.13. Resurrecting an old thread. I would like to find out: 1. Has there been any update on how to workaround this? 2. Does building 6.12 from macports (or from source on a macports enabled system) fix the problem? It seems like more than just GHC is affected by this, but I'm having trouble digging up solid information on the web about how to workaround it. Many sources (such as stackoverflow) point to this thread so posting a solution here would be a win. Thanks, Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
Limestraël limestr...@gmail.com writes: 2010/5/1 John Millikin jmilli...@gmail.com You might want to make a local version of ErrorT in your library, to avoid the silly 'Error' class restriction. This is pretty easy; just copy it from the 'transformers' or 'mtl' package. Yes, I wonder why mtl is not updated so as to remove this restriction. Presumably because its in maintenance mode (i.e. it only gets changed/updated to reflect changes in GHC that might affect it and the API is frozen). -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Shorthand method of enumerating a list a gotcha ... or is it just me?
The problem I see is that in both:
Version: September 2006 of hugs, which is the one that is current for
Ubuntu 9.10 release, and
ghci 6.10.4, they both exhibit a {I think} strange behaviour, in regards
to the shorthand way of calling out a list of enumerable values. I will
explain the problem that I have run into with examples:
Hugs [3,7..22]
[3,7,11,15,19] - OK
Hugs map (* 1.0) [3,7,11,15,19] - manual spec OK
[3.0,7.0,11.0,15.0,19.0]
Hugs map (* 1.0) [3,7..22] - same spec as first but !!! when
mapped to with a (*1.0) to
coerce
them to reals:
[3.0,7.0,11.0,15.0,19.0,23.0] - went one outside of range spec.
Exactly the same behaviour from ghci 6.10.4 :
Prelude [3,7..22]
[3,7,11,15,19]
Prelude map (* 1.0) [3,7..22] - using a range
[3.0,7.0,11.0,15.0,19.0,23.0] - it screws up
{at least it is not a
feature' to me}
Prelude map (* 1.0) [3,7,11,15,19] - spelled out it acts right.
[3.0,7.0,11.0,15.0,19.0]
This seems like a possible bug? or at least a sure fire trap waiting to
be sprung ... one of those nasties that could really create havoc if
someone is not aware of this behaviour and buries a function that include
something that unwittingly coerces from an Integral to a Realfrac or
Fractional. Is this a well known thing to watch out for..
or is it something that can be worked around, other then having to
enumerate every value in a list rather then use the handiness of
the range notation as shorthand?
cheers,
gene
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Re: [Haskell-cafe] Shorthand method of enumerating a list a gotcha ... or is it just me?
Gene A yumag...@gmail.com writes:
The problem I see is that in both:
Version: September 2006 of hugs, which is the one that is current for
Ubuntu 9.10 release, and
ghci 6.10.4, they both exhibit a {I think} strange behaviour, in regards
to the shorthand way of calling out a list of enumerable values. I will
explain the problem that I have run into with examples:
Hugs [3,7..22]
[3,7,11,15,19] - OK
Hugs map (* 1.0) [3,7,11,15,19] - manual spec OK
[3.0,7.0,11.0,15.0,19.0]
Hugs map (* 1.0) [3,7..22] - same spec as first but !!! when
mapped to with a (*1.0) to
coerce
them to reals:
[3.0,7.0,11.0,15.0,19.0,23.0] - went one outside of range spec.
[snip]
This seems like a possible bug? or at least a sure fire trap waiting to
be sprung ... one of those nasties that could really create havoc if
someone is not aware of this behaviour and buries a function that include
something that unwittingly coerces from an Integral to a Realfrac or
Fractional. Is this a well known thing to watch out for..
or is it something that can be worked around, other then having to
enumerate every value in a list rather then use the handiness of
the range notation as shorthand?
This is because the Enum instance for floating point numbers is screwy
and shouldn't be used in general (floating point rounding, etc.; don't
forget, they're defined in binary and not all fractional values can be
defined exactly in a finite binary value). A better way:
map fromIntegral [3,7..22]
--
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Shorthand method of enumerating a list a gotcha ... or is it just me?
