Haskell (programming language)

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Haskell (programming language)
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{{short description|Functional programming language}}

Lennart Augustsson, Dave Barton, Brian Boutel, Warren Burton, Joseph Fasel, Kevin Hammond, Ralf Hinze, Paul Hudak, John Hughes (computer scientist)>John Hughes, Thomas Johnsson, Mark Jones, Simon Peyton Jones, John Launchbury, Erik Meijer, John Peterson, Alastair Reid, Colin Runciman, Philip Wadler| developer = DATE=24 NOVEMBER 2009 MAILINGLIST=HASKELL FIRST=SIMON, DATE=28 APRIL 2016 MAILINGLIST=HASKELL-PRIME FIRST=HERBERT, | latest test date = Type inference>Inferred, static typing, strong typing>strongGlasgow Haskell Compiler>GHC, Hugs, NHC, JHC, Yhc, UHCHelium (Haskell)>Helium, GoferClean (programming language)>Clean,{{harvnb2003FP (programming language)>FP, Gofer (programming language), Hope (programming language)>Hope and Hope+, Id (programming language), ISWIM, Kent Recursive Calculator>KRC, Lisp (programming language), Miranda (programming language)>Miranda, ML (programming language) and Standard ML, Orwell (programming language)>Orwell, SASL (programming language), Scheme (programming language)>Scheme, SISALAgda (programming language)>Agda,HTTP://WWW.CSE.CHALMERS.SE/~ULFN/PAPERS/AFP08/TUTORIAL.PDF>TITLE=DEPENDENTLY TYPED PROGRAMMING IN AGDAFIRST=ULFPUBLISHER=CHALMERS UNIVERSITYLOCATION=GOTHENBURG, Bluespec, Inc.,{{sfn>HudakPeyton Jones2007C++11/Concepts (C++)>Concepts,DESIGN OF CONCEPT LIBRARIES FOR C++ >FIRST1=BJARNE AUTHORLINK1=BJARNE STROUSTRUP LAST2=SUTTON YEAR=2011 ARCHIVEURL=HTTPS://WEB.ARCHIVE.ORG/WEB/20120210041742/HTTP://WWW2.RESEARCH.ATT.COM/~BS/SLE2011-CONCEPTS.PDF C Sharp (programming language)>C#/Language Integrated Query,{{sfn>HudakPeyton Jones2007LAST=MEIJERDATE=1 OCTOBER 2009CHANNEL 9 (DISCUSSION FORUM)>CHANNEL 9ACCESSDATE=9 FEBRUARY 2012, HTTP://WWW.INFOQ.COM/INTERVIEWS/LINQ-ERIK-MEIJER>TITLE=ERIK MEIJER ON LINQFIRST=SADEKWORK=INFOQACCESSDATE=9 FEBRUARY 2012SAN FRANCISCO>SF 2008, CAL,{{Citation neededCayenne (programming language)>Cayenne,{{sfnHughesWadlerpp=12-45–46}} Clean (programming language),{{sfn>HudakPeyton Jones2007Clojure,HTTPS://WWW.AMAZON.COM/GP/RICHPUB/LISTMANIA/FULLVIEW/R3LG3ZBZS4GCTH DEAD-URL=YES TITLE=CLOJURE BOOKSHELF FIRST=RICH ACCESS-DATE=2017-10-03, CoffeeScript,HTTP://WWW.JAVAWORLD.COM/JAVAWORLD/JW-10-2011/111018-COFFEESCRIPT-VS-DART.HTML>TITLE=TURN UP YOUR NOSE AT DART AND SMELL THE COFFEESCRIPTFIRST=MARTINWORK=JAVAWORLDACCESSDATE=9 FEBRUARY 2012, Curry (programming language),{{sfn>HudakPeyton Jones2007Elm (programming language)>Elm, Epigram (programming language),{{Citation needed>date=February 2012}} Escher (programming language),HTTP://WWW.CS.BRIS.AC.UK/PUBLICATIONS/PAPERS/1000073.PDFACCESSDATE=2015-10-07, F Sharp (programming language),SYMEAUTHORLINK1=DON SYMEFIRST2=ADAMFIRST3=ANTONIOYEAR=2007APRESS>PAGE=2 SEQUENCE EXPRESSIONS AND WORKFLOWS., Frege (programming language)>Frege,WECHSUNG>FIRST=INGOURL=HTTP://WWW.FREGE-LANG.ORG/DOC/LANGUAGE.PDFHack (programming language)>Hack,HTTPS://WWW.WIRED.COM/2014/03/FACEBOOK-HACK/>TITLE=FACEBOOK INTRODUCES 'HACK,' THE PROGRAMMING LANGUAGE OF THE FUTUREJOURNAL=WIRED, Idris (programming language),IDRIS, A DEPENDENTLY TYPED LANGUAGEACCESSDATE=2014-10-26, Isabelle theorem prover,{{sfn>HudakPeyton