March 2016 - Haskell-Cafe

Reducing boilerplate
by Sylvain Henry 05 Mar '16

05 Mar '16

Hi, To write FFI bindings, I use c-storable-deriving [1] to automatically derive CStorable instances for many data types (the only difference between Storable and CStorable is that CStorable provides default methods for types that have Generic instances): {-# LANGUAGE DeriveGeneric #-} {-# LANGUAGE DeriveAnyClass #-} ... data X = X { fieldStatus :: Vector 24 Word8 , fieldPadding :: Word8 } deriving (Generic, CStorable) However I also need a Storable instance, hence I have to write (the "c*" methods are provided by CStorable): instance Storable X where peek = cPeek poke = cPoke alignment = cAlignment sizeOf = cSizeOf Is there a way to automatically generate this instance for every data that has an instance of CStorable? Ideally, I would like to say once and for all: instance CStorable a => Storable a where peek = cPeek poke = cPoke alignment = cAlignment sizeOf = cSizeOf As I don't think it is currently possible, would it be sensible to add the support for automatically derived instances attached to classes (as a GHC extension)? Regards, Sylvain [1] https://hackage.haskell.org/package/c-storable-deriving

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Digraphs With Text: More flexible than graphs, eager to hear from you
by Jeffrey Brown 05 Mar '16

05 Mar '16

This is a demonstration of DWT, a data structure built from and more flexible than graphs. It is powered by the *wonderful* Functional Graph Library. We beseech your involvement! DWT is open-source and actively seeking co-developers. I would happily trade any and all the privilege of determining tasks, teaching haskell or math, learning anything, and receiving obligations. We surely have much knowledge to trade! Even just a "hey why don't you do [this]!" could be precious to me. This transcript makes tiny digressions about what monads make possible. > let g = empty :: Mindmap -- g is now an empty mindmap (which is a kind of graph). > g <- pure $ insStr "frog" g -- This inserts a string into g. > -- "g <- pure $" because we use the IO monad to redefine g. > -- Now g has one thing, the word frog: > v g $ nodes g -- This views every expression in g. (0,"0: frog") > -- The 0 before the comma is a count of how many expressions refer to that expression. None do, because none yet exist. Such contexts offer many possibilities for tracking where you are (the data) and how you got there (also kind of the data, and perhaps enabling a desirable kind of removal of self|redaction). > -- The second 0 is an FGL Node, the address of the string "frog". > -- Let's add more words: > g <- pure $ insStr "moist" g > g <- pure $ insStr "springy" g > -- Now g has three words: > v g $ nodes g (0,"0: frog") (0,"1: moist") (0,"2: springy") > -- Let's indicate that moist and springy are both qualities of frogs: > -- First, we'll create a template for relationships about qualities. > g <- pure $ insTplt "_ is a quality of _" g > v g $ nodes g (0,"0: frog") (0,"1: moist") (0,"2: springy") (0,":3 _ #(is a quality of) _") > -- The template has been inserted at node 3. Its address is preceded by a : to indicate that it is a template, as opposed to the string "_ is a quality of _". (That will seem more natural in the context of how relationships are displayed.) > -- Now we'll use the template at 3 to insert two relationships among the other nodes: > -- We could have added them in a single stage: > g <- pure $ fromRight $ insRel 3 [2,0] g >>= insRel 3 [1,0] > -- insRel 3 [1,0] inserts "moist is a quality of frog". > -- insRel 3 [2,0] inserts "springy is a quality of frog". > -- Both relationships use the template at node 3, and in both the second member is frog, at node 0. > -- Since the template at 3 relates 2 expressions, each list has length two. Templates can have any arity -- for instance, "_ does _ to _" has arity 3. > -- I used the monadic bind operator (>>=) because that way I only need to escape one Either monad (using fromRight) rather than two of them, one containing the other. > -- Inserting those two relationships worked: > v g $ nodes g (2,"0: frog") (1,"1: moist") (1,"2: springy") (2,":3 _ #(is a quality of) _") (0,"4:3 2: springy ##(is a quality of) 0: frog") (0,"5:3 1: moist ##(is a quality of) 0: frog") > -- When showing a relationship, the node (integer) listed first, before the :, is it's address, and the node listed after the : is the address of its template. > -- After the first two, any other node in a relationship is the address of the symbol(s) it appears just left of. > -- Notice that now the frog is in two relationships. One of those relationships involves springy, the other involves moist. > -- The # symbols are better explained later. > -- DWT can encode meta-statements, statements about other statements. As an example, next let's encode that maybe frogs are springy because they use rubber bands. > -- First we should insert a new string and a couple new templates for relationships. > g <- pure $ insTplt "maybe _ because _" g > g <- pure $ insStr "rubber bands" g > g <- pure $ insTplt "_ uses _" g > v g $ nodes g (2,"0: frog") (1,"1: moist") (1,"2: springy") (2,":3 _ #(is a quality of) _") (0,"4:3 2: springy ##(is a quality of) 0: frog") (0,"5:3 1: moist ##(is a quality of) 0: frog") (0,":6 #maybe _ #because _") (0,"7: rubber bands") (0,":8 _ #uses _") > -- Now we can encode the subexpression that frog uses rubber bands. > g <- pure $ fr $ insRel 8 [0,7] g > v g $ nodes g (3,"0: frog") (1,"1: moist") (1,"2: springy") (2,":3 _ #(is a quality of) _") (0,"4:3 2: springy ##(is a quality of) 0: frog") (0,"5:3 1: moist ##(is a quality of) 0: frog") (0,":6 #maybe _ #because _") (1,"7: rubber bands") (1,":8 _ #uses _") (0,"9:8 0: frog ##uses 7: rubber bands") > -- From those elements, we can encode that maybe frogs are springy because they use rubber bands. > g <- pure $ fr $ insRel 6 [4,9] g > v g $ nodes g (3,"0: frog") (1,"1: moist") (1,"2: springy") (2,":3 _ #(is a quality of) _") (1,"4:3 2: springy ##(is a quality of) 0: frog") (0,"5:3 1: moist ##(is a quality of) 0: frog") (1,":6 #maybe _ #because _") (1,"7: rubber bands") (1,":8 _ #uses _") (1,"9:8 0: frog ##uses 7: rubber bands") (0,"10:6 ####maybe 4:3 2: springy ##(is a quality of) 0: frog ####because 9:8 0: frog ##uses 7: rubber bands") At last I can explain the # symbols: They indicate how fast an expression binds. In the last, at node 10, the highest-level|slowest-binding relationship is "maybe _ because _". In the first _ of the maybe-because relationship is another relationship, one that binds faster and hence has fewer # symbols, between springy and frog. The strings "springy", "frog" and "rubber bands" can be thought of as atomic, "binding" even before the first-level relationships bind. This illustrates one of DWT's advantages over graphs. In a graph, an edge cannot be a member of another edge. By contrast, in DWT a relationship can involve other relationships. -- Jeffrey Benjamin Brown

