- Haskell-Cafe - Haskell.org

Hackage down?
by Ozgur Akgun 06 Dec '10

06 Dec '10

http://downforeveryoneorjustme.com/http://hackage.haskell.org -- Ozgur Akgun

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Berlin Haskell Meeting
by Sönke Hahn 06 Dec '10

06 Dec '10

The Berlin Haskell meeting is due again: Date: Tuesday, December 7th Time: from 20:00 Location: c-base, Rungestrasse 20, 10179 Berlin See you there. Sönke

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Small strings
by Antoine Latter 06 Dec '10

06 Dec '10

Hi Haskell, I've recently created the 'smallstring' package[1] and put it on Hackage. The goal was to create a string-like type with as little memory overhead as possible, and to have equality and comparison operations be competitive with the native String type. The idea is that this type would make ideal keys into data structures like Data.Map. I've taken pains to make the library portable to other compilers, but this isn't really tested, and most of my recent development has been on GHC 7. The library is young and likely has places it could be improved, so your feedback is welcome. The API provided is small - to/fromString along with Eq and Ord instances. This isn't meant to be a replacement for the text[2] or bytestring[3] packages - the reduced size comes at a cost. Both of these libraries offer substring manipulation functions which allow the sharing of the backing memory buffers. Also, I haven't implemented any sort of string-like operations on the type as it isn't the right thing for that. I've borrowed heavily from the previously mentioned text package for the underlying array implementation, so thanks goes to Bryan O'Sullivan for maintaining the package and to all of the other authors as well. Take care, Antoine [1] http://hackage.haskell.org/package/smallstring [2] http://hackage.haskell.org/package/text [3] http://hackage.haskell.org/package/bytestring

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OverloadedStrings mixed with type classes leads to boilerplate type signatures
by Johan Tibell 06 Dec '10

06 Dec '10

Hi, I'm trying to generalize my string substitution library (http://hackage.haskell.org/package/template) to allow users to provide different kinds of key/value mappings (e.g. functions and association lists) for filling in the placeholders in a template. Here are two examples I'd like to work: ghci> :set -XOverloadedStrings ghci> "$name ate a banana." % [("name", "Johan")] "Johan ate a banana." ghci> "$name ate a banana." % (\v -> if v == "name" then "Johan" else error "KeyError") "Johan ate a banana." At the moment the context (i.e. the second argument to "%") is always a function type Context = T.Text -> T.Text I would like to generalize that to class Context a where lookup :: a -> T.Text -> T.Text Different key/value mappings fulfill different use cases: * Association lists have a small syntactic overhead, great for one-off string substitution. * Functions are flexible, allowing for arbitrary complex lookup logic, but are syntactically heavy (in this case.) Here's the gist of my implementation: {-# LANGUAGE FlexibleInstances #-} module Template where import Data.Maybe (fromMaybe) import qualified Data.Text as T import qualified Data.Text.Lazy as LT import Prelude as P class Context a where lookup :: a -> T.Text -> T.Text instance Context (T.Text -> T.Text) where lookup f = f instance Context [(T.Text, T.Text)] where lookup xs k = fromMaybe (error $ "KeyError: " ++ show k) (P.lookup k xs) -- | Perform string substitution. Example: -- -- > "$foo" % [("foo" :: T.Text, "bar" :: T.Text)] (%) :: Context c => T.Text -> c -> LT.Text (%) = undefined The problem is that the compiler is not able to deduce that string literals should have type 'Text' when used in 'Context's. For example ghci> :t "$foo" % [("foo", "bar")] <interactive>:1:8: No instance for (Context [(a, a1)]) arising from a use of `%' Possible fix: add an instance declaration for (Context [(a, a1)]) In the expression: "$foo" % [("foo", "bar")] This forces the user to provide explicit type signatures, which makes the construct more heavy weight and defeats the whole purpose of introducing the 'Context' class: ghci> :t "$foo" % [("foo" :: T.Text, "bar" :: T.Text)] "$foo" % [("foo" :: T.Text, "bar" :: T.Text)] :: LT.Text Is there any way to make the syntactically short `"$foo" % [("foo", "bar")]` work but still keep the 'Context' class? Johan

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Strange error when using Attoparsec and Enumerator
by Crutcher Dunnavant 06 Dec '10

06 Dec '10

I have spent a good chunk of the past week tracing code, trying to solve this problem. I'm seeing an error when using Enumerator and Attoparsec that I can't explain. This is a reduced form of the problem. In general, I've observed that debugging broken iterators and enumerators is very hard. We probably want some tooling around that; I'm looking at an identity enumeratee with debug.trace shoved in, or something like that, not sure yet what would help. {- Haskell 2010, ghc 6.12.3 array-0.3.0.2 attoparsec-0.8.2.0 attoparsec-enumerator-0.2.0.2 bytestring-0.9.1.7 containers-0.4.0.0 deepseq-1.1.0.2 enumerator-0.4.2 text-0.10.0.0 transformers-0.2.2.0 -} import Control.Applicative ((<|>)) import qualified Data.Attoparsec.Char8 as AP import qualified Data.Attoparsec.Combinator as APC import qualified Data.Attoparsec.Enumerator as APE import qualified Data.ByteString.Char8 as B import qualified Data.Enumerator as E import Data.Enumerator (($$)) import System.IO as IO parseLine :: AP.Parser B.ByteString parseLine = do AP.char '+' return . B.pack =<< APC.manyTill AP.anyChar endOfLineOrInput endOfLineOrInput :: AP.Parser () endOfLineOrInput = AP.endOfInput <|> AP.endOfLine pp :: Show a => AP.Parser a -> String -> IO () pp p s = do result <- E.run $ E.enumList 1 [ B.pack s ] $$ E.sequence (APE.iterParser p) $$ E.printChunks False case result of (Right _) -> return () (Left e) -> IO.hPutStrLn stderr $ show e main = pp parseLine "+OK" {- Observed output: ["OK"] *** Exception: enumEOF: divergent iteratee Problems with this: 1) I didn't write an iteratee, enumerator, or enumeratee in this code. Something's wrong. 2) If the parser is divergent, I _should_ be getting the error message: "iterParser: divergent parser" -} -- Crutcher Dunnavant <crutcher(a)gmail.com>

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New Xmobar maintainer: request for comments
by Jose A. Ortega Ruiz 06 Dec '10