Jones2007Java (programming language)>Java/Generics in Java,{{sfn>HudakPeyton Jones2007LiveScript,HTTP://LIVESCRIPT.NET/#INSPIRATIONACCESSDATE=2014-02-04, Mercury (programming language),{{sfn>HudakPeyton Jones2007Ωmega,{{Citation needed>date=February 2012}} Perl 6,HTTP://WWW.PERLFOUNDATION.ORG/PERL6/INDEX.CGI?GLOSSARY_OF_TERMS_AND_JARGON>TITLE=GLOSSARY OF TERMS AND JARGONPUBLISHER=THE PERL FOUNDATIONARCHIVE-URL=HTTPS://WEB.ARCHIVE.ORG/WEB/20120121145808/HTTP://WWW.PERLFOUNDATION.ORG/PERL6/INDEX.CGI?GLOSSARY_OF_TERMS_AND_JARGONDEAD-URL=YESPureScript,HTTPS://LEANPUB.COM/PURESCRIPT/READLAST=FREEMANYEAR=2016ACCESSDATE=23 APRIL 2017, Python (programming language),{{sfn>HudakPeyton Jones2007LAST=KUCHLINGWORK=PYTHON V2.7.2 DOCUMENTATIONACCESSDATE=9 FEBRUARY 2012, Rust (programming language),HTTPS://DOC.RUST-LANG.ORG/REFERENCE/INFLUENCES.HTMLTITLE=THE RUST REFERENCE: APPENDIX: INFLUENCES, Scala (programming language),{{sfn>HudakPeyton Jones2007LAST=FOGUSDATE=6 AUGUST 2010ACCESSDATE=9 FEBRUARY 2012, Swift (programming language),HTTP://NONDOT.ORG/SABRE/LAST=LATTNERDATE=2014-06-03PUBLISHER=CHRIS LATTNERTimber (programming language)>Timber,HTTP://WWW.TIMBER-LANG.ORG/INDEX_HISTCRED.HTML>TITLE=TIMBER/HISTORYVisual Basic .NET>Visual Basic 9.0{{sfnHughesWadlerpp=12-45–46}}ERIK MEIJER (COMPUTER SCIENTIST)>FIRST=ERIKTITLE=CONFESSIONS OF A USED PROGRAMMING LANGUAGE SALESMAN: GETTING THE MASSES HOOKED ON HASKELLCITESEERX=, 2006, | operating system = Cross-platform| license = weblink}}| file ext = .hs, .lhs}}Haskell {{IPAc-en|ˈ|h|æ|s|k|É™l}}MAILING LIST,weblink anybody can tell me the pronunciation of "haskell"?, 28 January 2008, 12 March 2011, Haskell-cafe, Chevalier, Tim, is a statically typed, purely functional programming language with type inference and lazy evaluation.Type inference originally using Hindley-Milner type inference{{sfn|Peyton Jones|2003}} Type classes, which enable type-safe operator overloading, were first proposed by Philip Wadler and Stephen Blott for Standard ML and implemented later in Haskell."Type classes, first proposed during the design of the Haskell programming language, ..." â€”John Garrett Morris (2013), "Type Classes and Instance Chains: A Relational Approach" WEB,weblink How to make ad-hoc polymorphism less ad hoc, Wadler, Philip, October 1988, live, Its main implementation is the Glasgow Haskell Compiler. It is named after logician Haskell Curry.{{sfn|Hudak|Hughes|Peyton Jones|Wadler|2007}}Haskell is based on the semantics, but not the syntax, of the Miranda programming language, which served to focus the efforts of the initial Haskell working group.Edward Kmett, Edward Kmett – Type Classes vs. the World The last stable release was made in July 2010 with the next standard planned for 2020.Haskell is used in academiaWEB,weblink Haskell in education, 15 February 2016, WEB,weblink Haskell in research, 15 February 2016, and industry.WEB,weblink Haskell in industry, 15 February 2016, As of September 2019, Haskell was the 23rd most popular programming language in terms of Google searchesWEB,weblink PYPL PopularitY of Programming Language index, 2019-09-06,, en, live, 2019-09-06, for tutorials and made up less than 1% of active users on the GitHub source code repository.WEB,weblink Ranking Programming Languages by GitHub Users, Frederickson, Ben,, live, 2019-09-06,


