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

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? : ) Best, On Sun, Nov 28, 2010 at 1:32 AM, Michael Snoyman wrote:

On Sat, Nov 27, 2010 at 6:59 PM, Jinjing Wang wrote:

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Dear list,

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From ghc 7.0.1 release notes:

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The Language.Haskell.TH.Quote.QuasiQuoter type has two new fields: quoteType and quoteDec.

Some of my code needs to be conditionally compiled to support both version 6 and 7, what is the recommended way to do it?

ref:

* http://new-www.haskell.org/ghc/docs/7.0.1/html/users_guide/release-7-0-1.htm...

Hi Jinjing,

I've done this in Yesod. I'm not sure if it's the best way, but basically I've added a ghc7 flag to the cabal file, and a block for the library that reads:

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

Then whenever I want to quasi-quote in the code, I write:

#if GHC7    [quasiquoter| #else    [$quasiquoter| #endif

Michael

-- jinjing