[Haskell-beginners] failed to install HTTP-4000.2.4 when executing `cabal install cabal-install`

[Daniel Fischer]

On Saturday 19 April 2014, 16:08:31, hengchu Zhang wrote:
> ​
> I am using Mac OS 10.8.4, and I installed haskell from homebrew. Does this
> mean something might have went wrong when I installed haskell?

No, it means that the HTTP package has no upper bound on its dependency on the 
network package, and the type of Network.URI.relativeTo changed in 
network-2.4.0.0 versus network-2.3.*

You can try either

cabal install --constraint="HTTP >= 4000.2.5" cabal-install

or

cabal install --constraint="network < 2.4" cabal-install

Either way, check with the --dry-run flag first whether cabal reports any 
problems.