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Month in Haskell Mode February 2016
by Gracjan Polak 04 Mar '16

04 Mar '16

Welcome Haskell Mode users, Haskell Mode progress report for February 2016. For previous issue see January 2015 <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…> . Reddit discussion <https://www.reddit.com/r/haskell/comments/48wrru/month_in_haskell_mode_febr…> . <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-February…>What is Haskell Mode? Haskell Mode is an umbrella project for multiple Emacs tools for efficient Haskell development. Haskell Mode is an open source project developed by a group of volunteers constantly looking for contributions. For more information how to help see https://github.com/haskell/haskell-mode. <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-February…>Important developments Fontification received improvements so that it closer follows Haskell lexical rules. It was necessary to change to syntax-propertize-function available only starting with Emacs 24. There was already an improvement to how modules are shown: We also have a Twitter account: @HaskellMode <https://twitter.com/HaskellMode>. Follow us! <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-February…>Issues closed in February - Disable Indentation #90 <https://github.com/haskell/haskell-mode/issues/90> - Break point highlighting #127 <https://github.com/haskell/haskell-mode/issues/127> - Type query from up to date file information #185 <https://github.com/haskell/haskell-mode/issues/185> - haskell-stylish-on-save with Yasnippet + ghc-mod sometimes removes import list #256 <https://github.com/haskell/haskell-mode/issues/256> - haskell-indentation mode can't parse -XDoAndIfThenElse syntax #321 <https://github.com/haskell/haskell-mode/issues/321> - haskell-indentation mode sometimes can't parse multiline string literals #324 <https://github.com/haskell/haskell-mode/issues/324> - Compatibility with column-enforce-mode and long literate (latex-style) comments #331 <https://github.com/haskell/haskell-mode/issues/331> - haskell-debug parse error #399 <https://github.com/haskell/haskell-mode/issues/399> - Use preprocessor highlighting from cc-mode #521 <https://github.com/haskell/haskell-mode/issues/521> - haskell-mode-contextual-space called on zero length identifier #572 <https://github.com/haskell/haskell-mode/issues/572> - In 12.34e-56 (a single number) both . and - are colorized as operators #628 <https://github.com/haskell/haskell-mode/issues/628> - haskell-doc-mode is not asynchronous wrt ghci process, unlike eldoc-mode #649 <https://github.com/haskell/haskell-mode/issues/649> - Fix haskell-customize #667 <https://github.com/haskell/haskell-mode/issues/667> - Use easy-mmode-defmap to define all keymaps #669 <https://github.com/haskell/haskell-mode/issues/669> - Multi line string editing #727 <https://github.com/haskell/haskell-mode/issues/727> - Implement backward-sexp #759 <https://github.com/haskell/haskell-mode/issues/759> - haskell-stylish-on-save causes double saving #788 <https://github.com/haskell/haskell-mode/issues/788> - haskell-mode becomes unresponsive when adding a language pragma #820 <https://github.com/haskell/haskell-mode/issues/820> - Use flycheck to manage error and warning overlays #821 <https://github.com/haskell/haskell-mode/issues/821> - [Discussion] Separation of concerns #836 <https://github.com/haskell/haskell-mode/issues/836> - [Discussion] Perhaps tag a release? Monthly releases? #842 <https://github.com/haskell/haskell-mode/issues/842> - Split up gifcasts.el and connect dependency to specific gifs in Makefile #848 <https://github.com/haskell/haskell-mode/issues/848> - Can't press enter in haskell interactive mode #876 <https://github.com/haskell/haskell-mode/issues/876> - haskell-process-load-or-reload and haskell-interactive-switch-back #955 <https://github.com/haskell/haskell-mode/issues/955> - Font lock should support mixed Bird and Latex style literate Haskell sources #1038 <https://github.com/haskell/haskell-mode/issues/1038> - Use syntax-propertize-function #1039 <https://github.com/haskell/haskell-mode/issues/1039> - Highlight errors inside string literals #1040 <https://github.com/haskell/haskell-mode/issues/1040> - Default indentation mode ought to support and use Johan Tibell's style by default #1042 <https://github.com/haskell/haskell-mode/issues/1042> - Support spaces in project paths for haskell-process-load-file or haskell-process-load-or-reload with errors in source file #1107 <https://github.com/haskell/haskell-mode/issues/1107> - haskell-process-path-* now allowed to be lists #1112 <https://github.com/haskell/haskell-mode/issues/1112> - haskell-font-lock-symbols no longer works #1120 <https://github.com/haskell/haskell-mode/issues/1120> - Indenting data types seems broken and not configurable #1125 <https://github.com/haskell/haskell-mode/issues/1125> - Error: defcustom for ‘haskell-indent-spaces’ fails to specify