sledorze / docker-haskell

Haskell on Docker

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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.

Contents

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

package	version
alex	3.1.3
cabal-install	1.20.0.3
happy	1.19.4
ghc	7.8.3

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.