This is the Elm compiler and server, allowing you to develop Elm applications that run in any modern browser.
If you intend to serve Elm code with a custom Haskell backend, be sure to read all the way to the "Installation for Haskell-Users" section.
Installation for General Use
Download the Haskell Platform 2012.2.0.0. This will give you access to the Haskell compiler (needed to build Elm) and Haskell's package distribution system (to make installation of Elm easier). Elm definitely works with version 7.4 of the Haskell compiler (i.e. GHC 7.4) which is bundled with version 2012.2.0.0 of the Haskell Platform.
If you are a Linux user and already have a copy of GHC installed and have downloaded a bunch of packages, it may be worthwhile to create new user account and just install Elm separately as described here. Dependency issues have been rampant lately with packages changing to support GHC 7.6.
Installing the compiler and server
Once the Haskell Platform is installed (even if it already was), you must update your listing of packages with:
This will ensure that the elm package is available. Then install Elm with:
cabal install elm
Assuming everything goes correctly (potential problems are discussed later), this
will install the
elm compiler on your machine.
elm is a standard compiler that
.elm files and produces
.js files. You can then use these
files with your favorite web-framework. Use
elm --help for more directions on how to use it.
If you have this installed you can write and compile Elm locally, so if the next step fails for you, it is safe to proceed without it.
You can also install
elm-server which is both a compiler and server, allowing
you to develop without designing and setting up a server yourself. Running
starts a server in the current directory. It will compile and serve any
.elm files in
the current directory and its sub-directories. This is how I prefer to develop
Elm programs. Install with:
cabal install elm-server
Dependency issues have been cropping up with this step, so if you run into issues,
please report them so they can be fixed! Once installed, use the command
to see some extra information.
Using the Elm compiler and server
To use these executables you need to add a new directory to your PATH. For me, the
executables were placed in
/home/evan/.cabal/bin which I appended to the end of my
PATH variable in my .bashrc file. Cabal should tell you where your executables are
located upon successful installation, so you can make a similar addition (see this
tutorial if you are new to changing your PATH in Unix/Linux).
You can use the commands
elm --help and
to get more information about using these tools.
That is almost everything. Now, we will create a simple Elm project. The following commands will set-up a very basic project and start the Elm server.
mkdir helloElm cd helloElm echo main = lift asText Mouse.position > main.elm elm-server
The first two commands create a new directory and navigate into it. The
command places a simple program into
main.elm (do this manually if you do not
echo). The final command starts the Elm server at localhost,
allowing you to navigate to
main.elm and see your first program in action.
Installation for Haskell-users
Yesod users should also install the
elm-yesod package which provides functions for idiomatically embedding Elm in Yesod:
cabal install elm-yesod
Some extra tips on Elm+Yesod can be found here.
An important note: When you install the
~/.cabal/share/Elm-x.y.z/. The runtime system will follow the name scheme
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.
Potential problems and their solutions
cabal install elm. This will give you access to the
elmexecutable (but not
These problems all appeared before Elm version 0.1.1.4:
- Install errors having to do with
happstack-server-7.0.2. This version of
happstack-serverhas stricter dependency restrictions that conflict with other libraries required by Elm. Try installing with an earlier version of
happstack-serverwith the following command:
cabal install elm --constrain="happstack-server<7.0.2"
- When installing on Debian,
blaze-html-0.4.3.2fails to compile. You must install
- 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
- 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.
If you are still stuck, email the list or ask a question in the #Elm IRC channel.