06 Dec '10

Hi, I've recently accepted Andrea Rossato's kind offer to take over maintainership of xmobar, and i wanted to ask for feedback to the community. My apologies for cross-posting to the cafe and xmonad, but xmobar didn't have a mailing list until a couple days ago. My immediate plans are to fix some low-hanging bugs, incorporate a handful of patches and contributions i have in my repo and make a new release (0.12). Besides that, i've created a mailing list (xmobar(a)projects.haskell.org, http://projects.haskell.org/cgi-bin/mailman/listinfo/xmobar, also mirrored at gmane.comp.lang.haskell.xmobar) and i will move xmobar's homepage to http://projects.haskell.org/xmobar (not done yet). Perhaps more disruptingly, i'm thinking of moving source code management from darcs to git (right now, i maintain a _mirror_ at github, http://github.com/jaor/xmobar) But xmobar has a very lively user base and many contributors, and i wouldn't like to alienate or disturb anyone: would that move be frown upon by the community? I also plan to keep hacking and adding (not many) features to xmobar in the future, and would be delighted to hear from you: please, do not hesitate to send your feature requests or any other comment directly to me or to the new list. Thanks in advance for your feedback, and special thanks to Andrea for creating xmobar and giving me this great chance of being more than a mere spectator of the haskell world. Cheers, jao -- Fools ignore complexity. Pragmatists suffer it. Some can avoid it. Geniuses remove it. - Alan Perlis, Epigrams in Programing

1 0

getErrorStatus in HXT
by Tobias Schoofs 05 Dec '10

05 Dec '10

Hi, I have some problems with the error processing in HXT. Here is a trivial example: e <- runX (transformDoc [] someRules src dst) transformDoc cfg rules src dst = configSysVars cfg >>> readDocument [] src >>> rules >>> -- some transformations writeDocument [] dst >>> getErrStatus I would expect "e" to contain an error value >= c_err for the case where any of the processing steps in transformDoc fails. But it does not, even with an io error on writeDocument. I guess I misunderstand "getErrStatus" in some way. Any idea? Thanks, Tobias

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Hackage have ghc 7.0 false positives builds
by Maciej Piechotka 05 Dec '10

05 Dec '10

Hackage seems to hae false positive builds. For example llvm is reported to have been built with ghc despite problems with cabal (type errors and after quick'n'dirty fix it has errors). Regards

1 0

Safer common subexpression elimination
by Joachim Breitner 05 Dec '10

05 Dec '10

Hi, although semantically it could, ghc does not do common subexpression elimination (CSE), at least not in every case. The canonical example where it would be bad is the function (with div to avoid numerical casting): > avg :: [Int] -> Int > avg n = (sum [0..n] `div` length [0..n]) The reason why [0..n] is not shared is because then it would be kept in memory completely after the evaluation of sum, because length will still need it, possibly overflowing the memory. In the non-shared form, though, the garbage collector can clean up directly behind sum and length, and the program runs in constant space. Note that the shared expression would be very large compared to the thunks. Now consider the program: > avg' :: [Int] -> (Int, Int) > avg' n = (sum [0..n] `div` length [0..n], length [0..n]) I’d say that CSE to > avg n = (sum [0..n] `div` l, l) > where l = length [0..n] is safe, because the shared expression (an Int) is smaller than the thunks and the compiler can tell. So I wonder: * Is sharing values of type Int (and Bool and similar small values) always safe? * If so: does GHC already do that? * Would it be technically possible? * Is there an established theory that can tell, for a sharing candidate, whether it is safe to share it? Thanks, Joachim -- Joachim "nomeata" Breitner mail: mail(a)joachim-breitner.de | ICQ# 74513189 | GPG-Key: 4743206C JID: nomeata(a)joachim-breitner.de | http://www.joachim-breitner.de/ Debian Developer: nomeata(a)debian.org

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Reduceron: reduced to numbers.
by Serguey Zefirov 04 Dec '10

04 Dec '10

I decided to calculate Reduceron's number of transistors (I had to, we have some argument here;). Reduceron allocate 14% of 17300 slices of Virtex-5 FPGA. If we assume that each slice correspond to 8 4-input NAND-NOT elements, we will get 20000 4-input NAND. Each 4-input NAND contains 8 transistors, so the count of logic transistors is about 160000. Reduceron use 90% of 1.5Kbyte RAM blocks. Using 6 transistors per RAM bit, we get 66K transistors more. So Reduceron should contain about 230K transistors if someone decides to go ASIC. It's 3 orders of magnitude less than x86, on par with most late chips of Chuck Moore (inventor of Forth, MISC concept and the one who develops some strange chips in GreenArrays http://greenarraychips.com/ now). The difference between Reduceron and GA144 of Chuck Moore is that Reduceron could be programmed much more easily, and that rocks. Clock frequency of 96MHz should go up too. My experience suggest numbers between 5 and 8 times. So single Reduceron should be of equal performance to Core2 Duo, at least. PS Of course, Reduceron in ASIC will require some cache memory, some controllers, etc. So it won't be that small, like 230K transistors. But, mzke it 2.3M transistors and it still be 2 orders of magnitude less than Core2 Duo... ;)

2 2

Wondering if this could be done.
by Magicloud Magiclouds 04 Dec '10

04 Dec '10

Hi, For example, I have a data A defined. Then I want to add (+) and (-) operators to it, as a sugar (compared to addA/minusA). But * or other stuff defined in class Num is meanless to A. So I just do: (+) :: A -> A -> A (+) a b = A (elem1 a + elem1 b) (elem2 a + elem2 b) -- I got errors here, for the (+) is ambiguous. So, just wondering, does this way work in Haskell? -- 竹密岂妨流水过山高哪阻野云飞

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"Out of memory" if compiled with -O2, why?
by Dmitry Kulagin 04 Dec '10

04 Dec '10

Hi, I have problems with memory leaks and can't find out how to avoid them. I tried to reduce sample to demonstrate the following problems: 1) when compiled without -O2 option, it iconsumes 1582MB (!) total memory 2) when compiled with -O2 option it terminates with "out of memory" Actually I don't understand the reasons, particulary why GC can't collect already processed objects g,...,n (see code below)? I would appreciate very much any help with this situation. Thanks! module Main where import qualified Data.Map as M len = 15*1024*1024 lst from = take len $ zip [from..] [0..] g = M.size $ M.fromList $ lst 0 h = M.size $ M.fromList $ lst 0 i = M.size $ M.fromList $ lst 0 j = M.size $ M.fromList $ lst 0 k = M.size $ M.fromList $ lst 0 l = M.size $ M.fromList $ lst 0 m = M.size $ M.fromList $ lst 0 n = M.size $ M.fromList $ lst 0 main = do mapM_ print [g,h,i,j,k,l,m,n]

4 5

regex libraries: matching operators (=~) and (=~~) are not methods
by José Romildo Malaquias 04 Dec '10

