Help understanding a dependency conflict

tsuraan tsuraan at
Fri Jan 7 22:31:44 CET 2011

> ghc-pkg doesn't list mtl as a dependency of parsec.  I didn't think I
> had mtl-1 installed (it's not in my .cabal directory), but now I see
> that it's part of the haskell base install.  So now I'm wondering why
> cabal felt that it needed to install mtl-2 for hslogger, when I
> apparently already had mtl-1 installed, and hslogger doesn't list a
> version for its mtl dep.  Is it because hslogger depends on base >= 4,
> while json depends on base >= 3?  Does that sound like a probable
> cause?

I think that was the problem.  I just did a new "cabal install json",
and it installed it linking against mtl-2 instead of mtl-1, and the
warning went away.  So, I'm happy now, and I learned some new tools.

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