C++23新特性

1. std::print

#include <print>

std::print("Hello, {}!\n", "World");
std::println("Value: {}", 42);
std::print(stderr, "Error: {}\n", message);

2. std::flat_map / std::flat_set

#include <flat_map>

std::flat_map<std::string, int> scores;
scores["Alice"] = 95;
scores["Bob"] = 87;

// 基于排序连续存储，缓存友好
// 适合小数据量、读多写少场景

3. std::expected

#include <expected>

std::expected<int, std::string> divide(int a, int b) {
    if (b == 0) return std::unexpected("division by zero");
    return a / b;
}

auto result = divide(10, 2);
if (result) {
    std::print("{}\n", result.value());  // 5
} else {
    std::print("{}\n", result.error());
}

4. std::generator

#include <generator>

std::generator<int> fibonacci() {
    int a = 0, b = 1;
    while (true) {
        co_yield a;
        auto tmp = a;
        a = b;
        b = tmp + b;
    }
}

5. 其他特性

• if consteval：编译期判断
• std::is_implicit_lifetime
• std::unreachable()
• std::string::contains()
• 多维下标运算符 operator[]