//
//  This loop is intended for an array with n elements.  It tries to read
//  n values into the array.  If it fails early, it breaks from the loop.
//
//  double data[n];
//
    for ( int = 0; i < n; i++ ) {
        cin >> data[i];
        if ( cin.fail() ) break;
    }
//
//  i is the number of elements of data successfully read
//