Haskell Platform

Haskell: Batteries Included

The Haskell Platform (HP) is the name of a new "blessed" library suite on which to build further Haskell libraries and applications, by taking the best libraries from the more than 900 libraries of haskell.org. It provides a comprehensive, stable and quality tested base for Haskell projects to work from.

The first image is a bubble graph of hackage, with the "platform" indicated, to give a visual sense of how the platform relates to the rest of hackage. The second image shows a graph of hackage dependencies, with a circle drawn around the densest part of the graph, to give an idea of how the platform satisfies a large proportion of dependencies.

Resources

• Haskell Platform project repository
• Project bug tracker: candidates for inclusion
• /FAQ

Community

• Mailing list: haskell-platform @ projects.haskell.org
• IRC channel: #ghc @ freenode.org

Documentation

• The Haskell Platform Proposal for the 2008 Haskell Symposium
• Slides from the Haskell Platform talk
• Haskell Platform discussion
• Bryan O'Sullivan's writeup of the future of Haskell discussion
• A discussion took place in June and July 2008 about the direction of the HLP.
• More occurred during the #ghc meeting

Quality Control

Inclusion or exclusion in the platform will be driven by metrics, objective measurements we can extract from code. Determining appropriate metrics is a milestone.

• cabal-installable libraries with haddocks.
• packages should follow the Package versioning policy
• The set of HP packages + core libs must be closed. In other words, all haskell dependencies must be from within the HP packages or core libs. Dependencies on C libs can be external.
• All packages in a particular HP version must have a consistent install plan.

That means only one version of each package and all dependencies on packages must be satisfied by the version in the HP package set.

There is code in cabal-install to check the last two requirements.

Other possible ideas for quality standards we might want to require:

• Uses base library types, to force API standardisation
• exposed module names must follow the hierarchical module name convention, meaning they must be in an appropriate place in the module namespace. In particular, no clash of module names should occur within the HP.

Other heuristics

Packages set for inclusion should:

• Have a maintainer
• Have a bug tracker
• Use the correct versioning
• Build with cabal
• Work on all arches.

Further goals:

• -Wall clean
• 100% coverage
• Have real world use.
• Answer a notable set of build dependencies.
• Have a declared correctness test suite.
• Have a declared performance test suite.

Distribution format

• Source distribution
• .tar.gz bundle compatible with extra-libs
• Windows Installed
• Native distro packages

The HP will be the first meta-package on hackage, that depends on the platform library set. With this,

   cabal install haskell-platform

will be possible.

Version policy

yyyy.major.minor,

• odd major numbers indicate unstable branches
• minor numbers indicate bug fixes only, no API changes.

Examples:

• 2008.0.0 -- first biannual major stable release
• 2008.0.1 -- minor release, bug fix only
• 2008.1 -- unstable branch leading to next major release
• 2008.2.0 -- second annual major release, API changes
• 2008.2.1 -- bug fixes
• 2008.3 -- unstable branch of 2008
• 2009.0.0 -- first release in 2009.

Additionally, if a library is accepted into the platform, it is suggested its version number be lifted to 1.0, if not already at 1.0.

Licenses

The initial release is expected to include only BSD3 licensed software.

Programs

The platform includes programs, such as haddock or cabal-install. These aren't nicely tracked from the cabal meta package yet.

Build system

Two ways to build the bundle:

• generate a sh script from the .cabal file

Or, build cabal-install, have the components of the platform as a mini, local hackage archive, and then ask cabal install to satisfy and install the dependencies from the platform meta-cabal file.

Related projects

• Python libraries
• Gnome's release process
• How to propose modules for GNOME
• OCaml Batteries

Developers

Haskell Platform core team:

• Duncan Coutts (Well Typed)
• Don Stewart (Galois)