Following the release of Miranda by Research Software Ltd. in 1985, interest in lazy functional languages grew. By 1987, more than a dozen non-strict, purely functional programming languages existed. Miranda was the most widely used, but it was proprietary software. At the conference on Functional Programming Languages and Computer Architecture (FPCA '87) in Portland, Oregon, there was a strong consensus that a committee be formed to define an open standard for such languages. The committee's purpose was to consolidate existing functional languages into a common one to serve as a basis for future research in functional-language design.{{sfn|Peyton Jones|2003|loc=Preface}}

Haskell 1.0 to 1.4

The first version of Haskell ("Haskell 1.0") was defined in 1990.{{sfn|Hudak|Hughes|Peyton Jones|Wadler|2007}} The committee's efforts resulted in a series of language definitions (1.0, 1.1, 1.2, 1.3, 1.4).File:Base-classes.svg|thumb|right|Type classType class

Haskell 98

In late 1997, the series culminated in Haskell 98, intended to specify a stable, minimal, portable version of the language and an accompanying standard library for teaching, and as a base for future extensions. The committee expressly welcomed creating extensions and variants of Haskell 98 via adding and incorporating experimental features.{{sfn|Peyton Jones|2003|loc=Preface}}In February 1999, the Haskell 98 language standard was originally published as The Haskell 98 Report.{{sfn|Peyton Jones|2003|loc=Preface}} In January 2003, a revised version was published as Haskell 98 Language and Libraries: The Revised Report.{{sfn|Peyton Jones|2003}} The language continues to evolve rapidly, with the Glasgow Haskell Compiler (GHC) implementation representing the current de facto standard.WEB, Haskell Wiki: Implementations,weblink 18 December 2012,

