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Where is Haskell Weekly News syndicated?
by Jeremy 06 Aug '15

06 Aug '15

Haskell Weekly News used to be syndicated on http://contemplatecode.blogspot.com/ and http://sequence.complete.org/hwn. sequence only has HWN up to March 2010, while contemplatecode goes up to the beginning of February. Is there any way that I can subscribe to HWN (preferably as RSS/Atom), and not other stuff that doesn't interest me? -- View this message in context: http://haskell.1045720.n5.nabble.com/Where-is-Haskell-Weekly-News-syndicate… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Voleon Capital Management Hiring Senior Software Engineer
by Charles Weitzer 05 Aug '15

05 Aug '15

Voleon Capital Management LP is a startup quantitative hedge fund located in Berkeley, California. We would like to hire a senior software engineer as soon as possible. Voleon's founders previously worked together at one of the most successful quantitative hedge funds in the world. Our CEO has a PhD in Computer Science from Stanford and has been CEO and founder of a successful Internet infrastructure startup. Our Chief Investment Officer has a PhD in Statistics from Berkeley. Voleon's team includes PhD's from leading departments in statistics, computer science, and mathematics. We have made several unpublished advances in the field of machine learning and in other areas as well. Here is our formal job description: ********************************************************** * Senior Software Engineer * Technology-driven investment firm employing cutting-edge statistical machine learning techniques seeks an exceptionally capable software engineer. You will architect and implement new production trading systems, machine learning infrastructure, data integration pipelines, and large-scale storage systems. The firm researches and deploys systematic trading strategies designed to generate attractive returns without being dependent on the performance of the overall market. Join a team of under 30 people that includes a Berkeley statistics professor as well as over ten PhD's from Berkeley, Chicago, CMU, Princeton, Stanford, and UCLA, led by the founder and CEO of a successful Internet infrastructure technology firm. The firm's offices are walking distance from BART and the UC Berkeley campus in downtown Berkeley, California. We have a casual and collegial office environment, weekly catered lunches, and competitive benefits packages. We seek candidates with a proven track record of writing correct, well-designed software, solving hard problems, and delivering complex projects on time. You should preferably have experience designing and implementing fault-tolerant distributed systems. Experience with building large-scale data infrastructure, stream processing systems, or latency-sensitive programs is a bonus. We are growing rapidly. Willingness to take initiative and a gritty determination to productize are essential. Required experience: - developing with C/C++/Python/Go in a Linux environment with a focus on performance, concurrency, and correctness. - experience with a functional programming language (Haskell, OCaml, Erlang) - working in TCP/IP networking, multi-threading, and server development. - working with common Internet protocols (IP, TCP/UDP, SSL/TLS, HTTP, SNMP, etc.). - architecting and designing highly available systems. - architecting and designing large-scale data management infrastructure. - working in large codebases and building modular, manageable code. Preferred experience: - debugging and performance profiling, including the use of tools such as strace, valgrind, gdb, tcpdump, etc. - working with build and test automation tools. - working with well-defined change management processes. - diagnosing RDBMS performance problems, exploiting indexing, using EXPLAIN PLAN, optimizing at the code layer, etc. - working with messaging queues (RabbitMQ, Redis, etc.) as well as distributed caching systems. Interest in financial applications is essential, but experience in finance is not a primary factor in our hiring. Benefits and compensation are highly competitive. ********************************************************** The above job description is just a starting point in terms of possible duties and seniority. We can be very flexible for the right person. If you are interested or if you know of anyone who might be interested, let me know the best way to get in touch and we can discuss details. Thank you, Charles Weitzer Senior Recruiter Voleon Capital Management LP Charles(a)Voleon.com<mailto:Charles@Voleon.com> Office: 510.704.9870 x 7012 Mobile: (510) 558-9182 www.Voleon.com

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Re: [Haskell-cafe] [Haskell-beginners] How would I increment or otherwise change a value in a record with “Simon-ness”
by Sumit Sahrawat, Maths & Computing, IIT (BHU) 05 Aug '15

05 Aug '15

More suitable for the haskell-cafe. Routing. On 6 August 2015 at 02:52, Michael Litchard <michael(a)schmong.org> wrote: > > The below code is from this tutorial http://dev.stephendiehl.com/hask/ > > it illustrates very well how to operate on values from records with > "Simon-ness" (illustrated below). What I am struggling with is how to > modify values inside records with "Simon-ness", say incrementing "age". I > keep thinking it has to do with the way Label is defined with the > constructor Get. Could I add another constructor Put? > > {-# LANGUAGE DataKinds #-}{-# LANGUAGE KindSignatures #-}{-# LANGUAGE MultiParamTypeClasses #-}{-# LANGUAGE FunctionalDependencies #-}{-# LANGUAGE FlexibleInstances #-}{-# LANGUAGE FlexibleContexts #-}{-# LANGUAGE StandaloneDeriving #-}{-# LANGUAGE ExistentialQuantification #-}{-# LANGUAGE ConstraintKinds #-} > > import GHC.TypeLits > newtype Field (n :: Symbol) v = Field { unField :: v } deriving Show > data Person1 = Person1 > { _age :: Field "age" Int > , _name :: Field "name" String > } > data Person2 = Person2 > { _age' :: Field "age" Int > , _name' :: Field "name" String > , _lib' :: Field "lib" String > } > deriving instance Show Person1deriving instance Show Person2 > data Label (l :: Symbol) = Get > class Has a l b | a l -> b where > from :: a -> Label l -> b > instance Has Person1 "age" Int where > from (Person1 a _) _ = unField a > instance Has Person1 "name" String where > from (Person1 _ a) _ = unField a > instance Has Person2 "age" Int where > from (Person2 a _ _) _ = unField a > instance Has Person2 "name" String where > from (Person2 _ a _) _ = unField a > > age :: Has a "age" b => a -> b > age pnt = from pnt (Get :: Label "age") > > name :: Has a "name" b => a -> b > name pnt = from pnt (Get :: Label "name") > -- Parameterized constraint kind for "Simon-ness" of a record.type Simon a = (Has a "name" String, Has a "age" Int) > > spj :: Person1 > spj = Person1 (Field 56) (Field "Simon Peyton Jones") > > smarlow :: Person2 > smarlow = Person2 (Field 38) (Field "Simon Marlow") (Field "rts") > > > catNames :: (Simon a, Simon b) => a -> b -> String > catNames a b = name a ++ name b > > addAges :: (Simon a, Simon b) => a -> b -> Int > addAges a b = age a + age b > > > names :: String > names = name smarlow ++ "," ++ name spj-- "Simon Marlow,Simon Peyton Jones" > > ages :: Int > ages = age spj + age smarlow-- 94 > > > _______________________________________________ > Beginners mailing list > Beginners(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners > > -- Regards Sumit Sahrawat

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Fwd: Syntax extension - adding import support to let/where bindings
by Mike Meyer 05 Aug '15

05 Aug '15

Arg. Didn't send this to the list. ---------- Forwarded message --------- From: Mike Meyer <mwm(a)mired.org> Date: Wed, Aug 5, 2015 at 12:16 PM Subject: Re: [Haskell-cafe] Syntax extension - adding import support to let/where bindings To: Evan Laforge <qdunkan(a)gmail.com> On Wed, Aug 5, 2015 at 11:43 AM Evan Laforge <qdunkan(a)gmail.com> wrote: > And while "you don't have to use it" is > always brought up, it seems to me the more successful the feature is > the more likely you do have to use it. > "You don't have to use it" is a canard, and that argument needs to be killed whenever and wherever it arises. Sure, I don't have to use it. But the tools I use have to support it, so it'll make them bigger and slower, so I'm paying the price for "it" even if I don't use it. If I'm on a team, I probably have to either waste time arguing with other people to get them not to use it, or at least explain why I didn't use it. And that latter will come up every time I share code with other people, which we do want to encourage people to do. And that brings us to the real issue of why "You don't have to use it" is simply false. Reusing other people's code is a critical part of any software development environment. If they use, I have to understand it in order to understand their code. Even more than I have to in order to explain why I don't use it. So, no matter what I think of some feature, if it exists, the tools I use will almost certainly have to support it, and I'll have to understand the feature well enough to decipher code that uses it, and probably defend my decision not to use it. I don't see that this is in any way less of a burden on me than if I chose to use it.

