效绵鼎 Non-Re Languages suppose the set of all languages is countable list characteristic vectors of all languages according to the bijection f: n f(n) Setx=1101. 10101010. where ith digit ith digit of f(i) x cannot be in the list! 21010011.. therefore,the language with 31110001.. characteristic vector x is not in the list 4 0100011..Non-RE Languages  suppose the set of all languages is countable  list characteristic vectors of all languages according to the bijection f: n f(n) _ 1 0101010… 2 1010011… 3 1110001… 4 0100011… … set x = 1101… where ith digit ≠ ith digit of f(i) x cannot be in the list! therefore, the language with characteristic vector x is not in the list