type #1126 <https://github.com/haskell/haskell-mode/issues/1126> - Reconsider word breaks for haskell-cabal-mode #1146 <https://github.com/haskell/haskell-mode/issues/1146> - haskell-forward-sexp should signal scan-error at the end of list like forward-sexp #1148 <https://github.com/haskell/haskell-mode/issues/1148> - Syntax highlighting is broken for quasiquoted code #1155 <https://github.com/haskell/haskell-mode/issues/1155> - Font lock module qualification differently #1157 <https://github.com/haskell/haskell-mode/issues/1157> - HTML manual Retina resolution animated gifs #1160 <https://github.com/haskell/haskell-mode/issues/1160> - Completion function hangs in REPL in multi-line editing mode #1173 <https://github.com/haskell/haskell-mode/issues/1173> - [Discussion] Interactive mode improvements #1176 <https://github.com/haskell/haskell-mode/issues/1176> - Fontification is too inefficient #1177 <https://github.com/haskell/haskell-mode/issues/1177> <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-February…>Pull requests merged in February - Use syntax-propertize-function #1050 <https://github.com/haskell/haskell-mode/pull/1050> - Require at least Emacs 24.1 #1055 <https://github.com/haskell/haskell-mode/pull/1055> - Define haskell-package struct's slots #1083 <https://github.com/haskell/haskell-mode/pull/1083> - Detect comma style #1099 <https://github.com/haskell/haskell-mode/pull/1099> - Cleanup haskell-compat.el #1103 <https://github.com/haskell/haskell-mode/pull/1103> - Ignore stack and cabal files from hasktags #1118 <https://github.com/haskell/haskell-mode/pull/1118> - Remove suggested imports completely #1121 <https://github.com/haskell/haskell-mode/pull/1121> - Support spaces in project directories #1123 <https://github.com/haskell/haskell-mode/pull/1123> - Use condition-case-unless-debug #1124 <https://github.com/haskell/haskell-mode/pull/1124> - Fontify True/False in cabal mode #1127 <https://github.com/haskell/haskell-mode/pull/1127> - Fix snapshot build #1128 <https://github.com/haskell/haskell-mode/pull/1128> - Add indentation tests for constructor and deriving #1129 <https://github.com/haskell/haskell-mode/pull/1129> - Align data declaration contructors in indentation #1130 <https://github.com/haskell/haskell-mode/pull/1130> - Remove haskell-package.el #1132 <https://github.com/haskell/haskell-mode/pull/1132> - Docstrings and documentation for haskell-process-path-*. #1135 <https://github.com/haskell/haskell-mode/pull/1135> - Add front-sticky property to read-only text in REPL #1136 <https://github.com/haskell/haskell-mode/pull/1136> - Stylish haskell after save #1137 <https://github.com/haskell/haskell-mode/pull/1137> - Make all define-key calls use kbd #1139 <https://github.com/haskell/haskell-mode/pull/1139> - Use haskell-interactive-switch in process-load #1140 <https://github.com/haskell/haskell-mode/pull/1140> - Revert "Stylish haskell after save" #1142 <https://github.com/haskell/haskell-mode/pull/1142> - Make keymap definition more consistent #1143 <https://github.com/haskell/haskell-mode/pull/1143> - Remove some outdated code #1144 <https://github.com/haskell/haskell-mode/pull/1144> - Fix #1146 by treating . as punctuation #1149 <https://github.com/haskell/haskell-mode/pull/1149> - Add test for forward-sexp-function #1151 <https://github.com/haskell/haskell-mode/pull/1151> - Better string animation #1152 <https://github.com/haskell/haskell-mode/pull/1152> - Properly find begin of a quasiquote #1156 <https://github.com/haskell/haskell-mode/pull/1156> - Implement backward case in haskell-forward-sexp #1158 <https://github.com/haskell/haskell-mode/pull/1158> - Improve font-lock #1159 <https://github.com/haskell/haskell-mode/pull/1159> - HTML manual fixup machinery #1161 <https://github.com/haskell/haskell-mode/pull/1161> - Deriving indentatation test #1162 <https://github.com/haskell/haskell-mode/pull/1162> - Make RET in REPL create new prompt with blank input #1163 <https://github.com/haskell/haskell-mode/pull/1163> - Revert "Remove suggested imports completely" #1165 <https://github.com/haskell/haskell-mode/pull/1165> - Fix haskell-hoogle to work with buffer local var #1167 <https://github.com/haskell/haskell-mode/pull/1167> - Support simple completions in non-interactive context. Support keyword completions #1172 <https://github.com/haskell/haskell-mode/pull/1172> <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-February…>Contributors active in February Arthur Fayzrakhmanov (Артур Файзрахманов), Chris Done, Christoph Ruegge, Daniel Bergey, Daniel Selinger, Fice T, Gracjan Polak, Kamil Dworakowski, Karl Smeltzer, Mike Sperber, Sergey Vinokurov, issue-dispenser, mrBliss <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-February…> Contributing Haskell Mode needs volunteers like any other open source project. For more information see: https://github.com/haskell/haskell-mode/wiki Also drop by our IRC channel: #haskell-emacs at irc.freenode.net. Thanks!