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Re: [Haskell-cafe] Syntax extension - adding import support to let/where bindings
by Oliver Charles 05 Aug '15

05 Aug '15

On Wed, Aug 5, 2015 at 3:12 PM Moritz Kiefer <moritz.kiefer(a)gmail.com> wrote: > Am Mittwoch, 5. August 2015 14:59:54 UTC+2 schrieb Mike Ledger: >> >> This would be really handy to have. You could also have import "blocks", >> like >> >> import Foo in { >> ... >> } >> >> Where {...} is a new layout block, I guess. >> > Is *let* not exactly this block feature? > Indeed, in my post I use let bindings to achieve this: let import CSS in [ width (px 50) ] You could also add other local bindings to your scope: let import CSS sizeInPx = px 50 in [ width sizePx, height sizeInPx ] (Note that just like let the other bindings have access to the symbols that were imported) *ocharles*

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Re: [Haskell-cafe] ambiguous module name Network.URI
by Kees Bleijenberg 05 Aug '15

05 Aug '15

Thanks Christopher, -----Oorspronkelijk bericht----- Check out the Hackage page for network-uri: https://hackage.haskell.org/package/network-uri The parseURI function is in the version of network you are using already so there is no need to import modules from network-uri. ---------------------------------------- If I remove the import of Network-URI and leave the import Network.Http and use parseURI, ghc complains: not in scope parseURI. Do I have to change someting in the packages? Kees

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Why is the no tuple syntax for sum types
by Silvio Frischknecht 05 Aug '15

05 Aug '15

Protuct types have this nice tuple syntax (a,Char,Int),(a,'c',1). Why is there no syntax like this for Sum types (a|Char|Int),(||1). This would be very usefull for some more explicit error handling. I.E. You have a library that has errors. Error1, .. ErrorN. Currently there are only two ways of making a function that can throw Error3 and Error8. Use 'Dynamic' typed Exceptions or make a general Error type that is the sum of all Errors. In both cases it is not clear from the type of the function what Errors can occur. With sumTuples you could just return (Result|Error3|Error8). Also, I guess I'm just one of those people who occasionally confuse Left and Right :) Silvio Frischknecht

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Re: [Haskell-cafe] ANNOUNCE: Haskell Platform 7.10.2-a
by Mark Lentczner 04 Aug '15

04 Aug '15

As promised in the Haskell Platform 7.10.2 announcement, we have now release Haskell Platform 7.10.2-a. The only changes from 7.10.2 are: text-1.2.1.3 - to work around the issue with text literals in GHC 7.10.2 fgl-5.5.2.1 - this release changes no APIs, but fixes builds with older GHCs Available, as always, from: https://www.haskell.org/platform/ - Mark

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Typeclassable typeclass?
by Zemyla 04 Aug '15

04 Aug '15

I apologize if this has been discussed and dismissed before, but I figured with Typeable being made entirely automatic by GHC, this might have a shot at working. What if there were a typeclass called Typeclassable, whose definition would be: class (Typeable a) => Typeclassable a where typeClass :: (Typeable c) => proxy c -> proxy' a -> ((c a) => b) -> b -> b So, for a simple example, you might have: nubT :: (Typeclassable a, Eq a) => [a] -> [a] nubT ls = typeClass (Proxy :: Proxy Ord) ls (nubOrd ls) (nub ls) where nubOrd is a suitable implementation of nub that requires Ord a. Basically, my first thought for the implementation of Typeclassable is that it contains all the dictionaries for a in a hashtable, and searches through them with the typeRep of c. So: 1) Can this be implemented with GHC as it is now? 2) Could this be implemented at all with any reasonable amount of work? 3) Should this be implemented? Would the benefits outweigh the costs?

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Freeze/thaw fusion
by William Yager 04 Aug '15

04 Aug '15

Has anyone done any research into fusing operations that involve thawing some data, mutating it, and then freezing it again? Data.Vector does something similar; it turns vectors into streams, operates on the streams, and then turns them back into vectors. It can fuse these operations by removing intermediate However, I've done a bit of preliminary work on a fusion system that works on operations of the form runST $ do x' <- thaw x foo x' freeze x' and yields promising results in some cases. This could be useful for data structures that aren't stream-able, but suffer from lots of unnecessary freezing and unfreezing. This seems like the sort of thing that someone would have already done, so I wanted to check if anyone knew of any previous work on this. Cheers, Will

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STM Finalizers
by Michael Schröder 04 Aug '15

04 Aug '15

Hi everyone, I want to finally announce some work I did as part of my master's thesis [1]. It's an extension to GHC's STM implementation. The main idea is to introduce a new primitive function atomicallyWithIO :: STM a -> (a -> IO b) -> IO b Like the existing atomically operation, atomicallyWithIO performs an STM computation. Additionally, it takes a *finalizer*, which is an arbitrary I/O action that can depend on the result of the STM computation, and combines it with the transaction in such a way that: 1. The finalizer is only performed if the STM transaction is guaranteed to commit. 2. The STM transaction only commits if the finalizer finishes without raising an exception. A motivation of why this is useful: Say we want to save the results of some STM transaction, i.e. persist them to disk. Currently, this is not possible in a transactionally safe way. The naive approach would be to first atomically perform some STM computation and then independently serialise its result: do x <- atomically m serialize x There are two issues with this. First, another thread could perform a second transaction and serialise it before we have finished serialising ours, which could result in an inconsistent state between the memory of our program and what is stored on disk. Secondly, the function serialize might not terminate at all; it could throw an exception or its thread could die. Again we would end up with an inconsistent state and possibly data loss. We might try to simply move serialisation into the atomic block, but to do this we have to circumvent the types, which should already be a huge red flag: atomically $ do x <- m unsafeIOToSTM (serialize x) The problem here is of course that an STM transaction can retry many times, which will also result in serialize being executed many times, which is probably not something we want. Furthermore, if the thread receives an asynchronous exception, the transaction will abort in an orderly fashion, while serialize, with its irrevocable side effects, cannot be undone. But with finalizers, the solution is easy: atomicallyWithIO m serialize I've written a small example application that uses finalizers and other stuff from my thesis to build a lightweight STM database framework: [2] There are more possible uses cases besides serialisation (such as interactive transactions) and some interesting issues surrounding finalizers (like nesting of transactions) which are discussed in greater detail in my thesis [1], which also includes a formal operational semantics of the whole thing. I have implemented finalizers in my fork of GHC [3], if any of you want to play around with them yourself. The atomicallyWithIO function is exported from the GHC.Conc.Sync module. Cheers, Michael [1] https://github.com/mcschroeder/thesis [2] https://github.com/mcschroeder/social-example [3] https://github.com/mcschroeder/ghc

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happstack-authenticate 2
by Corentin Dupont 04 Aug '15

04 Aug '15

Hello, I'm a bit confused about the routeAuthenticate and authenticateState bits in the new happstack-authenticate. It seems that I have to do this in the beginning of my application: (_, routeAuthenticate, authenticateState) <- liftIO $ initAuthentication Nothing (const $ return True) [ initPassword "http://localhost:8000/#resetPassword" "example.org" , initOpenId] Where this should be done? In the main? If possible I'd prefer to delay it because my main is web-agnotic. Where should I store those two values? Should I put them in my monad stack (I have a StateT)? Is the routeAuthenticate really necessary? It looks a bit cumbersome to carry it around everywhere in the states. Thanks, Corentin

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2 PhD studentships in Computer Science at the University of Dundee
by Ekaterina Komendantskaya 04 Aug '15

04 Aug '15

Hello, School of Sciences and Engineering, University of Dundee, advertises two PhD studentships in the area of Computer Science. Applicants interested in Programming languages, Logic and Automated/Interactive theorem proving are encouraged. Further details are available here: https://docs.google.com/document/d/1ggi4S2DBS1IqB3fqyFBkKbrArYJRUiOybIfW7Vd… Best regards, Katya Ekaterina Komendantskaya Senior Lecturer, Head of PhD Studies Room 1.04, Queen Mother Building School of Computing, University of Dundee Scotland, DD14HN Tel: (+44) 01382384820

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Type error depending on scope of pattern matching
by htebalaka 03 Aug '15

03 Aug '15

I'm curious if anyone can tell me why moving the pattern matching in these two examples makes it fail to compile, and what can be done to resolve the same issue in either of the latter two examples. As far as I can tell these should be equivalent. Unfortunately the solution used in the first examples won't work in the later ones due to the existential quantification. I've been asking on #haskell for a few days but haven't been able to find anyone who knows what the issue is. Code is available here: http://lpaste.net/137586 <http://lpaste.net/137586> -- View this message in context: http://haskell.1045720.n5.nabble.com/Type-error-depending-on-scope-of-patte… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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New Functional Programming Job Opportunities
by Functional Jobs 03 Aug '15

03 Aug '15

Here are some functional programming job opportunities that were posted recently: OCaml server-side developer at Ahrefs Research http://functionaljobs.com/jobs/8827-ocaml-server-side-developer-at-ahrefs-r… Cheers, Sean Murphy FunctionalJobs.com

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Different forms for RandomT?
by Zemyla 03 Aug '15

03 Aug '15

Normally, a monad transformer to provide a random number generator would be of the form StateT g, where g is a RandomGen. But I've seen some libraries (like QuickCheck) define their RandomT as: newtype RandomT g m a = RandomT { runRandomT :: g -> m a } with their monadic bind operation defined as (RandomT m) >>= f = RandomT $ \g -> let (ga, gb) = split g in m ga >>= (\a -> runRandomT (f a) gb) and return and fail as in ReaderT. Can someone describe the advantages and disadvantages of doing RandomT this way? I mean, if your generator has a subpar split operation (and most do), this will obviously exacerbate any problems with it. Does it give any comparable advantages?