From the Haskell 98 report (section 6.3.4): For Float and Double, the semantics of the enumFrom family is given by the rules for Int above, except that the list terminates when the elements become greater than e3+i/2 for positive increment i, or when they become less than e3+i/2 for negative i. So yes, it is surprising, but according to the specification. But then again the very concept of a type like Float having an Enum instance is a bit weird. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Would it be evil to add deriving Typeable to newtype Q?
begin Ivan Lazar Miljenovic quotation: Neil Mitchell ndmitch...@gmail.com writes: You might want to try Derive (http://community.haskell.org/~ndm/derive) if DrIFT doesn't work for you. They do roughly the same jobs, but Derive has more output formats (it can be spliced in as Template Haskell, generate #include files, output text etc) more derivations (but not quite overlapping - although both have Typeable), and is fully cabal-friendly on all platforms. I take it you haven't had the legal problems that DrIFT had when it used to be called Derive? http://www.dcs.gla.ac.uk/~nww/Derive/History.html Looks like derive.com is redirecting to a Texas Instruments site under ti.com, so they likely don't care about this particular trademark anymore since it is no longer maintained as an independent brand. Looks like they stopped selling it in June 2007, at least in the UK: http://education.ti.com/educationportal/sites/UK/productDetail/uk_derive6.html The other link I found redirected to a page that didn't mention Derive™ at all. -md ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
On May 4, 2010, at 01:52 , Maciej Piechotka wrote: After change of file you have to wait a long time as it compiles and links with yi. On my system (1 GB of RAM taken by system + 1 GB 'free' + 2 GB swaps, x86-64) it could in some situations it caused OOM. I'd prefer if the code was interpreted by ghci instead of compiled by GHC in this case (it should be as fast as most of the code was compiled anyway). On the one hand, this is doable with the GHC API. On the other, that more or less means your program contains what amounts to a full copy of GHC. -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
On Sat, May 08, 2010 at 07:49:57AM +1000, Ivan Lazar Miljenovic wrote: Limestraël limestr...@gmail.com writes: 2010/5/1 John Millikin jmilli...@gmail.com You might want to make a local version of ErrorT in your library, to avoid the silly 'Error' class restriction. This is pretty easy; just copy it from the 'transformers' or 'mtl' package. Yes, I wonder why mtl is not updated so as to remove this restriction. Presumably because its in maintenance mode (i.e. it only gets changed/updated to reflect changes in GHC that might affect it and the API is frozen). The API isn't frozen -- it can be changed with a library proposal, if you can get people to agree to it. As Ryan said, the Error constraint is there to support a definition of the fail method in the Monad instance for ErrorT. (Personally I think fail is a terrible wart, and should be shunned.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
On May 5, 2010, at 21:49 , Pierre-Etienne Meunier wrote: - all these =, significative indentation, You're from the past dude. Careful, or Guido (van Rossum) is going to show up on your doorstep -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
On May 6, 2010, at 11:08 , Donn Cave wrote: different ambitions. Who would pick Tcl for a programming language? but it has been popular for scripting (still? don't know.) It would I think Lua has superseded it, because it has the compactness advantage and easy embeddability of of the Tcl core but is enormously easier to write code in. -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
There is the package hint, which embeds the calls to GHC API. Quite easy to use: Let's say your configuration file (cfg/Script.hs) contains a function script that you want to get: type ScriptFun = IO () loadScript :: IO ScriptFun loadScript = do liftM (either (error . show) id) $ runInterpreter $ do path - get searchPath set [searchPath := (./cfg:path)] loadModules [Script] setTopLevelModules [Script] exports - getModuleExports Script if Fun script `elem` exports then *interpret script (as :: ScriptFun)* else error script function not found There is just the line I put in bold that bothers me. Can't we get the action script more easily than by re-interpreting some code? 2010/5/8 Brandon S. Allbery KF8NH allb...@ece.cmu.edu On May 4, 2010, at 01:52 , Maciej Piechotka wrote: After change of file you have to wait a long time as it compiles and links with yi. On my system (1 GB of RAM taken by system + 1 GB 'free' + 2 GB swaps, x86-64) it could in some situations it caused OOM. I'd prefer if the code was interpreted by ghci instead of compiled by GHC in this case (it should be as fast as most of the code was compiled anyway). On the one hand, this is doable with the GHC API. On the other, that more or less means your program contains what amounts to a full copy of GHC. -- 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