Haskell 2010

In early 2006, the process of defining a successor to the Haskell 98 standard, informally named Haskell Prime, began.WEB,weblink Welcome to Haskell', The Haskell' Wiki, This was intended to be an ongoing incremental process to revise the language definition, producing a new revision up to once per year. The first revision, named Haskell 2010, was announced in November 2009 and published in July 2010.Haskell 2010 is an incremental update to the language, mostly incorporating several well-used and uncontroversial features previously enabled via compiler-specific flags.
  • Hierarchical module names. Module names are allowed to consist of dot-separated sequences of capitalised identifiers, rather than only one such identifier. This lets modules be named in a hierarchical manner (e.g., Data.List instead of List), although technically modules are still in a single monolithic namespace. This extension was specified in an addendum to Haskell 98 and was in practice universally used.
  • The foreign function interface (FFI) allows bindings to other programming languages. Only bindings to C are specified in the Report, but the design allows for other language bindings. To support this, data type declarations were permitted to contain no constructors, enabling robust nonce types for foreign data that could not be constructed in Haskell. This extension was also previously specified in an Addendum to the Haskell 98 Report and widely used.
  • So-called n+k patterns (definitions of the form fact (n+1) = (n+1) fact n) were no longer allowed. This syntactic sugar had misleading semantics, in which the code looked like it used the (+) operator, but in fact desugared to code using (-) and (>=).
  • The rules of type inference were relaxed to allow more programs to type check.
  • Some syntax issues (changes in the formal grammar) were fixed: pattern guards were added, allowing pattern matching within guards; resolution of operator fixity was specified in a simpler way that reflected actual practice; an edge case in the interaction of the language's lexical syntax of operators and comments was addressed; and the interaction of do-notation and if-then-else was tweaked to eliminate unexpected syntax errors.
  • The LANGUAGE pragma was specified. By 2010 dozens of extensions to the language were in wide use, and GHC (among other compilers) provided the LANGUAGE pragma to specify individual extensions with a list of identifiers. Haskell 2010 compilers are required to support the Haskell2010 extension, and are encouraged to support several others which correspond to extensions added in Haskell 2010.
(File:Tagged_union_tree.svg|thumb|Haskell supports both sum types and product types )


{{See also|Glasgow Haskell Compiler#Extensions to Haskell}}(File:Black-box-strictness.png|thumb|right|Haskell features lazy evaluation of expressions, that is, 'call by need')Haskell features lazy evaluation, lambda expressions, pattern matching, list comprehension, type classes and type polymorphism. It is a purely functional language, which means that functions generally have no side effects. A distinct construct exists to represent side effects, orthogonal to the type of functions. A pure function can return a side effect that is subsequently executed, modeling the impure functions of other languages.Haskell has a strong, static type system based on Hindley–Milner type inference. Its principal innovation in this area is type classes, originally conceived as a principled way to add overloading to the language,JOURNAL, Wadler, P., S., Blott, 1989, How to make ad-hoc polymorphism less ad hoc, Proceedings of the 16th ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, Association for Computing Machinery, ACM, 60–76, 10.1145/75277.75283, 978-0-89791-294-5, but since finding many more uses.JOURNAL, Hallgren, T., January 2001, Fun with Functional Dependencies, or Types as Values in Static Computations in Haskell, Proceedings of the Joint CS/CE Winter Meeting, Varberg, Sweden,weblink The construct that represents side effects is an example of a monad. Monads are a general framework that can model different kinds of computation, including error handling, nondeterminism, parsing and software transactional memory. Monads are defined as ordinary datatypes, but Haskell provides some syntactic sugar for their use.Haskell has an open, published specification,{{sfn|Peyton Jones|2003}} and multiple implementations exist. Its main implementation, the Glasgow Haskell Compiler (GHC), is both an interpreter and native-code compiler that runs on most platforms. GHC is noted for its rich type system incorporating recent innovations such as generalized algebraic data types and type families. The Computer Language Benchmarks Game also highlights its high-performance implementation of concurrency and parallelism.Computer Language Benchmarks GameAn active, growing community exists around the language, and more than 5,400 third-party open-source libraries and tools are available in the online package repository Hackage.WEB,weblinkweblink" title="">weblink 2013-05-03, HackageDB statistics,, 2013-06-26,

