[tmhedberg]

The latest version of Cabal (1.18) includes built-in sandboxing support, which alleviates this problem to a significant extent. Prior to that, there were/are tools [^1][^2] for doing the same thing external to Cabal itself. Dependency hell has without a doubt been problematic with Cabal, but it is fast becoming a solved issue.

[^1]: http://hackage.haskell.org/package/cabal-dev [^2]: http://hackage.haskell.org/package/hsenv (Disclosure: I am the current maintainer of this project, though I am happy to see it becoming obsolete)

[clux]

I did use cabal-dev, and it only moved the problem from being a global problem to a local one. Is the problem that you cannot have several versions of the same package solved? Because this really needs to work, otherwise you effectively have a limit on how many modules you can use sensibly without expecting things to break.

[chongli]

You can have several versions of the same package. You can't have one package built multiple times to depend on different versions of the same package. This is the main cause of dependency hell.