Personally I think fail is a terrible wart, and should be shunned. So do I. I can't understand its purpose since monads which can fail can be implemented through MonadPlus. 2010/5/8 Ross Paterson r...@soi.city.ac.uk On Sat, May 08, 2010 at 07:49:57AM +1000, Ivan Lazar Miljenovic wrote: Limestraėl limestr...@gmail.com writes: 2010/5/1 John Millikin jmilli...@gmail.com You might want to make a local version of ErrorT in your library, to avoid the silly 'Error' class restriction. This is pretty easy; just copy it from the 'transformers' or 'mtl' package. Yes, I wonder why mtl is not updated so as to remove this restriction. Presumably because its in maintenance mode (i.e. it only gets changed/updated to reflect changes in GHC that might affect it and the API is frozen). The API isn't frozen -- it can be changed with a library proposal, if you can get people to agree to it. As Ryan said, the Error constraint is there to support a definition of the fail method in the Monad instance for ErrorT. (Personally I think fail is a terrible wart, and should be shunned.) ___ 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] IO (Either a Error) question
On May 7, 2010, at 4:54 PM, Limestraël wrote: Personally I think fail is a terrible wart, and should be shunned. So do I. I can't understand its purpose since monads which can fail can be implemented through MonadPlus. As far as I can tell, its purpose is to essentially allow you to catch pattern match errors in pure code and turn them into a value, since Haskell calls fail whenever there is a failed pattern match. (I am not saying that this is a good idea, only that this is not something that you would simply get by using MonadPlus.) Cheers, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
On May 7, 2010, at 19:51 , Limestraël wrote: then interpret script (as :: ScriptFun) There is just the line I put in bold that bothers me. Can't we get the action script more easily than by re-interpreting some code? Make up your mind: you don't want to have to compile the script, but you don't want to have to interpret the script. What exactly is supposed to be left? -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
On Sat, May 08, 2010 at 01:54:21AM +0200, Limestraël wrote:
Personally I think fail is a terrible wart, and should be shunned.
So do I.
I can't understand its purpose since monads which can fail can be implemented
through MonadPlus.
It was introduced to implement pattern match failure in do-notation,
in Section 3.14 of the Haskell Report:
do {p - e; stmts} = let ok p = do {stmts}
ok _ = fail ...
in e = ok
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Re: [Haskell-cafe] IO (Either a Error) question
On May 7, 2010, at 19:54 , Limestraël wrote:
Personally I think fail is a terrible wart, and should be shunned.
So do I.
I can't understand its purpose since monads which can fail can be
implemented through MonadPlus.
The translation of do syntax involves pattern matching (do
{ [x,y,z] - something; ... }), and needs to know what to do when the
pattern bind fails, so what it does is invoke fail. This is
arguably wrong but we're stuck with it now. (I have to admit I don't
see why we can't do exactly what the obvious (= \[x,y,z] - ...)
translation does, which is throw an exception. case, let, and
lambda binding don't invoke a special fail mechanism; why is do
special?)
--
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
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Re: [Haskell-cafe] IO (Either a Error) question
On Friday 07 May 2010 7:54:21 pm Limestraël wrote: Personally I think fail is a terrible wart, and should be shunned. So do I. I can't understand its purpose since monads which can fail can be implemented through MonadPlus. Understanding why fail exists requires going back to before Haskell 98. Back then, there was a MonadZero, and when you did pattern matching in do syntax, a MonadZero constraint would be generated in most cases, like: do Just x - m ... *But*, there were cases where MonadZero wasn't required. This happened when you did a match like: do (x, y) - m ... In this case, there's no need to fail 'in the monad', because either the value in question *is* of the form (x, y), or it is bottom, in which case the whole expression should be bottom anyhow (because we're not supposed to be able to detect bottoms like that). Patterns like the above had a special distinction, called unfailable. This is not the same as irrefutable, although the latter would be a special case of the former; unfailable patterns are those that can at most be refuted by a partially defined value, rather than refuted by a sum. So, for reasons that I don't recall off the top of my head (perhaps pedagogy), it was decided that Haskell 98 should no longer have this additional notion of unfailable pattern. However, when you get rid of them, there's a fair amount of valid code with a context of Monad m that now needs MonadZero (or, Plus, since Zero is gone), and that's rather inconvenient. So, fail was introduced into Monad so that pattern matching can be desugared in any Monad, and you're once again allowed to write: foo :: Monad m = m (a,b) - ... foo m = do (x, y) - m ... Which is always okay, even though other matches/etc. you can do with fail really isn't. Personally, I don't really understand why unfailable patterns were canned (they don't seem that complicated to me), so I'd vote to bring them back, and get rid of fail. But hind sight is 20/20, I suppose (or perhaps there exist cogent arguments that I haven't heard). -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
