(from AG01 3.40) (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)) plus(minus(x,s(0)),minus(y,s(s(z)))) -> plus(minus(y,s(s(z))),minus(x,s(0))) plus(plus(x,s(0)),plus(y,s(s(z)))) -> plus(plus(y,s(s(z))),plus(x,s(0))) )