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  • Lenny222/About Haskell
    ! What it means ! What it is good for
    586 bytes (72 words) - 21:57, 23 April 2021
  • Monomorphism
    ...s for several different types - and thus, a function is ''monomorphic'' if it works only for ''one'' type. As an example, <hask>map</hask> is polymorphic. It's type is simply
    692 bytes (112 words) - 20:01, 21 May 2017
  • BayHac2017/dynobud
    Be warned that it is non-trivial to get dynobud built as it requires somewhat tricky external C++ dependencies.
    325 bytes (45 words) - 00:24, 22 February 2017
  • BayHac2017/Karya
    To get sound you'll need VSTs, a VST host, and jack if it's linux. It's easy to set up on OS X, it might be complicated on linux, but anyone
    886 bytes (153 words) - 22:47, 5 April 2017
  • Abandoning a package
    ...it. You may wish to also orphan it in this case, to allow others to take it over or claim the namespace. ...package is still good and useful, but no longer have the time to maintain it, you can reach out via the usual community channels (the haskell-cafe maili
    957 bytes (167 words) - 22:55, 23 October 2016
  • First-class module
    Because it has also [[Dependent type]]s, it can leverage them so that it is not forced to have a separate module language and a core language.
    585 bytes (86 words) - 06:42, 10 August 2022
  • Diagrams/Install
    ...haskell.org/platform Haskell Platform], if you don't already have it. Then it should be enough to simply run it will be installed as well.
    757 bytes (105 words) - 01:44, 19 April 2015
  • Blueprint
    ...low reading a data structure like <hask>Data.Map</hask> while constructing it. It is discussed at length in
    346 bytes (51 words) - 15:19, 6 February 2021
  • Hie-bios
    ''This article is a stub. Please help expand it.'' ...ng Haskell programs using [[Cabal]], [[Stack]] and other package managers. It is used to specify how [[Haskell Language Server]] and [[ghcide]] set up a
    497 bytes (72 words) - 23:38, 31 July 2023
  • ZuriHac2015/Projects/Gipeda
    It generates static files, mostly json-files, using shake to keep track of wha ...ttp://perf.haskell.org/ghc. But it is kept generic and you are free to use it for your own projects as well.
    1 KB (201 words) - 08:12, 22 May 2015
  • Making GHCi scale better and faster
    ...stops being fun anymore and you start wishing you didn’t have to wait for it to load. If you want it on all the time, you can put the above line in a <code>.ghci</code> file ei
    1 KB (245 words) - 18:39, 2 October 2015
  • Cabal/How to install a Cabal package
    ...http://hackage.haskell.org/ Hackage] you'd like to try. How do you install it on your system? While it is possible to "install" a library package "globally" it is most certainly a [https://en.wikipedia.org/wiki/Dependency_hell bad idea
    1 KB (169 words) - 10:06, 10 March 2021
  • Diagrams/GSoC
    ..., and raise the profile of the Haskell programming language. Most of all, it's fun---you get to tangibly experience your contributions in the form of be
    1 KB (165 words) - 22:48, 5 March 2014
  • Haste
    ...ily modified version of [[haddock]] 1.x for Intellisense (tab-completion). It was [http://www.haskell.org/pipermail/haskell/2005-April/015667.html announ The development of Haste has been abandoned, and as of GHC 6.8.2, it is somewhat bitrotten. A snapshot of the last sources can be found at [[Med
    2 KB (310 words) - 05:54, 10 October 2013
  • Yhc/Primitives
    ...all. This allows for the possibility that the primitive might block and so it is run in a separate OS thread. ...'t run the primitive call in a separate OS-level thread because we promise it won't block.
    2 KB (288 words) - 01:58, 9 April 2021
  • $
    .../hask> has the lowest, right-associative binding precedence (infixr 0), so it sometimes allows parentheses to be omitted; for example: It is also useful in higher-order situations, such as <hask>map ($ 0) xs</hask
    1 KB (208 words) - 00:09, 1 October 2016
  • Strict semantics
    It means, that an undefined argument of a function leads to an undefined funct It may be implemented by [[eager evaluation]].
    363 bytes (53 words) - 15:18, 6 February 2021
  • Partial functions
    ...it much easier to reason about your code and makes "if your code compiles, it probably works" true for your code more often. Usually if you have a partial function, it's because your types are incorrect and you should fix your types rather tha
    1 KB (247 words) - 16:53, 15 November 2014
  • Haskell Web Server
    * Björn Bringert cleaned it up and put it to http://darcs.haskell.org/hws/
    543 bytes (85 words) - 03:32, 9 April 2021
  • Default method implementation
    It's always a design question, whether to provide default implementions of met ...duces the amount of implementation work for class instances. It also makes it more probable, that no extra super-classes are needed.
    2 KB (254 words) - 21:39, 19 September 2016
  • Xmonad/Notable changes since 0.12
    ...config. This is now the preferred way to use <code>ManageDocks</code>, as it can be kept up to date with any new hooks that might be added in the future ...W_TYPE_DOCK</code> window type (there is code to handle other windows, but it does not appear to be being used). Notably, this means that if you use <cod
    2 KB (420 words) - 18:27, 12 December 2017
  • Probabilistic Functional Programming
    It turns out that random variables establish a monad, namely a list monad wher ...ulate or randomize any simulation without altering the code which defines it.
    2 KB (271 words) - 22:15, 27 November 2016
  • Constant applicative form
    ...since it is not a [[lambda abstraction]] it contains no variables at all. It may however contain identifiers which refer to other CAFs, e.g. ...ome shared code which will overwrite itself with some graph the first time it is evaluated. A CAF such as
    2 KB (255 words) - 06:31, 12 June 2023
  • 99 questions/Solutions/54A
    are binary trees: it is just not possible to construct an invalid tree with this type. Hence, it is redundant to introduce a predicate to
    1 KB (156 words) - 13:35, 25 December 2016
  • Haddock
    ...cumentation of the standard libraries that come with [[GHC]] and [[Hugs]]. It is also supported by [[Cabal]].
    684 bytes (90 words) - 02:54, 28 November 2015
  • Intentionally omitted instance
    In an equation for `it': it = 2 + 3 :: Char It is ugly that you have to enable <hask>UndecidableInstances</hask> for this
    1 KB (209 words) - 14:08, 22 February 2015
  • Cabal
    ...y involved in the creation of packages and the building of their contents. It does not manage packages. ...all non cabal packaged dependencies, it cannot uninstall packages, nor can it automatically upgrade installations.
    2 KB (244 words) - 12:34, 2 October 2020
  • 99 questions/Solutions/40
    ...number theory that has not been proved to be correct in the general case. It has been numerically confirmed up to very large numbers (much larger than w .... Then it looks for a pair of odd numbers where both are prime and returns it as a tuple.
    1 KB (226 words) - 19:47, 18 January 2014
  • Space leak
    That means it should preferably leak even when compiled with the latest GHC -O2, but cert It's frustrating to study about leak when the examples given no longer leak fo
    1 KB (168 words) - 06:46, 4 February 2015
  • Infix operator
    Putting parentheses around an infix operator converts it into a prefix function: Putting <code>`</code>-marks around a prefix function allows us to use it like an infix function:
    1 KB (159 words) - 23:45, 25 June 2021
  • Commenting
    It is generally a good idea to write comprehensible programs, However it is not true that every program can be become comprehensible
    2 KB (315 words) - 02:39, 9 April 2021
  • Calling Haskell from C
    It is not uncommon to want to call a Haskell function from C code. Note the foreign export. When GHC sees this, it will generate stubs
    1 KB (215 words) - 17:08, 27 June 2019
  • Syntactic sugar
    ...ns]] to syntactic sugar. The goal generally being to balance the amount of it available in a language so as to maximise readability -- giving enough free ...of syntactic sugar is as cut-and-dried as some people appear to be making it.
    3 KB (490 words) - 01:44, 27 October 2017
  • NamedAction.dpatch
    This actually refers to a text darcs patch, but it works anyways.
    94 bytes (15 words) - 15:19, 6 February 2021
  • BayHac2018/CodeWorld
    == What It Is == ...CodeWorld is to be used for middle school aged children. Because of this, it defaults to a simplified variant of Haskell. However, a full Haskell versi
    2 KB (275 words) - 21:13, 6 April 2018
  • Kibro
    I've made this page for documenting it, and discussing ideas. ...with cabal install (to make sure all dependencies are there) and then run it on a port like 3000.
    1 KB (154 words) - 05:36, 24 April 2021
  • Multiple instances
    How is it possible? ...instance can be defined for the class/newtype pair and it is not orphan if it is defined where newtype is introduced.
    2 KB (336 words) - 08:58, 30 November 2016
  • Binary IO
    It's very simple to use, and provides a highly efficient, pure interface It is a part of the base package, so it comes with [[GHC]].
    2 KB (254 words) - 19:03, 23 October 2013
  • Web/Libraries/Templating
    ...syntax for defining your templates: a Haml-inspired syntax to be precise. It also has support for type-safe URLs, and achieves very high performance by ...e Java StringTemplate library by Terrence Parr, ported by Sterling Clover. It can be used for any templating purpose, but is often used for dynamically g
    1 KB (193 words) - 04:57, 26 April 2021
  • Gtk2Hs/Tutorials
    ...ses the deprecated Events module and to run some examples with gtk 0.10.1, it is necessary to include "import Graphics.UI.Gtk.Gdk.Events" in the program. A simple example how to show a list and select an entry from it.
    1,006 bytes (151 words) - 04:25, 26 April 2021
  • Diagrams/Dev/AlignedCompose
    It seems like a major wart that often, in order to compose diagrams in a certa ...some require <code>Traced</code> and some do not. That is, specifically, it is hard to imagine what type we could give to the hypothetical lens <code>a
    2 KB (397 words) - 20:05, 1 June 2015
  • ARM
    ...s a [http://en.wikipedia.org/wiki/RISC RISC] instruction set architecture. It is used in most of the mobile phones and in many other consumer electronics ...project with forking jhc.] Kiwamu Okabe created a fork of [[jhc]] and used it to program a [http://en.wikipedia.org/wiki/ARM_Cortex-M Cortex-M3] processo
    3 KB (409 words) - 07:55, 19 October 2015
  • Common Language Runtime
    ...H JS crew have made some good progress on creating a new target for GHC so it's doable at least. ...this spin, head over to github page, and follow the READMEs carefully. It it also the only Mono compatible solution (but again, may require manual steps
    2 KB (405 words) - 10:31, 9 February 2019
  • Haskell.org infrastructure
    ...It therefore also determines the policy on the uses of those machines that it pays for. If there are problems with infrastructure, it is good to check [https://status.haskell.org status.haskell.org] to see if
    1 KB (208 words) - 23:49, 17 May 2018
  • GHC/TypeSigsAndAmbiguity
    ...alas not always. Perhaps this is a deficiency in GHC, but here's one way it can happen: Now GHC finished typechecking the right hand side of <tt>f</tt>, so next it checks that the constraints ''needed'' in the RHS, namely <tt>(C a b1)</tt>
    4 KB (716 words) - 11:30, 24 January 2016
  • Maintenance of standard collection libraries
    ...rac (http://hackage.haskell.org/trac/ghc/wiki/CollectionLibraries) because it made better sense there.
    148 bytes (22 words) - 12:16, 8 June 2023
  • Hac NYC/Talks
    If you'd like to give a talk, announce it here; tell us your name, the title of the talk, a short description. Pleas ...tion of what "univalence" could be and why it is reasonable to expect that it should compute.
    2 KB (335 words) - 15:02, 5 April 2014
  • Hoare Property
    ...no bugs in it, or write code so complex that there are no obvious bugs in it.
    431 bytes (80 words) - 01:34, 17 June 2021
  • Emacs/Project navigation
    ...ll buffer which will jump directly to its definition. You can also now use it for [[Emacs/Autocompletion|autocompletion]]. or just <code>M-x customize-group haskell</code> and it's in there.
    1 KB (170 words) - 18:23, 11 April 2016
  • ILogBase
    ...based, it is limited in number sizes, and has accuracy errors that render it unusable even for simple purposes such as digit counting.
    1 KB (173 words) - 01:51, 14 July 2021
  • Url
    The URL library provides a module Network.URL that makes it easy to work with HTTP URLs. ...following example shows how to parse a URL and then add some parameters to it:
    829 bytes (129 words) - 15:18, 6 February 2021
  • Web/Projects and Ideas
    * See wai-handler-webkit, though it would be nice if it had better Windows support. Create a WAI handler which uses Webkit to conve ...ai-fastcgi. fastcgi handler for WAI. See the hack-handler-fastcgi package; it should be a simple port.
    1 KB (194 words) - 18:09, 27 January 2018
  • Foldl as foldr alternative
    ...>. Yes, there is already [[Foldl as foldr|such a page]]! This one explains it differently. ...ges in the recursion. It turns out things will be simpler later if we pull it out:
    5 KB (891 words) - 14:21, 3 January 2018
  • Infinity and efficiency
    In general, it is harder to reason about time and memory complexity of an implementation t We want to call it <code>dropWhileRev</code>.
    3 KB (422 words) - 21:22, 29 June 2021
  • Show instance for functions
    Why is there a Show instance, but it only prints the type? ...en optimized to <hask>\x -> x :: Int -> Int</hask>. If it's used anywhere, it might have been inlined and optimized to nothing.
    3 KB (430 words) - 00:30, 1 February 2016
  • GHC/Memory Management
    ...a new value. But GHC is able to efficiently manage garbage collection, so it's not uncommon to produce 1gb of data per second (most part of which will b ...pointed to from scratch. And since values are never modified, neither can it be pointed to later. This is the key property of immutable data.
    3 KB (490 words) - 21:19, 21 November 2022
  • HAC
    * Each contest should focus (e.g. graph-related logic) on one topic, but wrap it in some sort of fun game/competition ** By focussing on one topic it will most likely be more informative to people studying those topics
    1 KB (213 words) - 01:07, 12 July 2021
  • Alternatives and extensions for libraries
    ...nge of Haskell packages and modules. Your help is appreciated in expanding it. When editing this table, please try to keep it in alphabetical order (by package name, then by module name), maintain refl
    5 KB (633 words) - 15:16, 6 February 2021
  • Piq
    '''Note''': Piq is not ready for use yet. It's waiting for [[Reactive]] to get into better shape.
