Does "std::cin >> value" return a Zero if input is EOF?

Question

Consider the following code

int main(){ 
int sum = 0, value = 0;
while (std::cin >> value)
sum += value; 
std::cout << "sum is: " << sum << std::endl;
return 0;
}

What is the return value of >> operator, against which while loop is evaluated ? The program terminates on EOF input (Ctrl+Z for windows). Does that mean 0 is stored to cin in case of an EOF ? Does it have anything to do with ASCII value of EOF ?

`stringstream` or `cin` does not matter, answer holds for all `std::istream`s. — Baum mit Augen, Oct 20 '15 at 12:54
May be a stupid question. How could the return value terminate the while loop ? Is the return value zero if input is EOF ? — Paul259, Oct 20 '15 at 13:08

score 1 · Answer 1 · answered Oct 20 '15 at 12:52

1

It returns a reference to basic_ifstream:

basic_istream& operator>>

In the context of if, it converts to true unless std::ios_base::failbit or std::ios_base::badbit is set in its state.

answered Oct 20 '15 at 12:52

SingerOfTheFall

29,228
8
68
105

How could the return value terminate the while loop ? Is the return value zero if input is EOF ? – Paul259 Oct 20 '15 at 13:10
@Paul259, if the state of `cin` will be set to `failbit` of `badbit` (for example, if `cin >> some_integer_variable` reads something that is not a number), it will convert to `false` and the loop will end. – SingerOfTheFall Oct 20 '15 at 13:23

score 0 · Answer 2 · answered Oct 20 '15 at 12:52

0

According to this reference, the return type is istream&.

answered Oct 20 '15 at 12:52

Codor

17,447
9
29
56

score 0 · Answer 3 · answered Oct 20 '15 at 12:54

0

It returns a non-const reference to std::cin.

answered Oct 20 '15 at 12:54

Emil Laine

41,598
9
101
157

Does "std::cin >> value" return a Zero if input is EOF?

3 Answers3