This might have been mentioned in the book but I don't remember it as a standalone suggestion...
I believe there is a simple reusable pattern to combine
SwitchC to update a Cell via a Stream. For example, given the following (typescript syntax where T is generic):
sBar:Stream<(data:T) => T>
We can get a
cUpdatedFoo:Cell<T> which is derived as the stream + old cell via:
const cUpdatedFoo =
sBar.accum(cFoo, (fn, _c) => _c.map(fn))