[Haskell-beginners] Errors package

[Michael Snoyman]

I'm not sure why cabal has decided that it's best to reinstall a new
version of transformers, that seems very strange to me. You can probably
work around this by running:

    cabal install errors --constraint 'transformers == 0.3.0.0'

I *would* recommend upgrading to GHC 7.8, as a number of packages have
stopped supporting 7.6.3. (For the record, I don't believe any of the
packages you have installed have dropped backwards compatibility.) And
generally, I recommend using Stackage to avoid these kinds of versioning
problems. There are instructions at:

   http://www.stackage.org

Fair warning: I'm the primary Stackage maintainer.

On Fri Jan 02 2015 at 2:19:20 PM Andrew Bernard <andrew.bernard at gmail.com>
wrote:

> When attempting to install the package ‘errors’ I get the following:
>
> $ cabal install errors
> Resolving dependencies...
> In order, the following would be installed:
> exceptions-0.6.1 (reinstall) changes: mtl-2.1.2 -> 2.2.1,
> transformers-0.3.0.0
> -> 0.4.2.0
> transformers-base-0.4.3 (reinstall) changes: transformers-0.3.0.0 ->
> 0.4.2.0
> monad-control-1.0.0.1 (new version)
> transformers-compat-0.3.3.4 (reinstall) changes: transformers-0.3.0.0 ->
> 0.4.2.0
> contravariant-1.2 (reinstall) changes: transformers-0.3.0.0 -> 0.4.2.0
> distributive-0.4.4 (reinstall) changes: transformers-0.3.0.0 -> 0.4.2.0
> comonad-4.2.2 (reinstall) changes: transformers-0.3.0.0 -> 0.4.2.0
> semigroupoids-4.2 (reinstall) changes: transformers-0.3.0.0 -> 0.4.2.0
> bifunctors-4.2 (reinstall)
> profunctors-4.3.2 (reinstall) changes: transformers-0.3.0.0 -> 0.4.2.0
> free-4.10.0.1 (new version)
> either-4.3.2.1 (new version)
> errors-1.4.7 (new package)
> cabal: The following packages are likely to be broken by the reinstalls:
> temporary-1.2.0.3
> ghc-mod-5.2.1.1
> resourcet-1.1.2.3
> yaml-0.8.9.3
> stylish-haskell-0.5.11.0
> persistent-sqlite-1.3.0.5
> persistent-1.3.3
> persistent-template-1.3.2.2
> monad-logger-0.3.8
> hoogle-4.2.36
> conduit-extra-1.1.4.2
> conduit-1.2.3
> either-4.3.2
> monad-journal-0.5.0.1
> resource-pool-0.2.3.1
> monad-control-0.3.3.0
> lifted-base-0.2.3.0
> io-choice-0.0.5
> HTF-0.12.2.3
> free-4.9
> Use --force-reinstalls if you want to install anyway.
>
> I am using the ghc platform version 7.6.3.
>
> Is this package obsolete? Why are so many packages likely to be broken?
>
> With Haskell, how does one know what is a proper up to date package and
> what is not?
>
> Andrew
>
>
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