An example showing how to make a simple ref counted object. 
 
A Score on the distance between a pair of particles. 
 
A restraint on a list of particle pairs. 
 
A singleton modifier which wraps an attribute into a given range. 
 
Add a name to a particle. 
 
A restraint on a list of particle pairs. 
 
A Score on the distance between a pair of particles. 
 
A restraint to maintain the diameter of a set of points. 
 
Show how to manage a template class with Python.