04 Dec '10

Hello. When learning how to use the many regular expression libraries for Haskell, I noticed that the interface API from the regex-base package introduces several high level operations that are abstracted from the implementations (backends). This is done by means of classes. For instance, there are methods for compiling an external representation (like a string or a bytestring) into a regular expression. There are also methods for matching a regular expression and some text (like a string, or a bytestring). But the most high level functions for pattern matching using regular expressions, (=~) and (=~~), are not defined as methods in a class. They are independent functions defined for each backend in the corresponding package. This prevents one from writing a general function using these operators without deliberately choosing a regex backend. Why are those operators not defined as methods, like all other relevant functions? Romildo

1 1

Type families again
by Andrew Coppin 04 Dec '10

04 Dec '10

Yes, it's me. And yes, I come with yet more questions. With Haskell 98 (or, indeed, Haskell 2010) it is impossible to define a polymorphic version of "head" that works for [], Set and ByteString. You can use a higher-kinded type class for [], but that fails for Set (because you can't specify the Ord constraint) and fails spectacularly for ByteString (because it has the wrong kind). The basic problem is that the function's type needs to refer to the type of the container and the type of elements it contains, but the relationship between these types can be arbitrary. Type families allow you to neatly and cleanly fix the problem: class Head c where type Element c :: * head :: c -> Element c It's simple, comprehensible, and it /actually works/. Following this success, we can define functions such as tail, join, and so forth. What we /can't/ do is define a polymorphic map function. One might try to do something like class Functor f where type Element f :: * fmap :: (Element f2 ~ y) => (x -> y) -> f -> f2 instance Functor [x] where type Element [x] = x fmap = map However, this fails. Put simply, the type for fmap fails to specify that f and f2 must be /the same type of thing/, just with different element types. The trouble is, after spending quite a bit of brainpower, I literally cannot think of a way of writing such a constraint. Does anybody have any suggestions? Second, what's the difference between using "type", "newtype" and "data" in a class definition?

5 4

Digests
by Permjacov Evgeniy 04 Dec '10

04 Dec '10

The data integrity checks is well-known problem. A common soluting is use of 'checksums'. Most of them , however, are built in quite obfuscated manner (like md5) that results in ugly and error-prone implementations (see reference implementation for same md5). So, the question is: is there a checksum, that is easy to implement over stream of bytes and may work as good checksum and is good in sence that creation of messages with same checksum that given message has is very hard problem (at least 2^128 tries) ? The reason is that I wish a good checksum to be implemented im my stream-oriented library.

4 9

In what language...?
by Andrew Coppin 03 Dec '10

03 Dec '10

Yesterday I read a rather interesting paper: http://www.cl.cam.ac.uk/~mb566/papers/tacc-hs09.pdf It's fascinating stuff, and I *think* I understand the gist of what it's saying. However, the paper is utterly festooned with formulas that look so absurdly over-the-top that they might almost be a spoof of a mathematical formula rather than the real thing. A tiny fraction of the notation is explained in the paper, but the rest is simply "taken to be obvious". The paper also uses several ordinary English words in a way that suggests that they are supposed to have a more specific technical meaning - but I have no idea what. Does anybody have any idea which particular dialect of pure math this paper is speaking? (And where I can go read about it...)

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HStringTemplate and syb-with-class usage
by Christopher Lewis 03 Dec '10

03 Dec '10

I've seen questions on using HStringTemplate with syb-with-class on the list before, but haven't seen this issue addressed. I'm hoping it's a noob issue, and, therefore, thought I would check with the list before spending too much time digging around for solutions. I'm attempting to use HStringTemplate with the syb-with-class support. I've made sure HStringTemplate is installed with 'syb-with-class=True'. 'genericToSElem' is always failing on the 'True =' guard with an error of "Unable to serialize the primitive type [...]" with whatever primitive Haskell type I've included in my ADT; for example, "Unable to serialize the primitive type 'Prelude.Int'". I've made sure to include 'Text.StringTemplate.GenericWithClass', 'Data.Generics.SYB.WithClass.Basics', and 'Data.Generics.SYB.WithClass.Derive', and to derive instances of the 'Typeable' and 'Data' classes with '$(derive [''Test])', where 'Test' is my test ADT. This makes me think that the overloaded 'toSElem' functions defined by the instances in 'Text.StringTemplate.Instances' are not being called? A cursory comparison to RJson, which the HStringTemplate syb-with-class solution is based on, didn't lead me to any obvious differences that I was missing. For reference, my current configuration is (Sorry, it's an older configuration, but the one I'm stuck with for now) GHC 6.10.4 (Mac OS X 10.6.4, Intel) HStringTemplate 0.6.3 syb-with-class 0.6

1 0

Emacs mode for Happy?
by Edward Amsden 03 Dec '10

03 Dec '10

I'm planning on using Happy for my compiler construction class this quarter. The only problem so far is that emacs keeps trying to mangle my .y files because it assumes I mean them for yacc. Is there an emacs mode for Happy or is it maybe time to also buckle down to learning elisp and write one myself? ------ Edward Amsden Undergraduate Computer Science Rochester Institute of Technology

1 0

Most images broken on haskellwiki pages
by Eugene Kirpichov 03 Dec '10

03 Dec '10

Hello. I looked at a couple pages of mine http://www.haskell.org/haskellwiki/Splot , http://www.haskell.org/haskellwiki/Timeplot , and at a couple of random pages http://haskell.org/haskellwiki/Special:Random - and looks like the vast majority of images are not displaying. What's wrong? Does it have to do with the wiki redesign? What should, say, I personally do about my images regarding this? -- Eugene Kirpichov Senior Software Engineer, Grid Dynamics http://www.griddynamics.com/

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Re: [Haskell-cafe] [Haskell] haskell.org migration complete
by Simon Marlow 03 Dec '10

03 Dec '10

On 02/12/2010 23:48, Claus Reinke wrote: >> The haskell.org server migration is now complete. >> Please let us know if you have any problems. > > Beginning this week, the majority of mails from haskell.org > lists seem to end up in my ISP's spam filter. That would be > Yahoo! - I wonder whether others here have seen a similar > effect when checking their spam filters? > > I don't know whether this is caused by the migration, but > it made me wonder about something I recalled reading > about whitelisting mailing list senders with ISPs, and a > little search found the following: > > http://en.wikipedia.org/wiki/Whitelist > http://help.yahoo.com/l/us/yahoo/mail/postmaster/basics/ > http://help.yahoo.com/l/us/yahoo/mail/postmaster/forms_index.html > http://help.yahoo.com/l/us/yahoo/mail/postmaster/bulkv2.html > http://www.novablog.info/2008/10/21/5-simple-steps-to-improving-e-mail-deli… > > > So it might be related to the new server. Is whitelisting > something the mailing list hosting service should deal > with, or is that left to the customer? I'm fairly sure GMail at least whitelists haskell.org, because I get spam sent via the <list>-owner(a)haskell.org aliases that invariably ends up in my inbox, apparently bypassing GMail's usually very good spam filtering. Cheers, Simon