Code examples

{{See also|Haskell features#Examples}}A "Hello, World!" program in Haskell (only the last line is strictly necessary):module Main (main) where -- not needed in interpreter, is the default in a module filemain :: IO () -- the compiler can infer this type definitionmain = putStrLn "Hello, World!"The factorial function in Haskell, defined in a few different ways:-- Type annotation (optional, same for each implementation)factorial :: (Integral a) => a -> a-- Using recursion (with the "ifthenelse" expression)factorial n = if n < 2
then 1
else n * factorial (n - 1)
-- Using recursion (with pattern matching)factorial 0 = 1factorial n = n * factorial (n - 1)-- Using recursion (with guards)factorial n
| n < 2 = 1
| otherwise = n * factorial (n - 1)
-- Using a list and the "product" functionfactorial n = product [1..n]-- Using fold (implements "product")factorial n = foldl (*) 1 [1..n]-- Point-free stylefactorial = foldr (*) 1 . enumFromTo 1As the Integer type has arbitrary-precision, this code will compute values such as factorial 100000 (a 456,574-digit number), with no loss of precision.An implementation of an algorithm similar to quick sort over lists, where the first element is taken as the pivot:-- Type annotation (optional, same for each implementation)quickSort :: Ord a => [a] -> [a]-- Using list comprehensionsquickSort [] = [] -- The empty list is already sortedquickSort (x:xs) = quickSort [a | a >=) overlaid by a lambda (λ).


All listed implementations are distributed under open source licenses."Implementations" at the Haskell WikiImplementations that fully or nearly comply with the Haskell 98 standard, include: url=, The LLVM Backend, GHC Trac, CONFERENCE,weblink An LLVM Backend for GHC, Terei, David A., Chakravarty, Manuel M. T., 2010, ACM Press, Proceedings of ACM SIGPLAN Haskell Symposium 2010, GHC has become the de facto standard Haskell dialect.C. Ryder and S. Thompson (2005). "Porting HaRe to the GHC API" There are libraries (e.g., bindings to OpenGL) that work only with GHC. GHC is also distributed with the Haskell platform.
  • The Utrecht Haskell Compiler (UHC) is a Haskell implementation from Utrecht University.Utrecht Haskell Compiler It supports almost all Haskell 98 features plus many experimental extensions. It is implemented using attribute grammars and is currently used mostly for research on generated type systems and language extensions.
  • Jhc, a Haskell compiler written by John Meacham, emphasizes speed and efficiency of generated programs and exploring new program transformations.
    • Ajhc is a fork of Jhc.
  • LHC is a whole-program optimizing backend for GHC, based on Urban Boquist’s compiler intermediate language, GRIN.JOURNAL, Boquist, Urban, Johnsson, Thomas, The GRIN Project: A Highly Optimising Back End for Lazy Functional Languages, LNCS, 1996, 1268, 58–84, Older versions of LHC were based on Jhc rather than GHC.
Implementations no longer actively maintained include:
  • The Haskell User's Gofer System (Hugs) is a bytecode interpreter. It was once one of the implementations used most widely, alongside the GHC compiler,{{sfn|Hudak|Hughes|Peyton Jones|Wadler|2007|pp=12–22}} but has now been mostly replaced by GHCi. It also comes with a graphics library.
  • nhc98 is a bytecode compiler focusing on minimizing memory use.
    • The York Haskell Compiler (Yhc) was a fork of nhc98, with the goals of being simpler, more portable and efficient, and integrating support for Hat, the Haskell tracer. It also had a JavaScript backend, allowing users to run Haskell programs in web browsers.
  • HBC is an early implementation supporting Haskell 1.4. It was implemented by Lennart Augustsson in, and based on, Lazy ML. It has not been actively developed for some time.
Implementations not fully Haskell 98 compliant, and using a variant Haskell language, include:
  • Gofer was an educational dialect of Haskell, with a feature called constructor classes, developed by Mark Jones. It was supplanted by Hugs (see Haskell User's Gofer System, above).
  • Helium is a newer dialect of Haskell. The focus is on making learning easier via clearer error messages. It currently lacks full support for type classes, rendering it incompatible with many Haskell programs.
  • Eta and Frege are dialects of Haskell targeting the Java Virtual Machine.


