1 | 1. E: EventStruct 2. P: (|E| List) Prop 3. x,y:|E| List. P(x)  (x swap adjacent[True] y)  P(y) 4. x: |E| List 5. y: |E| List 6. P(x) 7. x
swap adjacent[ loc(E)(x) = loc(E)(y)
& is-send(E)(x) & is-send(E)(y) is-send(E)(x) & is-send(E)(y)] y x swap adjacent[True] y |