[Haskell-beginners] Happstack dependency problems

[Daniel Fischer]

On Tuesday 05 April 2011 20:25:36, Tom Murphy wrote:
> Hi all,
> 
> I'm having build troubles with Happstack. I'll let the error message
> speak for itself:
> 
> "
> $ export PATH=~/.cabal/bin:$PATH
> $ cabal update
> $ cabal install happstack
> Resolving dependencies...
> cabal: cannot configure unix-2.4.2.0. It requires base >=4.2 && <4.4
> For the dependency on base >=4.2 && <4.4 there are these packages:
> base-4.2.0.0, base-4.2.0.1, base-4.2.0.2, base-4.3.0.0 and base-4.3.1.0.
> However none of them are available.
> base-4.2.0.0 was excluded because of the top level dependency base -any
> base-4.2.0.1 was excluded because of the top level dependency base -any
> base-4.2.0.2 was excluded because of the top level dependency base -any
> base-4.3.0.0 was excluded because of the top level dependency base -any
> base-4.3.1.0 was excluded because of the top level dependency base -any
> "

Yes, that error message is terrible.
What it means is that for some reason, cabal can't choose any of these 
versions.

However, it's suspicious that it tries to install unix-2.4.2.0 at all.
You should have a unix package installed that came with your ghc, and that 
should be used.

Have you any packages in your user-db which shadow packages in the global 
db?
What does ghc-pkg check report, and what does

$ cabal install -v3 --dry-run happstack

say?

> 
> Thank you for any help!
> Tom