  • Darcs is a revision control system written in Haskell, with several innovative features, such as more precise control of patches to apply.
  • Cabal is a tool for building and packaging Haskell libraries and programs.WEB,weblink The Haskell Cabal, 8 April 2015,
  • Linspire GNU/Linux chose Haskell for system tools development.WEB,weblink Linspire/Freespire Core OS Team and Haskell, Debian Haskell mailing list, May 2006,
  • Xmonad is a window manager for the X Window System, written fully in
  • Git-annex is a tool to manage (big) data files under Git version control. It also provides a distributed file synchronization system (git-annex assistant).
  • GHC is also often a testbed for advanced functional programming features and optimizations in other programming languages.
  • Pandoc is a tool to convert one markup format into another.
  • The Shake build system, aiming to be reliable, robust, and fast.Shake Build System
  • ShellCheck – A shell script static analysis tool.ShellCheck


  • Facebook implements its anti-spam programsWEB,weblink Fighting spam with Haskell, 2015-06-26, Facebook Code, en-US, 2019-08-11, in Haskell, as open-source software.WEB,weblink Open-sourcing Haxl, a library for Haskell, 2014-06-10, Facebook Code, en-US, 2019-08-11,
  • Swift Navigation, a high precision GPS manufacturer, implements significant portions of its product in Haskell, providing some open source software.Swift-Nav (2018)
  • Bluespec SystemVerilog (BSV) is a language for semiconductor design that is an extension of Haskell. Also, Bluespec, Inc.'s tools are implemented in Haskell.
  • GitHub implemented Semantic, an open-source library for analysis, diffing, and interpretation of untrusted source code, in Haskell.{{Citation|title=Parsing, analyzing, and comparing source code across many languages: github/semantic|date=2019-06-07|url=|publisher=GitHub|access-date=2019-06-07}}
  • Cryptol, a language and toolchain for developing and verifying cryptography algorithms, is implemented in Haskell.
  • AmpersandWEB,weblink Documentation of Ampersand, en-US, , a language{{Citation|title=Software Development in Relation Algebra with Ampersand|author=Stef Joosten|date=2017-04-25|url=|publisher=Springer}} and toolchainWEB,weblink Ampersand: Build database applications faster than anyone else, and keep your data pollution free as a bonus, en-US, for building information systems with reactive behaviour, is being used by Ordina and TNO (both in the Netherlands) for purposes such as conceptual analysis, analysis of archimate-models, legal analysis and prototyping large information systems. The compilerWEB,weblink Ampersand Automates Agile Information System Development, en-US, is written in Haskell. Web applications realised with Ampersand comprise the Semantic TreehouseWEB,weblink SETU, en-US, and RAP3WEB,weblink Repository for Ampersand Projects, en-US, .
  • seL4, the first formally verified microkernel,
A formal proof of functional correctness was completed in 2009.
used Haskell as a prototyping language for the OS developer.{{rp|p.2}} At the same time, the Haskell code defined an executable specification with which to reason, for automatic translation by the theorem-proving tool.{{rp|p.3}} The Haskell code thus served as an intermediate prototype before final C refinement.{{rp|p.3}}


There are several web frameworks written for Haskell, including:WEB,weblink Web/Frameworks – HaskellWiki,, 2019-08-11,


