Re: [Haskell-cafe] Cabal: Disjunctive Build-Depends

Grand. Thanks! On 12/12/2011, Felipe Almeida Lessa wrote:

On Mon, Dec 12, 2011 at 6:25 PM, Matthew Farkas-Dyck 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