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

Augustsson, Lennart Lennart.Augustsson at sc.com
Tue Feb 23 09:23:18 UTC 2016

The easiest way to import Data.Foldable unqualified is to rename the functions in it.
And, IMO, there is the original problem: Data.Foldable is full of Prelude name clashes.

-----Original Message-----
From: Libraries [mailto:libraries-bounces at haskell.org] On Behalf Of Henning Thielemann
Sent: 23 February 2016 08:25
To: David Feuer
Cc: Haskell Libraries; Ryan Scott
Subject: Re: Haskell Foldable Wats (Was: Add conspicuously missing Functor instances for tuples)

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.
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