Yea, if you needed more dimensions you could continue just increasing the numbers.
It'd be nice to work out the CSG notation for all the regular polygons... the octagon was hard enough.
One thing I haven't clarified is that anything constructed is by default 2 units in the relavent dimension: from -1 to 1. This is why you have to use an argument of n>1 to get a torus (the radius of the hole is n-1).
Also, with single tapers, the +1 cross-section of the object is the original shape, and the -1 cross-section of the object is a point. With double tapers, the 0 cross-section is the original shape, and the +/-1 cross-section is a point. So double tapers are twice as "steep" as the single ones.