    835 bytes (127 words) - 03:18, 9 April 2021
  • Thunk
    It is used in Haskell systems that implement [[non-strict semantics]] by [[laz A lazy run-time system does not evaluate a thunk unless it has to.
    3 KB (450 words) - 20:07, 19 October 2020
  • Missing tutorials
    ...ications, inverses) with vectors and matrices. There are many packages and it takes a while to find the ones serving basic needs (i.e. small arrays, no s ...lications. There's two ways you could go about it. One might be to build it as a Haskell-for-Objective-C programmers, thing. Another might be Mac OS X
    1 KB (222 words) - 13:03, 5 March 2024
  • MonadPlus reform proposal
    It is proposed that MonadPlus be split like this: ...us for the Maybe monad should be used as an implementation of morelse, but it is also possible to give an unbiased mplus for Maybe:
    4 KB (609 words) - 18:22, 23 June 2015
  • Prelude
    If you wish to program without a prelude or to use a custom version of it you can suppress its automatic inclusion in several ways. The problem is al ...-XNoImplicitPrelude (or -fno-implicit-prelude in older [[GHC]]) that makes it not import Prelude implicitly. The option can be also specified by adding:
    1 KB (187 words) - 22:09, 28 June 2021
  • Denotative
    A programming language is trivially denotative if it only permits programs to be defined in terms of denotative expressions. ...O to be managed by the denotative language's implementation, with parts of it written in a non-denotative (I/O-capable) programming language.
    4 KB (488 words) - 04:24, 5 April 2024
  • Lazy evaluation
    '''Lazy evaluation''' is a method to evaluate a Haskell program. It means that expressions are not evaluated when they are bound to variables, ...o bypass undefined values (e.g. results of infinite loops) and in this way it also allows one to process formally infinite data.
    2 KB (291 words) - 15:20, 6 February 2021
  • Burton-style nondeterminism
    ...nvolved in determining a <code>Decision</code> value only occur once: when it is initially used; * Once it has been determined, a <code>Decision</code> value won't change: it remains constant, even if reused.
    2 KB (341 words) - 09:18, 22 February 2022
  • Jhc
    ...ient programs possible via whole program analysis and other optimizations. It also performs well as a cross compiler and is able to generate Windows prog ...project with forking jhc.] Kiwamu Okabe created a fork of [[jhc]] and used it to program a [http://en.wikipedia.org/wiki/ARM_Cortex-M Cortex-M3] processo
    2 KB (230 words) - 22:57, 23 May 2014
  • Anonymous function
    An anonymous function is a [[function]] without a name. It is a [[Lambda abstraction]] and might look like this: <hask>\x -> x + 1</ha ...So if I wanted to add one to each element of a list, here's one way to do it (without anonymous functions):
    2 KB (296 words) - 06:56, 12 April 2021
  • Safe Haskell
    Safe Haskell is a Haskell language extension. It is described in detail: As the Safe Haskell paper describes, it "hardens" the Haskell language by providing five properties:
    3 KB (471 words) - 03:00, 5 August 2021
  • Haskell/Lazy evaluation
    ...e up in #haskell, and it seemed instructive to take the discussion and sum it up into a simple tutorial on lazy evaluation. ...empty list, and any Int. The 'any Int' part is fine, so we need to know if it's passed an empty list. Answering that question forces one step in the eval
    4 KB (708 words) - 23:10, 19 April 2021
  • Euler problems
    ...:Euler problems|talk page]] for discussion. Many P.E. participants regard it as a global Internet competition which is being compromised by these readil <p><em>I solved it by using a search engine, does that matter?</em></p>
    2 KB (325 words) - 01:17, 13 February 2019
  • Xmonad/Guided tour of the xmonad source
    Do you know a little Haskell and want to see how it can profitably be ...ut of sync, report it on the xmonad mailing list, or -- even better -- fix it!
    3 KB (531 words) - 09:09, 15 August 2017
  • Humor/Dialogs
    so don't tell me how to spend it! I'll ask Mom instead. What do you care where I get them from? It's no extra work for you!
    3 KB (445 words) - 15:19, 6 February 2021
  • ZuriHac2015/Projects
    ...project. Feel free to add your project or your name to a project below as it was done for [[ZuriHac2014/Projects|ZuriHac 2014]]. ...ed Boltzmann Machines using Accelerate, compiled to Cuda and run on GPU's. It's about unsupervised machine learning. Later: Convolutional RBM's. || Marku
    3 KB (355 words) - 14:25, 30 May 2015
  • GHC/Kinds
    ...defines a ''promotable'' data type at the term level they are able to use it at the type level too. For instance, the user can write the following examp == How do I use it? ==
    2 KB (289 words) - 16:02, 28 February 2014
  • Applications and libraries/Robotics
    :Frob is an Embedded Domain Specific Language for controlling robots. It is built using the principals of Functional Reactive Programming, as develo ...It supports direct commands, messages and many sensors (also unofficial). It has also support for a simple message-based control of a NXT brick via remo
    1 KB (178 words) - 12:02, 8 June 2023
  • Avoiding partial functions
    we replace it by combination of check and computation of f. You may implement it with the partial function <hask>minimum</hask>.
    3 KB (506 words) - 04:03, 4 September 2017
  • Upgrading from MTL 1 to MTL 2
    ...version 2. Most of the remainder require only small changes to upgrade to it, though that will usually render them incompatible with version 1 without s ...mers] package. You may wish to check it's the same, so you can just delete it.
    2 KB (374 words) - 00:43, 9 April 2021
  • Gentoo
    ...packages that are distributed via [http://hackage.haskell.org/ Hackage] as it allows us to use automated tools. ...their dependencies changed (ala revdep-rebuild/reconcilio/etc.). That is, it will rebuild packages corresponding to the libraries listed by "ghc-pkg che
    4 KB (592 words) - 08:43, 1 September 2022
  • From a newbie II
    ...y good programmer I decided to take a look. Ugh, what the f*ck is this? So it never went past taking a glance from the examples in wikipedia or haskell.o ...r boredom I decided to resume my Haskell lessons. Naturally, I am enjoying it more than ever, since this 'feeling' that learning something \this\ new giv
    2 KB (390 words) - 15:19, 6 February 2021
  • HQK
    ...eless, you can [http://community.haskell.org/~jeltsch/hqk.tar.gz download] it. Here are some building tips from Sönke Hahn: ...Wolfgang Jeltsch]], would be happy to hear from you whether you think that it is sensible to transform the current version into something that can be rel
    2 KB (285 words) - 06:52, 22 June 2021
  • DDC/ReleaseNotes-Alpha1
    :The GC used to work on 64 bit machines also, but it hasn't been tested for a long time. [http://code.google.com/p/disciple/issu ...t support functions being partially applied to unboxed arguments. Nor does it support unboxed data being free in the closure of a function, or being used
    2 KB (394 words) - 11:57, 19 April 2021
  • Gtk2Hs/Tutorials/TreeView
    ...the web i could find. Therefore i post here the solution I have working - it is not optimal and I would appreciate comments. ...our names and after clicking on one it says which one you selected. i hope it is useful for others!
    2 KB (280 words) - 00:46, 9 April 2021
  • 99 questions/Solutions/5
    ...e wasteful than the one in Prelude as it repeatedly reconses the result as it is accumulated. The following variation avoids that, and thus computational
    1 KB (148 words) - 12:06, 11 August 2017
  • Physical units
    ...th integral seconds and fractional seconds). If this can in fact be done, it could also be used to model coordinate system axes in, say, Geometric Algeb ...y of handling it without forcing a choice of basis. I'm also not sure how it would work -- the whole point of GA is to incorporate areas, lengths, volum
    3 KB (521 words) - 07:04, 13 September 2016
  • Diagrams/GHC7.6
    ...in time to try to find an ''earlier'' version of diagrams which "works". It finds diagrams-0.2.2.3, which is quite old and happens to be the last time
    1 KB (207 words) - 15:18, 6 February 2021
  • Worker wrapper
    It is sometimes easier or more efficient to write functions which have particu however this will be more efficient if it were written
    2 KB (333 words) - 12:44, 4 June 2018
  • Diagrams/Dev/ReviewingAndMerging
    ...s reading carefully through their proposed changes and commenting; ideally it also means downloading and testing their code.</p><p>Some guidelines for co ** ''Be clear''. Make it clear what action(s) are necessary to improve or correct the code. Clearly
    4 KB (614 words) - 16:36, 9 May 2015
  • Quotes
    <LoganCapaldo> No, it just lifts a monad in each hand <oerjan> EvilTerran: no, it's for turning cotheorems into ffee.
    3 KB (561 words) - 02:55, 26 April 2021
  • ZuriHac2015/Projects/FRPGames
    ...re obvious caveats in all FRP implementations, Yampa included, so I'd love it for you to help me figure out how to make Yampa better. You do not need to ...esigners to share assets. I tend to use SDL2 and 2D graphics, only because it's easier. You can also talk to the LambdaCube3D people and combine FRP and
    3 KB (578 words) - 15:24, 29 May 2015
  • Budapest Hackathon 2016/Projects
    of course work assignments, mid-term and final examinations. It is almost fully implemented in Haskell based on the Snap framework, it uses the
    5 KB (679 words) - 14:07, 5 August 2016
  • Import modules properly
    ...ntifier that you never needed but only annoyed you, annoys you again, when it was meant to not bother you any longer! The first variant of import does no ...ll too often I find an old module that cannot be compiled any longer since it uses identifiers that do no longer exist. If the module imports implicitly
    5 KB (816 words) - 08:28, 2 May 2015
  • Num instance for functions
    It is possible to write a <hask>Num</hask> instance for functions in Haskell: The usefulness of this instance is debatable, and it is not currently part of [[Language and library specification|the language
    1 KB (145 words) - 01:24, 28 December 2014
  • Hack-Nix
    * It works the same way no matter which linux distribution you're using # In this example it's used to remove base >= 4 from the
    5 KB (726 words) - 10:39, 5 January 2018
  • Let vs. Where
    ...sense of "[[Declaration vs. expression style]]", however there is more to it. ...ortant to know that <hask>let ... in ...</hask> is an expression, that is, it can be written wherever expressions are allowed. In contrast, <hask>where</
    4 KB (716 words) - 07:41, 26 January 2019
  • Use of language extensions
    However, when it comes to designing libraries one should carefully think about which extensi ...ram and the compiler suggests to use a language extension to resolve that. It is a quick fix to solve the problem by enabling the extension, but if you d
    3 KB (387 words) - 05:21, 12 July 2021
  • Data declaration with constraint
    The designers of Haskell 98 do now think, that it was a bad decision to allow constraints on constructors. GHC as of version ...en something pattern matches a <hask>Cons x</hask>, the context comes with it.
    2 KB (312 words) - 23:26, 19 September 2016
  • Haskell-language-server
    .../ Ghcup] can install HLS, but after installation, you'll need to integrate it with an editor. The [https://github.com/haskell/haskell-language-server#con ...e-them-all.html</ref> Over time, this project became the HLS, which allows it to be used with many IDEs and code editors.
    1 KB (157 words) - 00:07, 26 April 2024
  • Web/Framework Interfaces
    ...like WAI, it uses lazy bytestrings for request and response bodies, making it easier to use for some. Many backends are available, for numerous backends;
    2 KB (217 words) - 12:02, 19 April 2024
  • QualifiedDo
    ...ps://gitlab.haskell.org/ghc/ghc/-/merge_requests/3436 merged] in 2020, and it is available in GHC 9 and later releases.
    347 bytes (52 words) - 23:50, 6 December 2020
  • Roll your own IRC bot/Source
    ...of the source code for the bot described in [[Roll your own IRC bot]], but it fell out of date with the article (and became uncompilable). That page alre
    284 bytes (52 words) - 00:57, 17 June 2015
  • A new list type
    ...lso computes and stores the size of the source list - if anybody still has it.) The really interesting case is <hask>select</hask> (which is equivalent t ...id]] for why you should try to avoid calling <hask>length</hask>. Although it probably requires quite a change of mindset for a non-Haskeller to apprecia
    3 KB (587 words) - 15:19, 6 February 2021
  • Diagrams/Install/Install-cairo
    ...through your operating system's package manager or otherwise. After that, it should ''ideally'' be enough to run ...hs-buildtools</code> in the past then you probably don't need to reinstall it; though note that in order to build <code>cairo</code> under GHC 7.6 you ne
    3 KB (511 words) - 01:45, 19 April 2015
  • Encoding issues
    ...ch a type is either a list of bytes, equivalent to <hask>[Word8]</hask> or it is a string, a list of character, <hask>[Char]</hask>. ...t will be the encoding from the current locale (usually UTF-8). On windows it will be based on a Byte order mark for file IO, while the output encoding c
    2 KB (307 words) - 13:45, 23 May 2021
  • 99 questions/Solutions/34
    ...ke coprime from the previous exercise and give it to filter, which applies it to each element of a list from 1 to one less than the number, returning onl This example uses Data.Ratio to ensure no precision is lost. It also relies on a function primeFactors (not shown) that returns a list of a
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  • 99 questions/Solutions/35
    ...imeFactors. primeFactors checks to make sure the factors are prime. If not it prime factorizes them. In the end a list of prime factors is returned. ...ial division, speeds it up a lot (especially as memoized). Or you can find it on [[prime numbers]] haskellwiki page.
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  • MultiCase
    It is proposed that Haskell allow multiple pattern matches in a case statement ...ntax. Using `,` is also a problem for nested options such as this, because it conflicts with pattern matching on tuples:
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  • Seq
    ..., and returns the second. However, it also has the important property that it is always strict in its first argument. In essence, <code>seq</code> is def ...esn't evaluate anything just by virtue of existing in the source file, all it does is introduce an artificial data dependency of one value on another: wh
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  • Lambdabot/Building
    Fortunately, the [[darcs]] repositories of most of these packages do support it. Apply a patch to lambdabot and install it:
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  • GHC/Type system/PolyKinds
    ...retin/papers/fc-kind-poly.pdf Giving Haskell a promotion], the paper about it. The former must mean what it always means in Haskell, namely
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  • Diagrams/Dev/IRCHooks
    It's helpful to have repositories in the diagrams organization on github gener ...ll be sent to the IRC channel for pushes and pull requests only. However, it is useful to get notifications for other sorts of events too. Strangely, t
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  • Cookbook/Files
    ...and will be closed when the resulting string is garbage collected. Closing it manually may result in a random truncation of the input.'' ...kes a function from <hask>string</hask> to <hask>string</hask> and applies it lazily to the input from stdin, writing the output to stdout.