1 0

Manatee Video.
by Andy Stewart 03 Dec '10

03 Dec '10

Hi all, Many people ask "What's Manatee?" A video worth a thousand words : here is video (select 720p HD) http://www.youtube.com/watch?v=weS6zys3U8k And i think the correct answer to "What's Manatee?" should be : Depend on you how to use it. :) Other information look : http://hackage.haskell.org/package/manatee Enjoy! -- Andy

4 8

How to cabal fetch mtl==2.0.0.0?
by Iain Alexander 03 Dec '10

03 Dec '10

<log> F:\Util\Haskell>cabal fetch mtl==2.0.0.0 Resolving dependencies... cabal: internal error: could not construct a valid install plan. The proposed (invalid) plan contained the following problems: The following packages are involved in a dependency cycle transformers-0.2.2.0, special-functors-1.0, mtl-2.0.0.0 F:\Util\Haskell>cabal -V cabal-install version 0.8.2 using version 1.8.0.2 of the Cabal library </log> Could someone please remind me of the correct incantation to make this work. (I observe that transformers-0.1.4.0 optionally (by cabal flag) depends on special-functors, and special-functors-1.0 depends on mtl. So given that mtl-2 no doubt depends on transformers, I can see the potential for confusion, but there presumably must be a way of breaking the (apparent) loop.) TIA, Iain. -- Iain Alexander ia(a)stryx.demon.co.uk

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Monadic design patterns for the web Kickstarter project
by Greg Meredith 02 Dec '10

02 Dec '10

Dear Haskellians, Last week i went in to record the 2nd and 3rd installments of the C9 monadic design patterns for the web videos. Charles Torre, the series producer, told me there were over 40K distinct views of the first video. i know that many of them came from this community. So, i really want to say thanks! i also want to mention that i just initiated a Kickstarter project<http://www.kickstarter.com/projects/1499410734/monadic-design-patterns-for-…>to raise enough money to complete the book. i've been finding that i'm at a point where the book needs a certain level of focus that doesn't mix well with juggling a ton of clients. i'm trying to raise just enough that i can clear off my desk and focus on completing the book and the source code that supports it. So, if it's of interest please let your friends and cronies know and donate yourself, if you can. For your amusement, here's a little video about it <http://www.youtube.com/watch?v=qOj0tgQDSeQ>. Best wishes, --greg -- L.G. Meredith Managing Partner Biosimilarity LLC 7329 39th Ave SW Seattle, WA 98136 +1 206.650.3740 http://biosimilarity.blogspot.com -- L.G. Meredith Managing Partner Biosimilarity LLC 1219 NW 83rd St Seattle, WA 98117 +1 206.650.3740 http://biosimilarity.blogspot.com

1 0

Fwd: typehash patch for base >= 4 && < 4.4
by Andrew Miller 02 Dec '10

02 Dec '10

Hi all, Typehash 1.4.0.0, the latest version of typehash in hackage, has a cabal constraint base < 4, making it difficult to use with packages that only support newer base versions. I sent a patch to fix this to the maintainer for the typehash package (Lennart Augustsson) on the 16th of November, but haven't heard anything back - it is possible that he doesn't read the e-mail address I sent it to, or is no longer interested in maintaining typehash. Does anyone who would be willing to know Lennart in person to confirm this? Failing this, does anyone want to be maintainer for the typehash package? If I don't hear any better ideas, I could simply upload a version 1.4.0.1 with my split base patch applied, and the maintainer changed to "haskell-cafe(a)haskell.org". Best wishes, Andrew -------- Original Message -------- Subject: typehash patch for base >= 4 && < 4.4 Date: Tue, 16 Nov 2010 17:55:13 +1300 From: Andrew Miller <andrew(a)amxl.com> To: lennart(a)augustsson.net diff -rbud typehash-1.4.0.0/src/Data/TypeHash.hs typehash-1.4.0.1/src/Data/TypeHash.hs --- typehash-1.4.0.0/src/Data/TypeHash.hs 2009-10-06 03:43:44.000000000 +1300 +++ typehash-1.4.0.1/src/Data/TypeHash.hs 2010-11-16 17:43:51.917333177 +1300 @@ -44,7 +44,7 @@ data Type = Name { typeName :: String } -- Abstract type, or recursive reference - | Data { typeName :: String, constrs :: [Constructor] } + | Data { typeName :: String, dconstrs :: [Constructor] } deriving (Eq, Ord, Show, Typeable, Data) type Constructor = (String, [Field]) type Field = (String, Type) -- a unique number is used for missing field names @@ -54,7 +54,7 @@ let tn = show $ fullTypeOf x in case dataTypeRep $ dataTypeOf x of AlgRep cs | tn `notElem` tns -> - Data { typeName = tn, constrs = map (gConstr (tn:tns) x) cs } + Data { typeName = tn, dconstrs = map (gConstr (tn:tns) x) cs } _ -> Name { typeName = tn } -- Use type name for truly abstract types and recursive types. gConstr :: (Data a) => [String] -> a -> Constr -> (String, [Field]) Only in typehash-1.4.0.1/src/Data: TypeHash.hs~ diff -rbud typehash-1.4.0.0/typehash.cabal typehash-1.4.0.1/typehash.cabal --- typehash-1.4.0.0/typehash.cabal 2009-10-06 03:43:44.000000000 +1300 +++ typehash-1.4.0.1/typehash.cabal 2010-11-16 17:40:55.496953710 +1300 @@ -1,5 +1,6 @@ Name: typehash -Version: 1.4.0.0 +Cabal-Version: >= 1.2 +Version: 1.4.0.1 License: BSD3 Author: Lennart Augustsson Maintainer: Lennart Augustsson @@ -10,6 +11,18 @@ Description: Produce a hash for a type that is unique for that type. The hash takes both actual type names and type structure into account. This is useful for checking the type of persisted values. -Hs-Source-Dirs: src -Build-Depends: base < 4, mtl, bytestring, pureMD5, binary -Exposed-modules: Data.TypeHash + +Flag base4 + Description: Use base-4.* + Default: True + +Library + Hs-Source-Dirs: src + Build-Depends: mtl, bytestring, pureMD5, binary + If flag(base4) + Build-Depends: + base >= 4 && < 4.4, + syb < 0.3 + else + Build-Depends: base < 4 + Exposed-modules: Data.TypeHash

2 1

Managing multiple installations of GHC
by Robert Clausecker 02 Dec '10

02 Dec '10

Hi folks! I want to test the new version 7 of GHC, but don't want to replace the packaged version 6.12 with it. I'm not very advanced with the internals of GHC and have some problems. So these are my questions: I installed GHC into a subdir of my homedir, let's call it ~/ghc7. How can I install additional libs there? How can I install GHC 7 parallel to GHC 6.12 with the option to choose? My OS is GNU/Linux, my Distro is Ubuntu (Lucid). Thank you very much, yours Robert Clausecker

