Evaluate stream object.
  Returns false if any of the error flags failbit or badbit is set. Otherwise returns true.
  This behavior is equivalent to member function fail.

Parameters.

none

 

Return Value.
  true if failbit or badbit is set.
  false otherwise.

Example.

// evaluating ios object
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ifstream is;
  is.open ("test.txt");
  if (!is)
    cerr << "Error opening 'test.txt'\n";
  return 0;
}

Basic template member declaration ( basic_ios<charT,traits> ):

bool operator ! () const;

See also.
  fail
  ios class