recursively change values in list of lists

[Carson Farmer]

Dear list,

I'm sure this is a relatively trivial problem, but I have been unable
to find any good examples/explanations on how to do this, so here
goes:

I have multi-polygon object, which is simply a list of polygons, where
each polygon is a list of lines, where each line is a list of points.
What I would like to do, is change the x and y values of each point,
all the while keeping the structure of the lists intact.

So in the end, the only thing that should be changed is the values,
not the lists themselves... clear as mud?

Any hints, and/or suggestions are greatly appreciated,


Carson