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Annotated ASTs, and the tension between Bound, Free, and Cofree...
by Merijn Verstraaten 02 Aug '15

02 Aug '15

Hi, So I'm playing around with using bound to define a simple AST using the bound library to deal with substitution/abstraction. Being a lazy haskeller I figured that ASTs map nicely onto Free and that I could get all the necessary Applicative, Monad, etc. instances for free by using something like: newtype Expr a = Expr { unExpr :: Free (ExprF Expr) a } deriving (Functor,Applicative,Monad,Foldable,Traversable) data ExprF f a = App (f a) (f a) | Lam Type (Scope () f a) | TmTrue | TmFalse | If (f a) (f a) (f a) deriving (Eq,Ord,Show,Read,Functor,Foldable,Traversable) Now, for an AST to be useful, it has to be annotated with things like source location, type info, etc. So I started looking into how to accomplish this in a way where it's easy to add/modify annotations on any node of the AST. My initial idea was to use FreeT with ((,) a) as a base monad for annotations, but I quickly realised this fails, because "((,) a)" is only a Monad if 'a' is a Monoid and there's no sensible Monoid for type information/source locations. Then I looked around more and realised that this actually sounds a lot like Cofree. But here's where I run into problems. Bound expects the type of variables to be in the functor position of my Expr type, whereas Cofree expects the type of *annotations* to be in the functor position. So I can't figure out an elegant way to both use bound to deal with substitution for me *and* use Cofree to deal with annotations, since there's no way to make the types line up sanely. So my question boils down too: Has anyone done all the hard work for me already? i.e. how can I have an annotated AST with substitution *and* an easy way to modify the annotations, without writing a ton of boiler plate to deal with substitution and/or annotations? Cheers, Merijn

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atomicity and visibility of readIORef / writeIORef
by Alexey Egorov 02 Aug '15

02 Aug '15

Hello haskellers, is there any guarantees of atomicity and visibility of read-write operations on IORefs, like Java have for volatile variables?

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ANNOUNCE: Haskell Platform 7.10.2
by Mark Lentczner 01 Aug '15

01 Aug '15

Haskellers, we are pleased to announce the release of Haskell Platform 7.10.2 *get it here... <https://www.haskell.org/platform/>* Highlights include: - GHC 7.10.2 - packages & tools bumped to very latest - major package updates to: - attoparsec - case-insensitive - cgi - GLUT, GLURaw, OpenGL, & OpenGLRaw - mtl - network - primitive & vector - QuickCheck - random - syb - text - new website - new installer script for linux - 10 bugs closed: Issues · haskell/haskell-platform <https://github.com/haskell/haskell-platform/issues?utf8=%E2%9C%93&q=is%3Acl…> This is our first release concurrent with GHC's release. You'll notice that the version number has changed to reflect that from now on, our aim is to keep HP releases sync'd to GHC releases. *Note:* Haskell Platform download pages are often cached - you may need to hit reload to see the release. *About the last minute update to text package:* *tl;dr: Vast majority of code will never notice the difference. Go ahead and get the HP now and start enjoying 7.10.2 You can always update to the point release when it comes out.* Despite all the testing, GHC central noticed just a day before release that there was a regression with text literals in 7.10.2. It was possible to work around the issue via a change to the text package, and text-1.2.1.3 was released just today. Alas, there wasn't enough time to re-build and test the platform installers between then and now, so this release has text-1.2.1.1. There will be a point release (7.10.2.1) of the Platform this weekend or next with the updated text package. The issue does not result in incorrect code, only slow compilation times for very text literal laden code (as in thousands of literals), and slightly higher one-time construction cost at run-time. In full stack builds and many other test builds, these slow downs were inconsequential. *Windows Notes:* The Haskell Platform on Windows now provides the MSys2 tools. These tools are needed when installing packages that use conf-tools (generally rare). These tools are not automatically placed onto the PATH in order avoid troubles due to MSys2 tools which have the same name as a standard Windows tool (e.g., echo, find, dir). - Mark "release monad" Lentczner Special thanks to Erik Rantappa, Wasif Hasan Baig, & Ben Gamari for the new web site. Randy Polen for Windows build wrangling.

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digestive-functors and listOf
by Neil 31 Jul '15

31 Jul '15

I've been able to use digestive-functors with simple forms successfully in a snap application; however, I'm getting stuck when trying to handle a list of hidden inputs. There is something I'm not quite getting on how to use 'listOf'. Can anyone point me in the right direction? Thanks. The rendered html from a previous page includes the following hidden fields: <div id='messageForm.recipients' class='inputList'> <input type='hidden' name='messageForm.recipients.indices' value='0' /> <input type='hidden' id='messageForm.recipients.-1.email' name='messageForm.recipients.-1.email' value /> <input type='hidden' id='messageForm.recipients.0.email' name='messageForm.recipients.0.email' value='emai1l(a)email.com' /> <input type='hidden' id='messageForm.recipients.1.email' name='messageForm.recipients.1.email' value='email2(a)email.com' /> </div> The data types are: data ConfirmMessage = ConfirmMessage { isoDate :: T.Text, subject :: T.Text, body :: T.Text, action :: T.Text, recipients :: [Recipient]} deriving (Show) data Recipient = Recipient { email :: T.Text } deriving (Show) The forms are: messageForm :: (Monad m) => Form T.Text m ConfirmMessagemessageForm = ConfirmMessage <$> "isoDate" .: stringRead "Missing ISOdate" Nothing <*> "subject" .: stringRead "Subject required" Nothing <*> "body" .: stringRead "Body required" Nothing <*> "action" .: stringRead "Missing action" Nothing <*> "recipients" .: listOf recipientForm' Nothing recipientForm' :: (Monad m) => Formlet T.Text m RecipientrecipientForm'= Recipient <$> "email" .: stringRead "Missing email" Nothing Error message: Couldn't match type `Text.Digestive.Form.Internal.FormTree m0 v0 m0 Recipient' with `Maybe Recipient -> Form T.Text m Recipient' Expected type: Formlet T.Text m Recipient Actual type: Text.Digestive.Form.Internal.FormTree m0 v0 m0 Recipient Relevant bindings include recipientForm' :: Formlet T.Text m Recipient (bound at src/Handler/TradeNotifyConfirm.hs:224:1) In the expression: Recipient <$> "email" .: stringRead "Missing email" Nothing In an equation for `recipientForm'': recipientForm' = Recipient <$> "email" .: stringRead "Missing email" Nothing Thanks in advance, Neil

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Taking over package erlang
by Poór Artúr 31 Jul '15

31 Jul '15

Hi, The package erlang (https://hackage.haskell.org/package/erlang) wasn't updated since 2008, and it became fairly outdated since then. The author was contacted half a year ago, but he didn't respond. So following the instructions on Hackage I state my intention to take over. I have made the package functional again, and I would like to make it available on Hackage. Artúr

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New GHC fails to specialize imported function
by William Yager 31 Jul '15

31 Jul '15

Hello all, I just installed the new Haskell platform for OS X. It seems to have caused a major performance regression for a program I'm working on, making it well over 25x slower. The culprit appears to be that the new GHC (7.10.2) fails to specialize an imported function. If I manually add a SPECIALIZE pragma, performance goes back to around what it used to be. The code in question is located at https://github.com/wyager/HNet . As it stands, the code takes about 30 seconds to run on my machine. With the previous haskell-platform, it only took about .9 seconds. If I modify Operations.hs and uncomment the SPECIALIZE pragma, runtime goes down to about 1.1 seconds (still slower for some reason, but not awful). To test, compile with -O2 (as the program makes heavy use of Data.Vector, which requires -fspec-constr for performance). Additionally, my experience doesn't seem to match https://downloads.haskell.org/~ghc/7.8.4/docs/html/users_guide/pragmas.html… in that if I add an INLINABLE pragma at the site of (••)'s definition and then try to SPECIALIZE it in a different file after importing, GHC tells me "Warning: SPECIALISE pragma on INLINE function probably won't fire: ‘••’". Cheers, Will

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Excessive whitespace with tasty all of a sudden
by Rogan Creswick 31 Jul '15

31 Jul '15

I recently have been refactoring chatter, and finally got the test suite semi-operational (after lots of extensive changes, both to the library and to the tests to add tests and to make them compatible with the new APIs). Somewhere during the changes, the whitespace output by tasty to format the test status lines nicely has grown out of hand. For example, tests that used to show the OK message on the same line, now look like this (see below). Has anyone else run across this? Does anyone have debugging suggestions? Thanks! Rogan NLP.POS.LiteralTagger Empty tagger always tags as UNK: OK +++ OK, passed 100 tests. Initial training Simple training test: OK Duplicate entries -- use the last value.: OK

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ANNOUNCE: GHC version 7.10.2
by Ben Gamari 30 Jul '15