5 4

doesDirectoryExist is always returning False
by Marcelo Sousa 02 Dec '10

02 Dec '10

Hi, I'm having currently a problem with System.Directory in my mac os. System Version: Mac OS X 10.6.5 Kernel Version: Darwin 10.5.0 Prelude System.Directory> let dirTest = do {dir <- getCurrentDirectory; doesDirectoryExist dir} Prelude System.Directory> dirTest False I noticed also that I can't change the searchable field in the permissions record. Prelude System.Directory> getPermissions "." Permissions {readable = True, writable = True, executable = True, searchable = False} I tried different versions of directory and filepath packages but with no success at the moment. Any suggestions?! Regards, Marcelo Sousa

4 4

Haskell Weekly News: Issue 160 - December 1, 2010
by Daniel Santa Cruz 02 Dec '10

02 Dec '10

Welcome to issue 160 of the HWN, a newsletter covering developments in the [1]Haskell community in the week of November 21 - 27. My apologies for proving a much shorter version of the weekly news this time around. I'm really short on time this week, but decided to send this abbreviated version rather than skipping it. Hope to resume full coverage next week. Cheers! Top Reddit Stories * Lisk - Lisp and Haskell Domain: chrisdone.com Score: 70, Comments: 83 On Reddit: http://www.reddit.com/r/haskell/comments/ec0kp/lisk_lisp_and_haskell/ Original: http://chrisdone.com/posts/2010-11-25-lisk-lisp-haskell.html * lazycatmanatee is building a enormous suite of graphical, desktop apps in Haskell. Here's the screenshot feed Domain: flickr.com Score: 58, Comments: 11 On Reddit: http://www.reddit.com/r/haskell/comments/eb5kd/lazycatmanatee_is_building_a… Original: http://www.flickr.com/photos/48809572@N02/ * Category theory for Haskell programmers Domain: geoffhulette.wordpress.com Score: 49, Comments: 7 On Reddit: http://www.reddit.com/r/haskell/comments/eatd6/category_theory_for_haskell_… Original: http://geoffhulette.wordpress.com/2010/11/22/category-theory-for-haskell-pr… * Duck typing in Haskell Domain: chrisdone.com Score: 45, Comments: 10 On Reddit: http://www.reddit.com/r/haskell/comments/ea99a/duck_typing_in_haskell/ Original: http://chrisdone.com/posts/2010-11-22-duck-typing-in-haskell.html * GHC 7 I/O manager status update: bugs fixed, performance improved, plans afoot! Domain: serpentine.com Score: 41, Comments: 0 On Reddit: http://www.reddit.com/r/haskell/comments/ecls3/ghc_7_io_manager_status_upda… Original: http://www.serpentine.com/blog/2010/11/27/ghc-7-io-manager-status/ * And here I thought they were using Haskell... Domain: i.imgur.com Score: 34, Comments: 11 On Reddit: http://www.reddit.com/r/haskell/comments/ebgnj/and_here_i_thought_they_were… Original: http://i.imgur.com/ApzhX.png * Fun with monad comprehensions Domain: blog.n-sch.de Score: 33, Comments: 9 On Reddit: http://www.reddit.com/r/haskell/comments/ecu0w/fun_with_monad_comprehension… Original: http://blog.n-sch.de/2010/11/27/fun-with-monad-comprehensions/ * The 'text' package has been accepted into the Haskell Platform! Domain: self.haskell Score: 31, Comments: 20 On Reddit: http://www.reddit.com/r/haskell/comments/eb7fd/the_text_package_has_been_ac… Original: /r/haskell/comments/eb7fd/the_text_package_has_been_accepted_into_the/ * Yesod 0.6.3 Released Domain: docs.yesodweb.com Score: 24, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/e9jfd/yesod_063_released/ Original: http://docs.yesodweb.com/blog/yesod-0-6-3/ * how subtraction works for combinatorial species Domain: byorgey.wordpress.com Score: 24, Comments: 2 On Reddit: http://www.reddit.com/r/haskell/comments/ec5mx/how_subtraction_works_for_co… Original: http://byorgey.wordpress.com/2010/11/24/species-subtraction-made-simple/ Top StackOverflow Questions * Avoiding namespace pollution in Haskell votes: 14, answers: 3 http://stackoverflow.com/questions/4260507/avoiding-namespace-pollution-in-… * Keeping State in a Stateless world votes: 7, answers: 2 http://stackoverflow.com/questions/4259800/keeping-state-in-a-stateless-wor… * Updating a Big State Fast in Haskell votes: 7, answers: 2 http://stackoverflow.com/questions/4265660/updating-a-big-state-fast-in-has… * What is the most efficient purely functional algorithm for generating all prefixes of a list? votes: 7, answers: 2 http://stackoverflow.com/questions/4290370/what-is-the-most-efficient-purel… * How can I make a graphical command line in haskell/gtk2hs? votes: 6, answers: 2 http://stackoverflow.com/questions/4281984/how-can-i-make-a-graphical-comma… * Point-free form versus style votes: 5, answers: 3 http://stackoverflow.com/questions/4235741/point-free-form-versus-style * How to catch (and ignore) a call to the error function? votes: 4, answers: 2 http://stackoverflow.com/questions/4243117/how-to-catch-and-ignore-a-call-t… * Persistent console history in ghci votes: 4, answers: 1 http://stackoverflow.com/questions/4249351/persistent-console-history-in-gh… * Common Lisp equivalent to Haskell's main function? votes: 4, answers: 2 http://stackoverflow.com/questions/4285718/common-lisp-equivalent-to-haskel… * How can I write a MST algorithm (Prim or Kruskal) in Haskell? votes: 4, answers: 3 http://stackoverflow.com/questions/4290163/how-can-i-write-a-mst-algorithm-… About the Haskell Weekly News New editions are posted to [2]the Haskell mailing list as well as to [3]the Haskell Sequence and [4]Planet Haskell. [5]RSS is also available, and headlines appear on [6]haskell.org. To help create new editions of this newsletter, please send stories to dstcruz * at * gmail * dot * com. The code used to produce this version of the newsletter is not yet publicly available, as it is a complete hack designed to get things started again. Until next time, Daniel Santa Cruz References 1. http://haskell.org/ 2. http://www.haskell.org/mailman/listinfo/haskell 3. http://sequence.complete.org/ 4. http://planet.haskell.org/ 5. http://sequence.complete.org/node/feed 6. http://haskell.org/

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Who's in charge of the new Haskell.org server?
by Christopher Done 02 Dec '10

