Constraints on definition of `length` should be strengthened

Sat Apr 8 02:27:13 UTC 2017

On 08/04/17 11:36, Anthony Clayden wrote:
> Contrast that `instance Foldable ((,) b)`
> appeared in GHC 7.8 ~2014,
> along with `instance Foldable Either`.

FWIW, both of these appeared in Functional Java in 2003 and Scalaz, in 2005.

I haven't properly followed this thread, so I am unsure what questions
were raised. Sorry if it was relevant to our other discussions and I
have ignored it.

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