On Sat, Nov 27, 2010 at 9:59 AM, Jinjing Wang <nfjinjing@gmail.com> wrote:
Thanks Michael,

So the user should use `cabal install --flags -ghc7 package-name` to
install the package, if I'm not mistaken?

Will it work if the package is installed as a dependency? Will the
flag environment be passed down from the root package?

Is there a way to detect GHC version automatically?

I see that others have provided answers on here, but another way is to change the check from:

   if flag(ghc7)
       build-depends:   base                      >= 4.3      && < 5
       cpp-options:     -DGHC7
   else
       build-depends:   base                      >= 4        && < 4.3

to this:
   if impl(ghc >= 7)
       build-depends:   base                      >= 4.3      && < 5
       cpp-options:     -DGHC7
   else
       build-depends:   base                      >= 4        && < 4.3

I hope that helps,
Jason