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Function that put elements in Left or Right side of Either depending on type
by Kristoffer Føllesdal 04 Mar '16

04 Mar '16

I want a function fun :: q -> Either a b where q is of type a or b. fun shall work in the following way fun x gives Left x if x :: a fun x gives Right x if x :: b Following is a more precise description of what I want. I have function fun1 and fun2 newtype Vec k b = V [(b,k)] deriving (Eq,Ord,Show) fun1 :: (Num k) => a -> Either a (Vec k a) fun1 = Left fun2 :: (Num k) => Vec k a -> Either a (Vec k a) fun2 = Right that work in the following way {- >>> fun1 6 Left 6 >>> fun2 (V[(6,1)]) Right (V [(6,1)]) -} I want a overloaded function ‘fun' such that {- >>> fun 6 Left 6 >>> fun (V[(6,1)]) Right (V[(6,1)]) -} I have tried to use a type class to do this (see code below). But when I try >>> fun 6 I get the following error Could not deduce (Num a0) from the context (Num a, Fun a b v) bound by the inferred type for ‘it’: (Num a, Fun a b v) => Either b (v b) at <interactive>:70:1-5 The type variable ‘a0’ is ambiguous When checking that ‘it’ has the inferred type it :: forall a b (v :: * -> *). (Num a, Fun a b v) => Either b (v b) Probable cause: the inferred type is ambiguous Is the someone that have know how I can solve this? Kristoffer ——— CODE ——— {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE FlexibleInstances #-} newtype Vec k b = V [(b,k)] deriving (Eq,Ord,Show) fun1 :: (Num k) => a -> Either a (Vec k a) fun1 = Left fun2 :: (Num k) => Vec k a -> Either a (Vec k a) fun2 = Right class Fun a b v where fun :: a -> Either b (v b) instance (Num k) => Fun t t (Vec k) where fun = fun1 instance (Num k) => Fun (Vec k t) t (Vec k) where fun = fun2

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Order of Map.fromListWith
by Niklas Hambüchen 03 Mar '16

03 Mar '16

Does anybody know why for fromListWith, the arguments to the combining function seem flipped? > import Data.Map > fromListWith (++) [('a',[1]),('a',[2])] fromList [('a',[2,1])] I often use it to group things by some key, e.g. postsByUserId :: Map Int [Int] postsByUserId = fromListWith (++) [ (userId, [postId]) | (userId, postId) <- posts ] and regularly get tricked by the postIds being reversed in the result. This is especially unintuitive to me since: > foldl (++) [] [[1],[2]] [1,2] > foldr (++) [] [[1],[2]] [1,2] Any ideas?