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  • How to get rid of IO
    ...ing the code expecting <code>regularThingie</code>: If you're able to make it into a function e.g: ...r <code>IO</code> value (The result will depend on the environment because it uses a value dependent of the environment).
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  • Cookbook/XML
    ...(limited) experience, I could only get [[HXT]] to do everything I wanted. It does make heavy use of [http://haskell.org/arrows/ Arrows].
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  • Bad type errors
    ...s you that your program doesn't make sense. Unfortunately, the description it provides for the problem '''''also''''' does not make sense.
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  • X-DSP
    ...unified interface to different audio signal processing systems. Currently it supports Csound.
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  • HDBC-ODBC MS SQL under Linux
    You can test it from a [[GHC/GHCi| ghci]] prompt (obviously you'll need to change the conne If you are not using a DSN, it's critical to explicitly set the Port in the connection string
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  • BayHac2018/haddock
    ...the markup types we don't have to pay the cost of 'String' and let GHC use it's efficient, internal string types.
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  • Xmonad/Config archive/Template xmonad.hs (darcs)
    If you want a good configuration to start from, it's quite simple. ...<code>hookName baseConfig <+></code> to the new value. (You may also make it the first item in a <code>composeAll</code> for the <code>manageHook</code>
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  • Functional programming/Old version
    No, there is more in it. On the one hand this is a powerful property, since it gives you guarantees you cannot have in imperative languages.
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  • Currying
    It holds however the curried form is usually more convenient because it allows [[partial application]].
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  • LondonInfrastructureHac2015
    ...e place in London during the two days following the Haskell eXchange 2015. It will be hosted at Pivotal Labs, London. Everyone is welcome, beginners and ...d merge projects started at the first and to hopefully celebrate progress. It is, however, not at all necessary to commit yourself to attending both Hack
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  • Type variables instead of concrete types
    But the signature is not as expressive as it could be. It is fixed to a concrete type, say <hask>Double</hask>.
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  • BayHac2017/CodeWorld
    == What It Is == ...CodeWorld is to be used for middle school aged children. Because of this, it defaults to a simplified variant of Haskell. However, a full Haskell versi
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  • Simple monad examples
    ...> on its left-hand side; or if its left-hand side is a <code>Just …</code> it strips off the <code>Just</code>, and passes the contents into the function
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  • Tomato-rubato
    == What is it? == ...o-openl] package which allows you to play raw audio data on your speakers. It has an extremely simple interface and uses [http://hackage.haskell.org/pack
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  • Type classes are for reusability
    (Actually, it was not necessary to bundle the number literal feature expressed by the <ha But it is generally accepted that number literals are reserved for objects that al
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  • Bottom
    ...as '&amp;perp;' and in LaTeX as '\bot' (within math mode). In plain ASCII, it's often written as the extremely ugly character sequence '<code>_|_</code>' If it were not, the compiler could solve the [http://en.wikipedia.org/wiki/Haltin
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  • Wadler's Law
    about half saying that > is wonderful, and half saying it is awful. Under these circumstances, Paul's ruling seems right: it is pointless
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  • Switching type classes at runtime
    It is possible to create a type class instance at runtime by coercing a value We'd like to turn this into a "IOError", so that it can be caught:
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  • Simple Unix tools
    tools, it is possible to compile a single monolithic binary and have it detect what name it is run by and then act appropriately. This is the
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  • Orphan instance
    ...ule somewhere. It is almost impossible to assert that, or put differently, it would reduce the composability of libraries considerably. ...d, too. If you want to define a new instance then the compiler will reject it immediately.
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  • Community server (defunct)
    It has now been retired: http://blog.haskell.org/post/7/the_future_of_communit
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  • PortAudio
    In Haskell it is supported by
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  • Generics
    ...resent in compiled code. So the word "generic" is somewhat overloaded, and it may be desirable to use "polymorphic" when possible. ...implementation is necessary, similarly to <hask>Show</hask>, for instance. It's described in a [[GHC.Generics|separate wiki page]].
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  • Hac Boston/Projects
    If you need a place to host a project so that others can help with it, we suggest ...have a project that you want to work on at the Hackathon, please describe it here.
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  • Applications and libraries/Bioinformatics
    ...rtunately is hard to tune to give optimal results. Unless you plan to fix it, use CAP3 instead. ...spe and L. De Raedt (1997) Mining Association Rules in Multiple Relations. It is described in Clare, A. and King R.D. (2003) "Data mining the yeast geno
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  • POSIX process group API reform proposal
    It is proposed that <tt>System.Posix.Types</tt> have a new type <tt>ProcessGro It is proposed that <tt>System.Posix.Process</tt> have these functions, (at le
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  • Web/Testing and Verification
    ...s to communicate with a Selenium Remote Control server. This package makes it possible to use Haskell to write test scripts that exercise web application ...ing WAI applications. Developed initially for testing wai-extra and Yesod, it should prove generally useful.
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  • Netwire
    ...mming]] library that provides both an applicative and an arrow interface. It allows you to express time-varying values with a rich event system. Netwire's FRP framework is intended to be used for continuous applications. It replaces the traditional big main loop with its global state and event call
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  • DDC/PolymorphicUpdate
    ...ype <hask>(forall a. [a])</hask>, but suppose we update the box containing it at two different types... ...calls to <hask>getSet2</hask>. When <hask>makeGetSet</hask> was evaluated it created a shared mutable object (the <hask>box</hask>) and then returned fu
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  • GPipe
    ...ng unit). It is an alternative to using OpenGl, and has the advantage that it is functional and statically typed as opposed to OpenGl's inherently impera ...have something to contribute with, just send me a patch and I might merge it into the trunk.
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  • Language extensions
    when it is useful]] and what risk it may bring to your program. * {{GHCUsersGuide|exts/tuple_sections||section on TupleSections}} It allows tuples to be partially applied.
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  • Scoped type variables
    ...possible to specify the particular type of a function in situations where it is not otherwise possible, which can in turn help avoid problems with the [ It is used like <hask>x `asTypeOf` y</hask> and has the same value like <hask>
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  • 99 questions/Solutions/49
    ...f n-1, prepend a 0 to each word, take the Gray code for n-1 again, reverse it and prepend a 1 to each word. At last we have to append these two lists. Fo ...etely different solution (using folds) that is way more efficient, because it needs just the space which is occupied by the list itself:
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  • Trash/DDC/ClosureTyping
    ...original definition of <hask>g</hask> so is shared between applications of it. ...t the <hask>Int</hask> is free in its closure so is shared by all calls to it. The type system does not generalize regions which are free in these closur
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  • Constructor
    ...] constructor''' may have zero or more arguments, if it has zero arguments it is called a ''nullary'' type constructor (or simply a '''type'''). An examp ...sk>, <hask>Maybe String</hask>, or even <hask>Tree b</hask>, in which case it will be a tree of tree of <hask>b</hask>. The data type is polymorphic (and
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  • ZuriHac2015/Projects/hackage-security
    hackage-security is an effort to bring security to the cabal environment. It is based on The Update Framework (TUF) that has been inspired by tor's buil ...g to hackage servers in sync. Re-write the download and/or upload part so it provides TUF security guarantees for the mirror and its users.
    2 KB (233 words) - 11:01, 27 May 2015
  • Cabal-dev
    cabal-dev is a tool for managing development builds of Haskell projects. It supports maintaining sandboxed cabal-install repositories, and sandboxed gh
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  • 99 questions/Solutions/6
    Here's one to show it done in a fold just for the fun of it. Do note that it is less efficient then the previous 2 though.
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  • Idiom brackets
    Since f is not a pure function, it's f :: x -> y -> m c. The correct form would be I thought I'd present it as a curio illustrating part of the design space, but
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  • Power function
    ...ately, the Haskell implementation does not try to be too clever here. But it does so at another point: One can refine the set of power functions further as it is done in the [[Numeric Prelude]]. In this library, the more general the
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  • Fairbairn threshold
    it or inlining it. There are reasonable exceptions for especially common idioms, but it does
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  • Composing functions with multiple values
    such that it meets the needs of <hask>(++)</hask>? It is
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  • Automatic Differentiation
    However, it becomes more difficult for vector functions, when computing the derivatives Forward mode is suitable when you have fewer arguments than outputs, because it requires multiple applications of the function, one for each input.
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  • Monad/ST
    ...read" of computation cannot exchange mutable state with the outside world, it can only exchange immutable state. ...llocate mutable memory, then you initialize and play with it, then you put it away and return a normal Haskell value.
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  • Section of an infix operator
    ...and it represents a function which intuitively takes an argument and puts it on the "missing" side of the infix operator.
    2 KB (233 words) - 17:58, 31 March 2017
  • Syntactic sugar/Pros
    ...ge shall give arguments why syntactic sugar is useful, give examples where it is useful and show why the arguments against syntactic sugar don't matter.
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  • DDC/ClassSystem
    ...ables. If a region variable in the return type of a function is quantified it means the region is ''fresh'', ie the data was allocated by the function it ...just static <hask>Float</hask> and not a function that does allocation, so it doesn't have a <hask>forall</hask>.
    5 KB (774 words) - 12:35, 8 June 2023
  • Gtk2Hs/Tutorials/ThreadedGUIs
    ...there was little accurate info on how to do multithreaded GUI in gtk2hs. It's trivial. ...you have to know, is that you MUST compile your program with -threaded for it to work properly. Otherwise you will get random hangs.
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  • Hat
    ...e Haskell debugger, see http://projects.haskell.org/hat/ for more details. It can be downloaded from [http://hackage.haskell.org/package/hat Hackage].
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  • Iteratee I/O
    ...r, while it is good enough for simple programs, its unpredictability makes it unsuitable for practical use. ...common beginner mistake is to close a file before one has finished reading it:
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  • Top-level vs. local recursion
    * It clearly shows that the <hask>f</hask> is not "altered" in the recursion. ...er in laziness or performance. Their names are only slightly different and it happened too often that after ''copy&paste&name-change'' the recursive call
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  • OCaml
    OCaml is strict by default, although it has some facility for introducing laziness. OCaml is impure: although it makes heavy use of immutable data, it also has mutable references and arrays available, and IO is performed by or
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  • Guess a random number
    ...self randomly generated. Along the way, it became a game. At this point, it also demonstrates simple interaction with the environment (prompting users, ...y or mind-blowing about it; it's my first Haskell program, and I just hope it can help out other newbies. Comments, criticism, and rewrites are welcome.
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  • Questions and answers
    ;Q. I just wrote this really cool program! Who can I show it to? ...s interesting program that someone else might find useful. Where can I put it?
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  • LLVM
    It is developed by the University of Illinois. It is implemented on many platforms, amongst others the [http://www.ipodobserv
    2 KB (204 words) - 11:22, 2 October 2020
  • Bluetile
    time is the most limited resource among the majority of users. It's good if you can configure a software in every respect. It's better if you
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  • Xml
    ...nce is anything which has some convention for generating an Element out of it. ...(qualified name) denotes a name with its qualifying namespace attached to it.
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  • Diagrams/Dev/Expression
    ...ntation for every existing class); others, e.g. algebraic data types, make it easy to add new operations (just write a new function) but annoying to add ...equire changing existing backends, which will simply not be able to render it) but also new backends.
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  • Glome
    Glome is a ray tracer written by Jim Snow. Originally it was written in Ocaml, but the more recent versions are written in Haskell. ...vailable on Hackage called glome-hs, which renders into an OpenGL window. It probably won't work with recent versions of GlomeTrace.)
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  • Applications and libraries/Data structures
    ....haskell.org/ghc/docs/edison/ earlier version of Edison] by Chris Okasaki. It provides sequences, finite maps, priority queues, and sets/bags. ([http://w :*It's easy to migrate from standard Lists/Sets/Maps to the new package. The pac
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  • Unde gasim lucrarea lui Graham Hutton despre fold ?
    ...tt.ac.uk/~gmh/foldl.pdf A tutorial on the universality of fold - Download it from here.]
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  • Computer science
    ...utabilty theory: [[Exact real arithmetic]]. For me, it was surprising, how it connected problems in mathematical analysis, arithmetic and computability t ...n experimentable, playable incarnation of [[recursive function theory]] -- it could yield a playground for learning concepts like [http://www.madore.org/
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  • Laziness is not always good
    You find that it is not <hask>mappend mempty undefined = undefined</hask>, but <hask>mappend I think it is the latter one, because a <hask>Monoid</hask> instance implicitly promis
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  • Xmonad/Installing xmonad
    # the contrib package depends on xmonad so it gets also installed It may also be convenient to perform various startup operations like adjusting
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  • BayHac2017/hopes
    * I will be happy any way it turns out but I would prefer pizza and swag. ...ith proficient Haskellers and walk through their code and my code. I hope it will be friendly and inviting.
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  • Case
    It is however in the [http://hackage.haskell.org/packages/archive/utility-ht/0 you may call it <hask>?</hask> like in C,
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  • Taking over a package
    * The current maintainer can do it directly on the package maintainer group page on Hackage: <code>https://hac This situation is more tricky because it involves overriding the normal rights of authors/maintainers.
