A couple of errors near the end for "How Many Hosts Were “Up” Last Month But Now It’s “Down”" and vice versa. The error is that using xor on the same item twic

A couple of errors near the end for "How Many Hosts Were “Up” Last Month But Now It’s “Down”" and vice versa. The error is that using xor on the same item twice is a no-op... (A xor B) xor A == B. The correct equations would be, !this_month and last_month = "up" last month, down now. and this_month and !last_month = "down" last month, up now.