Jan-Willem Maessen, in 2002, and Simon Peyton Jones, in 2003, discussed problems associated with lazy evaluation while also acknowledging the theoretical motives for it.Jan-Willem Maessen. Eager Haskell: Resource-bounded execution yields efficient iteration. Proceedings of the 2002 Association for Computing Machinery (ACM) SIGPLAN workshop on Haskell.Simon Peyton Jones. Wearing the hair shirt: a retrospective on Haskell. Invited talk at POPL 2003. In addition to purely practical considerations such as improved performance,WEB,weblink Lazy evaluation can lead to excellent performance, such as in The Computer Language Benchmarks Game, they note that, in addition to adding some performance overhead, lazy evaluation makes it more difficult for programmers to reason about the performance of their code (particularly its space use).Bastiaan Heeren, Daan Leijen, and Arjan van IJzendoorn in 2003 also observed some stumbling blocks for Haskell learners: "The subtle syntax and sophisticated type system of Haskell are a double edged sword – highly appreciated by experienced programmers but also a source of frustration among beginners, since the generality of Haskell often leads to cryptic error messages."JOURNAL, Bastiaan, Heeren, Daan, Leijen, Arjan, van IJzendoorn, 2003, Helium, for learning Haskell, Proceedings of the 2003 ACM SIGPLAN Workshop on Haskell,weblink To address these, researchers from Utrecht University developed an advanced interpreter called Helium, which improved the user-friendliness of error messages by limiting the generality of some Haskell features, and in particular removing support for type classes.Ben Lippmeier designed DiscipleWEB,weblink DDC – HaskellWiki,, 2010-12-03, 2013-06-26, as a strict-by-default (lazy by explicit annotation) dialect of Haskell with a type-and-effect system, to address Haskell's difficulties in reasoning about lazy evaluation and in using traditional data structures such as mutable arrays.Ben Lippmeier, Type Inference and Optimisation for an Impure World, Australian National University (2010) PhD thesis, chapter 1 He argues (p. 20) that "destructive update furnishes the programmer with two important and powerful tools ... a set of efficient array-like data structures for managing collections of objects, and ... the ability to broadcast a new value to all parts of a program with minimal burden on the programmer."Robert Harper, one of the authors of Standard ML, has given his reasons for not using Haskell to teach introductory programming. Among these are the difficulty of reasoning about resource use with non-strict evaluation, that lazy evaluation complicates the definition of data types and inductive reasoning,WEB,weblink The point of laziness, Robert Harper, {{Closed access}}
and the "inferiority" of Haskell's (old) class system compared to ML's module system.WEB,weblink Robert Harper, Modules matter most., {{Closed access}}
Haskell's build tool, Cabal, has historically been criticised for poorly handling multiple versions of the same library, a problem known as "Cabal hell". The Stackage server and Stack build tool were made in response to these criticisms.WEB,weblink Solving Cabal Hell,, 2019-08-11, .

Related languages

Clean is a close, slightly older relative of Haskell. Its biggest deviation from Haskell is in the use of uniqueness types instead of monads for I/O and side-effects.A series of languages inspired by Haskell, but with different type systems, have been developed, including: Java virtual machine (JVM) based:
  • Frege, a Haskell-like language with Java's scalar types and good Java integration.WEB,weblink Frege Programming Language, WEB,weblink Google Code Archive – Long-term storage for Google Code Project Hosting., WEB,weblink mmhelloworld, Marimuthu Madasamy, 2012-02-29,
  • Jaskell, a functional scripting language that runs in Java VM.WEB,weblink Codehaus, yes,weblink" title="">weblink 20 February 2006, dmy-all,
  • Eta-lang, which intends to be Haskell on the JVM.
Other related languages include:
  • Curry, a functional/logic programming language based on Haskell.
Haskell has served as a testbed for many new ideas in language design. There have been many Haskell variants produced, exploring new language ideas, including:
  • Parallel Haskell:
    • From Glasgow University, supports clusters of machines or single multiprocessors.WEB,weblink Glasgow Parallel Haskell, WEB,weblink 7.15. Parallel Haskell, Also within Haskell is support for Symmetric Multiprocessor parallelism.WEB,weblink 4.12. Using SMP parallelism,
    • From MIT.WEB,weblink Computation Structures Group- MIT- LCS, Todd Allen Amicon,
  • Distributed Haskell (formerly Goffin) and Eden.{{Citation needed|date=April 2009}}
  • Eager Haskell, based on speculative evaluation.
  • Several object-oriented versions: Haskell++, and Mondrian.
  • Generic Haskell, a version of Haskell with type system support for generic programming.
  • O'Haskell, an extension of Haskell adding object-orientation and concurrent programming support that "has ... been superseded by Timber."WEB,weblink O'Haskell,
  • Disciple, a strict-by-default (laziness available by annotation) dialect of Haskell that supports destructive update, computational effects, type directed field projections and allied functional aspects.
  • Hume, a strict functional language for embedded systems based on processes as stateless automata over a sort of tuples of one element mailbox channels where the state is kept by feedback into the mailboxes, and a mapping description from outputs to channels as box wiring, with a Haskell-like expression language and syntax.