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Local mirrors of hackage
by Victor Miller 03 Mar '16

03 Mar '16

I have a computer that I work on which isn't directly connected to the internet, that I want to use Haskell on. In order to do that I want a local version of hackage. I was previously able to do this using mirror_hackage.py, but since hackage 2 came around this no longer works. Doing this would involve running something on a computer that *is* attached to the internet, and then transferring a bunch of files over to the other computer. Can someone point me to a recipe for doing this? Victor

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ICFP 2016 Final Call for Papers
by Lindsey Kuper 03 Mar '16

03 Mar '16

ICFP 2016 The 21st ACM SIGPLAN International Conference on Functional Programming http://conf.researchr.org/home/icfp-2016 Final Call for Papers Important dates --------------- Submissions due: Wednesday, March 16 2016, 15:00 (UTC) https://icfp2016.hotcrp.com (now open) Author response: Monday, 2 May, 2016, 15:00 (UTC) - Thursday, 5 May, 2016, 15:00 (UTC) Notification: Friday, 20 May, 2016 Final copy due: TBA Early registration: TBA Conference: Monday, 19 September - Wednesday, 21 September, 2016 Please note ----------- For the sake of lightweight double-blind reviewing, the submission procedure may take a little more time than in previous ICFPs; we recommend that you register your submission as early as possible (you can update your paper until the deadline). Scope ----- ICFP 2016 seeks original papers on the art and science of functional programming. Submissions are invited on all topics from principles to practice, from foundations to features, and from abstraction to application. The scope includes all languages that encourage functional programming, including both purely applicative and imperative languages, as well as languages with objects, concurrency, or parallelism. Topics of interest include (but are not limited to): - Language Design: concurrency, parallelism, and distribution; modules; components and composition; metaprogramming; type systems; interoperability; domain-specific languages; and relations to imperative, object-oriented, or logic programming. - Implementation: abstract machines; virtual machines; interpretation; compilation; compile-time and run-time optimization; garbage collection and memory management; multi-threading; exploiting parallel hardware; interfaces to foreign functions, services, components, or low-level machine resources. - Software-Development Techniques: algorithms and data structures; design patterns; specification; verification; validation; proof assistants; debugging; testing; tracing; profiling. - Foundations: formal semantics; lambda calculus; rewriting; type theory; monads; continuations; control; state; effects; program verification; dependent types. - Analysis and Transformation: control-flow; data-flow; abstract interpretation; partial evaluation; program calculation. - Applications: symbolic computing; formal-methods tools; artificial intelligence; systems programming; distributed-systems and web programming; hardware design; databases; XML processing; scientific and numerical computing; graphical user interfaces; multimedia and 3D graphics programming; scripting; system administration; security. - Education: teaching introductory programming; parallel programming; mathematical proof; algebra. - Functional Pearls: elegant, instructive, and fun essays on functional programming. - Experience Reports: short papers that provide evidence that functional programming really works or describe obstacles that have kept it from working. If you are concerned about the appropriateness of some topic, do not hesitate to contact the program chair. Abbreviated instructions for authors ------------------------------------ - By Wednesday, March 16 2016, 15:00 (UTC), submit a full paper of at most 12 pages (6 pages for an Experience Report), in standard SIGPLAN conference format, including figures but ***excluding bibliography***. The deadlines will be strictly enforced and papers exceeding the page limits will be summarily rejected. ***ICFP 2016 will employ a lightweight double-blind reviewing process.*** To facilitate this, submitted papers must adhere to two rules: 1. ***author names and institutions must be omitted***, and 2. ***references to authors' own related work should be in the third person*** (e.g., not "We build on our previous work ..." but rather "We build on the work of ..."). The purpose of this process is to help the PC and external reviewers come to an initial judgement about the paper without bias, not to make it impossible for them to discover the authors if they were to try. Nothing should be done in the name of anonymity that weakens the submission or makes the job of reviewing the paper more difficult (e.g., important background references should not be omitted or anonymized). In addition, authors should feel free to disseminate their ideas or draft versions of their paper as they normally would. For instance, authors may post drafts of their papers on the web or give talks on their research ideas. We have put together a document answering frequently asked questions that should address many common concerns: http://conf.researchr.org/track/icfp-2016/icfp-2016-papers#Submission-and-R… (last