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  • 99 questions/Solutions/90
    This is easy to understand, but it's also quite slow, as it generates and tests N^N possible N-queen configurations. The key to speeding it up is to fuse the composition <hask>filter test . generate</hask> into a se
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  • Vogonism
    ...that manner, information is avoided to be present where recipients expect it due to related information already having been transmitted over the same ch ...y the authors, and not even those after a couple of months) can comprehend it, as well as to code that has problems understanding itself. Examples for th
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  • Distributions
    ...' can download GHC, [[Haskell Language Server]] and [[cabal-install]], and it can auto-update. ...is an easy-to-use integrated programming environment for Haskell on OS X. It is a one-click install of a complete Haskell system, including Haskell comp
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  • Haskell projects needing help
    Windows, X11, and MacOS X. Furthermore, it is a mature library (in There is no such project currently going on, but someone should start it. It probably needs several people to make sure that the project will run to til
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  • If-then-else
    ...ns, the <hask>if-then-else</hask> syntax was defined in Haskell98. However it could be simply replaced by the function <hask>if'</hask> with ...tool can process it without hassle. Haddock can generate documentation for it, a text editor can make suggestions for values to insert, Hoogle can retrie
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  • WxHaskell/Contribute
    However, it is hard to find out which features are particularly interesting, the hardne :(It is best to discuss this on the wxHaskell developer mailing list first.)
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  • AI/Genetic programming/Evolutionary chess
    So, for about 2 years or so, I've been batting around the idea of what it would look like to apply genetic programming to chess. Here's a non-technic ...platform on which to build this idea. To be a little more technical about it than I was in that overview, here's some more haskell-ish ideas.
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  • Memory leak
    but it is easily possible to produce memory leaks, especially in connection with [ Note that a leak will not only consume more and more memory but it will also slow down the [[garbage collector]] considerably!
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  • Hommage
    It was developed 2005-2006 and runs with the current version of the Glasgow Ha
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  • Homework help
    ...now Haskell well had to learn it once, and if they were creative, they did it in the appropriate way: First by attempting to understand each issue on th ...doesn't mean that you can't ask for homework help. Far from it! However, it does mean the following:
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  • KURE
    ...ped strategy control language in the tradition of Stratego and Strafunski. It is intended for writing reasonably efficient rewrite systems, makes use of ...ate Haskell) to provide the basic rewrite abilities inside [[Hera| HERA]]. It was rewritten in late 2008, and is published on hackage. KURE will be used
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  • Pairs of identifiers
    It is even better if many libraries would share the same scheme. It would be great if the discussion lead to a more streamlined collection
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  • ZuriHac2015/Projects/fficxx
    ...ugh this project has potentially significant effects on haskell ecosystem, it has been stalled for a quite long time. In this hackathon, we would like to Currently, it uses ugly string template approach, but we would like to use clean abstract
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  • Poorly named things
    * forkOS - forkOS does not create an OS-level thread. It creates a lightweight thread, the same as forkIO. The only difference is w
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  • Shared libraries and GHC
    * shared libraries include all code from a library, even if it is unused ...you can get when a majority of values are not strictly evaluated. However, it is only relatively efficient: evaluation jumps around a lot more than in st
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  • Threepenny-gui
    == What is it? == ...ML at your disposal when creating user interfaces. This is a blessing, but it can also be a curse, so the library includes a few layout combinators to qu
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  • Humor/Erlkönig
    > You're giving it a tuple of Int, so we can substitute Int for 'a' in It's Haskell with his child Hank;
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  • Simple RWST use
    ...putStrLn "I'm thinking of a number between 1 and 10, can you guess it?" (EQ, _) -> do lift $ putStrLn "Got it!"
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  • Live-Sequencer
    While doing so it highlights active terms and shows the result of the term reductions. The nice thing is, that the user can change the program while it is performed.
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  • Enumerator and iteratee
    ...e iteratee finishes, it outputs an accumulator. If the iteratee continues, it outputs nothing (i.e., <hask>()</hask>). The distinct feature of iteratee is that it can say after which list element an iteratee finishes. An iteratee says thi
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  • Frag
    Cheong. It is licensed under the GPL. The design and implementation of * Frag has portability problems. It is known to work on i386 and AMD64, and known not to work on big-endian sy
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  • Web/Databases and Persistence
    | http://acid-state.seize.it/ | [http://mirror.seize.it/acid-state/examples/ Stand-alone examples], [http://happstack.com/docs/cras
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  • Haiku
    It is like Haiku<br> It is only code!<br>
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  • Pure
    ...ked in a different context or at a different time with the same arguments, it will produce the same result. In comparison, <i>procedures</i> or <i>subrou * it only permits programs to be defined in terms of pure definitions,
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  • Diagrams/Dev
    ...askell-style-guide/blob/master/haskell-style.md Coding style guidelines]. It's not worth being super picky about these, but in general they are quite go ...s with ambiguous type variables. This comes up a lot when using diagrams, it would be nice to see this ticket resolved.
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  • Calitatea si inspectorul cozonacilor
    <!-- atravers: Perhaps there's an archived version you can use to restore it? (Remember to add the "Humor" tag.) -->
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  • Almost Haskell
    Almost code is code that sounds like it might be real Haskell, but isn't.
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  • HaskellImplementorsWorkshop
    ..., aimed at bringing together the people behind the Haskell infrastructure. It provides a forum where the people working on compilers, tools, or libraries
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  • Monoid
    ...when you combine it with others (this is called the ''identity'' element). It is closely related to the [[Foldable]] class, and indeed you can think of a -- defining sconcat is unnecessary, it has a default implementation
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  • Tail recursion
    1 to it, or consing another element onto the beginning of it), it is ...sk>). This allows the result of the function to be consumed lazily, since it can be evaluated up to the data constructor and the recursive call delayed
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  • Functor-Applicative-Monad Proposal
    ...ction] with [[Roles]]. Will "probably be fixed in the future", but for now it's off the table. ...e <hask>pure</hask>. Instead, leave <hask>return</hask> in Monad, and give it <hask>pure</hask> as default implementation.
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  • 99 questions/Solutions/27
    ...the possibilities for this choice in <hask>ts</hask>) or if we don't want it in the combination (<hask>ds</hask> collects the possibilities for this cas And a way for those who like it shorter (but less comprehensive):
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  • Hugs
    ...d, and is based on the stable but superseded Haskell 98 standard. However, it still works quickly and correctly, can be installed quickly without adminis ...xceptionally portable. If Hugs can't be installed on your machine, report it as a bug!
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  • Functor hierarchy proposal
    It might also be useful to split a <hask>Pointed</hask> class from the <hask>A ...k> functionality by itself could be useful, for example, in a DSL in which it is only possible to embed values and not to lift functions to functions ove
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  • HaskellITA
    [https://www.haskell-ita.it/ Haskell ITA] is an Italian community of Haskellers. * Other events are listed at https://www.haskell-ita.it/events/
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  • Foldl as foldr
    ...ttp://www.willamette.edu/~fruehr/haskell/evolution.html lean so far right] it came back left again.) It holds
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  • LUI
    ...has a very simple pure semantic model. It is a function from a model that it is editing to an image, size, and mapping of event groups to documentation ...ected child. A FocusDelegator will pass its focus to its selected child if it is in child mode, and stop doing so when going to self-mode.
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  • Performance/Data types
    ...detect when this is the case and optimise away the wasted evaluation, but it is hard to do this well (GHC does a poor job, currently). ...s, such as tuples. A single-constructor datatype can be ''unpacked'' when it is passed to a strict function. For example, given this function:
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  • HacFreiburg2017/ListOfProjects
    ...the data type itself. Currently when haddock sees a name in an export list it tries to find its corresponding declaration. From an ASTs viewpoint single ...ithub.com/haskell/haddock/pull/645 laid the groundwork for such a feature. It adds a command line parameter which dumps an interface file to json. If yo
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  • UnicodeByteString
    It provides a most general conversion function with type: -- | An error in the conversion process. If this occurs it will be the
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  • DDC/ReleaseNotes-Alpha1.1
    ...t support functions being partially applied to unboxed arguments. Nor does it support unboxed data being free in the closure of a function, or being used ...ining monomorphic type vars is unsound because client modules could update it at different types. [http://code.google.com/p/disciple/issues/detail?id=12
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  • Thompson-Wheeler logo
    It has been tested for TeXLive 2007 and TeXLive 2008. It requires a version of TikZ that includes the file pgfkeys.sty (unfortunatel ...se unfamiliar with TikZ, it stands for "TikZ ist kein Zeichenprogramm" and it allows one to make drawing ([http://www.texample.net/tikz/ like these]) dir
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  • TypeDirectedNameResolution
    It's hard to gauge how much people like proposals like this, so let's try the ...he language. I have not much missed it yet, so I don't feel strongly about it, though.)
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  • Brand
    ...top, using the dark blue color of the palette, with a border at the top of it using the lighter blue color. [http://tryhaskell.org/ocean/components.html# * The web site's logo should be below the navigation, not inside it, unless it is properly resized and looks cohesive with the Haskell logo.
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  • Monk upgrade
    ...askell.org (aka haskell.galois.com; aka monk) is in need of an OS upgrade. It's currently running Debian ''sarge''; the upgrade will be to ''etch'', the before doing the upgrade. Then upgrade postgres (it should migrate the data) and stop the server running to see if anyone compl
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  • Parallel/Glossary
    : ''TODO: non-Haskellers may have heard of MapReduce - what does it translate to in Haskell terms?'' : A deterministic parallel Haskell library. It provides an API that resembles Concurrent Haskell (without sacrificing pred
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  • Metaチュートリアル
    : ''and if you say no, it points you at a tutorial which explains it'' -- ndm on #haskell
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  • Maybe
    It allows the programmer to specify something may not be there. When the module is imported, it supplies a variety of useful functions including:
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  • WxAsteroids
    and unpack it; go to the directory with the game code ...b/master/reactive-banana-wx/src/Asteroids.hs version of the main program], it uses the package [http://hackage.haskell.org/package/reactive-banana reacti
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  • Cont computations as question-answering boxes
    ...just hang on to a value of type <code>t</code>, and answer questions about it truthfully, by simply applying them to the value. (The fun will happen late ...</code>. That's a bit brain-twisting, so let's think about how we might do it...
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  • Web/Servers
    ...rtions of the server are not cleanly separated into different packages, so it is not the best choice if you only need a low-level backend. ...rks#Snap Snap framework], the Snap HTTP server is similar to Hyena in that it provides a very fast low level web server.
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  • Failure
    * Error usually refers to a programming error. It can also refer to the "error" function, which in fact causes a runtime exce * Exception usually refers to an exception which is thrown in the IO monad. It can also refer to the actual typeclass "Exception" which was introduced alo
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  • Hackage
    ...'' is the Haskell community's central package archive. Package authors use it to publish their libraries and programs while other Haskell programmers use * The main [https://hackage.haskell.org/ web interface]. It also has [https://hackage.haskell.org/api interfaces] used by tools like [[
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  • Installing xmonad log applet
    ...highly experimental application that's seen very little testing. However, it's also small, simple, and unlikely to break other parts of your system. Fro ...space it's possible to build the applet on another host and simply install it on the small device, however that's outside the scope of this discussion.
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  • SDL/Windows
    ...ecompiled [https://www.libsdl.org/download-2.0.php SDL2 package] and unzip it to e.g. C:\Libs .... You might be able to get around this restriction with some symlinks, but it's really not worth the effort.
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  • CabalFind
    ...ost frequently a darcs repo) somewhere Google Bot or Yahoo Slurp may index it, and eventually information about your package will show up in search resul It will be necessary to parse the returned HTML for <a> tags containing filena
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  • Why not Pointed?
    ...tually abuses of ad hoc relationships it happens to have for the instances it does offer. The one law Pointed offers is how it interoperates with fmap:
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  • Installers
    ...your enthusiasm and, instead of just putting your own tool first, think of it as adding functionality to a whole box of Haskell tools. You may only chang ...tively replacing all handlers associated with the existing file types; but it would be nice if new installers would try to copy existing handlers before
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  • XMonadContribTour
    ...r for new users, but applied to the XMonad Contrib. Mainly because I think it's very difficult for newcomers to discover what extra features XMonad provi ...-docs/xmonad-contrib/XMonad-Hooks-DynamicLog.html XMonad.Hooks.DynamicLog] it provides some drop-in loggers and some helper functions to make your own lo
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  • MigratingWikiContent
    ...ror, so does uploading of new PDF files. The wiki admins are looking into it. ...t other markup inside &lt;hask> or &lt;haskell> tags. You can may rewrite it to use no syntax highlighting (using &lt;code>) or perhaps use Unicode symb
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  • Monad laws
    It's now easy to see that monad composition is an associative operator with le When we see a program written in a form on the left-hand side, we expect it to do the same thing as the corresponding right-hand side; and vice versa.
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  • Concurrency with oracles
    ...ith concurrency presents a challenge - the usual techniques for supporting it used by most other (imperative) languages cannot not be simply transferred ...am should depend on the order in which external events occur. For example, it might be desirable to merge the elements of two lists in the order in which
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  • Xmonad/Notable changes since 0.7
    ...e of XMonad.Layout.WindowNavigation that lets you navigate across screens. It has some bugs. ...rompt), and the URL string. If you want to replicate the old simpleEngine, it'd look like 'newEngine = searchEngine "" "http://..."'.
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  • Nitpicks
    ...s probably not important enough to justify the added complexity of tacking it on as an extension or breaking existing code. ...go back in time and fix it before it happened, we probably would, but now it would probably be too onerous.
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  • Extensible datatypes
    ...e this can be done with <tt>Dynamic</tt> too, by defining dummy types. But it's ugly. It's possible to define [[Dynamic]] using extensible datatypes. Here's a naive
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  • Scrap your boilerplate
    In the current GHC implementation, it consists of a set of modules (Data.Generics and its submodules) and derivin ...n alternative to recursive list concatenation - the latter is inefficient. It also illustrates how laziness automatically means that sublists of type [b]
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  • Yampa/reactimate
    ...nuous time but to evaluate a signal function (or a signal for that matter) it is necessary to sample the signals at discrete points in time. This is exac * The <code>init</code> action is rather self-explanatory; it executes an initial IO action (e.g. print a welcome message), which then yi
    5 KB (780 words) - 11:40, 6 June 2016
  • Partial application
    ...ng <hask>add</hask>. It is a new function that takes an integer, adds 1 to it and returns that as the result.
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  • DDC/EffectSystem
    In Haskell, because <hask>putStr</hask> prints to the screen it has the <hask>IO</hask> constructor in its return type: But wait, that's evil isn't it?
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  • Salsa
    It uses type families extensively to provide a type-safe mapping of the .NET ...ypographical error can trigger multiple pages of errors from GHC, or cause it to eat lots of memory.
