1 | 4. is-send(E)(x[(i+1)]) 5. is-send(E)(x[i]) loc(E)(x[i]) = loc(E)(x[(i+1)]) 6. ||swap(x;i;i+1)|| = ||x||  7. i,j,k: ||x||.
i < j 
is-send(E)(x[i]) 
is-send(E)(x[j]) 
tag(E)(x[i]) = tag(E)(x[j]) 
(x[j] =msg=(E) x[k]) & is-send(E)(x[k]) 
( k': ||x||. k' < k & (x[i] =msg=(E) x[k']) & is-send(E)(x[k']) & loc(E)(x[k']) = loc(E)(x[k])) 8. i@0: ||swap(x;i;i+1)|| 9. j: ||swap(x;i;i+1)|| 10. k: ||swap(x;i;i+1)|| i@0 < j 
is-send(E)(x[((i, i+1)(i@0))]) 
is-send(E)(x[((i, i+1)(j))]) 
tag(E)(x[((i, i+1)(i@0))]) = tag(E)(x[((i, i+1)(j))]) 
(x[((i, i+1)(j))] =msg=(E) x[((i, i+1)(k))]) & is-send(E)(x[((i, i+1)(k))]) 
( k': ||swap(x;i;i+1)||.
k' < k
& (x[((i, i+1)(i@0))] =msg=(E) x[((i, i+1)(k'))]) & is-send(E)(x[((i, i+1)(k'))])
& loc(E)(x[((i, i+1)(k'))]) = loc(E)(x[((i, i+1)(k))])) |