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# Backpack
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This is the launch page for Backpack, actively maintained by Edward (as of Aug 2017).
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This is the launch page for Backpack, actively maintained by Edward (as of Nov 2017).
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Backpack is a system for retrofitting Haskell with an applicative, mix-in module system. It has been implemented in GHC 8.2 and cabal-install 2.0, but it is [ not supported by Stack](https://github.com/commercialhaskell/stack/issues/2540).
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... | ... | @@ -45,6 +45,8 @@ Some more out-of-date documents: |
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**Can I use this with Template Haskell?** Yes, but you need GHC 8.2.2; GHC 8.2.1 has a critical bug which means that most real-world uses of TH will not work. See [ this issue](https://github.com/haskell/cabal/issues/4755) and [ this issue](https://github.com/haskell/cabal/issues/4865) for two examples of this occurring in the wild.
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**Can I use this with the C preprocessor?** No, this is buggy (you'll get an error `<command line>: unknown package: hole`). See [\#14525](https://gitlab.haskell.org//ghc/ghc/issues/14525) for the issue and a patch.
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**Make sure cabal-version is recent enough.** ([ \#4448](https://github.com/haskell/cabal/issues/4448)) If you set the `cabal-version` of your package too low, you may get this error:
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```wiki
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