isok = false;--逻辑运算符--规定nil为false--print( ms and isok)--print(4 and 5)--print (false and 13)--print(false and 13)--a or b a为true 返回a 否则返回b--print (4 and 5)--print(4 or 5)--三目运算符print((isok and 4) or 5)