[Haskell-cafe] Alternative dependencies in Cabal file

Hi, for a package I need to ensure the user uses a certain package configuration. So how would I rewrite the following pseudo-cabal description? Build-Depends: packageA < X, packageB < Y or packageA >= X && < X', packageB >= Y && < Y' or packageA >= X', packageB >= Y' Build-Depends: ... common dependencies ... where neither A nor B is the base package. Maybe I have to use if/else blocks, but I don't know what conditions to use then. Regards, Matthias