updated February 8, 2016). - Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. The material should be uploaded at submission time, as a single pdf or a tarball, not via a URL. This supplementary material may or may not be anonymized; if not anonymized, it will only be revealed to reviewers after they have submitted their review of your paper and learned your identity. - Each submission must adhere to SIGPLAN's republication policy, as explained on the web at: http://www.sigplan.org/Resources/Policies/Republication - Authors of resubmitted (but previously rejected) papers have the option to attach an annotated copy of the reviews of their previous submission(s), explaining how they have addressed these previous reviews in the present submission. If a reviewer identifies him/herself as a reviewer of this previous submission and wishes to see how his/her comments have been addressed, the program chair will communicate to this reviewer the annotated copy of his/her previous review. Otherwise, no reviewer will read the annotated copies of the previous reviews. Overall, a submission will be evaluated according to its relevance, correctness, significance, originality, and clarity. It should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. The technical content should be accessible to a broad audience. Functional Pearls and Experience Reports are separate categories of papers that need not report original research results and must be marked as such at the time of submission. Detailed guidelines on both categories are given below. Presentations will be videotaped and released online if the presenter consents. The proceedings will be freely available for download from the ACM Digital Library from at least one week before the start of the conference until two weeks after the conference. Formatting: Submissions must be in PDF format printable in black and white on US Letter sized paper and interpretable by Ghostscript. Papers must adhere to the standard SIGPLAN conference format: two columns, nine-point font on a ten-point baseline, with columns 20pc (3.33in) wide and 54pc (9in) tall, with a column gutter of 2pc (0.33in). A suitable document template for LaTeX is available at http://www.sigplan.org/Resources/Author/ Submission: Submissions will be accepted at https://icfp2016.hotcrp.com . Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. Author response: Authors will have a 72-hour period, starting at 15:00 UTC on Monday, 2 May, 2016, to read reviews and respond to them. ACM Author-Izer is a unique service that enables ACM authors to generate and post links on either their home page or institutional repository for visitors to download the definitive version of their articles from the ACM Digital Library at no charge. Downloads through Author-Izer links are captured in official ACM statistics, improving the accuracy of usage and impact measurements. Consistently linking the definitive version of ACM article should reduce user confusion over article versioning. After your article has been published and assigned to your ACM Author Profile page, please visit http://www.acm.org/publications/acm-author-izer-service to learn how to create your links for free downloads from the ACM DL. AUTHORS TAKE NOTE: The official publication date is the date the proceedings are made available in the ACM Digital Library. This date may be up to two weeks prior to the first day of your conference. The official publication date affects the deadline for any patent filings related to published work. Special categories of papers ---------------------------- In addition to research papers, ICFP solicits two kinds of papers that do not require original research contributions: Functional Pearls, which are full papers, and Experience Reports, which are limited to six pages. Authors submitting such papers may wish to consider the following advice. Functional Pearls ================= A Functional Pearl is an elegant essay about something related to functional programming. Examples include, but are not limited to: - a new and thought-provoking way of looking at an old idea - an instructive example of program calculation or proof - a nifty presentation of an old or new data structure - an interesting application of functional programming techniques - a novel use or exposition of functional programming in the classroom While pearls often demonstrate an idea through the development of a short program, there is no requirement or expectation that they do so. Thus, they encompass the notions of theoretical and educational pearls. Functional Pearls are valued as highly and judged as rigorously as ordinary papers, but using somewhat different criteria. In particular, a pearl is not required to report original research, but, it should be concise, instructive, and entertaining. Your pearl is likely to be rejected if your readers get bored, if the material gets too complicated, if too much specialized knowledge is needed, or if the writing is inelegant. The key to writing a good pearl is polishing. A submission you wish to have treated as a pearl must be marked as such on the submission web page, and should contain the words ``Functional Pearl'' somewhere in its title or subtitle. These steps will alert reviewers to use the appropriate evaluation criteria. Pearls will be combined