[Haskell-cafe] Control.Exception base-3/base-4 woes

[Antoine Latter]

On Fri, Sep 11, 2009 at 10:42 AM, David Menendez<dave at zednenem.com> wrote:
> On Fri, Sep 11, 2009 at 11:26 AM, Neil Brown <nccb2 at kent.ac.uk> wrote:
>>
>> Can anyone tell me how to fix this?  I don't think that changing to always
>> use Control.Exception would fix this, because I need to give a different
>> type for catch in base-3 to base-4, so there's still the incompatibility to
>> be dealt with.
>
> I'd try using a cabal flag to set a CPP flag.
>
> E.g., from cabal
>
>    Flag Base3
>        Description: Use Version 3 of Base
>        Default: False
>
>    Library/Executable
>        if flag(Base3)
>            CPP-Options: -D _BASE_3_
>            Build-Depends: base >= 3 && < 4
>
>        else
>            Build-Depends: base >= 4 && < 5
>
> And then do,
>
>    #if _BASE_3_
>    import qualified Control.Exception as C
>    #else
>    import qualified Control.OldException as C
>    #endif
>

I've had success with this. See:

http://hackage.haskell.org/packages/archive/uuid/1.0.2/uuid.cabal

Antoine