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accessing the RTS -M flag value from GHC.RTS.Flags

haskell-cafe - Tue, 04/05/2016 - 9:46pm
Given, import GHC.RTS.Flags main = do gcf <- getRTSFlags print (maxHeapSize (gcFlags gcf)) And running on x86-64 in GHC 7.10.3, $ ./ghcflags 0 $ ./ghcflags +RTS -M1M 256 $ ./ghcflags +RTS -M1024K 256 $ ./ghcflags +RTS -M4096K 1024 Is there anyway I can get access to the value stored in the -M flag and depend on that value being correct? I was not able find it in the user's guide or anywhere else for that matter. Thanks, Adam
Categories: Offsite Discussion

Text.Regex.matchRegex: Success is empty?

haskell-cafe - Tue, 04/05/2016 - 9:16pm
Esteemed Haskellers, It is working for me, but I am puzzled by the matchRegex function: > import Text.Regex > :i matchRegex matchRegex :: Regex -> String -> Maybe [String] -- Defined in ‘Text.Regex’ Searches that fail return Nothing: > matchRegex (mkRegex "z") "abracadabra" Nothing which makes sense. But why do searches that succeed return an empty list of Strings? > matchRegex (mkRegex "a") "abracadabra" Just [] >
Categories: Offsite Discussion

Documenting extensions

haskell-cafe - Tue, 04/05/2016 - 9:12pm
I'd like to believe the Haskell report is a bible. I learned H98 using the Prelude as a source of examples and Hugs as a testbed. That was a comfortable and rewarding combination. Later I discovered that by default GHC rejected almost all my report-conforming (H98 and H2010) code. Ironically, its website at the time asserted, "Haskell is a standard language." In fact, far from reflecting biblical authority, the de facto Haskell discussed in this cafe comes in some 2^99 flavors -- enough to use a different language for every run of the compiler for the life of the universe. Witness: ghc --supported-languages | grep -v '^No[A-Z]' | wc -l (99 is the answer for GHC 7.8.4. In fact not all combinations of -X options are legal, but you get the point.) Unfortunately there is no coherent discussion of all those Haskells. The extensions section of the GHC User Guide gives no formal syntax, often teaches semantics only by example, and is replete with sales pitches, partial analogies, inconsistent terminology, an
Categories: Offsite Discussion

Journal of Functional Programming - Call for PhDAbstracts

haskell-cafe - Tue, 04/05/2016 - 9:34am
If you or one of your students recently completed a PhD in the area of functional programming, please submit the dissertation abstract for publication in JFP: simple process, no refereeing, deadline 30th April 2016. Best wishes, Graham ============================================================ CALL FOR PHD ABSTRACTS Journal of Functional Programming Deadline: 30th April 2016 ============================================================ PREAMBLE: Many students complete PhDs in functional programming each year. As a service to the community, the Journal of Functional Programming publishes the abstracts from PhD dissertations completed during the previous year. The abstracts are made freely available on the JFP website, i.e. not behind any paywall. They do not require any transfer of copyright, merely a license from the author. A dissertation is eligible for inclusion if parts of it have or could have appeared in JFP, that is, if it is in the general area of f
Categories: Offsite Discussion

I can no longer maintain containers

libraries list - Mon, 04/04/2016 - 12:18am
Hi all, I am writing to let you know that I am no longer able to maintain the containers package. I have enjoyed working on containers for several years, but I can no longer find the time needed for the job (with two little kids and building a house). I am not sure what is the best future of the containers package -- it could go to CLC, or it could get a new maintainer. If you look at the commit logs and on the github issues/requests, you will find out that David Feuer has a thorough understanding of the package (notably Data.Sequence) and has been competently moderating the issues/requests for some time now, so he would be the first choice. (I did not contact him sooner, so it is surprise for him as well -- sorry, David :-) Could I humbly ask David/CLC members/anyone for comments? Cheers, Milan Straka
Categories: Offsite Discussion

Names for Data.Sequence pattern synonyms

libraries list - Sun, 04/03/2016 - 1:07am
Milan Straka and I agree that we want Data.Sequence to offer pattern synonyms to make it more convenient to work with the ends of sequences. I wanted to check with everyone here what names to use. Relevant names already exposed: 1. <|, |>, and empty for cons, snoc, and empty 2. data ViewL a = EmptyL | a :< Seq a, and the equivalent on the right. I suggested Empty, :<<, and :>> as the pattern synonyms, the latter chosen for the relative convenience of the double tap. Milan suggested (correctly, I suspect) that the greater clarity of Empty, :<|, and :|> is worth the price in typing. _______________________________________________ Libraries mailing list Libraries< at >
Categories: Offsite Discussion

A better type signature for `forM_`

libraries list - Fri, 04/01/2016 - 12:21am
Hi all, I was recently faced with some unexpected behaviour from a piece of code that type checks and has zero warnings (even with -Wall). The code is below (and depends on the hashtables package). The error was using the <$> operator instead of the =<< operator. Using the former, it just builds up a list of IO actions that never get run. As pointed out to me on IRC (thanks pjdeport), chaning the type signature of `forM_` to forM_' :: (Monad m, Foldable t) => t a -> (a -> m ()) -> m () would have resulted in an error. Yes, this change would break existing code (breaking code would require an explicit `void $` inside the `forM_`) but does anyone else think this is a good idea? Erik import Control.Monad import qualified Data.HashTable.IO as HT type EvenCache = HT.BasicHashTable Int Bool main :: IO () main = do ht <- buildTable xs <- HT.toList ht putStrLn $ "cache: length " ++ show (length xs) buildTable :: IO EvenCache buildTable = do ht <- forM_ pairs $ \ (k,v) -
Categories: Offsite Discussion

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Categories: Offsite Blogs

New gtk2hs 0.12.4 release

gtk2hs - Wed, 11/21/2012 - 12:56pm

Thanks to John Lato and Duncan Coutts for the latest bugfix release! The latest packages should be buildable on GHC 7.6, and the cairo package should behave a bit nicer in ghci on Windows. Thanks to all!


Categories: Incoming News