Haskell Foldable Wats (Was: Add conspicuously missing Functor instances for tuples)

[Henning Thielemann]

On Wed, 17 Feb 2016, David Feuer wrote:

> The big problem was the goal of allowing Data.Foldable and 
> Data.Traversable to be imported unqualified. This was fine for 
> Data.Traversable, but not for Data.Foldable. There are relatively few 
> cases where the Traversable generalization is confusing or otherwise 
> problematic, but Foldable is just too "wild".
> 
> Once that dubious goal was set, consistency and efficiency demanded some of the other changes.

If step A requires step B, step C and step D that become worse and worse, 
then for me this proves that already step A was wrong. Importing 
Data.Foldable and Data.Traversable without any notice is a slight 
simplification in some cases, but the consequences are a big pain.