Mon May 4 12:51:53 CEST 2009

invertable data structure pack/unpack

Instead of using a zipper, use polymorphic accessors that will
automatically perform the correct pack/unpack when modifying a data

I.e. an operation becomes: (unpack dosomething pack)

but instead it will be left at (unpack dosomething lazy-unpack) such
that the next 'pack will cancel the lazy-unpack.

Now explain this a bit better..