Conferences and workshops

The Haskell community meets regularly for research and development activities. The main events are: Since 2006, a series of organized hackathons has occurred, the Hac series, aimed at improving the programming language tools and libraries.WEB, Hackathon – HaskellWiki,weblink



Further reading

  • BOOK, Simon, Peyton Jones, Simon Peyton Jones, Haskell 98 Language and Libraries: The Revised Report,weblink 2003, Cambridge University Press, 978-0521826143, harv,
  • BOOK, Simon, Marlow, Simon Marlow, Haskell 2010 Language Report,weblink 2010,, harv,

  • BOOK, Antony, Davie, An Introduction to Functional Programming Systems Using Haskell, Cambridge University Press, 1992, 978-0-521-25830-2,
  • BOOK, Richard, Bird, Richard Bird (computer scientist), Introduction to Functional Programming using Haskell, 2nd, Prentice Hall Press, 1998, 978-0-13-484346-9,weblink
  • BOOK, Paul, Hudak, Paul Hudak, The Haskell School of Expression: Learning Functional Programming through Multimedia, Cambridge University Press, New York, 2000, 978-0521643382,weblink
  • BOOK, Graham, Hutton, Graham Hutton, Programming in Haskell, 2007, Cambridge University Press, 978-0521692694,weblink
  • BOOK, Bryan, O'Sullivan, Bryan O'Sullivan (computer programmer), Don, Stewart, Don Stewart (computer programmer), Goerzen, John, John Goerzen, Real World Haskell, 2008, O'Reilly, Sebastopol, 978-0-596-51498-3,  (full text), Real World Haskell,
  • BOOK, Simon, Thompson, Haskell: The Craft of Functional Programming, 3rd, Addison-Wesley, 2011, 978-0201882957,weblink
  • BOOK, Lipovača, Miran, Learn You a Haskell for Great Good!,weblink April 2011, No Starch Press, San Francisco, 978-1-59327-283-8, registration, (full text)
  • BOOK, Richard, Bird, Richard Bird (computer scientist), Thinking Functionally with Haskell, Cambridge University Press, 2014, 978-1-107-45264-0,

  • WEB,weblink A Gentle Introduction To Haskell, Version 98, June 2000, Paul, Hudak, John, Peterson, Joseph, Fasel,,
  • Yet Another Haskell Tutorial, by Hal Daumé III; assumes far less prior knowledge than official tutorial
  • JOURNAL, Yorgey, Brent, 12 March 2009, The Typeclassopedia, The Monad.Reader, 13, 17–68,weblink {{inconsistent citations, }}
  • BOOK, Sandy, Maguire, Thinking with Types: Type-Level Programming in Haskell, 2018,weblink

  • JOURNAL, Paul, Hudak, Paul Hudak, John, Hughes, John Hughes (computer scientist), Simon, Peyton Jones, Simon Peyton Jones, Philip, Wadler, Philip Wadler, A History of Haskell: Being Lazy with Class,weblink 10.1145/1238844.1238856, 2007, Proceedings of the Third ACM SIGPLAN Conference on History of Programming Languages (HOPL III), 12–1–55, 978-1-59593-766-7, harv,
  • JOURNAL, Hamilton, Naomi, 19 September 2008, The A-Z of Programming Languages: Haskell, Computerworld,weblink

External links

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