First, if you are on Mac or Windows just looking to use Elm, definitely use the installers linked here. Do not put yourself through this process if you do not have to!
Second, if you are on some linux OS and just want to use Elm, use the npm installer.
Finally, if you have made it this far, you are in some unique position where the other options do not cover you for some reason. You are about to actually build from source. I recommend you read this whole section before you start running anything.
There are two phases!
You will need Haskell to build this stuff. On some platforms the Haskell Platform will work for you, but read the rest of this paragraph before making any moves. You need GHC to compile the code. Developers typically build with GHC 7.10 but Elm versions before 0.16 should build with GHC 7.8 as well. You also need cabal 1.18 or higher. This will let you create a cabal sandbox which should make the build process much easier. Before getting Haskell Platform, make sure it is going to give you these things.
Note: Sometimes things go bad with cabal, so know that you can always blow it all up. I sometimes do this after a fresh install of GHC and cabal to make sure there are no globaly installed packages that are going to make things suck for me later.
At this point you should be in a world where your cabal version is greater than 1.18. It probably sucked getting here, so thank you for sticking with this!
Find a directory on your machine where you want the Elm Platform to live. You will soon run a script that creates a directory called Elm-Platform/0.17/* and builds all the necessary things. You should not move Elm-Platform/ after it is created, so choose carefully before progressing.
Now that you have chosen a home for Elm-Platform/, add the absolute path to Elm-Platform/0.17/.cabal-sandbox/bin to your PATH (like this). This is necessary to successfully build elm-reactor which relies on elm-make. This will also mean you can use elm commands from anywhere!
Okay, now run these commands:
# If you are on LINUX, you need to install a dependency of elm-repl.
# Uncomment the following lines and run them.
# sudo apt-get install libtinfo-dev
# sudo apt-get install zlib1g-dev
# if you are on windows, or some other place without curl, just download this file manually
curl https://raw.githubusercontent.com/elm-lang/elm-platform/master/installers/BuildFromSource.hs > BuildFromSource.hs
runhaskell BuildFromSource.hs 0.17Note: You can use the
BuildFromSource.hsscript to build any version of the compiler, so you can run the following to build all the latest versions of things:runhaskell BuildFromSource.hs master. Be aware, this is where active development happens, so not everything will be working at all times! You will want to change yourPATHto point to the right thing if you go down this road.