[Haskell-cafe] Conditional compilation for different versions of GHC?

[Jason Dagit]

On Sat, Nov 27, 2010 at 9:59 AM, Jinjing Wang <nfjinjing at 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
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