Registering multiple versions of packages with `ghc-pkg`?

Question

I'm trying to install GHC and Cabal on FreeBSD 8.1. I've installed GHC 7.0.1 (because it's current stable release) and now trying to install Cabal (to install cabal-install), but it fails with this error message.

%./Setup configure
Configuring Cabal-1.8.0.4...
Setup: At least the following dependencies are missing:
base >=4 && <3 && >=1 && <5, filepath >=1 && <1.2
%

Definitely I'm having too higher version of library.

%ghc-pkg list
/usr/local/lib/ghc-7.0.1/package.conf.d
   Cabal-1.10.0.0
   array-0.3.0.2
   base-4.3.0.0
   bin-package-db-0.0.0.0
   bytestring-0.9.1.8
   containers-0.4.0.0
   directory-1.1.0.0
   extensible-exceptions-0.1.1.2
   ffi-1.0
   filepath-1.2.0.0
   ghc-7.0.1
   ghc-binary-0.5.0.2
   ghc-prim-0.2.0.0
   haskell2010-1.0.0.0
   haskell98-1.1.0.0
   hpc-0.5.0.6
   integer-gmp-0.2.0.2
   old-locale-1.0.0.2
   old-time-1.0.0.6
   pretty-1.0.1.2
   process-1.0.1.4
   random-1.0.0.3
   rts-1.0
   template-haskell-2.5.0.0
   time-1.2.0.3
   unix-2.4.1.0
/home/eonil/.ghc/x86_64-freebsd-7.0.1/package.conf.d
   network-2.2.1.5
   parsec-2.1.0.1
%

Should I downgrade to GHC 6.x? Or can I install lower version of the packages? (or side-by-side install)

Answer 1

I had to downgrade GHC 6.x. Originally I did this for Happstack. However Happstack needs at least 6.12.x of GHC and installing Cabal on FreeBSD 8.1 with GHC 7.x is too hard. (I couldn't succeed)

I just downloaded and installed GHC 6.12.3 from GHC website, and everything worked magically! Cabal, Happstack installed at once. I failed just only once because of insufficient swapping space.