* On //n//th thought, suppose I remove the sortedness from the semantics of events. Just say that the semantics is a list of time/value pairs. For semantics, define @E = [] :. (,) T@ and use the resulting instances. So what is the meaning of @a `stepper` e@ sampled at @t@? Sort @e@ (stably), and use the value of the latest last future whose time is earlier than @t@.