It seems like you have time-1.4.2 installed, the latest GHC (7.10) comes with time 1.5.*. Are you sure you are on 7.10?

The core of the problem is that hakyll needs time >= 1.5, and unix is using the pre-installed time-1.4.2. This is rejected because only one version of a library can be used in the same install plan.

As the error message suggests you can you increase the backjump limit so I'd try that first. I typically pass --reorder-goals --max-backjumps=-1 to cabal-install. Running this sometimes takes a long time, but it will finish eventually.

You can also try installing an older version of hakyll that works with time-1.4.2 (see the hackage page for info on older versions).

Lastly, are you using a sandbox? It also helps with reducing problems. I never install anything in the global or user level package db, only in sandboxes.

HTH,

Adam

On Sat, Aug 1, 2015 at 2:36 PM, Peder Jakobsen <pjakobsen@gmail.com> wrote:

Hi,

Been with Haskell just for few days, and thought it would be a good exercise to run a static site generator to get familiar with various tools, and I’m already running into “cabal hell” I think. :(

$ cabal install hakyll
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: hakyll-4.7.2.0 (user goal)
next goal: time (dependency of hakyll-4.7.2.0)
rejecting: time-1.4.2/installed-d67... (conflict: hakyll => time>=1.5 && <1.6)
trying: time-1.5.0.1
trying: process-1.2.0.0/installed-3a4... (dependency of hakyll-4.7.2.0)
next goal: unix (dependency of process-1.2.0.0/installed-3a4...)
rejecting: unix-2.7.0.1/installed-8ad... (conflict: time==1.5.0.1, unix =>
time==1.4.2/installed-d67...)
rejecting: unix-2.7.1.0, 2.7.0.1, 2.7.0.0, 2.6.0.1, 2.6.0.0, 2.5.1.1, 2.5.1.0,
2.5.0.0, 2.4.2.0, 2.4.1.0, 2.4.0.2, 2.4.0.1, 2.4.0.0, 2.3.2.0, 2.3.1.0,
2.3.0.0, 2.2.0.0, 2.0 (conflict: process => unix==2.7.0.1/installed-8ad...)
Backjump limit reached (change with --max-backjumps).

I’m running OS X Yosemite 10.2.2 with all the latest versions of Haskell and cabal.

Thanks you for listening. :)

Peder

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