C++14 关键新特性

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

int main() {
    std::cout << "=== 飞翔科技统一日志格式化 (C++14) ===\n\n";

    // C++14 泛型 lambda：auto 参数
    auto logger = [](const auto& source, const auto& msg) {
        std::cout << "[" << source << "] " << msg << "\n";
    };

    // 同一 lambda 适用于多种类型组合
    logger("DB-Master", "连接池已就绪");
    logger(std::string("Cache-01"), "命中率: 95.2%");
    logger(42, "应答码");              // int + const char*
    logger("Web-01", 200);            // const char* + int

    std::cout << "\n";

    // C++14 lambda 初始化捕获
    std::vector<std::string> logs{
        "INFO: 服务启动",
        "WARN: 内存使用 85%",
        "ERROR: 连接超时",
        "INFO: 健康检查通过",
    };

    auto prefix = std::string("飞翔-");
    auto tagged = [pfx = std::move(prefix)](const std::string& log) {
        return pfx + log;
    };

    std::cout << "--- 带前缀日志 ---\n";
    for (const auto& log : logs)
        std::cout << "  " << tagged(log) << "\n";

    // C++14 泛型 lambda + 算法
    std::vector<int> cpuLoads{45, 62, 33, 78, 91, 55, 28};

    auto threshold = 60;
    auto highLoadCount = std::count_if(cpuLoads.begin(), cpuLoads.end(),
        [threshold](auto load) { return load > threshold; });

    std::cout << "\n--- CPU 负载分析 ---\n";
    std::cout << "负载数据: ";
    for (auto l : cpuLoads) std::cout << l << "% ";
    std::cout << "\n超过 " << threshold << "% 的节点数: " << highLoadCount << "\n";
}

#include <iostream>
#include <memory>
#include <vector>
#include <string>

// C++14 decltype(auto)：完美转发返回类型
template<typename Container>
decltype(auto) getElement(Container&& c, size_t idx) {
    return std::forward<Container>(c)[idx];
    // 返回类型自动推导为左值引用或右值引用
}

// C++14 constexpr 函数更灵活
constexpr int factorial(int n) {
    int result = 1;
    for (int i = 2; i <= n; ++i)  // C++14 允许循环
        result *= i;
    return result;
}

struct ServiceConfig {
    std::string name;
    int port;
    int maxConnections;

    ServiceConfig(std::string n, int p, int mc)
        : name(std::move(n)), port(p), maxConnections(mc) {}
};

int main() {
    std::cout << "=== 飞翔科技 C++14 特性展示 ===\n\n";

    // decltype(auto) 示例
    std::vector<int> loads{10, 25, 50, 75, 90};
    getElement(loads, 2) = 55;  // 返回 int&，可修改

    std::cout << "服务器负载 (修改后): ";
    for (auto l : loads) std::cout << l << "% ";
    std::cout << "\n\n";

    // std::make_unique (C++14)
    auto config = std::make_unique<ServiceConfig>(
        "飞翔-API-Gateway", 443, 10000);

    std::cout << "服务配置:\n";
    std::cout << "  名称: " << config->name << "\n";
    std::cout << "  端口: " << config->port << "\n";
    std::cout << "  最大连接: " << config->maxConnections << "\n";

    // make_unique 批量创建
    std::vector<std::unique_ptr<ServiceConfig>> services;
    services.push_back(std::make_unique<ServiceConfig>("Web-01", 80, 5000));
    services.push_back(std::make_unique<ServiceConfig>("Web-02", 80, 5000));
    services.push_back(std::make_unique<ServiceConfig>("DB-01",  3306, 200));

    std::cout << "\n服务列表:\n";
    for (const auto& svc : services)
        std::cout << "  " << svc->name << ":" << svc->port << "\n";

    // constexpr 编译期计算
    constexpr int fact5 = factorial(5);  // 编译期计算结果 120
    std::cout << "\n编译期 5! = " << fact5 << "\n";

    // 二进制字面量和数字分隔符
    auto permissions = 0b1111'0101;  // C++14
    std::cout << "权限位掩码: 0b" << "11110101"
              << " = " << permissions << "\n";
}

auto f = [](auto x) { return x + x; };
// 类型在调用时确定，不是运行时分派
// 每个不同参数类型生成独立的闭包实例

int x = 42;
auto        a = (x);          // int（去掉引用）
decltype(auto) b = (x);      // int&（保留引用）

// ❌ std::make_unique 不支持自定义删除器
// ✅ 需要时用 new + unique_ptr 构造
auto p = std::unique_ptr<FILE, decltype(&fclose)>(
    fopen("test.txt", "r"), &fclose);