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  • Diagrams/Dev/Gradients
    ...actually ''above'' the g transform node in the tree, but it seems perhaps it is actually looking at any path nodes which actually use the fill, although ...rmation (an 'M' node) instead of a split (:|:) and the only way to tell if it is frozen is to look for any splits below
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  • Performance/Monads
    ...line well and the library is in need of an optimization pass. As a result, it can often impose a performance hit of up to 300% (your code will run up to We can unroll it as follows:
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  • WxHaskell/Cygwin
    ...idgets also works without the mingw compiler, but all programs linked with it will fail mysteriously! ...t> to <tt>sh-org.exe</tt>. Next, make a copy of <tt>bash.exe</tt> and name it <tt>sh.exe</tt>.
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  • Darcs
    '''darcs''' is a peer-to-peer revision control system, written in Haskell. It is the standard RCS of the Haskell community. ...remove</tt>: add a change which empties the item and deletes it, but keep it as an unmanaged item.
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  • WxHaskell/Tips and tricks
    * read carefully [[WxHaskell/Quick start | Quick start]] - it contains more information than you think ...after version 0.90.1.0 of wxHaskell. However, to run wxHaskell inside ghci it may be necessary to pass the <code>-fno-ghci-sandbox</code> flag. ghci may
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  • Data.Semigroup
    ...>Monoid</hask>. The <hask>Monoid</hask> typeclass however does not enforce it's instances to already be instances of <hask>Semigroup</hask></div> <div>The <hask>Semigroup</hask> is a particularly forgiving typeclass in it's requirements, and datatypes may have many instances of <hask>Semigroup</h
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  • Yhc/Javascript/Programmers guide/EchoCPS2 demo source
    -- Line-mode output: create a <div> element, place a text in it, -- The "onkeypress" handler: it does all the job. Note the o argument:
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  • Diagrams/Dev/Fixpoint
    <blockquote>It's important that this is NOT a newtype, so we can freely use the <code>Rewrapped</code> instances for it anymore.</blockquote>
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  • Relational algebra
    ...s in Pointfree Functional Dependency Theory]. A concise and deep approach, it is [[pointfree]]. See also [http://www.di.uminho.pt/~jno/html/ the author's ...pper]]). Can <hask>Query</hask> be regarded as an [[arrow]], and if so, is it worth of doing so?
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  • What a Monad is not
    ...sed if you leave this page more confused than before. That just means that it has successfully destroyed your false assumptions, or that you've fallen fo ...t.wordpress.com/2009/01/31/reviving-the-gofer-standard-prelude-circa-1994/ It could be done differently and still work].
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  • 99 questions/Solutions/31
    Well, a natural number ''k'' is a prime number if it is larger than '''1''' and no natural number ''n >= 2'' with ''n^2 <= k'' i This one does not go as far as the previous, but it does observe the fact that you only need to check numbers of the form 6k +/
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  • Libraries and tools/MIME Strike Force
    It might also be nice if the combinators did not require a monadic interface. ...all the attachments, etc. In fact, a MTA might only care about RFC2822, so it should not have to be forced to deal with the rest of the layers added by a
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  • Mac OS X Common Installation Paths
    * Makes it easy for a user to locate all the Haskell components, especially user insta ...bles easy removal of a user installed package, whether they have installed it <tt>--user</tt> or <tt>--global</tt>.
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  • Real World Haskell
    it's for short, script-like programs or large and demanding applications. ...online, but the link is now dead. Please edit this if know where to find it.)
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  • GHC/Typed holes
    ...ic types. That's good! We can reuse those pieces, thanks to the types. But it can be difficult sometimes when writing a program to see how the polymorphi ...ce if we could have the compiler tell us the types of everything in scope? It'd be much easier to see how we can 'fit' them together like puzzle pieces.
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  • Terminator vs. separator
    Usually, we don't think much about it. ...insert them whereever you want. If you place every element at a line then it is easy to disable individual lines with a line comment (starting with <has
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  • Diagrams/Dev/Migrate1.2
    ...you have several options for replacing it, depending on how you were using it: * If you were just using it to get some lines to scale along with a diagram, use a <code>Local</code> l
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  • IO at work
    * it's a special file which seems to change anyway (e.g. terminal devices, named ...code> always yields the same result, for some built-in sense of equality), it could transform the program, calling the function more or less often, or ea
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  • Applications and libraries/Database interfaces
    : HDBC is modeled loosely on Perl's DBI interface, though it has also been influenced by Python's DB-API v2, JDBC in Java, and HSQL in H : This close integration makes it possible to do arbitrary computations on the database (like computing the t
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  • How to profile a Haskell program
    ...gather together the information contained in the case studies and present it here in reference form.'' ...o write a Haskell program]]. It's super easy, and you'll be happy you did it.
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  • Reactive-banana
    == What is it? == ...ns, [[Reactive-balsa|computer music]] or robot controllers. In particular, it promises to avoid the spaghetti code that is all too common in traditional
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  • Keyword arguments
    then be omitted. It is a type error to omit a required keyword argument.
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  • Grapefruit
    ...al Reactive Programming]] (FRP) with a focus on user interfaces. FRP makes it possible to implement reactive and interactive systems in a declarative sty * a record system which makes it possible that
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  • Action
    ...ode> in your program. When your program is run, the I/O will be performed. It isn't possible to perform I/O from an arbitrary function, unless that funct <code>Main.main</code> is also an action, so it requires a context as well. But unlike <code>ST s a</code>, that is provide
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  • Applications and libraries/Graphics
    :Blobs is a diagram editor for directed graphs. It is written in Haskell, using the platform-independent GUI toolkit wxHaskell ...ray-tracers simulate global illumination and eliminates the ambient term. It does this using a set of random techniques to simulate an integration model
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  • Equational reasoning examples
    ...bout repeating or elaborating on these things. But what, if anything, does it mean in programming practice? ...e that the equational reasoning formalists have their own forums/pages;-). It is not necessary to copy the examples here, but your explanatory text shoul
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  • Non-strict semantics
    ...f any subexpression fails to have a value, the whole expression fails with it. ...is why people say that Haskell lets you write your own control structures. It's also one of the motivations behind Haskell being a [[pure]] language (tho
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  • Performance/Strictness
    ...the expression in the heap in a ''suspension'' (or ''[[thunk]]'') in case it is evaluated later. Storing and evaluating suspensions is costly, and unne ...example. Strictness analysis sometimes does wonderful things; for example it is very good at optimising <hask>fac</hask>:
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  • 99 questions/Solutions/39
    ...s list produced by sieve of Eratosthenes to which it refers internally. So it'll be slower, but immediate, testing the numbers one by one. ...rs the relevant range out. [But this way is very slow and I only presented it because I wanted to show how nicely the ''Sieve of Eratosthenes'' can be im
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  • GHC/Coercible
    ...but the type checker ensures that it really is safe to use it. If you use it illegally like in ...olvalble – the role annotation on <hask>Set</hask> prevents coercing under it, and the newtype unwrapping cannot be used as <hask>MkSet</hask> is not in
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  • Merely monadic
    * the ''time of composition'': when it is defined; * the ''time of execution'': when it is used;
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  • 99 questions/Solutions/26
    -- We don't actually need this base case; it's just here to A funny solution using Applicative in Control.Applicative. Funny because it's the opposite of other solutions.
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  • Haskell mode for Emacs/Color chords
    ...ng software. It is very rewarding on an immediate and personal level, but it will also certainly help us make better software.
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  • Closure
    ...]], is a function that makes use of [[free variable]]s in its definition. It 'closes' around some portion of its environment. for example
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  • Budapest Hackathon 2016/Talks
    ...ell codebases. Then we will look into our extensive use of QuickCheck, how it's used and what we learned. ...Zeldspar is built on the top of a deep language stack, and I also show how it can be compiled to run efficiently on many-core devices such as Adapteva's
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  • Examples/Random list
    ...ts helper unpick' are strict in the entire list being operated on (forcing it all into memory at once). And IO [a] cannot lazily return any initial valu <hask>removeOne</hask> returns the output list lazily as soon as it has decided not to delete any element in a prefix of the input list.
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  • 99 questions/Solutions/28
    If you wanted to solve it without the <hask>comparing</hask> function, you could do: ...the problem (that is, lists appear in order of length frequency), although it does not give the same result as the example:
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  • Phantom type
    * it may help to [[No kind signatures|avoid kind signatures]] Phantom types are nearly always either <tt>newtype</tt> or <tt>data</tt>. It is possible to create "phantom type synonyms", but they are usually useless
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  • Diagrams/Dev/Arrows
    ...lection of "standard" arrowheads for the user to choose from. In addition it ought to be possible for the user to specify any diagram they like for use ...ght also want to have control over the middle of the arrow -- i.e. whether it curves, and if so how much and in which direction, etc.
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  • Hac φ/Talks
    <!--If you'd like to give a talk, announce it here; tell us your name, the title of the talk, a short description. Pleas
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  • List of Projects that use Haskell
    ...often ask, «Okay, Haskell looks like a fun language; but what's written in it?» : Not necessarily «free as speech», but people should be able to try it out and look at the source code.
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  • Raspberry Pi
    '''Note:''' GHCi does not work on ARM with older versions, but it has become available in GHC 7.8. See [http://www.haskell.org/pipermail/hask ...and it may still be possible to install it in an experimental manner, but it is not (currently) available in the Debian Raspberry Pi repository. [http:/
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  • Cabal/How to install a Cabal package remotely
    Sometimes, it is difficult or inconvenient to set up the entire virtual server. You may find it much easier to get just a working
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  • ThreadScope
    Next, check out the user guide. We call it the [[ThreadScope Tour]]. ...esponds to an operating system thread. For each thread you can see whether it is running a Haskell thread or performing garbage collection. You can find
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  • Applications and libraries/Network
    ...cess of downloading TV Series from [http://www.mininova.org mininova.org]. It will scan your downloaded files to find out what your interests are and dow :Ginsu is a client for the gale chat system. It is designed to be powerful and above all stable, as well as having a quick
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  • Formatting function types
    functions seemed very strange to me: "Okay, we give it a handle, and get '' I aggree with the argument, that for beginners it is hard to see what a function returns, but that has to do with currying. A
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  • Language and library specification
    ...shed in July 2010, and is the current definition of the Haskell language. It is freely available online, in the following formats: * read it online: [http://www.haskell.org/onlinereport/haskell2010 The Haskell 2010 R
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  • Introduction to IO
    ...page is intended as a quick introduction to how IO is treated in Haskell. It doesn't describe everything there is to know, but should give some idea of ...first performs the action <code>x</code>, and captures its result, passing it to <code>f</code>, which then computes a second action to be performed. Tha
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  • Yhc/RTS/Exceptions
    ...and an exception handler. It runs the IO action and if an exception occurs it runs the exception handler. throw simply throws an exception. For example ...sulted from a call to the 'error' function then it does nothing, otherwise it rethrows the exception.
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  • Toolmaking libraries
    ...ntyped core around this language, after going over it with a comb to check it's adequately expressive?: ...hoices to note: this isn't a supercombinator language or a variant of ANF, it's an ordinary untyped lambda calculus with minimal extensions to capture pa
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  • Catch
    ...e/total total] package does not search for incomplete pattern matches, but it does allow you to write compiler-checked exhaustive pattern matches. [http: *[[Xmonad]]'s central StackSet.hs module has been checked repeatedly, as it has evolved. Unfortunately currently this module goes beyond Haskell 98, bu
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  • How to work on lists
    ...le, <hask>filter odd xs</hask> returns a list of ''odd'' numbers. That is, it deletes everything that is ''not'' odd. :Find or write a function to convert foo into bar, and then apply it to the whole list using <hask>map</hask>.
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  • Extensible record
    ...n of the Haskell-like language [http://www.cs.uu.nl/~daan/morrow/ Morrow], it is based on the concepts of the article. And [http://www.cs.uu.nl/~daan/pu ...tem allows field selection and dropping of fields using pattern matching. It also supports defaulting.
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  • Cxx foreign function interface
    ...ace to a C++ library using the "export C" declaration (in C++) which makes it look like a C library. This seems to be the standard technique for bridgin ...ng to C++, using the mangled C++ names directly without using "export C". It also suggests the possibility of a more automated approach using gcc-xml.
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  • AtomicMemoryOps
    ...s a thin layer over the basic operations: GHC primops or foreign primops. It does, as of version 0.4, provide some useful operations for end-users, incl ...o point at the new one. The problem with that approach in Haskell is that it can be very hard to provide the old pointer with any reliability, due to th
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  • IO in action
    * if a function's result changes, it is <b>only</b> because one or more of it's arguments has changed. * For those who prefer it, John Launchbury and Simon Peyton Jones's [https://citeseerx.ist.psu.edu/vi
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  • PermissiveImportsProposal
    ...t them as such. There's no way to take advantage of the current behaviour; it just causes fewer programs to be accepted than are necessary, and given we' ...ead of String-based) requires a certain amount of friction. In these cases it is common to use the same identifiers for the same functionality, but this
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  • BayHac2014/Prolog
    ...to see it again :)—you'll probably have a chance. I'll also try to improve it based on feedback I've gotten; if you have anything to say, please email me
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  • Means of expression
    It is generally good style to remember the rule: Thus it is not good style to comment intensively if the language provides primary w
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  • Conduit
    Conduits are an approach to the streaming data problem. It is meant as an alternative to [[Enumerator_and_iteratee|enumerators/iterato
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  • Emacs/Inferior Haskell processes
    ...skell, the option is called <code>haskell-program-name</code>. You may set it to <code>"/some/where/ghci.exe"</code> or even <code>"cabal-dev ghci"</code ...as part of the haskell-mode package, so there is nothing special to do for it. On some systems, you may need this in your .emacs:
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  • Hac φ/Projects
    If you need a place to host a project so that others can help with it, we suggest using [http://github.com github] with [https://git-scm.com/ git ...have a project that you want to work on at the Hackathon, please describe it here.
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  • Safely running untrusted Haskell code
    ...our own monadic type that is a restricted subset of <code>IO</code>). But it's a lot more complicated than that... ...lls out to [http://hackage.haskell.org/package/mueval mueval], which while it uses many of the same techniques, is structured differently.''
