Requesting help with simple loop problem

[jbos1190]

I'm trying to have a while loop that reads integers into a vector, as long as cin.good(). The problem im having is the vector always ends up with a size() of 1 more than I expect. Here is the code:

int integer;
vector<int> integers;
while (cin.good())
	{
		cout << "Enter an integer\n";
		cin >> integer;
		integers.push_back(integer);
	}

If my input to this loop was, for example: 1 2 3 |(to terminate the loop)
Then integers.size() = 4, when i would expect it to only be size of 3.

If i loop through the vector and output each value in the vector, I get this:
1 2 3 3. Can anyone help me understand what is going on?

[RejjyL]

I suspect you are still doing the push back even on the exiting value and using the last actual interger entered.

I used the following and it gave me size of 3 instead of 4.

{
  int integer;
  vector<int> integers;
  do
	{
		cout << "Enter an integer\n";
		cin >> integer;
		if (cin.good()) integers.push_back(integer);
	} while (cin.good());

  cout << integers.size() << endl;
}

[jbos1190]

Thanks you for the response. Adding the if statement before the push_back statement worked.

I'm still a little confused. When using a while loop, does the loop break immediately when the while loop condition becomes false, or will it continue until the end of the block, and just not loop again?

[RejjyL]

It continues to the end of the loop regardless.

Your code, with the while on top, would still work too.
In your code the push_back is executed regardless if it was an interger or not. It only exit the loop once the loop tries to start over again.

I'm also new to C++. I believe there is a BREAK statement that could have been used to exit the loop from within it.

[Chervil]

    int integer;
    vector<int> integers;
    
    cout << "Enter an integer\n";
    while (cin >> integer)
    {
        integers.push_back(integer);
        cout << "Enter an integer\n";
    }

The problem with the original code, as you no doubt realise by now, is there was no test of success or failure in betwen the user input and the push_back().

Placing the actual input statement in the while condition means that whatever is contained in the body of the loop will only be executed after a successful input.

[jbos1190]

Yes, with a little tinkering I realized that I didn't fully understand while loops. I was under the false impression that they would break immediately when the condition became false. Thanks for helping to clear up my confusion.