一：功能

? ? ? 對區間內元素進行排序，保證相等元素的順序（穩定排序）

二：用法

#include <iostream>struct Record {std::string label;int rank;
};int main() {std::vector<Record> data {{"q", 1}, {"f", 1}, {"c", 2}, {"a", 1}, {"d", 3}};std::ranges::stable_sort(data, {}, &Record::label);    std::ranges::stable_sort(data, {}, &Record::rank);for (auto &v : data) {std::cout << v.label << "-" << v.rank << " ";}std::cout << "\n";
}

#include <algorithm>
#include <array>
#include <iostream>
#include <string>
#include <vector>struct Employee
{int age;std::string name; // Does not participate in comparisons
};bool operator<(const Employee& lhs, const Employee& rhs)
{return lhs.age < rhs.age;
}#if __cpp_lib_constexpr_algorithms >= 202306L
consteval auto get_sorted()
{auto v = std::array{3, 1, 4, 1, 5, 9};std::stable_sort(v.begin(), v.end());return v;
}
static_assert(std::ranges::is_sorted(get_sorted()));
#endifint main()
{std::vector<Employee> v{{108, "Zaphod"}, {32, "Arthur"}, {108, "Ford"}};std::stable_sort(v.begin(), v.end());for (const Employee& e : v)std::cout << e.age << ", " << e.name << '\n';
}