30 Jul '15

===================================================================== The (Interactive) Glasgow Haskell Compiler -- version 7.10.2 ===================================================================== The GHC Team is pleased to announce a new bug-fix release of GHC, 7.10.2. There have been a number of significant bug fixes since the 7.10.1 (with over 70 defects fixed). These include fixes affecting type-checker correctness, runtime stability, and compiler performance. For this reason we highly recommend that users of 7.10.1 upgrade quickly. Note that due to changes made in this release to GHC's optimizer, previously fragile-but-working rewrite rules may fail to fire. One example of this was found in the widely-used `text` package late in the release cycle, which manifested in long compilation times and poor code generation for `Text` literals (see [Trac #10528]). Users are advised to use text >=1.2.1.2 which includes more robust rewrite rules. The full release notes including a complete listing of the changes in this release can be found here, https://downloads.haskell.org/~ghc/7.10.2/docs/html/users_guide/release-7-1… [Trac #10528]: https://ghc.haskell.org/trac/ghc/ticket/10528 How to get it ~~~~~~~~~~~~~ Both binary and source tarballs of GHC itself are available on the release download page, https://www.haskell.org/ghc/download_ghc_7_10_2 For a more smoother, better integrated experience users are encouraged to find a Haskell distribution. While these alternatives may not yet include 7.10.2, they offer tools and libraries to quickly get users up and running, as well as potentially better integration with the host operating system and package manager. See, https://www.haskell.org/downloads for more details. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below), https://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms supported by GHC and the people responsible for them can be found here, https://ghc.haskell.org/trac/ghc/wiki/Platforms https://ghc.haskell.org/trac/ghc/wiki/CodeOwners Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: https://ghc.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ If you enjoy using GHC, you will likely also enjoy contributing to it! We are always looking for new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC developer site, https://ghc.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at https://www.haskell.org/mailman/listinfo/glasgow-haskell-users https://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see https://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: https://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: https://www.haskell.org/ghc/reportabug Hashes & Signatures ~~~~~~~~~~~~~~~~~ In https://downloads.haskell.org/~ghc/7.10.2/ you will find a signed copy of the SHA256 hashes for the tarballs, using my GPG key, Benjamin Gamari <ben(a)well-typed.com> Fingerprint: FFEB 7CE8 1E16 A36B 3E2D ED6F 2DE0 4D4E 97DB 64AD

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ANN: hsqml-datamodel(-vinyl) = data model for QML
by Marcin Mrotek 29 Jul '15

29 Jul '15

Hello, I've just uploaded a package that enables using Haskell records in QML table- or listviews: http://hackage.haskell.org/package/hsqml-datamodel There's also an implementation for Vinyl: http://hackage.haskell.org/package/hsqml-datamodel-vinyl Best regards, Marcin Mrotek

2 1

haskell-src-exts maintenance
by Matthew Pickering 28 Jul '15

28 Jul '15

Dear List, There are a large number of untriaged pull requests and issues currently open on the issue tracker for haskell-src-exts. The tool is widely used by tool writers but the last commit to the project is now over 6 months ago. I think it is important to get this work merged and update the parser to support modern language features introduced in GHC 7.8 and 7.10. I would personally be capable of helping with this effort but before doing so I would appreciate a comment from the current maintainers as to the current status of the project. So, 1. Does anyone know if Niklas or Peter plan to return to the project? 2. Is there anyone else who is interested in updating the HSE parser? Matt

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Names in a record changes read behavior?
by Mike Meyer 27 Jul '15

27 Jul '15

Ok, this all works as expected: λ> data Point = Point Float Float deriving (Show, Read) λ> Point 1.0 1.0 Point 1.0 1.0 λ> read "Point 1.0 1.0" *** Exception: Prelude.read: no parse λ> read "Point 1.0 1.0" :: Point Point 1.0 1.0 But now we add names to the values in the Point, and things change: λ> data Point = Point {x :: Float, y :: Float } deriving (Show, Read) λ> Point 1.0 1.0 Point {x = 1.0, y = 1.0} λ> read "Point 1.0 1.0" *** Exception: Prelude.read: no parse λ> read "Point 1.0 1.0" :: Point *** Exception: Prelude.read: no parse λ> read "Point {x = 1.0, y = 1.0 }" :: Point Point {x = 1.0, y = 1.0} OK, why won't read accept the same syntax as the REPL? I can see wanting Read and Show to be inverses of each other, though I think it's a bit misguided. But if we're going to be that strict about them being inverses, shouldn't we also insist that the READ eval print loop only accept what read will accept?

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Re: [Haskell-cafe] Strange "ambiguity" problems thanks to GADTs
by wren romano 27 Jul '15

27 Jul '15

On Tue, Jul 7, 2015 at 3:35 AM, Simon Peyton Jones <simonpj(a)microsoft.com> wrote: > If you post a repro case someone (even me) might help. The devil is always in the details. The smallest repro I can come up with (which is still related to the actual problem) is as follows. In case it matters for the solution, there are a number of important bits I've erased. Most importantly, the inferType function is actually mutually recursive with a checkType function, though that doesn't seem to be the cause of the problem. {-# LANGUAGE DataKinds, PolyKinds, GADTs #-} data Type = Fun Type Type data Sing :: Type -> * where SFun :: Sing i -> Sing j -> Sing (Fun i j) data AST :: (Type -> *) -> Type -> * where App :: ast (Fun a b) -> ast a -> AST ast b class ABT (abt :: Type -> *) where view :: abt a -> AST abt a unview :: AST abt a -> abt a class WellTypedABT (abt :: Type -> *) where unviewWT :: Sing a -> AST abt a -> abt a typeOf :: abt a -> Sing a data TypeCheckMonad a = TCM { unTCM :: a } instance Functor TypeCheckMonad where fmap f = TCM . f . unTCM instance Applicative TypeCheckMonad where pure = TCM TCM f <*> TCM x = TCM (f x) instance Monad TypeCheckMonad where return = pure TCM x >>= k = k x inferType :: (ABT abt, WellTypedABT abt') => abt a -> TypeCheckMonad (abt' a) inferType e0 = case view e0 of App e1 e2 -> do e1' <- inferType e1 case typeOf e1' of SFun typ2 typ3 -> do e2' <- inferType e2 return . unviewWT typ3 $ App e1' e2' -- Live well, ~wren

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Munich Haskell Meeting, 2015-07-29 @ 19:30
by Christian Neukirchen 27 Jul '15

27 Jul '15

Dear all, This week, our monthly Munich Haskell Meeting will take place again on Wednesday, July 29 at Cafe Puck at 19h30. For details see here: http://www.haskell-munich.de/dates If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-jul-2015/ Everybody is welcome! cu, -- Christian Neukirchen <chneukirchen(a)gmail.com> http://chneukirchen.org

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fun fact: value of truncate -Infinity depends on optimisation level
by Johannes Waldmann 26 Jul '15

26 Jul '15

Just for general amusement - I was debugging very strange behaviour in a straightforward deterministic program, where the output value seemed to depend on ghc's optimization level. Well, it turned out that I (accidentally) computed truncate (logBase 2 0) :: Int, and that's 0 with -O0, but -9223372036854775808 with -O2. https://github.com/jwaldmann/matchbox/issues/19

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ANN: haddock-2.16.1
by Mateusz Kowalczyk 24 Jul '15

24 Jul '15

Hi, We're glad to announce Haddock 2.16.1. It is mostly a bugfix release: I inline the changelog at the bottom. It should work fine with 7.10.x GHC family. The packages are already on Hackage: haddock for the executable, haddock-api for the guts and use from Haskell and haddock-library which is the comment parser. It should also be shipping with GHC 7.10.2. I think two things are worth mentioning before: * The pending mathjax PR[1] is going to be included in future release of Haddock. As it is likely to break the interface file version, I am putting it off a bit to bundle with other possibly interface-breaking changes. * Our GSOC student has successfully completed first part of his project[2]. It involves native source code highlighting and perhaps more excitingly, source hyperlinking: you should now be able to click on identifiers to be taken to their definitions. This change is not in 2.16.1 as it is rather recent so we erred on the side of safety when picking what to release with GHC 7.10.2. You can try it by building current Haddock master, should work with 7.10.x family. As usual, if you want to contribute, please do so on GitHub. We're also on IRC under #haddock. Thanks! Changes in version 2.16.1 * Don't default to type constructors for out-of-scope names (#253 and #375) * Fix Hoogle display of constructors (#361) * Fully qualify names in Hoogle instances output (#263) * Output method documentation in Hoogle backend (#259) * Don't print instance safety information in Hoogle (#168) * Expand response files in arguments (#285) * Build the main executable with -threaded (#399) * Use SrcSpan of declarations for inferred type sigs (#207) * Fix cross-module instance locations (#383) * Fix alignment of Source link for instances in Firefox (#384) [1]: https://github.com/haskell/haddock/pull/397 [2]: https://github.com/haskell/haddock/pull/410 -- Mateusz K.

