65 lines
3.5 KiB
Markdown
65 lines
3.5 KiB
Markdown
# What is Haskell?
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[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.
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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_%28software%29) provide advanced benchmarking, property-based testing, code coverage, and documentation generation.
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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.
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%%LOGO%%
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## About this image
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This image ships a minimal Haskell toolchain with the following packages:
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- `ghc`
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- `alex`
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- `cabal-install`
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- `happy`
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## How to use this image
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Start an interactive interpreter session with `ghci`:
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$ docker run -it --rm haskell:7.8
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GHCi, version 7.8.3: http://www.haskell.org/ghc/ :? for help
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Loading package ghc-prim ... linking ... done.
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Loading package integer-gmp ... linking ... done.
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Loading package base ... linking ... done.
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Prelude>
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Dockerize a [Hackage](http://hackage.haskell.org) app with a Dockerfile inheriting from the base image:
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FROM haskell:7.8
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RUN cabal update && cabal install MazesOfMonad
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VOLUME /root/.MazesOfMonad
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ENTRYPOINT ["/root/.cabal/bin/mazesofmonad"]
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Iteratively develop then ship a Haskell app with a Dockerfile utilizing the build cache:
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FROM haskell:7.8
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RUN cabal update
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# Add .cabal file
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ADD ./server/snap-example.cabal /opt/server/snap-example.cabal
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# Docker will cache this command as a layer, freeing us up to
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# modify source code without re-installing dependencies
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RUN cd /opt/server && cabal install --only-dependencies -j4
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# Add and Install Application Code
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ADD ./server /opt/server
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RUN cd /opt/server && cabal install
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# Add installed cabal executables to PATH
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ENV PATH /root/.cabal/bin:$PATH
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# Default Command for Container
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WORKDIR /opt/server
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CMD ["snap-example"]
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### Examples
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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).
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