On Sat, Aug 01, 2015 at 06:31:38AM +1000, Erik de Castro Lopo wrote:
I maintaing multiple versions of GHC on all the machines I use regularly for Haskell development. I have:
* ghc-7.6.3 installed under /usr/lib/ghc-7.6/ * ghc-7.8.4 installed under /usr/lib/ghc-7.8/ * ghc-7.10.2 installed under /usr/lib/ghc-7.10/
To switch between versions all I need to do is modify $PATH to remove say /usr/lib/ghc-7.6/bin and add /usr/lib/ghc-7.10/bin. This lets me have two terminal window side by side with different versions of GHC.
I use essentially the same setup, but found that cabal-install does not play nicely with this: No matter under which prefix I install cabal-install, it always assumes the same global path for its configuration file. This is a nuisance in particular when for some reason different versions of GHC need different versions of cabal-install --- apparently older GHCs don't work with newer versions of cabal-install? I did experiment with cabal-install's -w and sandboxes, and agree with what was previously mentioned: It only helps if you never use GHC without cabal-install. It would be nice if cabal-install had an installation-time option to set its prefix directory FOR EVERYTHING. The best cludge I found was scripts /usr/lib/ghc-*/bin/mycabal that call /usr/lib/ghc-*/bin/cabal with appropriate options... Wolfram