On Sat, Nov 20, 2010 at 05:25:23PM -0500, roconnor@theorem.ca wrote:
Data.Functor.Backwards is a wrapper for functors that allow Foldable, Traversable, and Applicative functors to be operated backwards. It is similar to Dual for Monoids. The Applicative instance runs effects in reversed order. The Foldable instance folds from right to left, The Traversable instance traverses from right to left.
The current version of the module is here: http://hackage.haskell.org/packages/archive/applicative-extras/0.1.6/doc/htm... I think this fits with transformers, and the implementation for Traversable is cute. My only question is whether a constructor that flips Applicatives should be identified with one that reverses the traversal order of containers.