Step_monad.EventAn event is a value that will at some point in time (possibly the past, possibly the future) transition from "undetermined" to "determined", with some value. One can wait_for an event in a computation.
val sexp_of_t : ('a -> Sexplib0.Sexp.t) -> 'a t -> Sexplib0.Sexp.tval value : 'a t -> 'a Base.option