DEPRECATED: please use the 'contravariant' package, here: http://hackage.haskell.org/package/contravariant
This is a simple Haskell library providing a contravariant functor class implementation, a useful construction for type that act as "sinks" or expose the left-hand side of a function.
Can be installed with:
cabal install cofunctor
See docs here: http://hackage.haskell.org/package/cofunctor