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Re: [Haskell-cafe] Discussion: The CLOEXEC problem
by Donn Cave 23 Jul '15

23 Jul '15

Quoth David Turner <dave.c.turner(a)gmail.com>, ... > Non-inheritable-by-default makes sense to me - if you forget to clear > FD_CLOEXEC when you meant to then your program breaks loudly and obviously; This is where we differ. First, it isn't fair to say we "forget" to clear FD_CLOEXEC, if in pre-existing software we didn't have a CLOEXEC bit to clear. Rather, in the existing set of applications that have an exec - whether in Haskell code or not - we can expect that some subset of them will start to behave differently. Maybe behave better, but in any case likely a surprise to everyone because we've reversed the default on some large subset of file descriptors. And I think it's very optimistic to predict that the breakage will be obvious - the obvious effects will naturally be obvious, but I personally am not up to accounting for all non-obvious cases. And there's the other FDs - inherited, non-Haskell, sockets - so we still need another solution if we're serious about fixing the problem. Donn

1 0

Bibliographic references on advantages of functional languages for refactoring
by Nicola Gigante 23 Jul '15

23 Jul '15

Hi all, I’m writing my master thesis, which is not itself about functional programming but I use Haskell as the language chosen for the implementation of whatever I’m talking about. To motivate the choice more than “I like the language” I’m arguing that since I’m implementing experimental stuff and I’ll need to change the code and refactor very often, a strongly typed language is what I need. I wrote this sentence: "Strongly-typed programming eases the refactoring process by leveraging the compiler to spot wrong transformations before they turn into runtime bugs” Since this thesis is not itself about functional programming this sentence needs to be backed by something. In other words I need to cite some published paper where this is said/surveyed/proved/whatever. So the question: can you help me find referentiable published work relative to how strongly-typed functional programming eases refactoring? A survey or some case-study report or some functional pearl, dunno. Thank you very much in advance, Nicola

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ghc-mod: cannot satisfy yesod-static
by Denis Shevchenko 22 Jul '15

22 Jul '15

Hi all! I'm trying to use ghc-mod with my Yesod-project, but I get this error: $ ghc-mod ghc-mod: <command line>: cannot satisfy -package-id yesod-static-1.4.0.4-c893310d859222b1b20461f9fdb4d916 (use -v for more information) My project builds correctly. In my .cabal-file I see this dependency: build-depends: base >= 4 && < 5 , yesod >= 1.4.0 && < 1.5 , yesod-core >= 1.4.0 && < 1.5 , yesod-auth >= 1.4.0 && < 1.5 , yesod-static >= 1.4.0 && < 1.5 ... I use LTS-2.18, and I see this package in ~/.stack/snapshots/x86_64-osx/lts-2.18/7.8.4/lib/x86_64-osx-ghc-7.8.4/: ... yesod-static-1.4.0.4 ... So, what can I do? Please help me. Sincerely, Denis.

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ANNOUNCE: fgl-5.5.2.0 and fgl-arbitrary-0.2.0.0
by Ivan Lazar Miljenovic 22 Jul '15

22 Jul '15

I'm pleased to announce that I've (finally!) just released version 5.5.2.0 of [fgl]. Major changes in this release include a test suite, refactorings, code clean-ups and the following potentially breaking changes (in that they were previously unspecified or incorrect): - `nodeRange` and `nodeRangeM` for the various graph data structures erroneously returned `(0,0)` for empty graphs (making them indistinguishable from graphs containing the single node `0`). They now match the default implementation of throwing an error. - The behaviour of `delLEdge` when dealing with multiple edges was unspecified; it now deletes only a single edge and the new function `delAllLEdge` deletes all edges matching the one provided. All changes can be found in the changelog. [fgl]: https://hackage.haskell.org/package/fgl Along with this I'm releasing version 0.2.0.0 of [fgl-arbitrary] (i.e. the "I finally build against the version on Hackage" release). [fgl-arbitrary]: https://hackage.haskell.org/package/fgl-arbitrary -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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Fwd: Re: Strange "ambiguity" problems thanks to GADTs
by Alexander Eyers-Taylor 22 Jul '15

22 Jul '15

Sorry I forgot to reply to the list Alex -------- Forwarded Message -------- Subject: Re: [Haskell-cafe] Strange "ambiguity" problems thanks to GADTs Date: Wed, 22 Jul 2015 13:24:56 +0100 From: Alexander Eyers-Taylor <aeyerstaylor11(a)gmail.com> To: Andres Loeh <mail(a)andres-loeh.de> Hi In this case what happens in the type checker is that after checking the start of the let we give the variable e1 a type (say abt0a) Then we enter the case. When entering the case, as SFun introduces a constaint (SFun is actually of type (a ~ Maybe j) => Sing a). As we have a constraint we cannot then unify the variables. The reason we can't unify is that we cant tell that (a ~ Maybe j) does not imply (abt0 ~ abt'). In GHC 6.12 the old type inference algotrithm was used. This had some problems as it didn't always infer a priciple type for GADTs. The new inference algorithm OutsideIn does this in a more principled way. In the non-indexed versions when we do the pattern match no constaints are introduced so we can typecheck as usual Alex On 22/07/15 07:59, Andres Loeh wrote: > Hi. > > I've drastically reduced the example. This program triggers the same error: > >> {-# LANGUAGE GADTs, KindSignatures #-} >> >> data Sing :: * -> * where >> SFun :: Sing (Maybe j) >> >> class WellTypedABT (abt :: * -> *) where >> typeOf :: abt a -> Sing a >> >> inferType :: (WellTypedABT abt') => abt a -> abt' a >> inferType e1 = >> let e1' = inferType e1 >> in case typeOf e1' of >> SFun -> e1' > Btw, this compiles fine with ghc-6.12 (as does a version of the > original program if we replace the data kinds involved by equivalent > kind-*-datatypes). > > Cheers, > Andres > > On Wed, Jul 22, 2015 at 1:11 AM, wren romano <winterkoninkje(a)gmail.com> wrote: >> On Wed, Jul 8, 2015 at 9:14 PM, Richard Eisenberg <eir(a)cis.upenn.edu> wrote: >>> I think GADTs are a red herring here -- this is the classic show/read ambiguity dressed up. In the code below, how should GHC determine the type of e1' or e2'? There's no way to know. >> Except that when I erase the indices, everything works just fine: >> >> >> {-# LANGUAGE KindSignatures, GADTs #-} >> >> data Type = Fun Type Type >> >> data AST :: * -> * where >> App :: ast -> ast -> AST ast >> >> class ABT (abt :: *) where >> view :: abt -> AST abt >> unview :: AST abt -> abt >> >> class WellTypedABT (abt :: *) where >> unviewWT :: Type -> AST abt -> abt >> typeOf :: abt -> Type >> >> data TypeCheckMonad a = TCM { unTCM :: a } >> >> instance Functor TypeCheckMonad where >> fmap f = TCM . f . unTCM >> >> instance Applicative TypeCheckMonad where >> pure = TCM >> TCM f <*> TCM x = TCM (f x) >> >> instance Monad TypeCheckMonad where >> return = pure >> TCM x >>= k = k x >> >> inferType >> :: (ABT abt, WellTypedABT abt') >> => abt >> -> TypeCheckMonad abt' >> inferType e0 = >> case view e0 of >> App e1 e2 -> do >> e1' <- inferType e1 >> case typeOf e1' of >> Fun typ2 typ3 -> do >> e2' <- inferType e2 >> return . unviewWT typ3 $ App e1' e2' >> >> >> -- >> Live well, >> ~wren >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

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Why there is no instance Generic Word?
by Alexey Vagarenko 21 Jul '15

21 Jul '15

There is instance Generic Int, but not Generic Word. Also no Generic instances for Int8, Int16, Int32, Int64, Word8, Word16, Word32, Word64.

1 0

Message passing library
by Corentin Dupont 21 Jul '15

21 Jul '15

Hello, what would you recommend as a message passing library? Essentially, I would to replace this library http://hackage.haskell.org/package/eprocess by something more mainstream. It is used in Hint-server: http://hackage.haskell.org/package/hint-server Thanks! Corentin

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Several Experienced Developers for Advanced Functional Programming - Ocaml, Haskell, Scala - compiler technology, LLVM, C, etcetera, and Martin-Löf type theory, static analysis, our main target is embedded software
by Johan Glimming 20 Jul '15

