The Haskell Platform is deprecated and no longer the recommended way to install Haskell. The recommended way is to follow the instructions on the Haskell.org Downloads page.
"Haskell Platform" is a combination of the GHC compiler and core libraries, plus additional tools and libraries covering a range of common programming tasks. The platform is maintained and released so as to be a consistent, stable base. It aims to be a quick way to a working Haskell environment, and a solid foundation on which to base production software.
While end-users can build the platform themselves, it is generally recommended, if possible, to use the prebuilt binaries available from https://www.haskell.org/platform/
The platform distribution and tooling are more intended instead for those wishing to package a platform installer for use by others.
Again: If you want to install the haskell platform, this is NOT the right location. You can download prebuilt installers for most systems from
https://www.haskell.org/platform/
From there you can get the following:
installer - For Windows and OS X, the platform is distributed as a standard installer for the operating system. It contains a fully built version of the platform, accompanying documentation, and additional scripts and files needed to integrate well with the standard environment and development tools.
Running the installer is all you need to get a working Haskell environment.
OS distribution packages - For many Linux, BSD, and other similar Posix, the platform has been packaged into packages for the local package manager. These can be selected and installed, from the appropriate package repos, with the standard package manager tools.
generic bindist - For Linux, there is a generic bindist. This is compiled against standard versions of the common system libraries, and if your system has those, you can generally just unpack this tarball, and run a script to get it setup.
If you really want to get the toolkit to build your own platform installer, then you're in the right spot.
The platform installer toolkit comes in several forms:
source tarball - This is a specially packaged version of the repo that includes the sources of the packages that make up the platform, and excludes some of the ancillary things in the source repo. You can use this to build the platform without access to hackage or even an internet connection. You still need a GHC bindist, as well as cabal and stack binaries, either built from source or available from their respective websites.
This is also available from https://www.haskell.org/platform/
source repo - This is the source of the system that builds the platform. It includes the file that defines the versions of GHC and other packages that make up the platform. You can use this to build the platform from just a GHC bindist.
You can check out the official release from github: http://github.com/haskell/haskell-platform
The master branch is always stable, and releases are tagged like "2014.2.0.0". Development usually happens in other branches.
You need the platform build files, either from the source repo or the source tarball. Build instructions are the same for either.
You need a GHC bindist that matches the OS you are compiling on. It must also match the GHC version used by the platform, which you can find by looking in the Releases*.hs files.
You can get the bindists from
https://www.haskell.org/ghc/download
The machine doing the build needs to have a working Haskell setup: Usually, GHC (7.4 or later), Cabal (1.24 or later), and haddock and HsColour must be on the $PATH.
You also need a proper version of the cabal and stack binaries to be bundled.
You can build a cabal directly from hackage and get a stack from http://docs.haskellstack.org
The platform is now built by a program called hptool. That tool is a shake based build system that creates both the traditional haskell-platform source tarball, and can build a complete, hermetic build of the platform for use in building OS installer packages.
In either the source repo or unpacked source tarball, simply run this:
./platform.sh $PATH_TO_GHC_BINDIST_TARBALL $PATH_TO_CABAL_EXECUTABLE $PATH_TO_STACK_EXECUTABLE
This will build the hptool itself, and then use that tool to build first the platform source tarball, and finally the hermetic build of all the platform packages.
By default this now builds a "minimal" installer that does not install libraries beyond core. To build a "full" installer with a broader range of libraries pre-installed in the global store, pass a "-f" option.
If you are building for a Posix like system (Linux, or BSD), then you can add the command line option --prefix to specify where, on the target system the tree of built things will be placed. It defaults to "/usr/local/haskell". The build will include another directory under that named "ghc-x.y.z-arch" and everything will be installed under there.
Adding -j (no space between the j and the number of cores) to the build invocation will enable building on multiple cores at once.
After the build completes, it will print instructions for how to take the build product and install it on systems. The build products are in: build/product
For OS X and Windows, the built product is just a standard installer. Copy it to the target system and install it.
For Posix like systems, the built product is a tarball, which should be unpacked at / (it includes the prefix spec'd in the build). Then, on the target, you must run the activate-hs script in the installed bin dir, usually: /usr/local/haskell/ghc-x.y.z-arch/bin/activate-hs That script will do the final package registrations, and symlink all the command line tools (ghc, haddock, etc..) into /usr/local/bin. Run the script with -n or -? to find out more.