(from AG01 3.4)
(VAR x y z)
(RULES
minus(x,0) -> x
minus(s(x),s(y)) -> minus(x,y)
quot(0,s(y)) -> 0
quot(s(x),s(y)) -> s(quot(minus(x,y),s(y)))
plus(0,y) -> y
plus(s(x),y) -> s(plus(x,y))
minus(minus(x,y),z) -> minus(x,plus(y,z))
)