In C++, sorting elements in a collection is a common task. By default, the sorting algorithm uses the less-than (<) operator to compare elements. However, in some cases, we may want to define our own custom sorting order. C++ provides a convenient way to achieve this by using sorting literals.

Defining a Custom Sorting Literal

To define a custom sorting literal, we need to define a comparison function that takes two arguments and returns a bool value. This function should define the desired sorting order for our elements.

Let’s assume we have a Person class with name and age attributes. We want to sort a collection of Person objects first by age and then by name.

class Person {
public:
    std::string name;
    int age;
};

bool comparePersons(const Person& a, const Person& b) {
    if (a.age == b.age) {
        return a.name < b.name;
    }
    return a.age < b.age;
}

The comparePersons function compares two Person objects based on their age and name attributes. It returns true if a should be placed before b in the sorting order.

Using Custom Sorting Literals

Once we have the comparison function defined, we can use it with various C++ algorithms that support custom sorting, such as std::sort or std::stable_sort.

std::vector<Person> people = {{"John", 25}, {"Alice", 30}, {"Bob", 20}};

std::sort(people.begin(), people.end(), comparePersons);

// Output: Bob, John, Alice
for (const auto& person : people) {
    std::cout << person.name << ", ";
}

In the example above, we create a vector of Person objects and sort it using the comparePersons function as the sorting literal. The resulting order of elements will be “Bob, John, Alice” because Bob is the youngest, followed by John, and then Alice.

Conclusion

Custom sorting literals in C++ allow us to define our own sorting order based on specific criteria. By providing a custom comparison function, we can effectively sort elements in a collection according to our desired order. This flexibility enhances the capabilities of the C++ standard library sorting algorithms and enables us to work with various types of data in a customized manner.

#References

• C++ Reference: std::sort
• C++ Reference: std::stable_sort