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