(VAR X XS N)
(RULES 
from(X) -> cons(X,n__from(s(X)))
after(0,XS) -> XS
after(s(N),cons(X,XS)) -> after(N,activate(XS))
from(X) -> n__from(X)
activate(n__from(X)) -> from(X)
activate(X) -> X
)