This package comes "Batteries Included" with many useful lenses for the
types commonly used from the Haskell Platform, and with tools for
automatically generating lenses and isomorphisms for user-supplied data
types.  The combinators in Control.Lens provide a highly generic toolbox
for composing families of getters, folds, isomorphisms, traversals,
setters and lenses and their indexed variants.

WWW: http://github.com/ekmett/lens/