StEvent - A real example: StAnalysisMaker::Make()
// See if this event survives the event filter.
// If not we stop here right away.
if (!accept(event)) return kStOK;
N.B.
bool StAnalysisMaker::accept(StEvent* event)
{
//
// This is a kind of very simple event filter.
// We select only events with a valid event vertex,
// i.e. event->primaryVertex() returns a non-zero
// pointer.
//
return event->primaryVertex();
}