How to know when a values changes or solve is done?

[RedHatter]

I've been messing with the library and it looks like it could be very useful but I'm slightly confused on how to use it.

Once I set all the constraints, how do I get notified when a value has changed? Or at least when the solver is done since all the values would be fully updated?

Do I simply have to poll them for changes? I would expect some type of listener or event interface.