[Haskell-cafe] Cabal dependencies

[José Lopes]

OK. Got it!

Do you have any suggestions to install xmobar in this particular case?

Thanks,
José

On 06-10-2012 19:08, Yuras Shumovich wrote:
> On Sat, 2012-10-06 at 18:25 +0200, José Lopes wrote:
>> OK.
>>
>> But, wouldn't it be possible for xmobar to use mtl-2.0.1.0 and for
>> parsec to use mtl-2.1.1, while xmobar would use this parsec version?
>> In this case, I am assuming that mtl-2.0.1.0 and mtl-2.1.1 are
>> considered two different libraries.
> Usually it leads to "strange" compilation errors.
>
> E.g.
> Package A:
>    data AA = AA String
>    func0 :: Int -> AA
>    func0 n = AA $ replicate n "A"
>    func1 :: AA -> Int
>    func1 (AA str) = length str
>
> Package B:
>    import A
>    func2 :: AA -> Int
>    func2 aa = func1 + 1
>
> Package C:
>
>    import A
>    import B
>    func3 :: Int -> Int
>    func3 n = func2 $ func0 n
>
> If C and B are compiled with different versions of C,
> then func3 will not compile. Compiler will say that
> AA returned by func0 doesn't match AA expected by func2
>
> More real examples:
> http://stackoverflow.com/questions/11068272/acid-state-monadstate-instance-for-update
> http://stackoverflow.com/questions/12576817/couldnt-match-expected-type-with-actual-type-error-when-using-codec-bmp/12577025#12577025
>
>
>> Thanks,
>> José
>

-- 
José António Branquinho de Oliveira Lopes
Instituto Superior Técnico
Technical University of Lisbon