[Haskell-cafe] Non-traversable foldables

Ross Paterson ross at soi.city.ac.uk
Fri Oct 9 11:03:09 EDT 2009

On Fri, Oct 09, 2009 at 04:45:01PM +0200, Henning Thielemann wrote:
> Recently I wondered, why Foldable is superclass of Traversable,
> since I have examples where 'traverse' makes sense, but 'fold' not.
> http://www.haskell.org/pipermail/libraries/2009-February/011361.html

That would be surprising, since fold can be defined in terms of traverse.
The link doesn't seem to contain any such examples.

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