Newbie: Can't understand cabal errors during install of hakyll

[Adam Bergmark]

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 at 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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