C++11核心特性全解析

好的，以下是C++11部分核心新特性的详细说明：

1.auto类型推导

作用：编译器自动推导变量类型，减少冗长类型声明。
适用场景：迭代器、模板代码、复杂类型（如函数指针）。
示例：

auto i = 42; // int auto str = "hello"; // const char* std::vector<int> vec; auto it = vec.begin(); // std::vector<int>::iterator

2. 范围for循环

作用：简化容器遍历语法。
语法：for (auto& element : container)
示例：

std::vector<int> nums = {1, 2, 3}; for (auto& num : nums) { num *= 2; // 修改元素 }

3. 智能指针

作用：自动管理内存，避免内存泄漏。

• std::unique_ptr：独占所有权，不可复制。
• std::shared_ptr：共享所有权，引用计数。
• std::weak_ptr：解决循环引用问题。
  示例：

std::unique_ptr<int> ptr(new int(10)); // 自动释放内存 auto shared = std::make_shared<std::string>("C++11"); // 引用计数

4. Lambda 表达式

作用：定义匿名函数对象，简化回调逻辑。
语法：[capture](params) -> ret { body }
示例：

std::vector<int> v = {3, 1, 4}; std::sort(v.begin(), v.end(), [](int a, int b) { return a > b; // 降序排序 });

5. 右值引用与移动语义

作用：避免深拷贝，提升性能（如转移资源所有权）。
关键语法：T&&和std::move()
示例：

std::string s1 = "hello"; std::string s2 = std::move(s1); // s1的资源转移到s2，s1变为空

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6. 统一初始化语法

作用：用{}统一变量、数组、容器的初始化方式。
示例：

int x{5}; std::vector<int> arr{1, 2, 3}; std::map<int, std::string> m = {{1, "one"}, {2, "two"}};

7.nullptr关键字

作用：明确表示空指针，替代NULL（避免歧义）。
示例：

int* p = nullptr; // 类型安全

8. 类型别名 (using)

作用：替代typedef，支持模板别名。
示例：

using Vec = std::vector<int>; // 等价于 typedef template<typename T> using Map = std::map<int, T>; // 模板别名

9. 强类型枚举 (enum class)

作用：避免传统枚举的名称冲突和隐式转换。
语法：enum class Name { value1, value2 }
示例：

enum class Color { Red, Green }; Color c = Color::Red; // 必须显式作用域

10. 标准库增强

• std::array：定长数组，替代C风格数组。
• std::tuple：异构元组。
• 线程库：std::thread,std::mutex等。

以上是C++11的核心特性，后续可继续探讨并发库、正则表达式等高级功能。