with ordinary papers, however, for the purpose of computing the conference's acceptance rate. Experience Reports ================== The purpose of an Experience Report is to help create a body of published, refereed, citable evidence that functional programming really works ? or to describe what obstacles prevent it from working. Possible topics for an Experience Report include, but are not limited to: - insights gained from real-world projects using functional programming - comparison of functional programming with conventional programming in the context of an industrial project or a university curriculum - project-management, business, or legal issues encountered when using functional programming in a real-world project - curricular issues encountered when using functional programming in education - real-world constraints that created special challenges for an implementation of a functional language or for functional programming in general An Experience Report is distinguished from a normal ICFP paper by its title, by its length, and by the criteria used to evaluate it. - Both in the proceedings and in any citations, the title of each accepted Experience Report must begin with the words ``Experience Report'' followed by a colon. The acceptance rate for Experience Reports will be computed and reported separately from the rate for ordinary papers. - An Experience Report is at most six pages long. Each accepted Experience Report will be presented at the conference, but depending on the number of Experience Reports and regular papers accepted, authors of Experience reports may be asked to give shorter talks. - Because the purpose of Experience Reports is to enable our community to accumulate a body of evidence about the efficacy of functional programming, an acceptable Experience Report need not add to the body of knowledge of the functional-programming community by presenting novel results or conclusions. It is sufficient if the Report states a clear thesis and provides supporting evidence. The thesis must be relevant to ICFP, but it need not be novel. The program committee will accept or reject Experience Reports based on whether they judge the evidence to be convincing. Anecdotal evidence will be acceptable provided it is well argued and the author explains what efforts were made to gather as much evidence as possible. Typically, more convincing evidence is obtained from papers which show how functional programming was used than from papers which only say that functional programming was used. The most convincing evidence often includes comparisons of situations before and after the introduction or discontinuation of functional programming. Evidence drawn from a single person's experience may be sufficient, but more weight will be given to evidence drawn from the experience of groups of people. An Experience Report should be short and to the point: make a claim about how well functional programming worked on your project and why, and produce evidence to substantiate your claim. If functional programming worked for you in the same ways it has worked for others, you need only to summarize the results?the main part of your paper should discuss how well it worked and in what context. Most readers will not want to know all the details of your project and its implementation, but please characterize your project and its context well enough so that readers can judge to what degree your experience is relevant to their own projects. Be especially careful to highlight any unusual aspects of your project. Also keep in mind that specifics about your project are more valuable than generalities about functional programming; for example, it is more valuable to say that your team delivered its software a month ahead of schedule than it is to say that functional programming made your team more productive. If your paper not only describes experience but also presents new technical results, or if your experience refutes cherished beliefs of the functional-programming community, you may be better off submitting it as a full paper, which will be judged by the usual criteria of novelty, originality, and relevance. If you are unsure in which category to submit, the program chair will be happy to help you decide. Organizers ---------- General Co-Chairs: Jacques Garrigue (Nagoya University) Gabriele Keller (University of New South Wales) Program Chair: Eijiro Sumii (Tohoku University) Program Committee: Koen Claessen (Chalmers University of Technology) Joshua Dunfield (University of British Columbia, Canada) Matthew Fluet (Rochester Institute of Technology) Nate Foster (Cornell University) Dan Grossman (University of Washington, USA) Jurriaan Hage (Utrecht University) Roman Leshchinskiy (Standard Chartered Bank) Keisuke Nakano (The University of Electro-Communications) Aleksandar Nanevski (IMDEA Software Institute) Scott Owens (University of Kent) Sungwoo Park (Pohang University of Science and Technology) Amr Sabry (Indiana University) Tom Schrijvers (KU Leuven) Olin Shivers (Northeastern University) Walid Taha (Halmstad University) Dimitrios Vytiniotis (Microsoft Research, Cambridge) David Walker (Princeton University) Nobuko Yoshida (Imperial College London, UK) External Review Committee: See http://conf.researchr.org/committee/icfp-2016/icfp-2016-papers-external-rev… .

