I have re-written the GTL polygon type to use the traits/concepts generic interface, similar to what we've been discussing vis-a-vi point types. The code compiles on gcc4.2.0 at least. Please see the attached file (1KLOC) which defines the polygon_traits, polygon_concept and provides some generic behaviors for the polygon_concept. (getting and setting polygon contents through iterator range semantics, construction from a rectangle, getting number of vertices and winding direction, bounding box/area/perimeter computation, point containment predicate algorithm, point projection, and translation algorithm.) While point makes a good conversation piece, because it's interfaces are trivial, it is the polygon types that are most important to provide a good generic interface. Once the new polygon interface is settled, I can port the heavier algorithms in the library to the new interfaces. Please have a look and let me know what you think. I'm happy with the interfaces as it stands now, and plan to continue to re-write the rest of the library in this style unless feedback from the community suggests a better approach. Fernando in particular should have some insight into the polygon interfaces. Thanks, Luke