[Haskell-cafe] Cabal: Disjunctive Build-Depends

[Matthew Farkas-Dyck]

Grand. Thanks!


On 12/12/2011, Felipe Almeida Lessa <felipe.lessa at gmail.com> wrote:
> On Mon, Dec 12, 2011 at 6:25 PM, Matthew Farkas-Dyck
> <strake888 at gmail.com> wrote:
>> I have written some code that can be compiled with either of two
>> libraries, with no modification. How can I tell Cabal?
>>
>> I tried "||" but it failed to parse.
>>
>> I could find which package is available in the build script, and then
>> call defaultMainNoRead with the appropriate GenericPackageDescription,
>> but I'm not sure how to find this system-agnostically.
>
> You just need to use flags.  Something like
>
> Flag usethis
>   Description:  Use this instead of that
>   Default:  False
>
> Library
>   Build-depends: ...everything else...
>   if flag(usethis)
>     Build-depends: this == 0.1.*
>   else
>     Build-depends: that == 4.0.*
>
> You don't need to care about usethis.  If 'that' is not installed but
> 'this' is, Cabal will automatically turn 'usethis' flag on.
>
> Cheers,
>
> --
> Felipe.
>


-- 
Matthew Farkas-Dyck