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To get a feel for what real world Haskell looks like, here are some
 
To get a feel for what real world Haskell looks like, here are some
examples from various popular Haskell projects.
+
examples from various popular [[Libraries_and_tools|Haskell projects]].
  +
To start learning the language, good places to start are
  +
[[Learning Haskell]],
  +
[[Haskell in 5 steps]], and
  +
[[Books and tutorials]].
  +
  +
More code may be found [http://www.haskell.org/haskellwiki/Category:Code on the wiki].
  +
  +
<!--
  +
Some lines are commented out for later update
  +
-->
   
 
=== Library code ===
 
=== Library code ===
   
 
Library code usually differs from application code: it is often highly
 
Library code usually differs from application code: it is often highly
structured, and documented with [http://haskell.org/haddock haddock],
+
structured, and documented with [http://www.haskell.org/haddock/ haddock],
and can be rather optimised. Some instructive examples:
+
and can be rather optimised. Some instructive examples (syntax
  +
highlighting by [http://www.cs.york.ac.uk/fp/darcs/hscolour/ hscolour]):
   
[http://darcs.haskell.org/packages/base/Data/List.hs List.hs], the standard [a] type
 
  +
* [http://www.haskell.org/ghc/docs/latest/html/libraries/base/src/Prelude.html A Haskell Prelude.hs], foundational Haskell library ([http://www.haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html docs])
   
[http://darcs.haskell.org/packages/base/Data/Map.hs Map.hs], the standard finite map
 
  +
* [[Simple_Unix_tools | Unix.hs]], simple unix tools, for beginner Haskellers
   
[http://darcs.haskell.org/packages/base/Data/Tree.hs Tree.hs], a tree type
 
  +
* [http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/Data.List.html Data.List], the standard list library ([http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-List.html docs])
   
[http://darcs.haskell.org/packages/base/Data/Graph.hs Graph.hs], a graph type
 
  +
* [http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/Data.Maybe.html Data.Maybe], the <code>Maybe</code> type ([http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Maybe.html docs])
   
[http://darcs.haskell.org/packages/base/Control/Monad.hs Monad.hs], basic monadic support
 
  +
* [http://hackage.haskell.org/packages/archive/containers/latest/doc/html/src/Data.Map.html Data.Map], the standard finite map ([http://www.haskell.org/ghc/docs/latest/html/libraries/containers-0.4.2.1/index.html docs])
   
[http://darcs.haskell.org/packages/QuickCheck/Test/QuickCheck.hs QuickCheck.hs], a testing framework
 
  +
* [http://hackage.haskell.org/packages/archive/containers/latest/doc/html/src/Data.Graph.html Data.Graph], a graph type ([http://hackage.haskell.org/packages/archive/containers/latest/doc/html/Data-Graph.html docs])
   
[http://darcs.haskell.org/packages/base/Text/PrettyPrint/HughesPJ.hs PrettyPrint.hs], a pretty printing library
 
  +
* [http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/Control.Monad.html Control.Monad], basic monad support ([http://hackage.haskell.org/packages/archive/base/latest/doc/html/Control-Monad.html docs])
   
[http://darcs.haskell.org/packages/monads/Monad/StateT.hs StateT.hs], a monad transformer library
 
  +
* [https://github.com/nick8325/quickcheck QuickCheck], a testing framework ([http://hackage.haskell.org/package/QuickCheck docs])
   
[http://darcs.haskell.org/haskore/src/Haskore/Music.lhs Music.lhs], a music composition system (literate latex-style Haskell)
 
  +
* [http://hackage.haskell.org/packages/archive/pretty/latest/doc/html/src/Text-PrettyPrint-HughesPJ.html PrettyPrint.hs], a pretty printing library ([http://hackage.haskell.org/package/pretty docs])
   
[http://www.ninebynine.org/Software/Swish-0.2.1/HaskellRDF/Dfa/Dfa.lhs Dfa.lhs], finite automata (literate Bird-style Haskell)
 
  +
* [http://hackage.haskell.org/packages/archive/transformers/latest/doc/html/src/Control-Monad-Trans-State-Lazy.html Control.Monad.Trans.State.Lazy], a state monad ([http://hackage.haskell.org/packages/archive/transformers/latest/doc/html/Control-Monad-Trans-State-Lazy.html docs])
  +
<!--
  +
* [http://www.cse.unsw.edu.au/~dons/data/Music.html Music.hs], a music composition system (literate latex-style Haskell) ([http://darcs.haskell.org/haskore/src/Haskore/Music.lhs raw], [http://www.haskell.org/haskore/ home])
  +
-->
   
