[Haskell-cafe] [Haskell] ANNOUNCE: tardis

Ben Millwood haskell at benmachine.co.uk
Tue Aug 7 10:26:07 CEST 2012

On Tue, Aug 7, 2012 at 7:04 AM, Dan Burton <danburton.email at gmail.com> wrote:
> As a side note, since the code base is relatively small, it can also serve
> as a simple demonstration of how to use a cabal flag
> in conjunction with CPP to selectively include swaths of code
> (see Control/Monad/Tardis.hs and tardis.cabal).

Eep, your API changes based on compile-time settings. I think this is
a bad idea, because other packages cannot depend on a flag, so
realistically other packages cannot depend on the instances existing,
so they're nearly useless.

UndecidableInstances is excessively maligned and usually fine anyway.
If it compiles, it won't go wrong.

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