96 lines
3.5 KiB
Markdown
96 lines
3.5 KiB
Markdown
# What is Haskell?
|
|
|
|
[Haskell](http://www.haskell.org) is a
|
|
[lazy](http://en.wikibooks.org/wiki/Haskell/Laziness), functional,
|
|
statically-typed programming language with advanced type system features such as
|
|
higher-rank, higher-kinded parametric
|
|
[polymorphism](http://en.wikibooks.org/wiki/Haskell/Polymorphism), monadic
|
|
[effects](http://en.wikibooks.org/wiki/Haskell/Understanding_monads/IO),
|
|
generalized algebraic data types
|
|
([GADT](http://en.wikibooks.org/wiki/Haskell/GADT)s), flexible [type
|
|
classes](http://en.wikibooks.org/wiki/Haskell/Advanced_type_classes), associated
|
|
[type families](http://en.wikipedia.org/wiki/Type_family), and more.
|
|
|
|
Haskell's [`ghc`](http://www.haskell.org/ghc) is a
|
|
[portable](https://ghc.haskell.org/trac/ghc/wiki/Platforms),
|
|
[optimizing](http://benchmarksgame.alioth.debian.org/u64q/haskell.php) compiler
|
|
with a foreign-function interface
|
|
([FFI](http://en.wikibooks.org/wiki/Haskell/FFI)), an [LLVM
|
|
backend](https://www.haskell.org/ghc/docs/7.8.3/html/users_guide/code-generators.html),
|
|
and sophisticated runtime support for
|
|
[concurrency](http://en.wikibooks.org/wiki/Haskell/Concurrency),
|
|
explicit/implicit [parallelism](http://community.haskell.org/~simonmar/pcph/),
|
|
runtime [profiling](http://www.haskell.org/haskellwiki/ThreadScope), etc. Other
|
|
Haskell tools like
|
|
[`criterion`](http://www.serpentine.com/criterion/tutorial.html),
|
|
[`quickcheck`](https://www.fpcomplete.com/user/pbv/an-introduction-to-quickcheck-testing),
|
|
[`hpc`](http://www.haskell.org/haskellwiki/Haskell_program_coverage#Examples),
|
|
and [`haddock`](http://en.wikipedia.org/wiki/Haddock_(software)) provide
|
|
advanced benchmarking, property-based testing, code coverage, and documentation
|
|
generation.
|
|
|
|
A large number of production-quality Haskell libraries are available from
|
|
[Hackage](https://hackage.haskell.org). The
|
|
[`cabal`](https://www.fpcomplete.com/user/simonmichael/how-to-cabal-install)
|
|
tool fetches packages and builds projects using the Hackage ecosystem.
|
|
|
|
%%LOGO%%
|
|
|
|
## About this image
|
|
|
|
This image ships a minimal Haskell toolchain with the following packages:
|
|
|
|
* `ghc`
|
|
* `alex`
|
|
* `cabal-install`
|
|
* `happy`
|
|
|
|
## How to use this image
|
|
|
|
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](http://hackage.haskell.org) 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](https://github.com/darinmorrison/docker-haskell/tree/master/examples/7.8.3/snap).
|