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Take over netlink-hs
by Markus Ongyerth 02 Mar '16

02 Mar '16

Hi, I want to take over the netlink package on hackage [1]. In accordance to [2] I want to announce that publicly on this list. I have tried to contact the auther in october 2015, and talked about it on the #haskell irc channel. I was able to reach the current maintainer, he told me that he forgot about it and doesn't know his hackage password anymore. Davean (on IRC) offerden to give me maintainer rights after checking back with Max himself. I didn't hear anything after that, neither have I made any effort in this matter since then. ongy [1] https://hackage.haskell.org/package/netlink [2] https://wiki.haskell.org/Taking_over_a_package

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How do I sort items in a wxhaskell listCtrl?
by Tilmann 02 Mar '16

02 Mar '16

Hi list, I couldn't find any clues googling and turn to you in the hope that someone might point me in the right direction: I found the function |listCtrlSortItems2| with type |ListCtrl a -> Closure b -> IO Bool| and |closureCreate| (which type is a bit involved..), but I have no idea how to use them.. In the end, I would like to have a listCtrl where clicking on column headers will sort the items and maybe even indicating sorting order with a little arrow. Any help is really appreciated, Tilmann

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Haskell 2016: Call for Papers
by Geoffrey Mainland 01 Mar '16

01 Mar '16

======================================================================== ACM SIGPLAN CALL FOR SUBMISSIONS Haskell Symposium 2016 Nara, Japan, 22-23 September 2015, directly after ICFP http://www.haskell.org/haskell-symposium/2016 ======================================================================== ** The Haskell Symposium has an early track this year ** ** See the Submission Timetable for details. ** The ACM SIGPLAN Haskell Symposium 2016 will be co-located with the International Conference on Functional Programming (ICFP 2016) in Vancouver, Canada. The Haskell Symposium aims to present original research on Haskell, discuss practical experience and future development of the language, and to promote other forms of denotative programming. Topics of interest include: * Language Design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, such as formal semantics of the present language or future extensions, type systems, effects, metatheory, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management, as well as foreign function and component interfaces; * Libraries, that demonstrate new ideas or techniques for functional programming in Haskell; * Tools, such as profilers, tracers, debuggers, preprocessors, and testing tools; * Applications, to scientific and symbolic computing, databases, multimedia, telecommunication, the web, and so forth; * Functional Pearls, being elegant and instructive programming examples; * Experience Reports, to document general practice and experience in education, industry, or other contexts. Papers in the latter three categories need not necessarily report original academic research results. For example, they may instead report reusable programming idioms, elegant ways to approach a problem, or practical experience that will be useful to other users, implementors, or researchers. The key criterion for such a paper is that it makes a contribution from which other Haskellers can benefit. It is not enough simply to describe a standard solution to a standard programming problem, or report on experience where you used Haskell in the standard way and achieved the result you were expecting. More advice is available via the Haskell wiki: (http://wiki.haskell.org/HaskellSymposium/ExperienceReports) Regular papers should explain their research contributions in both general and technical terms, identifying what has been accomplished, explaining why it is significant, and relating it to previous work, and to other languages where appropriate. In addition, we solicit proposals for: * System Demonstrations, based on running software rather than novel research results. These proposals should summarize the system capabilities that would be demonstrated. The proposals will be judged on whether the ensuing session is likely to be important and interesting to the Haskell community at large, whether on grounds academic or industrial, theoretical or practical, technical, social or artistic. Please contact the program chair with any questions about the relevance of a proposal. Travel Support: =============== Student attendees with accepted papers can apply for a SIGPLAN PAC grant to help cover travel expenses. PAC also offers other support, such as for child-care expenses during the meeting or for travel costs for companions of SIGPLAN members with physical disabilities, as well as for travel from locations outside of North America and Europe. For details on the PAC program, see its web page (http://pac.sigplan.org) Proceedings: ============ Accepted papers will be included in the ACM Digital Library. Authors must grant ACM publication rights upon acceptance (http://authors.acm.org/main.html) Authors are encouraged to publish auxiliary material with their paper (source code, test data, etc.); they retain copyright of auxiliary material. Accepted proposals for system demonstrations will be posted on the symposium website but not formally published in the proceedings. All accepted papers and proposals will be posted on the conference website one week before the meeting. Publication date: The official publication date of accepted papers is the date the proceedings are made available in the ACM Digital Library. This date may be up to two weeks prior to the first day of the conference. The official publication date affects the deadline for any patent filings related to published work. Submission Details: =================== Submitted papers should be in portable document format (PDF), formatted using the ACM SIGPLAN style guidelines (http://www.acm.org/sigs/sigplan/authorInformation.htm) The text should be in a 9-point font in two columns. The length is restricted to 12 pages, except for "Experience Report" papers, which are restricted to 6 pages. Papers need not fill the page limit---for example, a Functional Pearl may be much shorter than 12 pages. Each paper submission must adhere to SIGPLAN's republication policy, as explained on the web. Demo proposals are limited to 2-page abstracts, in the same ACM format as papers. "Functional Pearls", "Experience Reports", and "Demo Proposals" should be marked as such with those words in the title at time of submission. The paper submission deadline and length limitations are firm. There will be no extensions, and papers violating the length limitations will be summarily rejected. A link to the paper submission system will appear on the Haskell Symposium web site closer to the submission deadline. Submission Timetable: ===================== Early Track Regular Track System Demos ---------------- ------------------- --------------- 1st April Paper Submission 20th May Notification 6th June Abstract Submission 10th June Paper Submission 17th June Resubmission Demo Submission 8th July Notification Notification Notification 31st July Camera ready due Camera ready due Deadlines stated are valid anywhere on earth. The Haskell Symposium uses a two-track submission process so that some papers can gain early feedback. Papers can be submitted to the early track on 1st April. On 20th May, strong papers are accepted outright, and the others will be given their reviews and invited to resubmit. On 17th June, early track papers may be resubmitted and are sent back to the same reviewers. The Haskell Symposium regular track operates as in previous years. Papers accepted via the early and regular tracks are considered of equal value and will not be distinguished in the proceedings. Although all papers may be submitted to the early track, authors of functional pearls and experience reports are particularly encouraged to use this mechanism. The success of these papers depends heavily on the way they are presented, and submitting early will give the program committee a chance to provide feedback and help draw out the key ideas. Program Committee: =================== James Cheney University of Edinburgh Iavor Diatchki Galois David Duke University of Leeds Richard Eisenberg University of Pennsylvania Ken Friis Larsen University of Copenhagen Andy Gill University of Kansas Zhenjiang Hu National Institute of Informatics Ranjit Jhala UC San Diego Yukiyoshi Kameyama University of Tsukuba Geoffrey Mainland (chair) Drexel University Mary Sheeran Chalmers University of Technology David Terei Stanford Niki Vazou UC San Diego Dimitrios Vytiniotis Microsoft Research =====================================================================

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