20 Jul '15

Hi folks, There are openings at Functor, Sweden, including also remote work, except for Scala consultants who must immediately relocate: Do you want to be part of the journey as the Functor startup research spin-off innovates the future of software engineering? Do you want to make a difference? Do you want to devote your talents where it can have incredible impact on the entire software industry? Functor, Sweden, is again looking for brilliant minds, essentially co-founders as a generous equity program will after a certain threshold time make sure developers, building the company indeed, also own what they are building. Please apply on LinkedIn, closing soon take action if interested: https://www.linkedin.com/jobs2/consumer/overview/60296037 We use Haskell, OCaml, LLVM and our tools are closely tied to the C programming language and indeed to functional programming. Embedded software market is one target market, and skills in compiler design, type systems and operational semantics is key to our teams though we look for optimised teams as a whole, and your particular skill set may or may not include a PhD, but surely industrial experience. We have openings for Research Engineers and have some renown Research Engineers already. Research collaboration is key to our success and projects planned including a large EU project CONSTRUCTOR next year. We have strong industrial partners and some very high-profile customers internationally. The customer-driven journey is still at an early stage, while founded in 2011, and your contributions would be key to our success. Scala consultants will be sent straight from the top down into projects at Ericsson for very challenging work. For these three consultants we require an exceptionally strong background with Scala projects as we team up with Typesafe and secure projects that can only be matched by exceptional Scala developers. Our Functor Scalor™ is oriented somewhat differently than Scala, see www.domainspecific.org<http://www.domainspecific.org> for some initial information on that products that appeals to very large companies at this stage, while Functor Prevent™ is suitable for just about any software development projects, currently doing static analysis with dependent types and automatic testing for C code, such as the Erlang code base, Twitter’s MySQL branch or embedded software at large, see www.functorprevent.com<http://www.functorprevent.com> or www.static-analysis.org<http://www.static-analysis.org>, and also the standalone tool www.functor.se/prevent<http://www.functor.se/prevent> which secures systems including a project at a customer with a range of 100 MEUR/each equipment investments, all relying on the VxWorks C code where our Functor Prevent™ delivers its value to prevent up to 50% of the bugs in certain projects, already with its current R1 feature set! [cid:BA7C0361-C40F-4993-820E-420FB0B1543B@in.functor.se]<https://www.linkedin.com/jobs2/consumer/overview/60296037> Instructions and information, please read carefully the last paragraph on what we need to evaluate candidates adequately: https://www.linkedin.com/pulse/openings-functional-programmers-swedish-star… Read up with links above to our webpages (last link), and postings on LinkedIn and Facebook: https://www.linkedin.com/pulse/future-software-engineering-johan-glimming?t… Facebook eg: http://www.facebook.com/functor Webpage has more information, linked to one the main posting above for some key webpages to check: www.functor.se<http://www.functor.se> [3230fbd.png]<https://www.linkedin.com/pulse/openings-functional-programmers-swedish-star…> Welcome to apply and be part of an exciting journey ahead with a very important mission to turn software engineering into a discipline at last, backed by industrial productification for years and R&D that have never reached the software industry due to its inherent complexity, now mature, and now with proven market fit with Functor Prevent™ and Functor Scalor™ being used in heavy duty projects but much more to come! It’s Martin-Löf / dependent type theory inside our tools. Best, Johan — Dr Johan Glimming Chief Executive Officer at Functor AB, Chairman at Functor Group AB Request a meeting or schedule a call: www.doodle.com/glimming<http://www.doodle.com/glimming> Mobile: +46-76-7646000<tel:+46-76-7646000> Direct: +46-8-55005505<tel://+46-8-55005505> Main: +46-8-55005500<tel:+46-8-55005500> Assistant: +46-8-55005501<tel://+46-8-55005501> Skype: glimming<skype://glimming> Twitter: @glimming<https://www.twitter.com/glimming> LinkedIn: se.linkedin.com/in/glimming<http://se.linkedin.com/in/glimming> Functor AB, Box 7070, 164 07 Kista, SWEDEN<x-apple-data-detectors://3/1> Web: www.functorgroup.com<http://www.functorgroup.com/> Twitter: @functors<https://www.twitter.com/functors/> UK tel: +44-1223-911400<tel:+44-1223-911400> US tel: +1-(415)-513-0090 — ANY INFORMATION DISCLOSED DIRECTLY OR INDIRECTLY IN, OR IMPLIED BY, THIS EMAIL, INCLUDING ATTACHMENTS, EXTERNAL REFERENCES OR APPENDICES, IS STRICTLY CONFIDENTIAL AND/OR PROPRIETARY AND IS INTENDED ONLY FOR USE BY FUNCTOR GROUP AB, SWEDEN, REG. NR. 556972-3736, AND ITS SUBSIDIARIES – OR BY A THIRD PARTY STRICTLY IN FUNCTOR GROUP AB’S OR ITS SUBSIDIARIES' DIRECT INTEREST, BUT ONLY FOR THOSE PARTIES LISTED AS DESIGNATED RECIPIENTS AND PARTIES WITH PRIOR WRITTEN PERMISSION. ANY UNAUTHORISED RELEASE OR USE OF THIS INFORMATION IS PROHIBITED AND PUNISHABLE BY LAW. YOU SHOULD IMMEDIATELY UPON RECEIVING THIS E-MAIL, YOU SHOULD IMMEDIATELY CONTACT THE SENDER OR FUNCTOR. OUR LAWYERS AT LEGAL(a)FUNCFTORGROUP.COM<mailto:LEGAL@FUNCFTORGROUP.COM> OR +46-8-55005517 ARE AVAILABLE AS NEEDED.

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Where else is EclipseFP available since SourceForge seems to be partially down?
by KC 20 Jul '15

20 Jul '15

Where else is EclipseFP available since SourceForge seems to be partially down? -- -- Sent from an expensive device which will be obsolete in a few months! :D Casey

4 3

Add IsNumeric (similar to IsString and IsList)
by Michael Baikov 19 Jul '15

19 Jul '15

Hi Cafe! Now that we have OverloadedList and OverloadedStrings extensions it might make sense to add something similar for numerals - right now if you want to be able to specify some items as numbers you have to implement Num instance, unfortunately not everything that can be represented as number can have sensible operations required by Num: negation makes no sense for set of natural numbers for example, multiplication for some applications of currency values which results in Num instance full of (*) = error "No multipication for Foos", (+) = error "No addition for Foos". I don't have any statistics from hackage or github, but in codebase I'm working with there are 3 such instances. Proposal: add OverloadedNumerals language pragma, IsNumeric typeclass and some methods to make that class useful with behavior similar to Lists and Strings.

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Re: [Haskell-cafe] The evil GADTs extension in ghci 7.8.4 (maybe in other versions too?)
by Edward Z. Yang 19 Jul '15

19 Jul '15

GHC used to always generalize let-bindings, but our experience with GADTs lead us to decide that let should not be generalized with GADTs. So, it's not like we /wanted/ MonoLocalBinds, but that having them makes the GADT machinery simpler. This blog post gives more details on the matter: https://ghc.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 Edward Excerpts from Ki Yung Ahn's message of 2015-06-04 20:37:27 -0700: > Such order dependent could be very confusing for the users. I thought I > turned off certain feature but some other extension turning it on is > strange. Wouldn't it be better to decouple GADT and MonoLocalBinds? > > 2015년 06월 04일 20:31에 Edward Z. Yang 이(가) 쓴 글: > > This is because -XGADTs implies -XMonoLocalBinds. > > > > Edward > > > > Excerpts from Ki Yung Ahn's message of 2015-06-04 20:29:50 -0700: > >> \y -> let x = (\z -> y) in x x > >> > >> is a perfectly fine there whose type is a -> a. > >> (1) With no options, ghci infers its type correctly. > >> (2) However, with -XGADTs, type check fails and raises occurs check. > >> (3) We can remedy this by supplying some additional options > >> (4) Howver, if you put -XGADTs option at the end, it fails again :( > >> > >> > >> kyagrd@kyahp:~$ ghci > >> GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help > >> Loading package ghc-prim ... linking ... done. > >> Loading package integer-gmp ... linking ... done. > >> Loading package base ... linking ... done. > >> Prelude> :t \y -> let x = (\z -> y) in x x > >> \y -> let x = (\z -> y) in x x :: t -> t > >> Prelude> :q > >> Leaving GHCi. > >> > >> > >> kyagrd@kyahp:~$ ghci -XGADTs > >> GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help > >> Loading package ghc-prim ... linking ... done. > >> Loading package integer-gmp ... linking ... done. > >> Loading package base ... linking ... done. > >> Prelude> :t \y -> let x = (\z -> y) in x x > >> > >> <interactive>:1:30: > >> Occurs check: cannot construct the infinite type: t0 ~ t0 -> t > >> Relevant bindings include > >> x :: t0 -> t (bound at <interactive>:1:11) > >> y :: t (bound at <interactive>:1:2) > >> In the first argument of ‘x’, namely ‘x’ > >> In the expression: x x > >> Prelude> :q > >> Leaving GHCi. > >> > >> > >> ~$ ghci -XGADTs -XNoMonoLocalBinds -XNoMonomorphismRestriction > >> GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help > >> Loading package ghc-prim ... linking ... done. > >> Loading package integer-gmp ... linking ... done. > >> Loading package base ... linking ... done. > >> Prelude> :t \y -> let x = (\z -> y) in x x > >> \y -> let x = (\z -> y) in x x :: t -> t > >> Prelude> :q > >> Leaving GHCi. > >> > >> > >> ~$ ghci -XNoMonoLocalBinds -XNoMonomorphismRestriction -XGADTs > >> GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help > >> Loading package ghc-prim ... linking ... done. > >> Loading package integer-gmp ... linking ... done. > >> Loading package base ... linking ... done. > >> Prelude> :t \y -> let x = (\z -> y) in x x > >> > >> <interactive>:1:30: > >> Occurs check: cannot construct the infinite type: t0 ~ t0 -> t > >> Relevant bindings include > >> x :: t0 -> t (bound at <interactive>:1:11) > >> y :: t (bound at <interactive>:1:2) > >> In the first argument of ‘x’, namely ‘x’ > >> > > _______________________________________________ > > Glasgow-haskell-users mailing list > > Glasgow-haskell-users(a)haskell.org > > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users > > >

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Re: [Haskell-cafe] Type signature for function where function parameter is used twice?
by Ivan Lazar Miljenovic 19 Jul '15