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  • Unary operator
    It is syntactic sugar for the <hask>Prelude.negate</hask> function and allows With it enabled, expressions like <hask>(n !)</hask> are parsed as <hask>((!) n)</h
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  • Web/Libraries/XML and HTML
    ...the XHTML package by being faster and having a convenient monad instance. It looks like this: ...L documents, including the DTD subset and the document subset, in Haskell. It contains an XML parser, an HTML parser, namespaces are supported, XPath exp
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  • WxHaskell/Mac
    ...ded, but if you want to do it anyway, download the source code and install it with the following flags <li>Now it's time to install the wxHaskell libraries proper:
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  • Command line option parsers
    | {{HackagePackage|id=argparser}} || - || None (though it depends on package containers, which uses extensions) || GHC 9.0 build succ ...uccessful (2021-10-23) || 254k || Applicative Functor; for wrong arguments it does not show a specific error message but the general usage pattern
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  • Mutually recursive modules
    This way it is not possible to find a sequence to compile them one after another. Up to version 6.10 it is not possible to create mutually recursive class definitions across modul
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  • Applications and libraries/Generic programming/Template
    <li><p>Does it support generic functions with different arities?</p></li> <li><p>Is the approach extensible, if not can we do anything about it?</p></li>
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  • Context alias
    ...be restructured without breaking compatibility to a certain degree. Also, it would make fine-grained class hierarchies usable. ...straintKinds extension ({{GHCUsersGuide|exts/constraint_kind||a section on it}}), you can write:
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  • List notation
    However it is [[syntactic sugar]] for <hask>(0:1:2:3:[])</hask>. :Thus it is more theoretically sound and easier to edit.
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  • Applications and libraries/Music and sound
    ...3. It is written in Haskell. It is designed to be simple, fast and robust. It's very stable, with one instance running for several months. ...synthesizing sound produced by musical instruments, for example, although it does capture the way certain (real or imagined) instruments permit control
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  • Programming performance/hay.steve Python
    ...sses with that data. I originally said it took 2 hours, but I am bringing it down to 1.5 because I was eating dinner while and watching a movie while co # iterates through a heap while destroying it (side effect)
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  • Newtype
    ...the type has ''exactly one constructor'' with ''exactly one field'' inside it. ...ant to make a type abstract, you can wrap it in a <hask>newtype</hask> and it'll be considered distinct to the type-checker, but identical at runtime. Yo
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  • WxHaskell
    == What is it? == ...ajor GUI platforms; including GTK, Windows, X11, and MacOS X. Furthermore, it is a mature library (in development since 1992) that supports a wide range
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  • Sox
    You can use it to write, read and play audio signals in Haskell applications.
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  • GHC under Wine
    [[GHC]] runs flawlessly under Wine. Here's a guide on how to get it working. ...e haskell program to compile. Hello World examples are good. Try compiling it:<br/>
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  • Hac NYC/Projects
    If you need a place to host a project so that others can help with it, we suggest [http://hub.darcs.net/ darcs hub], which offers free hosting fo ...have a project that you want to work on at the Hackathon, please describe it here.
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  • Dynamic programming example
    ...or boxes of 20 pieces. You can only buy zero or more such boxes. Therefore it is impossible to buy exactly 5 pieces, or exactly 7 pieces, etc. Can you bu ...ught, or <hask>Just (x,y,z)</hask> if i pieces can be bought, and moreover it can be done by x boxes of 6, y boxes of 9, and z boxes of 20. Below the cod
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  • Diagrams/Dev/Transformations
    ...rix by such a unit vector picks out a column of the matrix, as I claimed. It's also not too hard to see that the matrix's action on any other vector is Now, if one has a matrix <math>M</math> it is easy to compute its transpose, and not too difficult to compute its inve
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  • The Monadic Way
    ...ok like and what they are useful for, from the perspective of a ... lover. It could be an introduction to "The Monadic Way" tutorial. ...cifically StateT. This part is just a skeleton, since, for the time being, it contains only the code.
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  • MapReduce as a monad
    ...general technique for massively parallel programming developed by Google. It takes its inspiration from ideas in functional programming, but has moved a ...OP framework, which is very complex and somewhat temperamental. Moreover, it is necessary to write HADOOP-specific code into mappers and reducers. My p
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  • Cabal-make
    ...kages software can do so entirely with [[Cabal]] commands. In particular, it's a bit hairy to get the best results from [[Haddock]] & [[hscolour]]. ...ine by itself, ''including'' the first one in the list (instead of placing it aside the Cabal directive). You can use "<code>make show-modules</code>" to
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  • Web/Existing software
    Suggests that you travel through a parallel web with translated content. It's based on Simon Marlow's Haskell Web Server.
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  • .lhs
    (must use "https://wiki.haskell.org/index.php?title=.lhs&redirect=no" to view it).
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  • Ghc-gc-tune
    It can also generate .svg output:
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  • News/1990
    ...that a 3rd Haskell implementation is underway at Imperial College. Notably it compiles to native assembly.
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  • High-level option handling with GetOpt
    Sven Panne's GetOpt module does a fine job at parsing command line options. It required argument). It can even produce a nice usage info from option
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  • Incompatibilities between MTL 1 and MTL 2
    and mtl-2. It makes transformers more useful on its own, and also saves clients of mtl fr ''Rationale:'' This makes the instance Haskell 98, so it can be included in the
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  • Benchmarks Game
    ...8.8.1 is installed on the Benchmarks Game servers, please make full use of it! There is an immediate need for a complete revamp of all the entries to fix ...many of the benchmarks with no clear rational for the different versions. It'd be better to have entries for "GHC" be clean, short, functional code and
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  • Import
    Note that multiple import statements for the same module are also allowed, so it is possible to mix and match styles if its so desired (for example, importi ...sy to read. Typically a module only redefines a few prelude functions, and it's simpler to just hide the ones you don't want to clash with.
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  • Performance
    ...is along the general lines of "Can I write this program in Haskell so that it performs as well as, or better than, the same program written in some other Moreover, it's often not clear if two programs which supposedly have the same functional
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  • Web/Literature/Static linking
    ...t of date, it refers to GHC 6.8 and Database.SQLite. Please someone update it with a more recent example, if necessary.'''
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  • Parsing a simple imperative language
    "Principles of Program Analysis" by Nielson, Nielson and Hankin). It includes only a few statements and basic boolean/arithmetic expressions, which makes it
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  • ZuriHac2016/Projects
    I thought it might be insteresting to discuss about it with people. Being myself a recent "Haskeller" I find it quite hard
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  • Diagrams/Contributing
    ...ething or ask a question, you can be sure that someone will eventually see it and respond.) ...lan to make any modifications to the code in a certain repo, you may clone it directly instead of first forking on github and then cloning from your fork
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  • MonadFix
    ...o extension. {{GHCUsersGuide|exts/recursive_do||a section on RecursiveDo}} It is useful for building cyclic data in monadic code. == What it is not and what it is ==
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  • Pronunciation
    | just as inconvenient to convey grouping verbally, whether it's layout or punctuation
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  • Implementations
    ...ugs, it runs more slowly, and it needs more memory. However, the programs it produces run ''much'' faster. ...ing for time and space, and supports concurrent and parallel programming. It is available for most common platforms, including Windows, Mac OS X, and se
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  • Diagrams/Dev/Migrate1.3
    ...pe, potentially paving the way for things like automatic differentiation. It does, however, mean that many types are now slightly different. ...rete vector. Basically this means whenever you saw <code>v</code>, replace it by <code>v n</code>. So:
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  • Functional programming
    ...ations as the evaluation of expressions. This article is meant to describe it briefly; however, the best way to understand functional programming is to l ...difficult to determine statically when those resources can be released, so it is necessary to use automatic [[memory management]].
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  • Functional programming/Alternative 1
    ...ations as the evaluation of expressions. This article is meant to describe it briefly, however the best way to understand functional programming is to le ...pe. If such a function '''escapes''' their block after being returned from it, the '''local variables''' must be '''retained''' in memory as they might b
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  • Parsec
    Haskell. It can parse context-sensitive, infinite look-ahead grammars but it performs best on predictive (LL[1]) grammars.
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  • Eta conversion
    Extensive use of &eta;-reduction can lead to [[Pointfree]] programming. It is also typically used in certain compile-time optimisations.
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  • Haskell 2010
    ...l/2009-November/021750.html announced] at November 24th 2009; GHC supports it since revision 7.0.1.
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  • Cloud Haskell
    ...e purpose is to make it easier to write programs for clusters of machines. It provides a message passing communication model, inspired by and very simila ...package/distributed-process-azure distributed-process-azure] backend makes it possible to run Cloud Haskell applications on Microsoft Azure virtual machi
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  • Case comprehensions
    ...ing, suggesting the idea of ''drawn from'' as in a list comprehension. But it is very nice to reuse precisely the list comprehension syntax. but when it's used in case expressions:
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  • Haddock/FAQ
    In fact it does, but you have to add spaces between parentheses and the infix symbols
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  • Applicative functor
    It has turned out that many applications do not require monad functionality bu This is obviously necessary in some cases, but in other cases it is disadvantageous.
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  • WxHaskell/Building
    Getting wxHaskell is easy on MacOS X and Linux. It's slightly less easy on Windows. * Linux - the wxWidgets that ships with your system (as long as it's the 2.8 one and not the 2.6 one) should work.
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  • List comprehension
    ...say <tt>@undo</tt> and then your list comprehension, it will shoow you how it expands: .../docs/html/users_guide/exts/monad_comprehensions.html MonadComprehensions] it would.
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  • Internationalization of Haskell programs using gettext
    ...t does the same thing for haskell files --- '''hgettext'''. You could find it on Hackage. It will gather all strings containing the function '__' from the Main.hs and w
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  • HNN
    ...ewrite. If you're interested in getting involved or just keeping an eye on it, check the [http://trac.haskell.org/HNN/ project page] and the [http://proj The instructions to get it and build it are :
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  • Haskell in web browser/Calc example
    ...ent with visible border: it encloses all other elements of the calculator. It is also responsible for receiving keyboard input. ...p</hask>. All buttons use the same ''Message Box'' <code>calcmb</code>, so it is passed to each button's creation function. Each button uses its own char
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  • Opting for oracles
    ...udgets_thesis_color.pdf the Fudgets thesis] refers to this implementation. It was fairly pleasant to work with and quite practical. ...- one classic example being ''concurrency''. For a language to support it, it must provide computations some means of allowing multiple sub-computations
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  • The Monad.Reader/Discuss Issue11
    ...unfamiliar with FingerTrees, but very pleased with what I found. Indeed, it is easy to directly implement Incremental Maps with FingerTrees. I've atta
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  • Emacs
    ...-language-server.readthedocs.io/en/latest/configuration.html#emacs setting it up with Emacs] It provides a [http://spacemacs.org/layers/+lang/haskell/README.html Haskell d
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  • Reactive-banana/Examples
    ...et up an event network with your own event loop and how to pause or resume it. : A wave-like pattern. Not the most beautiful code, but it demonstrates that you can generate timed events.
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  • Lifting
    ...>), you will notice that <hask>fmap</hask> already is a lifting operation: It transforms a function between simple types <hask>a</hask> and <hask>b</hask If the size of the containers isn't fixed, it's not always clear how to make lifting operations for them. The <hask>[]</h
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  • Mac OS X
    ...tallers of the full Haskell Platform development environment. We recommend it: ...is an easy-to-use integrated programming environment for Haskell on OS X. It is a one-click install of a complete Haskell system, including Haskell comp
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  • 99 questions/Solutions/47
    Java operator precedence (descending) as far as I could fathom it:
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  • Himerge
    It technically stands for "Haskell Interface for eMerge" ; though I personally ...le ghc, you should upgrade ghc first and then run ghc-updater. Either way, it would be good to emerge ghc first, then emerge himerge.
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  • Haskell a la carte
    ...). Sorts not only integers but anything that can be compared. But granted, it's not in-place. ::The ''infinite'' list of fibonacci numbers. Just don't try to print all of it.
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  • Real World Applications/Event Driven Applications
    In the following, I will show a way to architecture a Haskell system so that it can scale from small "toy" applications (dealing with low level IO events) So please contribute your (clearly superior of course) alternative way to do it here: [https://www.haskell.org/haskellwiki/Real_World_Applications Real Wor
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  • Gtk2Hs/Mac
    ...work with other versions of gcc that you already have installed. However, it will not work with gcc versions <= 4.2. Try running the gtk-demo program. Does it also fail?
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  • Concurrency demos/Haskell-Javascript concurrency
    ==Try it out==
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  • Tetris Cube
    The Tetris Cube is a three dimensional puzzle. It consists of 12 pieces. There are three colors, and there are four pieces of
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  • IO then abstraction
    Even so, it is fair to object that the ‘monadified’ definition is ugly compared ...kely to disappear from the functional programming landscape any time soon, it is vital that we, as the functional programming community, somehow overcome
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  • UTF-8
    ...bin/hackage-scripts/package/utf8-string utf8-string package] from Galois. It
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  • Inlining and Specialisation
    The <code>INLINE</code> pragma can be applied to top-level definitions. It behaves like the <code>INLINABLE</code> pragma but makes GHC very keen to i It is a sledgehammer and without care you can make the compiler take a long ti
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  • Foldable and Traversable
    When you've been using it for a little while, there seem to be some baffling omissions from the API. In other words, it is a type which supports "<hask>foldr</hask>".
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  • HaRe
    ...ll 98/2010 refactoring tool for automated refactoring of Haskell programs. It is integrated with Emacs. It is being rewritten to use the GHC API.
