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1Elm
2===
4If you are new to Elm, learn more about the language [here](http://elm-lang.org/)
5and try it out in the [online interactive editor](http://elm-lang.org/try).
7This is the Elm compiler and server, allowing you to natively develop Elm
8applications that run in any modern browser. The compiler generates HTML and JS
9files, and the server just serves .elm files directly.
11If you intend to serve Elm code with a custom Haskell backend, be
12sure to read all the way to the "Installation for Haskell-Users" section.
15Installation for General Use
16----------------------------
18Download the [Haskell Platform 2012.2.0.0](http://hackage.haskell.org/platform/).
19This will give you access to the Haskell compiler (needed to build Elm) and Haskell's
20package distribution system (to make installation of Elm easier). Elm definitely works with
21version 7.4 of the Haskell compiler (i.e. GHC 7.4) which is bundled with
22version 2012.2.0.0 of the Haskell Platform.
24If you are a Linux user and already have a copy of GHC installed and have
25downloaded a bunch of packages, it may be worthwhile to create new user account
26and just install Elm separately
27[as described here](https://groups.google.com/forum/?fromgroups=#!topic/elm-discuss/cNNJ6YM77zs).
28Dependency issues have been rampant lately with packages changing to support GHC 7.6.
30If you run into issues, check [the mailing list][list] for advice or go to the
31[#Elm IRC channel][irc].
33 [list]: https://groups.google.com/forum/?fromgroups#!forum/elm-discuss "Mailing List"
34 [irc]: http://webchat.freenode.net/?channels=elm "#elm channel"
36#### Installing the compiler and server
38Once the Haskell Platform is installed (even if it already was), you must update your listing of packages with:
40 cabal update
42This will ensure that the elm package is available. Then install Elm with:
44 cabal install elm
46Assuming everything goes correctly (potential problems are discussed later), this
47will install the `elm` compiler on your machine. `elm` is a standard compiler that
48takes `.elm` files and produces `.html` and/or `.js` files. You can then use these
49files with your favorite web-framework. Use `elm --help` for more directions on how to use it.
51If you have this installed you can write and compile Elm locally,
52so if the next step fails for you, it is safe to proceed without it.
54You can also install `elm-server` which is both a compiler and server, allowing
55you to develop without designing and setting up a server yourself. Running `elm-server`
56starts a server in the current directory. It will compile and serve any `.elm` files in
57the current directory and its sub-directories. This is how I prefer to develop
58Elm programs. Install with:
60 cabal install elm-server
62Dependency issues have been cropping up with this step, so if you run into issues,
63please report them so they can be fixed! Once installed, use the command `elm-server --help`
64to see some extra information.
66#### Using the Elm compiler and server
68To use these executables you need to add a new directory to your PATH. For me, the
69executables were placed in `/home/evan/.cabal/bin` which I appended to the end of my
70PATH variable in my .bashrc file. Cabal should tell you where your executables are
71located upon successful installation, so you can make a similar addition (see this
72tutorial if you are new to changing your PATH in [Unix/Linux](http://www.cyberciti.biz/faq/unix-linux-adding-path/)).
74You can use the commands `elm --help` and `elm-server --help`
75to get more information about using these tools.
77That is almost everything. Now, we will create a simple Elm project.
78The following commands will set-up a very basic project and start the Elm server.
80 mkdir helloElm
81 cd helloElm
82 echo main = lift asText Mouse.position > main.elm
83 elm-server
85The first two commands create a new directory and navigate into it. The `echo`
86command places a simple program into `main.elm` (do this manually if you do not
87have `echo`). The final command starts the Elm server at [localhost](http://localhost:8000/),
88allowing you to navigate to `main.elm` and see your first program in action.
91Installation for Haskell-users
92------------------------------
94The `elm` package provides support for [compilation of Elm code directly in Haskell](http://hackage.haskell.org/packages/archive/Elm/0.1.2/doc/html/Language-Elm.html) and [QuasiQuoting](http://hackage.haskell.org/packages/archive/Elm/0.1.2/doc/html/Language-Elm-Quasi.html). See the [Examples/](https://github.com/evancz/Elm/tree/master/Examples) directory for information and examples on how to get started with Elm+Haskell.
96Yesod users should also install the `elm-yesod` package which provides functions for idiomatically embedding Elm in Yesod:
98 cabal install elm-yesod
100Some extra tips on Elm+Yesod can be found [here](https://github.com/evancz/Elm/wiki/Elm-with-Yesod:-Getting-Started).
102An important note: When you install the `elm` compiler, it automatically downloads Elm's JavaScript runtime system to `~/.cabal/share/Elm-x.y.z/`. The runtime system will follow the name scheme `elm-runtime-x.y.z.js` where `x.y.z` matches the version number of the compiler. If you want to serve this file from a different location, *copy* it from its home and always be sure that code compiled with version `x.y.z` of the compiler is served with version `x.y.z` of the runtime system.
105Potential problems and their solutions
106--------------------------------------
108* Try `cabal install elm`. This will give you access to the `elm` executable (but not `elm-server`).
110These problems all appeared before Elm version 0.1.1.4:
112* Install errors having to do with `happstack-server-7.0.2`. This version of `happstack-server` has stricter dependency restrictions that conflict with other libraries required by Elm. Try installing with an earlier version of `happstack-server` with the following command: `cabal install elm --constrain="happstack-server<7.0.2"`
113* When installing on Debian, `blaze-html-0.4.3.2` fails to compile. You must install `blaze-html-0.4.3.1` instead.
114* Elm does not appear to work with the latest versions of `containers` (i.e. 0.4.2.*). I know it works with earlier versions of containers, so to avoid this problem, you can try: `cabal install elm --constrain="containers==0.4.1.0" --force-reinstall`
115* On Windows, HAppStack has trouble installing because of issues with the "network" package. I struggled with this problem on Windows 7 until I found the suggestion at the bottom of [this page](http://hackage.haskell.org/trac/ghc/ticket/5159).
117If you are still stuck, email the list or ask a question in the [#Elm IRC channel](http://webchat.freenode.net/?channels=elm).