Applications and libraries

The number of Haskell packages is growing rapidly. The section 'Haskell library collections' gives an ordering of all these packages by relative importance. In the section 'Haskell applications and libraries' an ordering by category is given. Finally some guidelines for developers of new packages are presented.

Haskell library collections

Haskell Prelude

The most important Haskell library is called the Prelude. It is implicitly imported by default, and includes the most commonly used functions. Make sure you know what they do and how to use them effectively.

The Haskell 2010 libraries

The Haskell 2010 Language and library specification defines a set of libraries with basic functionality which all Haskell implementations should support, including the Prelude. Changes to these libraries are handled by the Haskell' process.

Haskell modules that almost everybody uses are in this group, for example: Control.Monad, Data.List and System.IO. In GHC these are all grouped into the 'base' package.

The GHC standard libraries

GHC comes with an expanded version of the Haskell 2010 libraries. Together these are called the GHC standard libraries. Changes to these libraries are handled by the package maintainer if one exists, or the Library submissions process if not. Hoogle - the Haskell API Search Engine - indexes the GHC standard libraries.

Examples of libraries, or packages, that belong to this group are: bytestring, containers and Win32.

Haskell Platform libraries

On top of the GHC standard libraries, the Haskell Platform comes preinstalled with some additional packages that together form the Haskell Platform libraries. These libraries have been thoroughly tested before being included. The addition of these libraries with the Haskell Platform is what makes it 'batteries included'.

Examples of included packages are: Monad transformer library, parallel and QuickCheck.

The Hackage database

Hackage is the final layer of the Haskell library collections. Hackage aims to provide a comprehensive collection of released Haskell packages, similar to Perl's CPAN or Python's PyPI.

Start on Hackage if you are looking for some functionality that did not come preinstalled with the Haskell Platform.

See also the Hackage wiki page and how to install a Cabal package.

Haskell applications and libraries

Applications, libraries and tools for Haskell or written in Haskell have been classified below, but you should check Hackage for the latest list.

• Audio, music and sound
• Bioinformatics
• Concurrency and parallelism
• Compilers and interpreters
• Compiler construction, lexing, parsing, pretty printing
• Cryptography and hashing
• Data Structures and IO Libraries
• Database interfaces
• Editors written in Haskell and editors for Haskell.
• Extended Haskell
• Games
• Generic programming
• Genetic programming
• Graphical User Interface (GUI) Libraries
• Graphics
• Hardware verification
• Linguistics and natural language processing
• Mathematics and physics
• Network
• Operating systems and systems programming (also emulators)
• Program development
• Robotics
• Theorem provers
• Tools for interfacing with other languages
• Web, HTML, XML

Other places to look include:

• The Library hierarchy page on this wiki.
• The Haskell community reports.
• The mailing list for discussion of issues related to libraries.

You can also propose and vote on new libraries that you'd like on reddit, and look at our past Summer of Code proposals.

Guidelines for developers

Built with Cabal

Developer guides:

• How to write a new Haskell library
• How to propose changes to the standard libraries
• Creating a .deb from a Haskell Cabal package (in the Web Archive)
• Creating a Haskell library by example
• Guide to making standard library submissions
• If you notice the library documentation is lacking, or could be improved, please report it here
• Google Code Search can help identify common idioms, improving your API.
• Future projects, more projects people would like.
• Project activity for some of the larger Haskell projects is graphed here.
• Cabal, The Common Architecture for Building Applications and Libraries, is a framework for packaging, building, and installing any tool developed in the Haskell language.
• Hack-Nix, a set of tools based on the Nix package manager to manage multiple setups to build a project

Proposals for the module name space layout that can be used to guide the construction of new libraries.

• Almost current guide
• Proposal 1
• Proposal 2

Libraries for other languages

If you are thinking about designing a new library for Haskell, you ought to look what has been done in other languages. Here are standard library definitions for

• Clean
• Standard ML
• Objective Caml
• Scheme