C++ Sentinels

[qingquan-li]

Concept: A sentinel is a special value that marks the end of a list of values.

A sentinel is a special value that cannot be mistaken as a member of the list and signals that there are no more values to be entered. When the user enters the sentinel, the loop terminates.

#include <iostream>

using namespace std;

int main() {
    const int SENTINEL_VAL = -1;
    float quiz_grade;
    float total_grade = 0;
    int num_quizzes = 0;

    cout << "Type a quiz grade (type -1 if you don't have any more quiz grades): ";
    cin >> quiz_grade;
    while (quiz_grade != SENTINEL_VAL) {
        num_quizzes++;
        total_grade += quiz_grade;
        // Update quiz_grade:
        cout << "Type a quiz grade (type -1 if you don't have any more quiz grades): ";
        cin >> quiz_grade;
        // total_grade += quiz_grade; // SENTINEL_VAL will be included in the running total_grade
    }
    cout << "Total grade: " << total_grade << endl;
    cout << "Average grade: " << total_grade / num_quizzes << endl;
    return 0;
}

The value -1 was chosen for the sentinel in the program because it is not possible for a team to score negative points.