(from AG01 3.5b) (VAR x y) (RULES le(0,y) -> true le(s(x),0) -> false le(s(x),s(y)) -> le(x,y) minus(0,y) -> 0 minus(s(x),y) -> if_minus(le(s(x),y),s(x),y) if_minus(true,s(x),y) -> 0 if_minus(false,s(x),y) -> s(minus(x,y)) mod(0,y) -> 0 mod(s(x),0) -> 0 mod(s(x),s(y)) -> if_mod(le(y,x),s(x),s(y)) if_mod(true,s(x),s(y)) -> mod(minus(x,y),s(y)) if_mod(false,s(x),s(y)) -> s(x) )