attempt to summarise again
   - it seems fun to make value tracers for uniform sums. this might
   involve three classes: uniform distributions, scalars, and sums.
   - example heuristic tracers could produce a possible value with
   incorrect distribution
   - later, real tracers could consider a range of trees and calculate
   distributions backward from the distribution of sums
   simplify:
   - heuristic "+" expression value tracers for uniform distributions
   could open design options up. all they would do would be to produce a
   possible sample given known values.
   - it might not end up being productive to do, but gives an avenue of
   work. another consideration is brownian distributions.