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What is Haskell?

Haskell is a lazy, functional, statically-typed programming language with advanced type system features such as higher-rank, higher-kinded parametric polymorphism, monadic effects, generalized algebraic data types (GADTs), flexible type classes, associated type families, and more.

Haskell's ghc is a portable, optimizing compiler with a foreign-function interface (FFI), an LLVM backend, and sophisticated runtime support for concurrency, explicit/implicit parallelism, runtime profiling, etc. Other Haskell tools like criterion, quickcheck, hpc, and haddock provide advanced benchmarking, property-based testing, code coverage, and documentation generation.

A large number of production-quality Haskell libraries are available from Hackage. The cabal tool fetches packages and builds projects using the Hackage ecosystem.

%%LOGO%%

Contents

This image ships a minimal Haskell toolchain with the following packages:

  • ghc 7.8.3
  • alex 3.1.3
  • cabal-install 1.20.0.3
  • happy 1.19.4

Usage

  • Start an interactive interpreter session with ghci:

    $ docker run -it --rm haskell:7.8 GHCi, version 7.8.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude>

  • Dockerize a Hackage app with a Dockerfile inheriting from the base image:

    FROM haskell:7.8 RUN cabal update && cabal install MazesOfMonad VOLUME /root/.MazesOfMonad ENTRYPOINT ["/root/.cabal/bin/mazesofmonad"]

  • Iteratively develop then ship a Haskell app with a Dockerfile utilizing the build cache:

    FROM haskell:7.8

    RUN cabal update

    Add .cabal file

    ADD ./server/snap-example.cabal /opt/server/snap-example.cabal

    Docker will cache this command as a layer, freeing us up to

    modify source code without re-installing dependencies

    RUN cd /opt/server && cabal install --only-dependencies -j4

    Add and Install Application Code

    ADD ./server /opt/server RUN cd /opt/server && cabal install

    Add installed cabal executables to PATH

    ENV PATH /root/.cabal/bin:$PATH

    Default Command for Container

    WORKDIR /opt/server CMD ["snap-example"]

Examples

See the application snippet above in more detail in the example snap application.