Shit ! I'll have to explain him how to add monads in python 3 ;-) El 07/05/2010, a las 19:31, Brandon S. Allbery KF8NH escribió: On May 5, 2010, at 21:49 , Pierre-Etienne Meunier wrote: - all these =, significative indentation, You're from the past dude. Careful, or Guido (van Rossum) is going to show up on your doorstep -- 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] Re: Haskell and scripting
By the way, I do not know the GHC API well enough to say if it is possible to embed a super small bytecode interpreter, but : - If it is the case, then users who do not want to write scripts can use it. Others would want to compile haskell code, therefore they need GHC anyway. - If it is not, then a cool thing to do for the GHC team would be to add one ;-) In both cases, if someone on haskell-cafe knows the answer, could he write it on the wiki in the page about the ghc api ? Cheers, PE El 07/05/2010, a las 19:22, Brandon S. Allbery KF8NH escribió: On May 4, 2010, at 01:52 , Maciej Piechotka wrote: After change of file you have to wait a long time as it compiles and links with yi. On my system (1 GB of RAM taken by system + 1 GB 'free' + 2 GB swaps, x86-64) it could in some situations it caused OOM. I'd prefer if the code was interpreted by ghci instead of compiled by GHC in this case (it should be as fast as most of the code was compiled anyway). On the one hand, this is doable with the GHC API. On the other, that more or less means your program contains what amounts to a full copy of GHC. -- 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
There is a also a problem with polymorphic actions of functions. The GHC API is typesafe only when returning elements of the Typeable class. Else you can do an unsafeCoerce, but I assume that hint uses Typeable, with a wrapper class to ensure monomorphism. But if your script action returns a monomorphic type, you can use the GHC API directly instead and unsafeCoerce. El 07/05/2010, a las 20:12, Brandon S. Allbery KF8NH escribió: On May 7, 2010, at 19:51 , Limestraël wrote: then interpret script (as :: ScriptFun) There is just the line I put in bold that bothers me. Can't we get the action script more easily than by re-interpreting some code? Make up your mind: you don't want to have to compile the script, but you don't want to have to interpret the script. What exactly is supposed to be left? -- 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell interface to Frama-C
I just started using Frama-C [1] for analyzing some of our embedded C programs. Pretty awesome suite of tools. Especially its ability to describe and verify function contracts with ACSL [2]. The tool suite is primarily build with OCaml. Has anyone considered building a Haskell interface to Frama-C? I lack the expertise and time for such a project. But it sure would be nice to be able to write verification plug-ins with Haskell. -Tom [1] http://frama-c.com/ [2] http://en.wikipedia.org/wiki/ANSI/ISO_C_Specification_Language ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell and the Software design process
On May 3, 2010, at 12:14 , Henning Thielemann wrote: Ketil Malde schrieb: Henning Thielemann lemm...@henning-thielemann.de writes: http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Control-Exception.html#v%3Athrow I see. This should be forbidden, at all! :-) Why is this worse than or different from 'error'? To me it looks like 'error', only with a non-string parameter. Because it encourages the use in a non-error way, that is, catching such an exception is regarded as good use. One could argue that it's a more comprehensible to mortals version of Control.Monad.Cont. -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell and scripting
Daniel Fischer daniel.is.fisc...@web.de writes: On Wednesday 05 May 2010 23:36:26, Limestraël wrote: but you will not object if I say that scheme is quicker to learn than Haskell. Well, I do object. Learning Haskell went like a breeze (not to perfection, but well enough). Only Python was nearly as easy and quick to learn. Learning Lisp dialects is much harder (to a large part because of the parentheses, which makes them near impossible to parse). Perhaps you need perfect lisp editor (emacs) to help you parse those parentheses. :) Looks below extension to highlight parentheses if you're emacser. It help you parse parentheses when you through *parentheses forest*. http://www.emacswiki.org/emacs/HighlightParentheses -- Andy ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell and the Software design process
