[Haskell-cafe] Cabal + yi + alex problem.

Austin Seipp mad.one at gmail.com
Wed Jul 30 17:21:30 EDT 2008

Excerpts from John Dorsey's message of Wed Jul 30 13:58:26 -0500 2008:
> Is something amiss with cabal-install?  Shouldn't it have automatically
> installed alex?  Or does it only do that with libraries, by design?

AFAICT, dependencies are only downloaded and installed if they are
listed in a .cabal files 'dependency' field (providing they aren't
already installed) which yes, means libraries by design. I've not had
cabal-install ever track down necessary applications in my

As well, this issue came up on #haskell the other day and my
conclusion is that no, cabal does not track down and install any
*applications* that are necessary (someone tried to install yi, needed
alex, build failed, and after 'cabal-install alex' everything was

> For that matter, "ghc-pkg list | grep -i alex" doesn't list anything,
> after I cabal-installed it.  How does cabal verify the prerequisite alex
> version?  (Or does it?)

ghc-pkg lists libraries that are registered with the ghc package
manager (globally and locally); alex is simply an application, not a
library, so there's really nothing for GHC to register. As for telling
what version is necessary, I haven't the slightest.

Duncan, can you shed some light here?


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