Do input operands introduce boolean values ​​in C ++?

Question

Reading through accelerated C ++, they give an example that I don't understand. This is a while loop with the condition (cin → x). At this point, script x is declared as double. I understand that the loop is executed as long as x successfully receives the input, but returns → a boolean? I think I just need to help a little to understand what it is → and <do .... Also, while we are in the topic, what is the difference between iostream, ios and iomanip

Answer 1

in fact, they return, i.e.

std::cin >> foo

- ( ), std::cin. , iostream bool, , , false, .