On May 4, 2010, at 12:31 , Gregory Crosswhite wrote: On May 4, 2010, at 5:22 AM, John Lato wrote: Crashing at the point of the error isn't necessarily useful in Haskell due to lazy evaluation. The code will crash when the result of the partial function is evaluated, which may be quite far away (in terms of function calls) from where the programmer would expect. But hypothetically, suppose that you decided to use safeSecondElement anyway; now you have to deal with a Nothing in your code. Since, again, you don't know how to recover from this (as if you did, you wouldn't have gotten a Nothing in the first place), the only thing you can do is propagate it through the calculation, until it reaches someone who can recover from it, which means that now your whole calculation has to be muddled up with Maybe types wrapping every result purely to capture the Using Maybe as a monad helps a lot here. possibility of a bug (or hardware fault, I suppose). If your program relied on this calculation, then it *still* has no choice but to terminate, and it *still* doesn't know where the error occurred It occurs to me that combining Error and Writer gives you traceback. -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: test-framework 0.3.0
Max Bolingbroke batterseapo...@hotmail.com writes: I'm pleased to announce the release of version 0.3 of test-framework (http://hackage.haskell.org/package/test-framework-0.3.0). ... * There is a new command line option (--plain), which tells the test runner to avoid using any ANSI features - this can be handy if you are (for example) viewing test output in Emacs I don't see this one, although the junit option is there: ./dist/build/testsuite/testsuite --plain unrecognized option `--plain' Usage: testsuite [OPTIONS] --help show this help message -j NUMBER--threads=NUMBER number of threads to use to run tests --test-seed=NUMBER|randomdefault seed for test random number generator -a NUMBER--maximum-generated-tests=NUMBER how many automated tests something like QuickCheck should try, by default --maximum-unsuitable-generated-tests=NUMBER how many unsuitable candidate tests something like QuickCheck should endure before giving up, by default -o NUMBER--timeout=NUMBER how many seconds a test should be run for before giving up, by default --no-timeout specifies that tests should be run without a timeout, by default -t TEST-PATTERN --select-tests=TEST-PATTERN only tests that match at least one glob pattern given by an instance of this argument will be run --jxml[=FILE]Set the output format to junit-xml, and (optionally) writes to FILE instead of STDOUT G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] darcs to mercurial migration
Hi Günther, tehre is a fast darcs to git tool. Maybe you can convert to mercurial easily then. Ping me on irc (MarcWeber) or write back if you're interested. I'll digg the link up then. Marc Weber ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
You might have misunderstood me. When using hint, one wants the script to be interpreted. It is interpreted when called loadModules [Script] , but if we call later interpret *something* (as :: Something) , the *something *can be any Haskell code, not just a function name, which means hint has also to interpret the *something*. So, IMO, a double interpretation is done when a function such as getSymbol *functionName *(as :: FuncType), which would simply get the function, would be sufficient. I don't know if hint/GHC API allows to do such a thing... 2010/5/8 Brandon S. Allbery KF8NH allb...@ece.cmu.edu On May 7, 2010, at 19:51 , Limestraël wrote: then *interpret script (as :: ScriptFun)* There is just the line I put in bold that bothers me. Can't we get the action script more easily than by re-interpreting some code? Make up your mind: you don't want to have to compile the script, but you don't want to have to interpret the script. What exactly is supposed to be left? -- 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] IO (Either a Error) question
On Fri, May 07, 2010 at 08:27:04PM -0400, Dan Doel wrote: Personally, I don't really understand why unfailable patterns were canned (they don't seem that complicated to me), so I'd vote to bring them back, and get rid of fail. But hind sight is 20/20, I suppose (or perhaps there exist cogent arguments that I haven't heard). What counts as unfailable? (x,y) probably, but what about data Foo = Foo x y If we don't allow it, we add 'magic' to tuples, which is a bad thing, if we do allow it, there are some odd consequences. adding another constructor to Foo will suddenly change the type of do notations involving it non locally. said constructor may not even be exported from the module defining Foo, its existence being an implementation detail. All in all, it is very hacky one way or another. Much more so than having 'fail' in Monad. John -- John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