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  • 99 questions/54A to 60
    A binary tree is either empty or it is composed of a root element and two successors, which are binary trees th Since a "leaf" node is a branch with two empty subtrees, it can be useful to define a shorthand function:
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  • POV-Ray SDL project
    ...fectively a scene ''construction'' language now, since a few releases back it become a Turing-complete programming language. This has heralded a new era in POV-Ray. Before it was 'just' a very powerful ray tracer. Now people routinely construct elabo
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  • Diagrams/Dev/Freezing
    Some rough notes/explanations on freezing and how it relates to optimizing the backend API. Eventually these notes should go in ...ller circle. Diagrams are supposed to be scale-invariant but in actuality it would be surprising for them to be truly scale-invariant with regards to li
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  • Abstract data type
    it is not necessary to completely hide the representation of data, so a normal This type is ''abstract'' because it leaves some aspects of its structure undefined, to be provided by the user
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  • Applications and libraries/Concurrency and parallelism
    ...supported concurrency with lightweight threads for more than a decade, and it [http://shootout.alioth.debian.org/gp4/benchmark.php?test=threadring&lang=a :hMPI is an acronym for HaskellMPI. It is a Haskell binding conforming to MPI (Message Passing Interface) standard
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  • Monad Transformers
    ...nads-fd monads-fd]: this was the prototype of the new mtl implementation. It is now obsolete, and simply re-exports mtl version 2. But because it lacks the monad classes, you'll have to lift operations to the composite mo
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  • Applications and libraries/Interfacing other languages
    ...port/haskell2010/haskell.html Haskell 2010 Language Report]. You may learn it by example at the :A tool to simplify the process of interfacing C libraries to Haskell. It is less powerful than HaskellDirect, but easier to use and more portable.
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  • Real World
    An exciting, upcoming book from O'Really! Don't miss it!
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  • Continuation tutorials timeline
    Please update this list as it becomes outdated! If you find a tutorial, article, post, comment, or messag *:"As I understand it we can achieve a continuation passing style of programming by passing in th
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  • Web/Libraries/Formlets
    ...a nothing, it won't have a default value. If you pass in a (Just "value"), it will be pre-populated with the value "value". ...irs with a value and the corresponding label, a possible default-value and it will return something of type a.
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  • EclipseOn Mac OS X
    [[EclipseFP]] seems to work ok on [[Mac_OS_X]], but it doesn't seem like there is much testing on OS X. Installing per instructio
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  • HaskellImplementorsWorkshop/2016/Call for Contributions
    2016 this year in Nara. It is a forum for people involved in the It is important to distinguish the Haskell Implementors' Workshop from
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  • Bogre-Banana
    ...ll.org/package/bogre-banana Bogre-Banana] is a 3D game-engine for Haskell. It uses Haskell bindings to the [http://www.ogre3d.org/about OGRE 3D engine] a ...an find more information about it at [[Reactive-banana | it's wiki page]]. It is highly recommended that you read the [[FRP_explanation_using_reactive-ba
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  • Monads as containers
    A [[monad]] is a container type together with a few methods defined on it. one time must be the same type (it is homogeneous).
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  • Haskell in web browser
    ...ial does not focus on the specifics of DOM/CSS/XMLHTTP programming per se; it contains information how to ''use'' these interfaces in a Haskell program.
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  • 99 questions/Solutions/60
    ...ight-balanced binary tree of height H. What is the maximum number of nodes it can contain? ...his question is more difficult. Try to find a recursive statement and turn it into a function <hask>minNodes</hask> that returns the minimum number of no
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  • Google summer of code
    counting it as a success but I am waiting for a new release of HSE and ...0c4/687474703a2f2f692e696d6775722e636f6d2f3759586f5666742e676966 demo] of it working
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  • OpenWRT
    ...the text; I originally wrote it as a blog post. Please feel free to edit it to be more third-person and wiki-appropriate.) Since my OpenWRT box has an x86_64 processor, it could almost run the
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  • AutoForms
    ...orms is a library to ease the creation of Graphical User Interfaces (GUI). It does this by using generic programming to construct GUI components. ...UI. While this transformation is implemented, it is not as 'inteligent' as it could be.
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  • Modest GHC Proposals
    It cannot attach to exports (i.e. if we wish to not deprecate "foo" but only i It also cannot attach to methods within classes.
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  • Logic programming example
    ...ode is a full solution to a relatively simple, but classic, logic puzzle. It uses properties of the List Monad, in a straightforward way, to declarative fashion. Then it is just a matter of testing each combination to make sure it
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  • Handling errors in Haskell
    There is simply no value there. This isn't a problem in the system. It means you don't care why there isn't a value, or you already know. <hask>Ma Again, depends on the code and the person writing it whether an explicit case is used. Often monads like <hask>Maybe</hask> are
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  • Gtk2Hs/Tutorials/Intro
    Then we compile it... How to compile it with GHC on linux/mac/win32
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  • Dependent type
    It seems to me that the dependent type construct ..., eager evaluation, and optional lazy evaluation via laziness annotations. It has a very Haskell-like syntax and is available on [http://hackage.haskell.
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  • The JavaScript Problem
    ...guage.''' JavaScript, the language, has some issues that make working with it inconvenient and make developing software harder : ...re working to achieve this, in varying forms. There are various ways to do it, but we ought to opt for compiling an existing language, Haskell, to JavaSc
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  • BayHac2017/Clash
    ...its syntax and semantics from the functional programming language Haskell. It provides a familiar structural design approach to both combinational and sy * Or set it to dim lights that show the slowly diminishing state of each of the process
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  • GHC/Stand-alone deriving declarations
    because the instance declaration would have a non-standard context. It would have to look like this: ...) should obviously work in a standalone deriving setting too. But perhaps it can be generalised a little. Currently you can only say
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  • Programming performance
    The goal is to measure how long it takes to implement solutions to a standard problem in your programming lang ...amount of time required. If you wish, you may look at other solutions but it is preferable that you do not.
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  • XHB
    ...st that it draws a window (or several windows), and ask the server to send it any input the user sends to these windows. Thus, several clients may connec ...rogram to be responsive to the user input, as well as to refresh requests, it needs to handle each event in a rather short period of time (e.g. less that
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  • Module signature
    There's a package on Hackage, you want to use it, but it has some signatures and you're not sure what to do (we call this an ''indef ...has not defined a pre-instantiated package, you may be able to instantiate it yourself. First, you have to find a package which provides implementations
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  • Rhine
    Rhine is an arrowized [[FRP]] library with '''type level clocks'''. It is designed with multi-rate FRP in mind, combining synchronous arrowized FR ...ype. This clock type gives ''clock safety'' since throughout the framework it is ensured that every signal function is run at the speed of this clock.
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  • Es/Librerias y Herramientas/Estructuras de Datos
    :A bundle for generic programming. It provides programming support for generic traversal as useful in the impleme :The Partial library provides a partial order class. It also provides routines for generating a Hasse diagram from a set and a part
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  • BayHac2017
    <!-- Hide the "plz register" banner, it's basically too late now ...ndy Maguire: '''[http://reasonablypolymorphic.com/dont-eff-it-up Don't Eff It Up: Free Monads in Action]''' ([https://youtu.be/gUPuWHAt6SA video 46m])
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  • Chaitin's construction
    ...that is lacking yet, the formulae and the concepts are not correct without it.''''' ..., a binary code for Combinatory Logic or Lambda Calculus does not suffice. It's also necessary to apply the encoded term on the binary data that follows
    10 KB (1,527 words) - 09:31, 24 April 2024
  • Parsing expressions and statements
    ...e a few fields. A minimalist preset is <hask>emptyDef</hask> and we change it with: ; <tt>m_identifier</tt> : parses and returns an identifier, checking that it does not clash with a reserved word.
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  • Untypeable Haskell 98
    Here we document code that looks like it should be valid Haskell98, but
    772 bytes (147 words) - 15:19, 6 February 2021
  • Embedded domain specific language
    ...y/039639.html Designing DSL with explicit sharing (was: I love purity, but it's killing me)] ...slated to [[LLVM]] assembly language. This warrants very fast computation. It uses shallow embedding.
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  • Tutorials/Programming Haskell/Introduction
    It's about time we got some job done in [[Haskell]], eh? Now, one of my "Programming Perl". It was full of lots of practical examples of Perl
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  • Avoiding IO
    ...type signature says more or less that almost everything must be expected. It is hard to test them, because they can in principle depend on every state o Thus in order to maintain modularity you should avoid I/O wherever possible. It is too tempting to unsafely disguise the use of I/O, so here instead are so
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  • Parallelism vs. Concurrency
    To this end, it can even be an advantage to do the same computation twice on different unit nonetheless it may benefit from multiple processing units with respect to speed.
    3 KB (477 words) - 10:52, 28 March 2018
  • HaskellImplementorsWorkshop/2015/Call for Contributions
    2015 this year in Vancouver. It is a forum for people involved in the It is important to distinguish the Haskell Implementors' Workshop from
    4 KB (536 words) - 12:15, 4 August 2015
  • New monads
    It seems that the liftIO function from MonadIO can be generalized to access wh It is a new version of the mtl package with base monads: Id, and Lift, and tra
    4 KB (648 words) - 09:43, 9 December 2014
  • Monad Transformers Tutorial
    ...ts result in MaybeIO then we just have to use runMaybeIO there, and that's it. What happens if we now have some "print" in between? ...k> to an <hask>IO (Maybe a)</hask> that doesn't "fail" our Maybe monad. So it just means putting a <hask>Just</hask> in there:
    5 KB (801 words) - 19:04, 8 February 2014
  • Output/Input
    ...side effect can’t be in the functional program, it will have to be outside it. It can also be used to provide access to external resources:
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  • Informatics 1 - Functional Programming
    ...textbook is Simon Thompson: Haskell, the Craft of Functional Programming. It is also recommended that students explore Miran Lipovača: Learn You a Hask ...t extra challenges and in-depth work. These sessions are quite popular, so it is expected that students have made an attempt at some of the optional exer
    3 KB (537 words) - 01:42, 20 October 2016
  • Xmonad/Using xmonad in Gnome/0.6
    ...herwise, the nautilus desktop will be raised into the floating layer where it covers all your other windows.) ...use be able to use the keyboard to e.g. getting rid of dialogues we rebind it to the left ''logo key'':
    7 KB (1,095 words) - 15:16, 6 February 2021
  • Do notation considered harmful
    ....haskell.org/cgi-bin/hackage-scripts/package/binary-0.4.1 Binary] package. It contains the <hask>Put</hask> monad, which in principle [http://www.haskell In fact it is a <hask>Writer</hask> monad using the <hask>Builder</hask> type, and all
    10 KB (1,589 words) - 01:08, 27 September 2021
  • Solution4.html
    If the compiler cannot guess which MonadPlus to use you will need to specify it when the function is called. So, <hask>parent someSheep :: Maybe Sheep</has
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  • Package versioning policy
    ...rials for versioning: it allows packages to specify their own version, and it allows dependencies that specify which versions of the dependent package ar ...ime there has been an informal policy in use in the Haskell community, but it became clear that we were running into trouble with incorrectly-specified d
    9 KB (1,408 words) - 20:31, 2 October 2016
  • Merchandise
    *[http://www.cafepress.com/doitmonad Do it in a Monad] (monad laws on back) *[http://www.cafepress.com/monadpure "Do it in a Monad ... and remain pure!"] (various shirts with logo on front, monad
    4 KB (629 words) - 17:52, 12 January 2023
  • Manatee
    You can consider it is new environment mix Gnome and Emacs. Like Gnome to provide friendly grap ...nclude core) running in separate process to protected core won't crash. So it
    12 KB (1,458 words) - 02:36, 26 April 2021
  • Diagrams/Dev/Constraints
    ...the SMT solver people) gain many useful constraint-solving algorithms, so it was a good library to use. ...my proposal (or its comments, rather), and so that was what I implemented. It wasn't really any effort, since there was already a type family (V) to use.
    10 KB (1,671 words) - 03:59, 16 August 2014
  • Exception
    The great thing about Haskell is that it is not necessary to hard-wire the exception handling into the language. but we can handle situations where it is unacceptable for the caller to check a priori whether the call can succe
    10 KB (1,404 words) - 06:22, 22 January 2020
  • Base package
    ...ging from data structures to parsing combinators and debugging utilities. It is specific to the GHC implementation of Haskell. .../wikis/commentary/libraries/version-history. The below is retained because it goes back further in history.
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  • Haskell Governance
    ...system. This page collects them and lists their domains of responsibility. It can be used to figure out where to direct contributions, questions, or conc
    1 KB (180 words) - 06:14, 10 December 2020
  • The Monad.Reader/Issue3/Functional Programming vs Object Oriented Programming
    ...of the pros and cons of functional or object-oriented programming. Rather, it's a guide for a new Haskell programmer coming from languages like Java, C#/ ...t and replace just the bits you want to change. This isn't as expensive as it sounds, due to the extensive data sharing that immutable objects make possi
    10 KB (1,718 words) - 07:14, 10 August 2022
  • DDC/FieldProjections
    ...efinition is similar to a regular <hask>instance</hask> definition in that it defines a set of functions associated with a particular type (in this case, ...f the first argument of <hask>(.)</hask> to decide what projection to use, it needs to be constrained to a data type (not just a type variable). Usually
    3 KB (430 words) - 11:59, 19 April 2021
  • CSound
    ...nd-expression}} is a framework for computer music that is based on Csound. It generates Csound code from Haskell code. The user can create music on the f
    1 KB (184 words) - 10:13, 16 September 2015
  • Time
    ...he first few data types in this guide are not widely used in practice, but it is important to understand their associated concepts before moving onto the Although <tt>AbsoluteTime</tt> is appropriate for many tasks, it is rarely used in applications and you will likely never use this data type
    11 KB (1,837 words) - 06:28, 8 October 2022
  • Functional dependencies
    That, however, isn't really what we want. As it stands, even a simple expression like this has an ambiguous type unless you and it will infer the type <haskell>v :: Char</haskell>
    4 KB (706 words) - 22:41, 21 July 2021
  • WxHaskell/Development/Environment
    ...release, so it pays well to ensure new code will work with both versions. It is possible to safely co-habit two versions of wxWidgets. When you do, wxHa Firstly, see [[WxHaskell/Building#Source_Release|Source Release]], however it is recommended that you do the following, instead of following the instruct
    5 KB (713 words) - 19:14, 31 January 2016
  • Curry-Howard-Lambek correspondence
    ...ore, ''given'' a value of type <hask>a</hask> (a proof of <hask>a</hask>), it ''constructs'' a value of type <hask>b</hask> (so the proof is ''transforme ...ng</hask> can be pattern matched against the constructors to see which one it proves.
