Feed feed1(1000.); Feed feed2(2000.); Stream stream1(feed1); Stream stream2(feed2); Unit mixer; mixer < stream1; mixer < stream2;A later call to change the mass of the feed causes a cascade of updates to all the other plant items which depend on feed1. This can be generalised to any change of parameter.
feed1.SetMass(2000.);See also ObjectFunctionalImplementation