Why Haskell and GHC?

• Functional purity and immutability
• Statically and strongly typed
• Good concurrency
• Lazy evaluation
• Native executables
• Garbage collected

https://www.snoyman.com/blog/2017/12/what-makes-haskell-unique

Famous Haskell projects?

Haskell projects

• Pandoc
• ShellCheck
• Xmonad and xmobar
• git-annex
• hledger
• Hakyll
• Shake
• Weldr

Haskell also great for writing programming languages

eg: ghc, Purescript, Elm, Agda, idris, …

Enterprise Haskell

• Facebook
• Banks (financial trading, etc)
• Cardano blockchain
• etc

Consulting: Well Typed, FP Complete, …

Hackage

http://hackage.haskell.org

main Haskell upstream package source repository

Haskell packages

• Cabal packaging system

• cabal-install package tool

Cabal packages

Package .cabal files have detailed metadata including dependencies allowing most packages to be packaged completely automatically

• Hackage has revisions of dependency bounds!

• example package

Hackage

currently total nearly 13,000 packages!

(of course not all still maintained)

Stackage

http://stackage.org

Stable consistent buildable Haskell package sets

Currently about 2300 packages

• example package

stack build tool

Fedora Haskell SIG

Started in 2007

https://fedoraproject.org/wiki/Haskell_SIG

Fedora Haskell challenges

currently ~480 Haskell sources packages in Fedora

GHC has strict version binary dependencies:

updating ghc or libraries requires a lot of rebuilding

Fedora Haskell Packagers

Many people have contributed including:

• Currently active: Elliott Sales de Andrade,
  Robert-André Mauchin, Jens Petersen

• Packagers: Ben Boeckel, Ricky Elrod, Zach Oglesby

Former: Bryan O’Sullivan, Yaakov Nemoy, Conrad Meyer, Lakshmi Narasimhan, Shakthi Kannan, Michel Salim, et al

cabal-rpm

RPM packaging tool

• converts Haskell package .cabal files to RPM .spec files
• can update packages and refresh packaging

OpenSuse has also used cabal-rpm

Demo of cabal-rpm

fedora-haskell-tools

• fhpkg: clones, diff’s, pulls, commits packages
• fhbuild: builds locally, in mock, Koji “chain” builds
• fhbz: closes Update bugs with builds or refreshes missing deps

Demo of
fedora-haskell-tools

rpmbuild-order

New tool that orders packages by build dependencies

Demo of rpmbuild-order

Improvements to tools

• async parallel building
• containers for local building
• performance: caching of built package info
• editor for .spec files

• push the Haskell types

• querying for Fedora (Haskell) packages
  (in the post-pkgdb world)

Distro Haskell competition

• Nixos: all of Hackage!
• OpenSuse: Stackage LTS

Continuous integration?

To keep Fedora in sync with Stackage LTS

Copr: build a subset of Stackage?

Koschei and Fedora CI

Contact me

Mail: petersen@redhat.com

Twitter: @juhp

More information

• Fedora Haskell SIG: https://fedoraproject.org/wiki/Haskell_SIG
• https://github.com/juhp/cabal-rpm
• https://github.com/fedora-haskell/fedora-haskell-tools
• https://github.com/juhp/rpmbuild-order