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

[Duncan Coutts]

On Wed, 2008-07-30 at 14:58 -0400, John Dorsey wrote:
> > [problems with cabal install yi]
> 
> Curious, I tried this out, on a Debian etch box with GHC 6.8.3.
> 
> "cabal update ; cabal install yi --global"
> complained about needing alex >=2.0.something and <3.
> 
> Then "cabal install alex" happily installed alex version 2.2.  Finally,
> "cabal install yi --global" worked fine.
> 
> Is something amiss with cabal-install?  Shouldn't it have automatically
> installed alex?  Or does it only do that with libraries, by design?

Right, currently it only tracks library dependencies, not tools. See:

http://hackage.haskell.org/trac/hackage/ticket/227
  "cabal-install does consider build-tools as dependencies"

> For that matter, "ghc-pkg list | grep -i alex" doesn't list anything,
> after I cabal-installed it.

The ghc package database is of libraries. Applications are not
registered anywhere.

> How does cabal verify the prerequisite alex version?  (Or does it?)

It calls alex --version

> I'm enjoying cabal since I've begun using it, but it's still somewhat
> opaque to me.

There's still plenty of work to do. You and indeed everyone else is most
welcome to get involved and have a go at fixing bugs or adding
frequently requested features.

Easy tickets:
  http://hackage.haskell.org/trac/hackage/report/13

Guide to the source code:
  http://hackage.haskell.org/trac/hackage/wiki/SourceGuide


Duncan