19 Jul '15

(Re-CC'ing Cafe) I think what's happening here is that when you do "apply f1 f1", the two c's and d's don't actually match with each other. But when you do it with applyBoth, they *have* to match each other. As a comparison, compare: :t (read, read) (read, read) :: (Read a, Read a1) => (String -> a, String -> a1) and :t Control.Monad.join read Control.Monad.join (,) read :: Read a => (String -> a, String -> a) I'm not sure how you could define such a function to do what you're requesting; my attempt is this: applyBoth :: (forall a b a2 b2. arr a b -> arr a2 b2) -> D arr a b -> D arr a2 b2 applyBoth f = apply f f but whilst ghci accepts it, I couldn't actually seem to use it (lots of errors about being unable to match types). On 19 July 2015 at 17:15, Clinton Mead <clintonmead(a)gmail.com> wrote: > Thanks for your reply Ivan > > Here's a full code example ( http://ideone.com/1K3Yhw ): > > --- > > data D c a b = D (c a b) (c b a) > > apply :: (c a b -> c a2 b2) -> (c b a -> c b2 a2) -> D c a b -> D c a2 b2 > apply f1 f2 (D x y) = D (f1 x) (f2 y) > > applyBoth f = apply f f > > f :: Int -> String > f = show > > g :: String -> Int > g = read > > h :: Int -> Int > h = (*2) > > join :: (a -> b) -> (c -> d) -> ((a, c) -> (b, d)) > join f g (x, y) = (f x, g y) > > x1 = D f g > > f1 = join h > > y1 = apply f1 f1 x1 -- This compiles > y2 = apply g g x1 where g = f1 -- Also works > > z1 = applyBoth f1 x1 -- This fails > > main = return () > > --- > > You see, with "y1" and "y2", a different "f1" instantiation (is that the > right word) of "f1" is chosen. Even when I let "g = f1", each "g" passed to > apply is different, the first operates on "Int -> String", the second, > "String -> Int". > > On the face of it, if: > > f x = g x x > > Then well, you should be able to replace "g x x" with "f x" wherever you see > it. > > But it seems in this case this doesn't work. Surely Haskell doesn't require > me to "repeat myself", and there's a way to write "applyBoth", instead of > having to write "apply f f" (note the repetition of f) all the time? > > I assume there's some type signature I can give "applyBoth f" so it can be > used just like "apply f f" but I can't work out what it is. > > On Sun, Jul 19, 2015 at 10:23 AM, Ivan Lazar Miljenovic > <ivan.miljenovic(a)gmail.com> wrote: >> >> On 19 July 2015 at 10:13, Clinton Mead <clintonmead(a)gmail.com> wrote: >> > Lets say I've got the following data type: >> > >> > data D c a b = D (c a b) (c b a) >> > >> > And I define a function to manipulate it: >> > >> > apply :: (c a b -> c a2 b2) -> (c b a -> c b2 a2) -> D c a b -> D c a2 >> > b2 >> > apply f1 f2 (D x y) = D (f1 x) (f2 y) >> > >> > This is all fine. But I want a shorter function if (f1 = f2). So I >> > write: >> > >> > applyBoth f = apply f f >> > >> > I originally thought that if "apply f f" is valid, then logically >> > "applyBoth >> > f" should also be valid. But it seems that type inference results in >> > applyBoth only working for functions "c a a -> c a2 a2". >> >> applyBoth f = apply f f >> >> In apply, (f1 :: c a b -> c a2 b2) and (f2 :: c b a -> c b2 a2). >> >> So for "apply f f" to typecheck, we must have that a ~ b and a2 ~ b2 >> (as the above two type signatures must match since f1 = f2). >> >> So we must have that (f :: c a a -> c a2 a2). >> >> > >> > Is there a way to type "applyBoth" so it works for all functions that >> > would >> > work simply by repeating them twice in "apply"? >> >> I'm not sure what you mean; what else would make sense? Can you >> provide an example? >> >> -- >> Ivan Lazar Miljenovic >> Ivan.Miljenovic(a)gmail.com >> http://IvanMiljenovic.wordpress.com > > -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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Type signature for function where function parameter is used twice?
by Clinton Mead 19 Jul '15

19 Jul '15

Lets say I've got the following data type: data D c a b = D (c a b) (c b a) And I define a function to manipulate it: apply :: (c a b -> c a2 b2) -> (c b a -> c b2 a2) -> D c a b -> D c a2 b2 apply f1 f2 (D x y) = D (f1 x) (f2 y) This is all fine. But I want a shorter function if (f1 = f2). So I write: applyBoth f = apply f f I originally thought that if "apply f f" is valid, then logically "applyBoth f" should also be valid. But it seems that type inference results in applyBoth only working for functions "c a a -> c a2 a2". Is there a way to type "applyBoth" so it works for all functions that would work simply by repeating them twice in "apply"?

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ICFP 2015 Call for Participation
by David Van Horn 18 Jul '15

18 Jul '15

[ Early registration ends 3 August. ] ===================================================================== Call for Participation ICFP 2015 20th ACM SIGPLAN International Conference on Functional Programming and affiliated events August 30 - September 5, 2015 Vancouver, British Columbia, Canada http://icfpconference.org/icfp2015/ ===================================================================== ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. The conference covers the entire spectrum of work, from practice to theory, including its peripheries. A full week dedicated to functional programming: 1 conference, 1 symposium, 11 workshops, tutorials, programming contest results, student research competition, and mentoring workshop * Program: http://icfpconference.org/icfp2015/program.html * Accepted Papers: http://icfpconference.org/icfp2015/accepted.html * Affiliated Events: http://icfpconference.org/icfp2015/affiliated.html * Local arrangements (including travel and accommodation): http://icfpconference.org/icfp2015/local.html * Registration is available via: https://regmaster4.com/2015conf/ICFP15/register.php Early registration is due 3 August, 2015. * Programming contest, 7-10 August, 2015: http://icfpcontest.org/ * Follow @icfp_conference on twitter for the latest news: http://twitter.com/icfp_conference There are several events affiliated with ICFP: Sunday, August 30 Haskell Implementors Workshop Workshop on Higher-order Programming with Effects Workshop on Generic Programming Programming Languages Mentoring Workshop Ally Skills Tutorial Monday, August 31 – Wednesday, September 2 ICFP Thursday, September 3 Workshop on Functional High-Performance Computing Haskell Symposium – Day 1 ML Family Workshop Commercial Users of Functional Programming – Day 1 Friday, September 4 Erlang Workshop Haskell Symposium – Day 2 OCaml Workshop Commercial Users of Functional Programming – Day 2 Scheme and Functional Programming Workshop Saturday, September 5 Functional Art, Music, Modeling and Design Commercial Users of Functional Programming – Day 3 Conference Organizers General Chair: Kathleen Fisher, Tufts University Program Chair: John Reppy, University of Chicago Local Arrangements Chair: Ronald Garcia, University of British Columbia Industrial Relations Chair: Anil Madhavapeddy, University of Cambridge Workshop Co-Chairs: Tom Schrijvers, KU Leuven Nicolas Wu, University of Bristol Programming Contest Chair: Joe Kiniry, Galois Student Research Competition Chair: Andrew Kennedy, Microsoft Research Mentoring Workshop Co-Chairs: Ronald Garcia, University of British Columbia Stephanie Weirich, University of Pennsylvania Publicity Chair: David Van Horn, University of Maryland Video Chair: Iavor Diatchki, Galois Student Volunteer Co-Chairs: Felipe Bañados Schwerter, University of British Columbia Gabriel Scherer, INRIA Mobile App Chair: Reid Holmes, University of Waterloo Industrial partners: Platinum partners Jane Street Capital Gold partners Anonymous donor Ahrefs Google Mozilla Research Oracle Labs Silver partners Bloomberg Tsuru Capital Galois The University of Chicago Bronze partners Erlang Solutions FireEye IntelliFactory PivotCloud Systor Vest =====================================================================

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Strange error message with PolyKinds
by Nikolay Amiantov 17 Jul '15

17 Jul '15

Hi Cafe, I've bumped into a strange error message -- it looks like an obvious bug, but maybe there's something that I'm just not aware of: GHCi, version 7.10.1: http://www.haskell.org/ghc/ :? for help ghci> type Test a = a ghci> type Huh = Test <interactive>:3:1: Type synonym ‘Test’ should have 1 argument, but has been given none In the type declaration for ‘Huh’ So far, so good: ghci> :set -XPolyKinds ghci> type Test a = a ghci> type Huh = Test <interactive>:6:1: Type synonym ‘Test’ should have 2 arguments, but has been given 1 In the type declaration for ‘Huh’ (Notice the number of arguments reported in the second case) -- Nikolay.

