f(i) halts, the invertHalt will hang (i.e., wouldn't halt), and if f(i) hangs, the invertHalt will halt.unknown(unknown) halt? What should doesItHalt({unknown, unknown}) return?true. Then, it means that doesItHalt({unknown, unknown}) returned false because invertHalt(b) would've hung otherwise. Therefore, this contradicts our supposition that doesItHalt({unknown, unknown}) returns true.false. Then, it means that doesItHalt({unknown, unknown}) would return true because invertHalt wouldn't hang otherwise. Therefore, this contradicts our supposition that doesItHalt({unknown, unknown}) returns false.unknown cannot hang nor halt; therefore, no such doesItHalt can exist.No comments yet. Be the first to share your thoughts.