02 Dec '10

If someone will allow me to send them an extension for WikiMedia I will write one. It shouldn't be complex at all, so code review will be trivial. Please let me know! I'm sure other people here are interested to know who to go to to get things like this done. It would be cool to write an extension to support an embedded Haskell prompt (e.g. tryhaskell.org abd http://haskell.quplo.com/) inside the wiki. It's possible to extend the parser to support custom token types[1], so this could be a neat addition. For instance, the _Blow your mind_ article is full of examples, you can link to them with tryhaskell.org[3], but that's not as cool, why not make these runnable inside the page? :-) If tryhaskell.orgever goes down the script can just fall back to displaying code. Ciao [1]: http://www.mediawiki.org/wiki/Category:Parser_extensions [2]: http://haskell.org/haskellwiki/Blow_your_minds [3]: http://tryhaskell.org/?input=foldr%20(\a%20~(x,y)%20-%3E%20(a:y,x))%20([],[…

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Unable to install packages
by Roland Senn 01 Dec '10

01 Dec '10

I learned a little bit Haskell with Hugs on Windows and now I want to develop on Linux. I installed the Haskell Platform on Unbunto 10.10. There were no problems. Then I tried to install Leksah with sudo cabal install leksah --global It failed with: Resolving dependencies... /tmp/gtksourceview2-0.11.12661/gtksourceview2-0.11.1/Gtk2HsSetup.hs:25:0: warning: #warning Setup.hs is guessing the version of Cabal. If compilation of Setup.hs fails use -DCABAL_VERSION_MINOR=x for Cabal version 1.x.0 when building (prefixed by --ghc-option= when using the 'cabal' command) [1 of 2] Compiling Gtk2HsSetup ( /tmp/gtksourceview2-0.11.12661/gtksourceview2-0.11.1/Gtk2HsSetup.hs, /tmp/gtksourceview2-0.11.12661/gtksourceview2-0.11.1/dist/setup/Gtk2HsSetup.o ) [2 of 2] Compiling Main ( /tmp/gtksourceview2-0.11.12661/gtksourceview2-0.11.1/Setup.hs, /tmp/gtksourceview2-0.11.12661/gtksourceview2-0.11.1/dist/setup/Main.o ) Linking /tmp/gtksourceview2-0.11.12661/gtksourceview2-0.11.1/dist/setup/setup ... Configuring gtksourceview2-0.11.1... Preprocessing library gtksourceview2-0.11.1... Building gtksourceview2-0.11.1... [ 1 of 13] Compiling Graphics.UI.Gtk.SourceView.Signals ( dist/build/Graphics/UI/Gtk/SourceView/Signals.hs, dist/build/Graphics/UI/Gtk/SourceView/Signals.o ) Graphics/UI/Gtk/SourceView/Signals.chs:51:46: Module `System.Glib.UTFString' does not export `maybePeekUTFString' cabal: Error: some packages failed to install: gtksourceview2-0.11.1 failed during the building phase. The exception was: ExitFailure 1 leksah-0.8.0.8 depends on gtksourceview2-0.11.1 which failed to install. I searched the Internet on "gtksourceview2 maybePeekUTFString" and found a patch: http://www.mail-archive.com/gtk2hs-devel@lists.sourceforge.net/msg00971/gtk… As a newby with the Haskell tools, I searched the Internet on how to install a patch. I found dpm and I tried to install it with: sudo cabal install dpm --global It failed with: configure: error: in `/tmp/terminfo-0.3.1.31936/terminfo-0.3.1.3': configure: error: curses headers could not be found, so this package cannot be built See `config.log' for more details. cabal: Error: some packages failed to install: DPM-0.2.1 depends on terminfo-0.3.1.3 which failed to install. darcs-2.5 depends on terminfo-0.3.1.3 which failed to install. haskeline-0.6.3.2 depends on terminfo-0.3.1.3 which failed to install. terminfo-0.3.1.3 failed during the configure step. The exception was: ExitFailure 1 So after installing Haskell Platform, I only found broken packages! What can I do to install Leksah?

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Cabal sdist bug patch
by John D. Ramsdell 01 Dec '10

01 Dec '10

So as far as I can tell, it's easy to fix the cabal sdist bug. The module that generates a distribution simply has to use insntallOrdinaryFile when copying files, not the version of copyFile that is exported by Distribution.Simple.Util. I'll respond to the open ticket with this patch later today. John $ diff -ur ocabal-1.8 cabal-1.8 Only in cabal-1.8: .darcs-boring diff -ur ocabal-1.8/Distribution/Simple/SrcDist.hs cabal-1.8/Distribution/Simple/SrcDist.hs --- ocabal-1.8/Distribution/Simple/SrcDist.hs 2010-12-01 11:16:00.629309262 -0500 +++ cabal-1.8/Distribution/Simple/SrcDist.hs 2010-12-01 11:18:37.449933651 -0500 @@ -78,7 +78,7 @@ ( Version(versionBranch) ) import Distribution.Simple.Utils ( createDirectoryIfMissingVerbose, withUTF8FileContents, writeUTF8File - , copyFiles, copyFileVerbose + , installOrdinaryFile, installOrdinaryFiles , findFile, findFileWithExtension, matchFileGlob , withTempDirectory, defaultPackageDesc , die, warn, notice, setupMessage ) @@ -341,6 +341,12 @@ createDirectoryIfMissingVerbose verbosity True (takeDirectory targetFile) copyFileVerbose verbosity file targetFile +copyFileVerbose :: Verbosity -> FilePath -> FilePath -> IO () +copyFileVerbose = installOrdinaryFile + +copyFiles :: Verbosity -> FilePath -> [(FilePath, FilePath)] -> IO () +copyFiles = installOrdinaryFiles + printPackageProblems :: Verbosity -> PackageDescription -> IO () printPackageProblems verbosity pkg_descr = do ioChecks <- checkPackageFiles pkg_descr "." $

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[ANNOUNCE] A general data-flow framework
by Mitar 01 Dec '10

01 Dec '10

Hi! I have just published my library which provides a general data-flow framework: http://hackage.haskell.org/package/Etage Sadly it requires current GHC HEAD branch because of this: http://hackage.haskell.org/trac/ghc/ticket/1769 Short description: A general data-flow framework featuring nondeterminism, laziness and neurological pseudo-terminology. It can be used for example for data-flow computations or event propagation networks. It tries hard to aide type checking and to allow proper initialization and cleanup so that interfaces to input and output devices (data or events producers or consumers) can be made (so that created models/systems/networks can be used directly in real world applications, for example robots). I am more than open to any suggestions and comments. Mitar

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ANN: HaLVM 1.0: the Haskell Lightweight Virtual Machine
by Adam Wick 01 Dec '10