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OCL 2015: ** Deadline Extension ** Submit Your Paper Until July 26, 2015
by Achim D. Brucker 17 Jul '15

17 Jul '15

(Apologies for duplicates) If you are working on the foundations, methods, or tools for OCL or textual modelling, you should now finalise your submission for the OCL workshop! *** The submission deadline has been extended to July 26th, 2015! *** CALL FOR PAPERS 15th International Workshop on OCL and Textual Modeling Tools and Textual Model Transformations Co-located with ACM/IEEE 18th International Conference on Model Driven Engineering Languages and Systems (MODELS 2015) September 28th, 2015, Ottawa, Canada http://ocl2015.lri.fr Modeling started out with UML and its precursors as a graphical notation. Such visual representations enable direct intuitive capturing of reality, but some of their features are difficult to formalize and lack the level of precision required to create complete and unambiguous specifications. Limitations of the graphical notations encouraged the development of text-based modeling languages that either integrate with or replace graphical notations for modeling. Typical examples of such languages are OCL, textual MOF, Epsilon, and Alloy. Textual modeling languages have their roots in formal language paradigms like logic, programming and databases. The goal of this workshop is to create a forum where researchers and practitioners interested in building models using OCL or other kinds of textual languages can directly interact, report advances, share results, identify tools for language development, and discuss appropriate standards. In particular, the workshop will encourage discussions for achieving synergy from different modeling language concepts and modeling language use. The close interaction will enable researchers and practitioners to identify common interests and options for potential cooperation. Topics of interest include (but are not limited to) =================================================== - Mappings between textual modeling languages and other languages/formalisms - Algorithms, evaluation strategies and optimizations in the context of textual modeling languages for -- validation, verification, and testing, -- model transformation and code generation, -- meta-modeling and DSLs, and -- query and constraint specifications - Alternative graphical/textual notations for textual modeling languages - Evolution, transformation and simplification of textual modeling expressions - Libraries, templates and patterns for textual modeling languages - Tools that support textual modeling languages (e.g., verification of OCL formulae, runtime monitoring of invariants) - Complexity results for textual modeling languages - Quality models and benchmarks for comparing and evaluating textual modeling tools and algorithms - Successful applications of textual modeling languages - Case studies on industrial applications of textual modeling languages - Experience reports -- usage of textual modeling languages and tools in complex domains, -- usability of textual modeling languages and tools for end-users - Empirical studies about the benefits and drawbacks of textual modeling languages - Innovative textual modeling tools - Comparison, evaluation and integration of modeling languages - Correlation between modeling languages and modeling tasks This year, we particularly encourage submissions describing tools that support - in a very broad sense - textual modeling languages (if you have implemented OCL.js to run OCL in a web browser, this is the right workshop to present your work) as well as textual model transformations. Venue ===== The workshop will be organized as a part of MODELS 2015 Conference in Ottawa, Canada. It continues the series of OCL workshops held at UML/MODELS conferences: York (2000), Toronto (2001), San Francisco (2003), Lisbon (2004), Montego Bay (2005), Genova (2006), Nashville (2007), Toulouse (2008), Denver (2009), Oslo (2010), Zurich (2011, at the TOOLs conference), 2012 in Innsbruck, 2013 in Miami, and 2014 in Valencia, Spain. Similar to its predecessors, the workshop addresses both people from academia and industry. The aim is to provide a forum for addressing integration of OCL and other textual modeling languages, as well as tools for textual modeling, and for disseminating good practice and discussing the new requirements for textual modeling. Workshop Format =============== The workshop will include short (about 15 min) presentations, parallel sessions of working groups, and sum-up discussions. Submissions =========== Three types of papers will be considered: * short papers (between 6 and 8 pages) describing ideas, * tool papers (between 6 and 8 pages), and * full papers (between 12 and 16 pages) in LNCS format. Submissions should be uploaded to EasyChair (https://easychair.org/conferences/?conf=ocl20150) The program committee will review the submissions (minimum 2 reviews per paper, usually 3 reviews) and select papers according to their relevance and interest for discussions that will take place at the workshop. Accepted papers will be published online in a pre-conference edition of CEUR (http://www.ceur-ws.org) Important Dates =============== Submission of papers: July 26, 2015 (extended) Notification: August 21, 2015 Workshop date: September 28, 2015 Organizers ========== Achim D. Brucker, SAP SE, Germany Marina Egea, Indra Sistemas S.A., Spain Martin Gogolla, University of Bremen, Germany Frederic Tuong, Univ. Paris-Sud - IRT SystemX - LRI, France Programme Committee =================== Mira Balaban, Ben-Gurion University of the Negev, Israel Tricia Balfe, Nomos Software, Ireland Achim D. Brucker, SAP SE, Germany Fabian Buettner, Inria - Ecole des Mines de Nantes, France Jordi Cabot, Inria - Ecole des Mines de Nantes, France Dan Chiorean, Babes-Bolyai University, Romania Robert Clariso, Universitat Oberta de Catalunya, Spain Tony Clark, Middlesex University, UK Manuel Clavel, IMDEA Software Institute, Spain Carolina Dania, IMDEA Software Institute, Spain Birgit Demuth, Technische Universitat Dresden, Germany Marina Egea, Indra Sistemas S.A., Spain Geri Georg, Colorado State University, USA Martin Gogolla, University of Bremen, Germany Shahar Maoz, Tel Aviv University, Israel Istvan Rath, Budapest University of Technology and Economics, Hungary Bernhard Rumpe, RWTH Aachen, Germany Frederic Tuong, Univ. Paris-Sud - IRT SystemX - LRI, France Claas Wilke, Technische Universitat Dresden, Germany Edward Willink, Willink Transformations Ltd., UK Burkhart Wolff, Univ. Paris-Sud - LRI, France Steffen Zschaler, King's College, UK -- Dr. Achim D. Brucker, SAP SE, Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe Phone: +49 6227 7-52595, http://www.brucker.ch/

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very general directed hypergraphs over text
by Jeffrey Brown 17 Jul '15

17 Jul '15

I'm writing a graph class that generalizes the traditional mathematical graph: Nodes can be statements or relationships, and relationships ("edges") can involve any number of nodes, including other relationships. [1] describes the motivation in a little more detail. [2] explains the idea behind the major types -- Graph, Node, Stmt, and Rel. Of the .hs files in the project, at this time I believe only the primary one, Dwt.hs [3], deserves your attention. It is only about 100 lines of code. I am interested in any kind of feedback at all, no matter how minute in detail or expansive in scope. [4] lists what I already think might be likely problems and solutions. In particular I wonder whether I should interpret these two patterns: "case ni of Rel -> .. Stmt -> .." and "if (Maybe.isJust nMb) ... else error ..." as signs that I'm not completely solving the problem. I suspect it might be helpful to make the graph operations Maybe or Either, and use <|> on them -- but while I can monkey those words, I don't really know what I'm saying. [1] https://github.com/JeffreyBenjaminBrown/digraphs-with-text/blob/master/engl… [2] https://github.com/JeffreyBenjaminBrown/digraphs-with-text/blob/master/engl… [3] https://github.com/JeffreyBenjaminBrown/digraphs-with-text/blob/master/src/… [4] https://github.com/JeffreyBenjaminBrown/digraphs-with-text/blob/master/engl… Thank you, Jeff

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Call for Contributions: Haskell Implementors' Workshop 2015
by Josef Svenningsson 17 Jul '15

17 Jul '15

Call for Contributions ACM SIGPLAN Haskell Implementors' Workshop http://haskell.org/haskellwiki/HaskellImplementorsWorkshop/2015 Vancouver, Canada, 30 August, 2015 Co-located with ICFP 2015 http://www.icfpconference.org/icfp2015/ Important dates --------------- Proposal Deadline: Monday, 3 August, 2015 (midnight, anywhere on earth) Notification: Monday, 10 August, 2015 Workshop: Sunday, 30 August, 2015 The 7th Haskell Implementors' Workshop is to be held alongside ICFP 2015 this year in Vancouver. It is a forum for people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure, to share their work and discuss future directions and collaborations with others. Talks and/or demos are proposed by submitting an abstract, and selected by a small program committee. There will be no published proceedings; the workshop will be informal and interactive, with a flexible timetable and plenty of room for ad-hoc discussion, demos, and impromptu short talks. Attendance figures clearly reflect the growth of the Haskell user community and a constant interest in implementation aspects. Scope and target audience ------------------------- It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2015. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides and presented data available with the consent of the speakers. In the Haskell Implementors' Workshop, we hope to study the underlying technology. We want to bring together anyone interested in the nitty-gritty details behind turning plain-text source code into a deployed product. Having said that, members of the wider Haskell community are more than welcome to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- At this stage we would like to invite proposals from potential speakers for talks and demonstrations. We are aiming for 20 minute talks with 10 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 300 words. Submissions should be made via HotCRP. The website is: https://icfp-hiw15.hotcrp.com/ We will also have a lightning talks session which will be organised on the day. These talks will be 5-10 minutes, depending on available time. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Organisers ---------- * Richard Eisenberg (University of Pennsylvania) * Edward Kmett (S&P Capital IQ) * Hans-Wolfgang Loidl (Heriot-Watt University) * Trevor L. McDonell (Indiana University) * Deian Stefan (Stanford University) * Josef Svenningsson - chair (Chalmers University of Technology) Contact ------- * Josef Svenningsson <josef.svenningsson at chalmers.se>

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wiki username request: Eric
by Eric O'Connor 16 Jul '15

16 Jul '15

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