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

[Henning Thielemann]

On Wed, 17 Feb 2016, Bart Massey wrote:

> The whole point of importing Data.List (either directly or from the 
> Prelude) is to get functions that work on lists.

Foldable and Traversable generalizations in Data.List are an interim 
solution, driven by the habit of some programmers to import complete 
Data.List without qualification and expecting that coinciding names in 
Data.List and Prelude actually refer to the same function. It would have 
been better to first warn about these cases, eliminate them and then 
implement FTP (if at all).

Summarized, generalizing list functions in Prelude was a concession to 
programmers who are too lazy to import from Data.Foldable and 
Data.Traversable and generalizing functions in Data.List was a concession 
to programmers who are too lazy to import identifiers explicitly or with 
qualification from Data.List.