Using Custom Comparison in replace()

std::ranges::replace() relies on the == operator to determine if an element should be replaced.

To use a custom comparison, you'll need to write a custom predicate and use std::ranges::replace_if(), which accepts a predicate function. Here's an example:

1#include <algorithm>
2#include <iostream>
3#include <vector>
4#include <string>
5
6struct Player {
7  std::string Name;
8  int Score;
9};
10
11bool custom_compare(const Player &p) {
12  return p.Name == "Anna";
13}
14
15int main() {
16  std::vector<Player> Players = {
17    {"Anna", 10},
18    {"Bob", 20},
19    {"Anna", 30},
20    {"Carol", 40}
21  };
22
23  std::ranges::replace_if(
24    Players, custom_compare, Player{"Unknown", 0}
25  );
26
27  for (const auto &p : Players) {
28    std::cout << p.Name << ": " << p.Score << "\n";
29  }
30}

1Unknown: 0
2Bob: 20
3Unknown: 0
4Carol: 40

In this example, we replace all Player objects where the Name is "Anna" with a default Player object using std::ranges::replace_if(). The custom_compare() function determines which elements to replace.

If your comparison logic is more complex, you can encapsulate it in a lambda function. This approach provides flexibility and maintains readability.

Using custom comparisons allows you to tailor the behavior of replace_if() to fit your specific needs, making it a powerful tool for more advanced scenarios.