ANN: time-extras 1.1.4

Duncan Coutts duncan.coutts at
Mon Dec 28 21:42:49 EST 2009

On Wed, 2009-12-23 at 00:45 -0800, Ashley Yakeley wrote:
> time-extras 1.1.4 contains Data instances for types defined in 
> time-1.1.4. They are in a separate package because they require 
> RankNTypes, which is not Haskell 2010.

Can you remind us why it's not reasonable to have the time package
(conditionally) provide Data instances?

I don't think we can say that we must restrict ourselves to the Haskell
2010 language extensions when the base package is using Rank2Types in
its public API.

We clearly need a general solution. It's silly to have every package
have a separate companion that provides Data instances. In this
instance, CPP doesn't seem like too bad a solution. The people who want
to use the Data class are clearly not using compilers that do not
support Rank2Types.


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