C++: What is std::format (C++20)?

1#include <format>
2
3// Basic formatting
4std::string s = std::format("Hello, {}! You are {}.", "Alice", 25);
5
6// Positional arguments
7std::cout << std::format("{1} {0}", "world", "hello");
8
9// Number formatting
10std::cout << std::format("{:.2f}", 3.14159);   // 3.14
11std::cout << std::format("{:#x}", 255);       // 0xff
12std::cout << std::format("{:08d}", 42);       // 00000042
13
14// Alignment
15std::cout << std::format("{:>10}", "right");   // "     right"
16std::cout << std::format("{:<10}", "left");    // "left      "
17std::cout << std::format("{:^10}", "center");  // "  center  "
18
19// Custom type
20struct Point { int x, y; };
21template<>
22struct std::formatter<Point> : std::formatter<std::string> {
23    auto format(const Point& p, auto& ctx) const {
24        return std::format_to(ctx.out(), "({}, {})", p.x, p.y);
25    }
26};
27std::cout << std::format("{}", Point{1, 2});  // (1, 2)