(COMMENT variant of AG01 4.30)
(VAR x y z)
(RULES
minus(x,x) -> 0
minus(0,x) -> 0
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,y) -> if_quot(minus(x,y),y,le(y,0),le(y,x))
if_quot(x,y,true,z) -> divByZeroError
if_quot(x,y,false,true) -> s(quot(x,y))
if_quot(x,y,false,false) -> 0
)