Cabal/How to install a Cabal package

You've found an interesting Haskell package on HackageDB. How do you install it on your system?

1. Check whether the package came with your Haskell implementation.
2. If your operating system has a packaging system (e.g. most Linux or BSD distributions), check whether it is already packaged there.
3. Otherwise, you'll have to build and install the package. A program to automate this process, called cabal-install, is under development. In the meantime, you'll have to do it manually:
   1. First, ensure that all the packages it depends on are installed (by following these instructions recursively).
   2. Unpack the tar file (yes, this assumes a Unix system; sorry about that (how to unpack a tar file in windows)):

      tar xzf PACKAGE-VERSION.tar.gz

   3. Move into the directory this creates:

      cd PACKAGE-VERSION

   4. This directory should contain a file Setup.hs or Setup.lhs. In order to install a package globally, perform the following commands for the appropriate file (see the Cabal documentation for more details):

      runghc Setup.hs configure

      runghc Setup.hs build

      runghc Setup.hs install

   If instead of installing globally, you just wish to install a package for your normal user account, you could instead use the following configure command, which would register the install in the user-specific database and install binaries and libraries in $HOME/bin, $HOME/lib, and so forth:

   runghc Setup.hs configure --user --prefix=$HOME

   You can get more information about any of these commands by adding --help after the command. For example, to see all the options available for the configure step, you could use the following command:

   runghc Setup.hs configure --help

   Lastly, if you encounter unsatisfied dependencies when you run the configure step, that is when you recurse and first install the missing package.

Note: If you have more than one Haskell compiler on your system, use the --with-compiler option for the configure step. That will ensure that Cabal uses the correct compiler during the entire installation process. For example:

 runghc Setup.hs configure --with-compiler=ghc-6.8.2
 runghc Setup.hs build
 runghc Setup.hs install