Input not cleared.

Question

As the question says, for some reason my program is not flushing the input or using my variables in ways that I cannot identify at the moment. This is for a homework project that I've gone beyond what I had to do for it, now I just want the program to actually work :P

Details to make the finding easier:

The program executes flawlessly on the first run through. All throws work, only the proper values( n > 0 ) are accepted and turned into binary.

As soon as I enter my terminate input, the program goes into a loop and only asks for the termiante again like so:

When I run this program on Netbeans on my Linux Laptop, the program crashes after I input the terminate value. On Visual C++ on Windows it goes into the loop like just described.

In the code I have tried to clear every stream and initialze every variable new as the program restarts, but to no avail. I just can't see my mistake.

I believe the error to lie in either the main function:

int main( void )
{
vector<int> store;
int terminate = 1;

do
{
    int    num   =  0;
    string input = "";

    if( cin.fail() )
    {
        cin.clear();
        cin.ignore( numeric_limits<streamsize>::max(), '\n' );
    }

    cout << "Please enter a natural number." << endl;
    readLine( input, num );

    cout << "\nThank you. Number is being processed..." << endl;
    workNum( num, store );

    line;
    cout << "Go again? 0 to terminate." << endl;
    cin >> terminate // No checking yet, just want it to work!

    cin.clear();
}while( terminate );

cin.get();
return 0;
}

or in the function that reads the number:

void readLine( string &input, int &num )
{
    int buf = 1;
    stringstream ss;
    vec_sz size;

    if( ss.fail() )
 {
        ss.clear();
     ss.ignore( numeric_limits<streamsize>::max(), '\n' );
 }

    if( getline( cin, input ) )
    {
       size = input.size();
       for( int loop = 0; loop < size; ++loop )
           if( isalpha( input[loop] ) )
               throw domain_error( "Invalid Input." );

    ss << input;
    ss >> buf;

    if( buf <= 0 )
        throw domain_error( "Invalid Input." );

    num = buf;

    ss.clear();
    }
}

Answer 1

When you call cin >> terminate, it will read the value of terminate, but leave the newline following it in the input stream. Late when you call getline(cin, input), it will read up to the newline, which means it will get an empty string.

You can discard all characters up to the newline by adding this after cin >> terminate:

cin.ignore(99, '\n');

Or avoid mixing operator >> and getline.

Answer 2

Don't mix those >> and getline operators as interjay mentioned. Also, if you want to clear your code, I assume it can be rewritten the folllowing way:

int main() {
   while (true) {
      std::cout << "Please enter a natural number" << std::endl;
      int num;
      std::cin >> num;

      // Exception handling here can be done easily
      // like this
      // if (!(std::cin >> num) || num < 0)
      //    throw std::domain_error("TROLOLOLO");

      std::cout << "Thank you. Number is being processed..." << std::endl;
      //workNum(num, store) here

      std::cout << "Go again? 0 to terminate." << std::endl;

      int terminate;
      std::cin >> terminate;
      if (terminate == 0) break;
   }
}