ios operator !() function in C++ with Examples

The operator!() method of ios class in C++ is used to any error flag of this stream is set. This includes the failbit or the badbit.

Syntax:

bool operator!()  const;

Parameters: This method does not accept any parameter.

Return Value: This method returns true if any error bit is set of this stream, else false.

Example 1:

// C++ code to demonstrate
// the working of operator!() function

#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Stream
    stringstream ss;

    // Using operator!() function
    if (!ss) {
        cout << "Error bit is set.\n";
    }
    else {
        cout << "No error bit is set.\n";
    }

    return 0;
}

Output:

No error bit is set.

Example 2:

// C++ code to demonstrate
// the working of operator!() function

#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Stream
    stringstream ss;
    ss.clear(ss.failbit);

    // Using operator!() function
    if (!ss) {
        cout << "Error bit is set.\n";
    }
    else {
        cout << "No error bit is set.\n";
    }

    return 0;
}

Output:

Error bit is set.

Reference: hhttp://www.cplusplus.com/reference/ios/ios/operator!/