[Haskell-cafe] checking types with type families

Eduard Sergeev Eduard.Sergeev at gmail.com
Thu Jul 1 15:58:16 EDT 2010

Simon Peyton-Jones wrote:
> I'm interested in situations where you think fundeps work and type
> families don't.  Reason: no one knows how to make fundeps work cleanly
> with local type constraints (such as GADTs).  
> If you think you have such as case, do send me a test case.

As an example, is it possible to implement something like:
http://okmij.org/ftp/Haskell/deepest-functor.lhs with TF only? I believe the
following wiki-page http://www.haskell.org/haskellwiki/GHC/AdvancedOverlap 
also points out that "However, there's a problem: overlap is not allowed at
all for type families!!" (c) or is it just a question of implementing closed
type families?

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