[http://www.polyomino.f2s.com/david/haskell/hs/redblacktree.hs.txt RedBlackTree.hs], a red-black tree
 
  +
* [http://www.ninebynine.org/Software/Swish-0.2.1/HaskellRDF/Dfa/Dfa.lhs Dfa.lhs], finite automata (literate Bird-style Haskell)
   
[http://andrew.bromage.org/darcs/numbertheory/Math/Prime.hs Prime.hs], prime numbers
 
  +
* [http://www.polyomino.f2s.com/david/haskell/hs/RedBlackTree.hs.txt RedBlackTree.hs], a red-black tree
  +
<!--
  +
* [http://www.cse.unsw.edu.au/~dons/data/Prime.html Prime.hs], prime numbers ([http://andrew.bromage.org/darcs/numbertheory/Math/Prime.hs raw])
  +
-->
   
[http://darcs.haskell.org/packages/base/Data/Foldable.hs Foldable.hs], traversable data structures
+
* [http://hackage.haskell.org/packages/archive/base/latest/doc/html/src/Data.Foldable.html Data.Foldable], traversable data structures ([http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Foldable.html docs])
   
[http://darcs.haskell.org/packages/base/Data/ByteString.hs ByteString.hs], high-performance string type
 
  +
* [https://github.com/haskell/bytestring Data.ByteString], high-performance string type ([http://code.haskell.org/bytestring/Data/ByteString.hs raw], [http://hackage.haskell.org/package/bytestring docs])
   
[http://darcs.haskell.org/packages/ndp/Data/Array/Parallel/Stream/Flat/Combinators.hs Combinators.hs], array combinators
 
  +
* [https://github.com/feuerbach/smallcheck SmallCheck], a testing framework ([https://raw.github.com/feuerbach/smallcheck/master/Test/SmallCheck.hs raw], [http://hackage.haskell.org/package/smallcheck docs])
   
[http://www.cse.unsw.edu.au/~dons/code/lambdabot/scripts/SmallCheck.hs SmallCheck.hs], a testing framework
 
  +
* [http://www.haskell.org/haskellwiki/Darcs_repositories More code ...]
 
[http://haskell.org/haskellwiki/Darcs_repositories A large collection of online Haskell source]
 
   
 
=== Application code ===
 
=== Application code ===
   
Code from popular Haskell applications. Such code often makes use of an
+
Code from popular Haskell applications. Such code often makes use of a
monadic IO, and sometimes other advanced features (such as concurrency):
+
monadic IO, and sometimes other advanced features such as concurrency:
 
[http://www.abridgegame.org/repos/darcs-unstable/PatchCommute.lhs Darcs], a revision control system (uses literate latex Haskell style)
 
 
[http://svn.openfoundry.org/pugs/src/Pugs/Eval.hs Pugs], a perl6 implementation
 
 
[http://www.cse.unsw.edu.au/~dons/code/yi/Yi/Core.hs Yi], a text editor
 
 
[http://j.mongers.org/pub/haskell/darcs/conjure/Conjure/Torrent.hs Conjure], a bittorrent client
 
 
[http://darcs.haskell.org/~lemmih/downNova/src/Torrent.hs DownNova], a file downloading program
 
 
[http://www.cs.york.ac.uk/fp/darcs/cpphs/Language/Preprocessor/Cpphs/Tokenise.hs cpphs], an implementation of the C preprocessor
 
 
[http://darcs.haskell.org/ghc/compiler/simplCore/Simplify.lhs GHC], a Haskell compiler (literate latex style)
 
   
[http://www.augustsson.net/Darcs/Djinn/LJT.hs Djinn], a theorem prover
 
  +
<!--
  +
* [http://nanardon.zarb.org/darcs/darcs/PatchCommute.lhs Darcs], a revision control system (uses literate latex Haskell style) ([http://darcs.net home])
  +
-->
  +
* [http://svn.openfoundry.org/pugs/src/Pugs/Eval.hs Pugs], a perl6 implementation ([http://pugscode.org home])
   
[http://darcs.haskell.org/c2hs/c2hs/c/CTrav.hs c2hs], a C to Haskell interface generator
 
  +
* [https://github.com/yi-editor/yi/blob/master/yi-core/src/Yi/Core.hs Yi], a text editor, ([http://www.haskell.org/haskellwiki/Yi home], [https://raw.githubusercontent.com/yi-editor/yi/master/yi-core/src/Yi/Core.hs raw], [http://hackage.haskell.org/package/yi doc])
  +
<!--
  +
* [http://darcs.haskell.org/~lemmih/downNova/src/Torrent.hs DownNova], a file downloading program
  +
-->
   
