This package provides first class functional references. In addition to the usual operations of getting, setting and composition, plus integration with the state monad, lens families provide some unique features:

• Polymorphic updating

• Traversals

• Cast projection functions to read-only lenses

• Cast toList functions to read-only traversals

• Cast semantic editor combinators to modify-only traversals

For optimal first-class support use the lens-family package with rank 2/rank N polymorphism. Lens.Family.Clone allows for first-class support of lenses and traversals for those who require Haskell 98.