On Thu, Apr 8, 2010 at 13:49, Bas van Dijk wrote:

On Thu, Apr 8, 2010 at 11:00 AM, Sean Leather wrote:

...

I created a few tools to help me manage multiple GHC distributions in a Bash shell environment. Perhaps it's useful to others.

http://github.com/spl/multi-ghc

Feedback welcome. I'd also like to know if something similar exists.

Does this also work with a system installed ghc? These are usually installed in /usr (I'm using Gentoo Linux):

$ ls -l /usr/bin/ghc* lrwxrwxrwx 1 root root 10 dec 22 00:22 /usr/bin/ghc -> ghc-6.12.1 -rwxr-xr-x 1 root root 279 dec 22 00:20 /usr/bin/ghc-6.12.1 lrwxrwxrwx 1 root root 11 dec 22 00:22 /usr/bin/ghci -> ghci-6.12.1 -rwxr-xr-x 1 root root 61 dec 22 00:20 /usr/bin/ghci-6.12.1 lrwxrwxrwx 1 root root 14 dec 22 00:22 /usr/bin/ghc-pkg -> ghc-pkg-6.12.1 -rwxr-xr-x 1 root root 262 dec 22 00:20 /usr/bin/ghc-pkg-6.12.1

The ghc-config Bash script in multi-ghc uses symlinks to determine which is the "current" version to use. The instructions on the GitHub page explain it in detail, but here's how my setup works. * I create /opt/ghc for storing GHC, clone the multi-ghc repository (or copy the files) here. * I create /opt/ghc/6.10.4/src, download http://www.haskell.org/ghc/dist/6.10.4/ghc-6.10.4-i386-unknown-linux-n.tar.b..., and untar it here. * cd ..; ln -s ../Makefile; make install ghc-config creates a $HOME/.ghc-config directory for tracking the current version and symlinks. Now, the key for your situation (I think) is your $PATH. If you append $HOME/.ghc-config/ghc/bin to your $PATH after /usr/bin, then you can use ghc-6.10.4 to call this specific version. Unfortunately, there is still a problem. ghc-config also manages $HOME/.cabal as a symlink for the current version. So, that would most likely conflict with your setup. There may be a way to fix that, though I haven't looked into it, or I could separate the cabal configuration from the ghc configuration.

If so, I think I'm going to use this tools since I occasionally like to try out ghc-HEAD.

multi-ghc should also work for doing this. As long as you install it as /opt/ghc/6.13.blah (or whichever directory you want to use instead of /opt/ghc). This was one of the goals of the design. There's more documentation in the README.md and scripts. I'm happy to improve upon it if something doesn't work. Sean

On Thu, Apr 8, 2010 at 14:00, Bernie Pope wrote:

On 8 April 2010 19:00, Sean Leather wrote:

...

I created a few tools to help me manage multiple GHC distributions in a Bash shell environment. Perhaps it's useful to others.

http://github.com/spl/multi-ghc

Feedback welcome. I'd also like to know if something similar exists.

I wonder if you could achieve the desired result with the "Modules Project":

http://modules.sourceforge.net/

We use it at work for managing multiple versions of lots of different programs on a shared machine.

It looks interesting! Thanks. It makes me sad to see it written in Tcl. I spent way too much time with the language at my last job and did not enjoy it. But I grant that that is not a reason to avoid using it. I actually started out doing as they do, changing the PATH, but I decided that was not a great solution for two reasons: (1) It's inflexible and precludes the ability to set my PATH as I like. (2) It requires sourcing a script instead of executing it. I didn't like having no separation between my environment and the script's environment. It was too easy to introduce spurious environment variables. It would be nice if such a tool can potentially be written to work on Windows as well. Regards, Sean