01 Dec '10

Galois, Inc. is pleased to announce the immediate release of the Haskell Lightweight Virtual Machine (or HaLVM), version 1.0. The HaLVM is a port of the GHC runtime system to the Xen hypervisor, allowing programmers to create Haskell programs that run directly on Xen's "bare metal." Internally, Galois has used this system in several projects with much success, and we hope y'all will have an equally great time with it. What might you do with a HaLVM? Pretty much anything you want. :) Explore designs for operating system decomposition, examine new notions of mobile computation with the HaLVM and Xen migration, or find interesting network services and lock them inside small, cheap, single-purpose VMs. The HaLVM is the result of many years of effort, by many people inside Galois. Although it is not yet totally bug-free, we have decided that broad adoption wins over perfection and thus we are releasing it for general review. As such, there will be some rough edges, and we urge you to read the documentation to understand the platforms we test on. We are releasing the HaLVM under a non-restrictive BSD3 license. You can find it here: http://halvm.org We welcome user feedback, feature requests, bug notices, patches, and feature additions; see the page above for guidelines on getting involved. Finally, we'd like to give many things to the GHC and Xen communities, without which this work would not be possible. If you have any questions or concerns, please don't hesitate to contact the HaLVM's maintainers at halvm-devel(a)community.galois.com. Have a lovely day! - Adam

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Test
by Ian Lynagh 01 Dec '10

01 Dec '10

A1

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Re: [Haskell-cafe] DPH and GHC 7.0.1
by Andrew Coppin 30 Nov '10

30 Nov '10

On 29/11/2010 01:42 AM, Manuel M T Chakravarty wrote: > Andrew Coppin: >> I was wondering about this myself, actually. I'm especially surprised since I thought the DPH implementation was hard-wired into the compilter itself (in which case, how can you distribute it seperately?) >> >> Then again, I've never yet even tried using DPH. (The wiki page looks very out of date, so I don't know how much to trust its information.) > As David said, we will release the DPH libraries separately, but at the same time as GHC 7.0.2. DPH consists essentially of two components (a) the vectoriser, a program transformer hardwired into GHC and (b) the DPH libraries. At the request of the Haskell Platform people we separated the DPH library packages from the standard GHC distribution and will distribute them via Hackage. > > The wiki page will be updated in time for that release. > > Manuel I would have thought that the two components would be so tightly coupled that this wouldn't work. But then again, you presumably know a lot more about it than I ever will. Anyway, thanks for the clarification.

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System.Console.Haskeline
by michael rice 30 Nov '10

30 Nov '10

How do I load this module? Michael ============= *Main> :m + System.Console.Haskeline <no location info>: Could not find module `System.Console.Haskeline': it is not a module in the current program, or in any known package. *Main>

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Crazy idea, building ghc with cabal?
by Joris Putcuyps 30 Nov '10

30 Nov '10

Hello Could it be done and would it be interesting, building 'ghc' using cabal? * 'lhc' does it * Use 'cabal-rpm' and 'cabal2arch' to create packages for linux distributions * As ordinary user, install specific versions in your home directory. cabal install ghc => $HOME/.cabal/bin/ghc * Get base packages as a dependency. Greetings Joris

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Transparent identity instances
by Jafet 29 Nov '10

29 Nov '10

Hi, Does it make sense to declare a transparent identity instance for Functor, Applicative, Monad, etc? For example, I might want to generalize ($) = (<*>) where > ($) :: (a -> b) -> a -> b > (<*>) :: (Functor f) => f (a -> b) -> f a -> f b The traditional definition makes Identity a newtype: > newtype Identity a = Identity a > instance Applicative Identity where > pure a = Identity a > (Identity f) <*> (Identity a) = Identity (f a) But using this instance becomes unwieldy. If using Identity was transparent, eg. if it was a type synonym > {-# LANGUAGE TypeSynonymInstances #-} > type Identity a = a > instance Applicative Identity where > -- something like > pure a = a > f <*> a = f a But GHC does not accept type synonym instances unless they are fully applied. Is it sound for such an instance to exist? If so, how might it be defined? -- Jafet

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Load testing
by Tony Morris 29 Nov '10

29 Nov '10

Does there exist a package for convenient load-testing against a website? e.g. making lots of HTTP requests against a server, including timing, and collecting the results? -- Tony Morris http://tmorris.net/

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Re: Template Haskell: exchanging information between 'splicers'
by jean-christophe mincke 29 Nov '10

29 Nov '10

Oleg, I am using GHC 6.12.3 Here a reproduction: in the file Template.hs proc () = runIO $ do runQ [|1+1|] proc' () = [|1+1|] In the file Main.hs i1 = $(proc ()) -- fails at compile time with "Segmentation fault/access violation in generated code". Maybe is it the expected behavior, I do not know. i2 = $(proc' ()) -- sucessfull i3 = proc() -- sucessful but proc is executed at "runtime" main = ... Hope it is clear enough otherwise let me know. Regards J-C On Mon, Nov 29, 2010 at 4:45 AM, <oleg(a)okmij.org> wrote: > > Hello! > > > But, please, correct me if I am wrong, in your example, the splicer are > > executed at run time and not at compile time. > > With TH, it becomes a bit difficult to tell what is exactly `compile > time'. One can say however that when the code is ready to be spliced > in at the top level, the IO actions in its splices must have been > completed. > > > I have modified your example to make it run at compile time and I get a > > (compile time) segmentation fault. > > As I mentioned, the code was specifically designed to cause something > like segmentation fault. Sneaking out free variables is definitely the > bad thing. The principle of exchanging data between splices (using > runQ/runIO) is valid and could be used for good things, too. > > I am wondering though what GHC version and command-line parameters are > you using? On my system. with GHC 6.10.3, I tried running the original > and modified code in GHCi and GHC (with and without -O2) and did not > get segmentation fault. Could you provide more details about your > system so to reproduce the segfault? I think Simon Peyton-Jones would > really like to know all that. > > Cheers, > Oleg >

1 0

DPH and GHC 7.0.1
by Gregory Propf 29 Nov '10

29 Nov '10

I was hoping to play around with Data.Parallel.Haskell (dph) but noticed that it seems to have been exiled from ghc 7.0.1 which I just installed. It also doesn't seem to be in cabal. Anybody know how to use dph with 7.0.1 or has it been abandoned or something?

