Using <=> for Sorting

Yes, the <=> (spaceship) operator can be used for sorting algorithms in C++20. The spaceship operator allows you to define a single comparison function that can be used by sorting algorithms to determine the order of elements.

How It Works

When you define the <=> operator for your custom type, you provide a way to compare two instances of that type. Sorting algorithms, like std::sort(), can then use this comparison logic to sort a collection of your custom objects.

Example

Let’s consider a Player class where we want to sort players by their scores using the spaceship operator:

1#include <iostream>
2#include <vector>
3#include <algorithm>
4#include <compare>
5#include <string>
6
7class Player {
8public:
9  Player(std::string name, int score)
10    : Name{name}, Score{score} {}
11
12  std::strong_ordering operator<=>(
13    const Player& Other) const {
14    return Score <=> Other.Score;
15  }
16
17  std::string Name;
18  int Score;
19};
20
21int main() {
22  std::vector<Player> players{
23    {"Alice", 20}, {"Bob", 15}, {"Charlie", 25}
24  };
25
26  std::sort(players.begin(), players.end());
27
28  for (const auto& player : players) {
29    std::cout << player.Name
30      << " - " << player.Score << "\n";
31  }
32}

1Bob - 15
2Alice - 20
3Charlie - 25

Explanation

In this example, we define the <=> operator for the Player class to compare players by their scores. When we call std::sort(), it uses this comparison logic to sort the players in ascending order of their scores.

Benefits

• Consistency: Defining the <=> operator ensures that all comparisons are consistent across your program.
• Simplicity: You write less code, as you only need to define one comparison operator.
• Flexibility: The same comparison logic can be reused in different contexts, such as sorting, searching, and other algorithms.

Conclusion

Using the <=> operator with sorting algorithms in C++20 simplifies your code and ensures consistency in how your custom types are compared. It leverages the power of the spaceship operator to provide a clear and concise way to define sorting logic.