Integration of Conditional Models

From ASCEND

At present we can detect boundaries during integration of conditional models with IDA, but can't yet force IDA to stop and re-analyse the integration problem. To do this will require LRSlv to be connected to IDA, and there will need to be some reviewing of the architecture of the IDA integrator as it stands.

So, currently we support this bit:

CONDITIONAL
    before: t < t1;
    after:  t > t2;
END CONDITIONAL;

But we don't yet support

WHEN(SATISFIED(before)):
    CASE TRUE:
        USE myfirsteq;
    OTHERWISE:
        USE myothereq;
END WHEN;

In general, derivative and differential variables will be able to be turned on and off in the conditional model, so restarting a model will require that the integrator_ida_analyse routine be re-run. This has the unfortunate side effect of causing the list of observation variables to be rebuild: there will need to be a provision for observed variables to be 'blanked out' when they are not active in the model.