(from AG01 4.30a)
(VAR x y)
(RULES
minus(x,0) -> x
minus(s(x),s(y)) -> minus(x,y)
le(0,y) -> true
le(s(x),0) -> false
le(s(x),s(y)) -> le(x,y)
quot(0,s(y)) -> 0
quot(s(x),s(y)) -> s(quot(minus(s(x),s(y)),s(y)))
)