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while loop. While cin >> !=

kmce (180)
Hi, I am doing a drill from the book I am learning from, and i need to run a while loop until '|' is entered. I have been trying such things as while cin >> != '|' and cin != '|' but none of them work, so I assume it can not be done this way. Could someone possibly let me know how this is actually meant to be done. How am I meant to keep taking input until '|' is entered. I have included different versions of the code I have been trying below.

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int main()
{
	int one, two;
	while (cin >> )
	{
		cout << "Enter 2 values \n";
		cin >> one >> two;
		cout << one << two;
	}

	system("pause");
	return 0;
}


int main()
{
	int one = 0 , two = 0;
	char quit = '|';
	while (one != quit)
	{
		cout << "Enter 2 values \n";
		cin >> one >> two;
		cout << one << two;
	}

	system("pause");
	return 0;
dutch (2548)
Your spec is unclear. Perhaps this:

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#include <iostream>
using namespace std;

int main() {
    char ch;
    cin >> ch;
    while (ch != '|') {
        cout << "You entered: " << ch << '\n';
        cin >> ch;
    }
}
kmce (180)
Sorry I should have stated what I was actually meant to be doing. The drill is

Write a program that consists of a while loop that reads in two ints and then prints them. Exit the program when a terminating '|' is entered
dutch (2548)
This conforms to your spec (since you don't specify what to do with errant data I choose to quit, therefore I can simply process the '|' as errant data).

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#include <iostream>
using namespace std;

int main() {
    int a, b;
    while (cin >> a >> b)
        cout << a + b << '\n';
}

Alternatively:

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#include <iostream>
using namespace std;

int main() {
    for (char ch; cin >> ch && ch != '|'; ) {
        cin.putback(ch);
        int a, b;
        if (!(cin >> a >> b)) {
            cerr << "WTF?\n";
            cin.clear();
            cin.ignore(9999, '\n');
        }
        else
            std::cout << a + b << '\n';
    }
}
Last edited on
Niccolo (720)
If that's Stroustrup's book, at some point he explains that any string input to an integer type will cause cin to return false, so cin >> one should stop the loop when the user enters "|" instead of an integer.
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