[http://www.cse.unsw.edu.au/~dons/code/lambdabot/LBState.hs Lambdabot], an IRC bot
 
  +
* [http://www.cs.york.ac.uk/fp/darcs/cpphs/Language/Preprocessor/Cpphs/Tokenise.hs cpphs], an implementation of the C preprocessor ([https://archives.haskell.org/projects.haskell.org/cpphs/ home])
   
[http://www.cse.unsw.edu.au/~dons/code/hmp3/Core.hs hmp3], an curses mp3 player
 
  +
* [http://darcs.haskell.org/ghc/compiler/simplCore/Simplify.lhs GHC], a Haskell compiler (literate latex style) ([http://www.haskell.org/ghc/ home])
   
=== Wiki examples===
 
  +
* [http://darcs.augustsson.net/Darcs/Djinn/Djinn/LJT.hs Djinn], a theorem prover ([http://darcs.augustsson.net/Darcs/Djinn/ home])
   
Here is a list of other random code collected on this wiki, replacing
 
  +
* [http://code.haskell.org/c2hs/src/C2HS/C/Trav.hs c2hs], a C to Haskell interface generator ([https://github.com/haskell/c2hs home])
[http://haskell.org/hawiki/CodeOnTheWiki CodeOnTheWiki]. Contributors
 
of code to the old area are encouraged to bring their code over here.
 
This should only be done by the original author because anything on
 
these pages is automatically licensed under the Simple Permissive
 
License ([[HaskellWiki:Copyrights]]).
 
   
[[Prelude extensions]]: Simple things you've always wished were in the Prelude.
 
  +
* [http://code.haskell.org/lambdabot/LBState.hs Lambdabot], an IRC bot ([http://www.haskell.org/haskellwiki/Lambdabot home])
   
[[Gallery]]: Complete small programs.
 
  +
* [http://code.haskell.org/~dons/code/hmp3/Core.hs hmp3], a curses mp3 player
   
[[Blow_your_mind|Blow your mind]]: Short, useful, cool, magical examples, which should incite the reader's curiosity and (hopefully) lead him to a deeper understanding of advanced Haskell concepts.
 
  +
* [http://www.haskell.org/haskellwiki/Darcs_repositories More code ...]
   
[[Sudoku]]: Solvers for popular puzzle [http://en.wikipedia.org/wiki/Sudoku Sudoku].
 
  +
== Examples ==
   
[[NewMonads]]: Useful monads that are not in the main library.
 
  +
; [[Tying the Knot]] : An example that illustrates different ways to define recursive data structures. The example defines a simple language (illustrating how to define some recursive structures) and an interpreter for the language (illustrating how to work with the recursive structures).
   
[[PrincipalVariationSearch]]: Principal variation search
 
  +
; [http://members.chello.nl/hjgtuyl/tourdemonad.html A tour of the Haskell Monad functions]: Small usage examples of the basic Haskell monad functions
   
[http://haskell.org/hawiki/ShootoutEntry Shootout Entries]: Examples still on the old wiki for the [http://shootout.alioth.debian.org/index.php The Computer Language Shootout Benchmarks].
 
  +
[[Category:Code]]

Latest revision as of 09:43, 21 October 2019

To get a feel for what real world Haskell looks like, here are some examples from various popular Haskell projects. To start learning the language, good places to start are Learning Haskell, Haskell in 5 steps, and Books and tutorials.

More code may be found on the wiki.


Library code

Library code usually differs from application code: it is often highly structured, and documented with haddock, and can be rather optimised. Some instructive examples (syntax highlighting by hscolour):

  • Unix.hs, simple unix tools, for beginner Haskellers
  • Dfa.lhs, finite automata (literate Bird-style Haskell)

Application code

Code from popular Haskell applications. Such code often makes use of a monadic IO, and sometimes other advanced features such as concurrency:

  • cpphs, an implementation of the C preprocessor (home)
  • GHC, a Haskell compiler (literate latex style) (home)
  • c2hs, a C to Haskell interface generator (home)
  • hmp3, a curses mp3 player

Examples

Tying the Knot 
An example that illustrates different ways to define recursive data structures. The example defines a simple language (illustrating how to define some recursive structures) and an interpreter for the language (illustrating how to work with the recursive structures).
A tour of the Haskell Monad functions
Small usage examples of the basic Haskell monad functions