How can I uninstall a version of a Cabal package?

Question

Happstack Lite is breaking on me because it\'s getting blaze-html version 0.5 and it wants version 0.4. Cabal says that both versions 0.4.3.4 and 0.5.0.0 are insta

Answer 1

If you are outside a sandbox:

ghc-pkg unregister --force regex-compat-0.95.1

If you are inside a cabal sandbox:

cabal sandbox hc-pkg -- unregister attoparsec --force

The first -- is the argument separator for hc-pkg. This runs ghc-pkg in a sandbox aware manner.