On Fri, May 7, 2010 at 10:26 PM, John Meacham j...@repetae.net wrote: On Fri, May 07, 2010 at 08:27:04PM -0400, Dan Doel wrote: Personally, I don't really understand why unfailable patterns were canned (they don't seem that complicated to me), so I'd vote to bring them back, and get rid of fail. But hind sight is 20/20, I suppose (or perhaps there exist cogent arguments that I haven't heard). What counts as unfailable? (x,y) probably, but what about data Foo = Foo x y If we don't allow it, we add 'magic' to tuples, which is a bad thing, if we do allow it, there are some odd consequences. adding another constructor to Foo will suddenly change the type of do notations involving it non locally. said constructor may not even be exported from the module defining Foo, its existence being an implementation detail. All in all, it is very hacky one way or another. Much more so than having 'fail' in Monad. I wonder how often people rely on the use of fail in pattern matching. Could we get by without fail or unfailable patterns? ensureCons :: MonadPlus m = [a] - m [a] ensureCons x@(_:_) = return x ensureCons _ = mzero do ... x:xs - ensureCons $ some_compuation This is more flexible than the current situation (you can easily adapt it to throw custom exceptions in ErrorT), but gets cumbersome when you're doing nested patterns. Also, it does the match twice, but presumably the optimizer can be improved to catch that if the idiom became popular. -- 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] installing haskell platform on 64-bit ubuntu 10.04 (Lucid)
Has anyone had problems getting Haskell Platform installed on Ubuntu 10.04? I've got GHC 6.12.1 installed via apt-get, and I've downloaded/untarred haskell-platform-2010.1.0.0.tar.gz. But when I run ./configure, it fails fairly quickly, with an error 'cause it can't build the hello world test program, complaining: command line: unknown package: haskell98 Anyone else seen this? Am I missing something obvious? --Andy ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
On May 7, 2010, at 22:18 , Limestraël wrote: When using hint, one wants the script to be interpreted. It is interpreted when called loadModules [Script] , but if we call later interpret something (as :: Something) , the something can be any Haskell code, not just a function name, which means hint has also to interpret the something. Not entirely clear to me, actually: the earlier one might generate bytecode and the later one run it. (I haven't looked at hint, but have some idea of what GHC-API can do.) So, IMO, a double interpretation is done when a function such as getSymbol functionName (as :: FuncType), which would simply get the function, would be sufficient. I don't know if hint/GHC API allows to do such a thing... GHC API should let you look up names directly; as above, I don't know if hint does. hs-plugins used to do this also but it is obsolete (was far too dependent on GHC internal data and had to be rewritten for every GHC release; the GHC API is more stable). -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
Limestraël limestr...@gmail.com writes: Personally I think fail is a terrible wart, and should be shunned. So do I. I can't understand its purpose since monads which can fail can be implemented through MonadPlus. Polyparse uses it, and I believe Parsec does as well... -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
David Menendez d...@zednenem.com writes: I wonder how often people rely on the use of fail in pattern matching. Could we get by without fail or unfailable patterns? ensureCons :: MonadPlus m = [a] - m [a] ensureCons x@(_:_) = return x ensureCons _ = mzero do ... x:xs - ensureCons $ some_compuation This is more flexible than the current situation (you can easily adapt it to throw custom exceptions in ErrorT), but gets cumbersome when you're doing nested patterns. Also, it does the match twice, but presumably the optimizer can be improved to catch that if the idiom became popular. Well, any time you have a do-block like this you're using failable patterns: maybeAdd :: Maybe Int - Maybe Int - Maybe Int maybeAdd mx my = do x - mx y - my return $ x + y -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
On Sat, May 8, 2010 at 12:15 AM, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com wrote:
David Menendez d...@zednenem.com writes:
I wonder how often people rely on the use of fail in pattern matching.
Could we get by without fail or unfailable patterns?
ensureCons :: MonadPlus m = [a] - m [a]
ensureCons x@(_:_) = return x
ensureCons _ = mzero
do ...
x:xs - ensureCons $ some_compuation
This is more flexible than the current situation (you can easily adapt
it to throw custom exceptions in ErrorT), but gets cumbersome when
you're doing nested patterns. Also, it does the match twice, but
presumably the optimizer can be improved to catch that if the idiom
became popular.
Well, any time you have a do-block like this you're using failable
patterns:
maybeAdd :: Maybe Int - Maybe Int - Maybe Int
maybeAdd mx my = do x - mx
y - my
return $ x + y
This is true in the sense that the translation for the do syntax in
the Haskell report uses fail.
do { p - e; stmts } =
let ok p = do { stmts }
ok _ = fail ...
in e = ok
However, it's also true that the fails introduced by the translation
of maybeAdd will never be invoked, since the two patterns are
irrefutable. That is, maybeAdd would work exactly the same if the do
syntax translation were changed to read:
do { p - e; stmts } = e = \p - do { stmts }
This would not be the case if refutable patterns were used.