    8 KB (1,303 words) - 15:42, 18 November 2019
  • Category theory/Natural transformation
    Let us define the <math>\eta : \Phi \to \Psi</math> natural transformation. It associates to each object of <math>\mathcal{C}</math> a morphism of <math>\ Thus, we want to build a parser combinator (we could notate it graphically with something like <math>\mathrm?\!\!\to\!\!\mathrm*</math>) w
    9 KB (1,305 words) - 03:17, 23 September 2014
  • Stanamic typing
    verifies the balancing constraint at compile time -- if it can. If the
    788 bytes (130 words) - 15:19, 6 February 2021
  • Foldable Traversable In Prelude
    ...ntended to summarize the proposal as it now stands as of 28 January, 2015. It is a work in progress, done as best as possible, but should not be taken as ...was a large appetite in the community to "modernize" the Prelude and bring it into line with the current widespread usage of classes such as Applicative,
    14 KB (2,640 words) - 11:47, 26 November 2023
  • Xmonad/Guided tour of the xmonad source/StackSet.hs
    corrupting pollutants such as the IO monad and the X server, it is data structures used to store the state of xmonad. It is heavily
    16 KB (2,690 words) - 16:02, 26 December 2022
  • Rank-N types
    ...all</hask> can be floated out of the right-hand side of <hask>-></hask> if it appears there, so: is also a Rank-1 type because it is equivalent to the previous signature.
    4 KB (693 words) - 13:33, 15 April 2024
  • Web/Frameworks/HSP
    everything pertaining to literal XML syntax. In particular it contains injected by trhsx. It also nominally contains generic combinators for
    4 KB (597 words) - 10:39, 19 April 2021
  • WxHaskell/2.8
    ...d making sure that you have the C++ compiler option installed for MinGW as it is 'not' the default: ...path/to/wxWidgets/gcc_dll, which you will need to copy to a location where it can be found when running your executables.
    7 KB (1,057 words) - 03:54, 14 August 2021
  • Disposing of dismissives
    ...seems the ideal task for the implementation's garbage collector...provided it isn't carrying out a full collection each time a program e.g. uses up its q ...ogram state. Fortunately, as the technique is based on garbage collection, it can benefit from the extensive prior research, development and experience i
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  • Mastermind
    It is a nice task to let the computer guess a code.
    1 KB (173 words) - 11:37, 4 January 2016
  • Web/Frameworks/HAppS
    ...mentation, you may find yourself looking at blog post tutorials, but since it is rapidly changing, about half of these tutorials are out of date. ...functions. You don't need most of them, but because documentation is poor, it can be intimidating.
    4 KB (517 words) - 05:52, 8 June 2023
  • Foldr Foldl Foldl'
    If you want you can copy/paste this article into your favorite editor and run it. ...s that it can't be made smaller (reduced) until the very last moment, when it's already too late.
    16 KB (2,235 words) - 10:26, 29 March 2019
  • Real World Applications
    It is not always clear how to scale up from small "batch oriented" Haskell app
    978 bytes (130 words) - 14:09, 2 July 2014
  • GADTs for dummies
    ...d what [[Generalised algebraic datatype]]s were or how they could be used. It almost seemed a conspiracy of silence &mdash; people who understood GADTs t Now that I have an idea of how it works, I think that it was really obvious. :) So, I want to share my understanding of GADTs. Mayb
    14 KB (2,322 words) - 13:55, 24 November 2023
  • Non-empty list
    ...<hask>head</hask> says that the function applies to any list. In reality, it can only be meaningfully applied to non-empty lists. One can eliminate such It must be emphasized that we can eliminate head-of-empty-list errors
    8 KB (1,274 words) - 20:23, 18 July 2014
  • Lazy vs. non-strict
    ...uction" to "evaluation"). So when the evaluation engine sees an expression it builds a [[thunk]] data structure containing whatever values are needed to ...equired by the outer expression, and converts those into eager evaluation. It can do this because the semantics (in terms of "bottom") don't change. Prog
    4 KB (643 words) - 23:33, 5 April 2021
  • ZuriHac2016/BBQ
    ...ly. The weather is forecast to be a bit cloudy, but without any rain, yay! It should work out, but please don't blame us for a bit of rain, if the Swiss
    3 KB (488 words) - 13:14, 23 July 2016
  • Converting numbers
    ...nge can be much larger: on the x86-64 version of Glasgow Haskell Compiler, it can store any signed 64-bit integer. ...sk> and <hask>RealFrac</hask>tional types. The name "real" indicates that it excludes <hask>Complex</hask> numbers.
    6 KB (867 words) - 01:28, 14 April 2016
  • Compose Unconference 2016
    ...ve a project that you want to work on at the unconference, please describe it here.
    1 KB (198 words) - 22:03, 29 January 2016
  • Xmonad/Using xmonad in XFCE
    ...atter is often touted as the most "nimble" of the lot. In my own opinion, it is simpler to use than KDE but with more configuration options (and a saner ...ake sure that xfwm4 (Xfce's default WM) is no longer started. Preferably, it'd be nice if we could have XMonad started this way as well (or even set in
    11 KB (1,742 words) - 10:28, 28 October 2013
  • UnnamedStandard
    ...ypeclasses and lack of hierarchy, and the four different monoid classes in it), and most people using Haskell today use various extensions. Haskell' is t
    896 bytes (132 words) - 22:53, 19 April 2021
  • Happy
    ...do the parsing. Typical usage in in the second stage of a compiler, where it will be used to generate an abstract syntax tree.
    859 bytes (138 words) - 12:00, 19 April 2021
  • Compatibility Modules
    It can be difficult to write code that maintains compatibility with multiple v This module makes it into base version 4.6 but then, when releasing base 4.7, we decide that the
    7 KB (1,079 words) - 08:57, 23 May 2021
  • Lub
    It provides a <hask>lub</hask> function that is consistent with the [[unamb]]
    1 KB (187 words) - 21:38, 4 February 2014
  • Budapest Hackathon 2016
    ...Hackathon2014 info about the first hackathon]), and this time we will hold it in LogMeIn’s Budapest office. ...quirement really, so you can join us even if you didn't fill out the form, it just help us with the organization.
    6 KB (957 words) - 16:10, 20 August 2016
  • OpenGLTutorial1
    ...permission. Parts of the tutorial have been modified and extended to keep it up to date.'' ...rite down the steps I actually can get to work in a tutorial-like fashion. It may be a good idea to read this in paralell to the tutorial linked, since P
    10 KB (1,585 words) - 09:22, 20 September 2013
  • HsLua
    What is Lua? It's a scripting language (like Perl) targeted to be easily integrated into any host application. You can do it in
    13 KB (2,016 words) - 18:34, 20 August 2017
  • Attribute grammar
    It is no wonder that it is exactly a compiler project homepage that provides good circular programm
    4 KB (598 words) - 07:06, 26 January 2018
  • ZuriHac2013/Projects
    ...e involved and would probably work out better with more than one person on it.
    1 KB (168 words) - 22:02, 28 August 2013
  • HaskellImplementorsWorkshop/2013/Call for Talks
    this year in Boston. There will be no proceedings; it is an informal It is important to distinguish the Haskell Implementors' Workshop from
    4 KB (589 words) - 14:46, 1 August 2013
  • Haskell.org domain
    ...easonably well organised, while still helping people do useful things with it.
    1 KB (241 words) - 16:44, 28 May 2015
  • CPlusPlus from Haskell
    Haskell (on Linux, compiled with g++). I refer to it as the "The Hard Way" because it is a tedious, hand done method of generating C++
    15 KB (2,199 words) - 00:32, 23 May 2017
  • Unboxed type
    generally the type system is extended to type these unboxed values. how it underscore to indicate an unboxed type. However it does use the trailing
    3 KB (470 words) - 09:25, 12 June 2023
  • ZuriHac2015/BBQ
    ...The weather is forecast to be sunny with a few clouds, yay! Nevertheless, it will get quite chilly in the evening so '''do bring some warm clothes'''; a
    3 KB (465 words) - 21:17, 27 May 2015
  • Arrow tutorial
    ...combines the output from two other arrow values using a binary operation. It works by splitting a value and operating on both halves and then combining What is <code>h</code>? How does it work?
    8 KB (1,316 words) - 00:00, 17 June 2021
  • WxHaskell/Download
    ...'Note:''If you have an older version of wxHaskell installed, please remove it before installing this version. Older releases can be uninstalled by clicki It is recommended to read the [[WxHaskell/Building_on_MacOS_X|notes]] on using
    5 KB (640 words) - 18:31, 31 January 2016
  • Introduction to Haskell IO/Actions
    it provides as a result (for example String). We say that the action that not take any arguments. Consider '''putStrLn'''. It has the following
    14 KB (2,254 words) - 20:41, 10 November 2020
  • Dealing with binary data
    ...l properties like coverage of the Unicode space and laziness, however when it comes to dealing with bytewise data, <hask>String</hask> involves a space-i Note that we are using strict bytestrings here. (It's quite common to import the
    17 KB (2,795 words) - 04:06, 16 June 2020
  • HStringTemplate
    ...Java StringTemplate library] by Terrence Parr, ported by Sterling Clover. It can be used for any templating purpose, but is often used for dynamically g ...if you write the Stringable instance. The template has a single 'hole' in it called 'name', delimited by dollar signs.
    12 KB (1,726 words) - 15:16, 6 February 2021
  • Applications and libraries/Generic programming/SyB
    ...cast is implemented in GHC. However other compilers do not support it and it is not going to be part of Haskell'. ...n on its own but there is no Haskell implementation that actually supports it. However, type class abstraction can be emulated using MPTC.
    5 KB (827 words) - 04:00, 6 April 2021
  • Humor/Wanda
    Rolls-Royce for $2.75, it would do three million miles to the gallon, and it would deliver enough power to drive the Queen Elizabeth II. And if you
    8 KB (1,343 words) - 09:02, 13 March 2016
  • Continuation
    ...gies or metaphors, that illustrate this difficult concept, or an aspect of it. ...de>goto</code> instruction... The point about <code>call/cc</code> is that it is not a ''static'' (lexical) <code>goto</code> instruction but a ''dynamic
    10 KB (1,560 words) - 12:02, 15 April 2024
  • Peano numbers
    ...tural numbers using only a zero value and a successor function. In Haskell it is easy to create a type of Peano number values, but since unary representa ...and may take a long time doing so, although after you have seen only one, it is obvious that the list is not empty.
    4 KB (571 words) - 20:38, 26 November 2022
  • Contstuff
    It essentially gives you access to the current continuation, which means that it lets you label certain points of execution and reuse these points later in .../hask> type can be polymorphic most of the time. You only need to specify it, if you use some of the CPS effects like <hask>abort</hask>.
    12 KB (2,067 words) - 05:43, 9 March 2021
  • Bravo
    ...s necessary. If the application is supposed to be released in binary form, it's not necessary to ship the template files with the application. ...nd leads to a cleaner separation of program logic and layout. Beyond that, it helps to decrease the number of templates.
    9 KB (1,381 words) - 22:32, 29 June 2021
  • Syntactic sugar/Cons
    It's not amazing that Haskell provides a lot of syntactic sugar. It's amazing that every syntactic sugar has pure functional explanations.
    16 KB (2,610 words) - 17:17, 4 February 2023
  • 99 questions/Solutions/56
    It could be misunderstood that an equality checker just ignoring the branch na
    1 KB (179 words) - 13:36, 25 December 2016
  • 99 questions/Solutions/14
    \y z -> y:y:z -- making it look nicer
    2 KB (220 words) - 20:45, 28 December 2014
  • WebApplicationInterface
    ...e made easy to implement so the investment in supporting it is low, making it more likely to be widely used. ...defined in the interface) to the web servers and applications implementing it.
    14 KB (2,193 words) - 05:45, 12 July 2021
  • Xmonad/Using xmonad on Apple OSX
    ...ig up a Haskell Platform for Leopard PPC (G4, ppc7450) if needed, although it will not be the latest version because my PPC machine died. * Full-screen mode is a good idea (to the extent that it ever is; it does not interact nicely with Exposé/Mission Control or Alt-Tab applicatio
    11 KB (1,893 words) - 17:07, 5 November 2014
  • Specification and proof
    ...tica Project] has an expressive logic called P-logic, and tools supporting it
    1 KB (218 words) - 01:58, 24 March 2018
  • Web/Frameworks/Inactive
    ...orks are suspected to be inactive. If you see that one is not, please move it to the [[Web/Frameworks|Frameworks]] page. Lemmachine is a REST'ful web framework that makes it easy to get HTTP right by exposing users to overridable hooks with sane def
    13 KB (1,880 words) - 07:32, 27 August 2020
  • Cabal/Developer-FAQ
    ...sted extensions. Cabal will pass the appropriate flags to the compiler and it even checks that the compiler supports those extensions. # The best way to do it, if you know your users are using GHC 6.8.x is the new LANGUAGE pragma. Thi
    7 KB (998 words) - 12:32, 2 October 2020
  • Xmonad/Guided tour of the xmonad source/Core.hs
    The next source file to examine is Core.hs. It defines several core data types and some of the core functionality of xmona ...nId = Int</hask>? The reason is that if <hask>type ScreenId = Int</hask>, it would be possible to accidentally do arithmetic with <hask>ScreenId</hask>s
    13 KB (2,057 words) - 10:15, 28 September 2017
  • 99 questions/Solutions/48
    infixl 3 `equ'` -- was 7, changing it to 3 got me the same results as in the original question :(
    899 bytes (132 words) - 19:51, 18 January 2014
  • Xmonad
    ...ame as <code>import XMonad; main = xmonad defaultConfig</code> except that it prevents you from seeing the result of xmonad upgrades.
    4 KB (590 words) - 23:41, 14 June 2017
  • State Monad
    ...ample that demonstrates the use of the standard Control.Monad.State monad. It's a simple string parsing algorithm. -- this is it, the State transformation. Add 1 to the state, return -1*the state as the
    7 KB (1,055 words) - 15:06, 21 December 2018
  • Haskell Platform
    ...rm is a single, standard [[Haskell]] development environment for everyone. It offers a set of blessed libraries and tools, to save you the task of pickin
    2 KB (260 words) - 13:28, 21 January 2020

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