[pstricks] Complex computations with Latex lengths

[Jay Bloodworth]

This is not a purely pstricks issue, but I this is the best forum I know
to ask and I think it likely that other pstricks users might sometime
need to do something like this.

I used the FP fixed-point arithmetic package a lot to do calculations
within a document of where to put things.  This works great if all of
the values used in the calculations are user supplied values.  But I
have a situation where I need to measure the dimensions of a box (using
\settowidth) and then use that value in an FP computation.  Can anyone
tell me how to get the value of a latex length register into an FP
variable?

I could probably also do what I need to if someone can suggest a way to
use the max (or min) of two latex lengths.

Thanks,
Jay