win-hp-path: Work with multiple Haskell Platform versions on Windows

This project provides the use-hp command for working with multiple versions of the Haskell Platform on Windows.

Quick start

Installation

1. Make sure the folder C:\Program Files\Haskell\bin exists.
2. Get the latest Haskell Platform. Run cabal install win-hp-path and copy the resulting executable use-hppath.exe into C:\Program Files\Haskell\bin.
3. Download use-hp.bat from this GitHub project and copy it into C:\Program Files\Haskell\bin.
4. Install whatever other Haskell Platform versions you need. Ignore the warning about having more than one Haskell Platform version.
5. Download find-hp.bat from this GitHub project. Edit it so that the paths point to where you have Haskell Platform versions installed. Copy it into C:\Program Files\Haskell\bin.
6. Optional - if you want to use the same version of cabal.exe with all of your Haskell Platform versions, copy it into C:\Program Files\Haskell\bin.

In the future, when you install or remove Haskell Platform versions, edit find-hp.bat and keep the paths up-to-date.

Usage

1. Open a command prompt window.
2. Run use-hp <ghc-version-number>. For example: use-hp 7.8.3

Optional - pick one version of Haskell Platform that you want to be your default. Do the above steps to activate it in one window. Run echo %PATH%, and use that information to correct the values of your path permanently in System Properties. Now any new command prompt will work with your default Haskell Platform right from the start without having to run use-hp.

Running use-hp enters a "sub-shell" within the same command prompt window and temporarily modifies the path to use the Haskell Platform you specified. To return to the original environment, enter the command exit.