module 'free-4.6.1:Main' is defined in multiple files

[Mikhail Glushenkov]

Hi,

On 24 March 2014 22:33, Mateusz Kowalczyk <fuuzetsu at fuuzetsu.co.uk> wrote:
> On 24/03/14 21:26, Mikhail Glushenkov wrote:
>> Hi,
>>
>> On 24 March 2014 18:54, Mateusz Kowalczyk <fuuzetsu at fuuzetsu.co.uk> wrote:
>>>
>>> PS: How does one go about downgrading Cabal and cabal-install? If we
>>> wanted to check whether cabal is the problem, how?
>>
>> You can force the Cabal lib version to use (in case you have multiple
>> versions installed) with 'install --cabal-lib-version'. To downgrade
>> cabal-install itself to some older version you need to compile and
>> install that version.
>>
>
> About cabal-install, I'm mostly concerned about not breaking my whole
> existing system by installing an old version. Are there any steps I can
> take to retain sane setup? I don't have an OSX machine and I can't
> exactly ask people volunteering to break their Haskell environments.

Use a sandbox to compile the cabal-install executable:

$ cd cabal/cabal-install
$ cabal sandbox init
$ cabal sandbox add-source ../Cabal
$ cabal install --dependencies-only && cabal build

And then copy it to somewhere in PATH:

$ cp dist/build/cabal/cabal ~/bin/cabal-1.18

> Are there any catches to having multiple Cabal libs installed or will
> the latest one always be used if not specified?

Yes, the latest one is always used.