[Haskell-cafe] Overlapping/Incoherent instances

wren ng thornton wren at freegeek.org
Sun Oct 12 17:08:42 EDT 2008

J. Garrett Morris wrote:
> Hello everyone,
> As part of a project to formalize the theory of overlapping instances,
> I'm looking for examples of overlapping and incoherent instances and
> their usage.  One such example would be the old version of the Monad
> Transformer Library, which used overlapping instances together with
> MonadTrans.  Any other examples or suggestions would be greatly
> appreciated!

I use overlapping instances extensively with my (unpublished) work on 
heterogeneous and extensible unification. In particular, the portion 
based on Swierstra's _Data Types a la Carte_[1]. I'm sure other folks 
have been using DTalC for interesting projects as well.

[1] http://wadler.blogspot.com/2008/02/data-types-la-carte.html

Live well,

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