(VAR X XS N)

(RULES 
from(X) -> cons(X,from(s(X)))
head(cons(X,XS)) -> X
2nd(cons(X,XS)) -> head(XS)
take(0,XS) -> nil
take(s(N),cons(X,XS)) -> cons(X,take(N,XS))
sel(0,cons(X,XS)) -> X
sel(s(N),cons(X,XS)) -> sel(N,XS)
)