[Haskell-cafe] containers-deepseq?

Michael Snoyman michael at snoyman.com
Tue Nov 29 06:43:11 CET 2011

Hi all,

Since the release of deepseq 1.2, we've had a bit of a problem: when
using the newest versions of packages on Hackage, there is no NFData
instance available for the containers types. When GHC 7.4 comes out
with its newer version of containers, this will be addressed, but
we'll still have problems for users of older GHC releases.

I'd like to suggest a solution: a new package called
containers-deepseq. Using conditional compilation, it will provide an
orphans NFData instance for all containers types when deepseq >= 1.2
and containers < 0.5. Packages (e.g., aeson) would then depend on
containers-deepseq and simply import the module whenever they rely on
the NFData instances. When GHC 7.4 comes out, the package will
essentially be a no-op.

Does this make sense?


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