viewM l = do { x:xs - return l; return (x,xs) }
--
Dave Menendez d...@zednenem.com
http://www.eyrie.org/~zednenem/
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Re: [Haskell-cafe] IO (Either a Error) question
David Menendez d...@zednenem.com writes:
On Sat, May 8, 2010 at 12:15 AM, Ivan Lazar Miljenovic
Well, any time you have a do-block like this you're using failable
patterns:
maybeAdd :: Maybe Int - Maybe Int - Maybe Int
maybeAdd mx my = do x - mx
y - my
return $ x + y
This is true in the sense that the translation for the do syntax in
the Haskell report uses fail.
do { p - e; stmts } =
let ok p = do { stmts }
ok _ = fail ...
in e = ok
However, it's also true that the fails introduced by the translation
of maybeAdd will never be invoked, since the two patterns are
irrefutable.
Huh? What about maybeAdd (Just 2) Nothing ?
That is, maybeAdd would work exactly the same if the do syntax
translation were changed to read:
do { p - e; stmts } = e = \p - do { stmts }
Wait, are you using irrefutable as it will still work if we make do
blocks work the way I want?
--
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] IO (Either a Error) question
On May 8, 2010, at 01:16 , Ivan Lazar Miljenovic wrote: David Menendez d...@zednenem.com writes: On Sat, May 8, 2010 at 12:15 AM, Ivan Lazar Miljenovic Well, any time you have a do-block like this you're using failable patterns: maybeAdd :: Maybe Int - Maybe Int - Maybe Int maybeAdd mx my = do x - mx y - my return $ x + y This is true in the sense that the translation for the do syntax in the Haskell report uses fail. Huh? What about maybeAdd (Just 2) Nothing ? Isn't that handled by the definition of (=) in Maybe, as opposed to by invoking fail? instance Monad Maybe where -- ... Nothing = _ = Nothing (Just x) = f = f x -- 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 PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: IO (Either a Error) question
On Fri, 2010-05-07 at 19:26 -0700, John Meacham wrote: On Fri, May 07, 2010 at 08:27:04PM -0400, Dan Doel wrote: Personally, I don't really understand why unfailable patterns were canned (they don't seem that complicated to me), so I'd vote to bring them back, and get rid of fail. But hind sight is 20/20, I suppose (or perhaps there exist cogent arguments that I haven't heard). What counts as unfailable? (x,y) probably, but what about data Foo = Foo x y If we don't allow it, we add 'magic' to tuples, which is a bad thing, if we do allow it, there are some odd consequences. adding another constructor to Foo will suddenly change the type of do notations involving it non locally. said constructor may not even be exported from the module defining Foo, its existence being an implementation detail. All in all, it is very hacky one way or another. Much more so than having 'fail' in Monad. John Sorry I'm asking but why: do Constructor x y z - f g x y z is not compiled into: f = \(Constructor x y z) - g x y z Hence using exactly the same way or reporting errors as pure functions? I.e. why fail !== error[1] Regards [1] Well - what came to my mind is something like: func :: Either a b - Maybe b func f = do Right x - f return x But: 1. It's IMHO vary bad style as it silently fails in cases mentioned above. 2. It is not obvious knowing rest of Haskell. I expected until now a pattern failure error. signature.asc Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO (Either a Error) question
Brandon S. Allbery KF8NH allb...@ece.cmu.edu writes: On May 8, 2010, at 01:16 , Ivan Lazar Miljenovic wrote: Huh? What about maybeAdd (Just 2) Nothing ? Isn't that handled by the definition of (=) in Maybe, as opposed to by invoking fail? instance Monad Maybe where -- ... Nothing = _ = Nothing (Just x) = f = f x Yes, but isn't the y - Nothing pattern failure handled by invoking fail? -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
On the one hand, this is doable with the GHC API. On the other, that more or less means your program contains what amounts to a full copy of GHC. And the result is that your binary will grow by 35mb, add a few seconds to launch time, the first expression will take 3 or 4 seconds to evaluate, and add around 10 seconds to the link time. After that it's pretty reasonable though. I've actually thought of embedding a version of hugs, that should be smaller and faster, but as soon as you want to use significant amounts of libraries it gets to be a hassle to keep the source around and it may not even be hugs compatible anyway. GHC's big advantage is it can load the same binary libraries the rest of the program uses. I don't know if hugs was really designed to be embedded anyway. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