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Re: [Haskell] haskell.org downtime: Tuesday Nov 30th
by Henning Thielemann 28 Nov '10

28 Nov '10

Ian Lynagh schrieb: > We plan to have some haskell.org downtime on Tuesday Nov 30th, while we > migrate to the new server. Is there a simple way for me to get a local copy of the Wiki content? I have contributed to several articles and could rest more easily with a local backup before the server is migrated. :-)

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ANNOUNCE: iteratee-compress 0.1.2
by Maciej Piechotka 28 Nov '10

28 Nov '10

Iteratee-compress provides compressing and decompressing enumerators including flushing. Currently only gzip is provided but at bzip and LZMA are planned. This is bug-fixing release Changes from previous version: - Fix infinite loop/segfault bug - Fix bug in which part of the output was lost - Support for iteratee 0.5 and 0.6 Next goals: - BZip support - LZMA support - Generic interface for flushing To think about: - Should inner iteratee be able to request flushing? Regards

1 1

ANNOUNCE: iteratee-parsec 0.0.6
by Maciej Piechotka 28 Nov '10

28 Nov '10

Iteratee-parsec is a library which allows to have a parsec (3) parser in Iteratee monad. It contains 2 implementations: - John Lato's on public domain. It is based on monoid and design with short parsers in mind. - Mine on MIT. It is based on single-linked mutable list. It seems to be significantly faster for larger parsers - at least in some cases - but it requires a monad with references (such as for example IO or ST). The version 0.0.6 uses reference library. Regards

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ANNOUNCE: iteratee-compress 0.1.2
by Maciej Piechotka 28 Nov '10

28 Nov '10

Iteratee-compress provides compressing and decompressing enumerators including flushing. Currently only gzip is provided but at bzip and LZMA are planned. This is bug-fixing release Changes from previous version: - Fix infinite loop/segfault bug - Fix bug in which part of the output was lost Next goals: - BZip support - LZMA support - Generic interface for flushing To think about: - Should inner iteratee be able to request flushing? Regards

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Return stack buffer vs Haskell compilers
by Florian Weimer 28 Nov '10

28 Nov '10

Are there any Haskell compilers which use a calling convention which is friendly to return stack buffers found in many modern CPUs? Such a calling convention uses CALL/RET pairs for function calls. Tail calls are implemented with JMP and may require shuffling the stack, including the return address, if the number of arguments passed on the stack differs between tail caller and callee. Such an approach means that the CPU can use the return stack buffer, which allows exact prediction of the jump target of the RET instruction (as long as the return stack buffer does not overflow). In contrast, if an indirect jump is used to implement RET, it enters the same prediction logic as any other indirect call, which is less precise and affects predicition of other indirect calls. This is especially important on the Intel Atom and VIA Nano CPUs, which are reported (Agner Fog, "The microarchitecture of Intel, AMD and VIA CPUs", last updated 2010-09-25) to have a return stack buffer, but a very simple indirect branch predictor which uses the last target as the next predicted target.

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Why does cabal sdist still make tarballs with incorrect file modes?
by John D. Ramsdell 28 Nov '10

28 Nov '10

As I played with GHC 7.0.1, I noticed that Cabal sdist is still hosed. Since ten months ago, cabal sdist fails to preserve the file mode bits of the source files put into the tarball being generated (Ticket #627 reported by draconx). An executable shell script and a source file world readable both have a mode of 600 in the tarball. Does anyone know why this bug is difficult to fix? Why can't one revert to the code used in Cabal 1.6.0.1, which is know to work? John

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Bulletproof resource management
by Florian Weimer 28 Nov '10

28 Nov '10

At least in my experience, in order to get proper resource management for things like file or database handles, you need both a close operation and a finalizer registered with the garbage collector. The former is needed so that you can create resources faster than the garbage collector freeing them. The latter is a safety net in cases where proper resource management is not follwoed (perhaps in GHCi). When the explicit close operation or the finalizer has been invoked, the object must somehow be disabled, so that further operations on it fail (otherwise, you might dereference a dangling pointer). What's the idom for implementing this in Haskell (or GHC)? It seems that a ForeignPtr cannot be written to (otherwise I'd change it to a null pointer when the resource is freed). It's also not possible to check if the finalizers have been run. Can the finalizers hold a reference to the object which in turn holds the ForeignPtr to be finalized? Or would that prevent the finalizers from running at all? Is there a way to avoid the extra level of indirection (or is GHC sufficiently smart to optimize it away)?

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GHC Out of memory
by John Smith 28 Nov '10

28 Nov '10

I get an out-of-memory error about two thirds of the way through building qtHaskell. If I start again, the remaining modules are compiled successfully, although GHC's memory usage creeps up to about 1.5Gb by the time it's finished. Is there a memory leak? (Compiling on Win64 with 4Gb RAM.)

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qtHaskell signal and slots
by c8h10n4o2 27 Nov '10

27 Nov '10

I have the following code that tries to resize window after a click. But nothing happens. If I use a builtin slot that does not need a function, such as "close", "quit" it works, however for any other slot it seems my function is ignored. Which slot/signal should I use and how? module Main where import Qtc.Classes.Qccs import Qtc.Classes.Gui import Qtc.Gui.Base import Qtc.Gui.QApplication import Qtc.Gui.QPushButton import Qtc.Core.QFile import Qtc.Tools.QUiLoader import Qtc.Enums.Core.QIODevice import Qtc.Core.Base import Qtc.ClassTypes.Gui import Qtc.Gui.QAbstractButton main = do app <- qApplication () loader <- qUiLoader () uiFile <- qFile "slide.ui" open uiFile fReadOnly ui <- load loader uiFile close uiFile () add <- findChild ui ("<QPushButton*>", "pushButton") connectSlot add "clicked()" add "click()" $ t ui qshow ui () qApplicationExec () t :: QWidget () -> QWidget () -> IO () t ui _= resize ui (500::Int ,500::Int) -- View this message in context: http://haskell.1045720.n5.nabble.com/qtHaskell-signal-and-slots-tp3282748p3… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

1 0

Is EclipseFP alive?
by Dušan Kolář 27 Nov '10

27 Nov '10

Hello, I tried to install EclipseFP using instructions on http://eclipsefp.sourceforge.net/, nevertheless, without any success - after downloading scion I cannot build it > cabal install Resolving dependencies... cabal: dependencies conflict: ghc-6.12.3 requires Cabal ==1.8.0.6 however Cabal-1.8.0.6 was excluded because scion-0.1.0.6 requires Cabal ==1.6.* Running Setup.hs through runhaskell seems not to work as well: > runhaskell Setup.hs configure Configuring scion-0.1.0.6... Setup.hs: At least the following dependencies are missing: AttoJson >=0.5.2, binary ==0.5.*, derive -any, ghc-paths ==0.1.*, ghc-syb -any, ghc-syb-utils -any, hslogger ==1.0.*, list-tries -any, multiset >=0.1 && <0.3, uniplate -any Even if, for instance: > cabal info binary * binary (library) Synopsis: Binary serialisation for Haskell values using lazy ByteStrings Latest version available: 0.5.0.2 Latest version installed: 0.5.0.2 Is there any chance to make it install or should I give up? Dusan

2 1