diff --git a/auto/index.html b/auto/index.html
index 68f3624..2357241 100644
--- a/auto/index.html
+++ b/auto/index.html
@@ -256,7 +256,7 @@
- auto 推导为引用
+ auto 推导为引用
@@ -279,31 +279,31 @@ 返回类型 auto
闹了半天，还是要写返回类型，就只是挪到后面去好看一点……
当初引入后置返回类型实际的用途是 auto f(int x) -> decltype(x * x) { return x * x; } 这种情况，但很容易被接下来 C++14 引入的真正 auto 返回类型推导平替了。
-C++14 引入了函数返回类型推导，auto 才算真正意义上能用做函数返回类型，它会自动根据函数中的 return 表达式推导出函数的返回类型。
+但是 C++14 引入了函数返回类型推导，auto 才算真正意义上能用做函数返回类型，它会自动根据函数中的 return 表达式推导出函数的返回类型。
auto f(int x) {
- return x * x; // 表达式 `x * x` 的类型为 int，所以 auto 类型推导为 int
+ return x * x; // 表达式 `x * x` 的类型为 int，所以 auto 类型推导为 int
}
// 等价于：
int f() {
- return x * x;
+ return x * x;
}
如果函数中没有 return 语句，那么 auto 会被自动推导为 void，非常方便。
auto f() {
- std::println("hello");
+ std::println("hello");
}
// 等价于：
void f() {
- std::println("hello");
+ std::println("hello");
}
值得注意的是，返回类型用 auto 来推导的函数，如果有多条 return 语句，那么他们必须都返回相同的类型，否则报错。
auto f(int x) {
- if (x > 0) {
- return 1; // int
- } else {
- return 3.14; // double
- }
+ if (x > 0) {
+ return 1; // int
+ } else {
+ return 3.14; // double
+ }
} // 错误：有歧义，无法确定 auto 应该推导为 int 还是 double
auto 还有一个缺点是，无法用于“分离声明和定义”的情况。因为推导 auto 类型需要知道函数体，才能看到里面的 return 表达式是什么类型。所以当 auto 返回类型被用于函数的非定义声明时，会直接报错。
@@ -316,7 +316,41 @@ 返回类型 auto
因此，auto 通常只适用于头文件中“就地定义”的 inline 函数，不适合需要“分离 .cpp 文件”的函数。
参数类型 auto
C++20 引入了模板参数推导，可以让我们在函数参数中也使用 auto。
-TODO: 介绍
+在函数参数中也使用 auto 实际上等价于将该参数声明为模板参数，仅仅是一种更便捷的写法。
+void func(auto x) {
+ std::cout << x;
+}
+// 等价于:
+template <typename T>
+void func(T x) {
+ std::cout << x;
+}
+
+func(1); // 自动推导为调用 func<int>(1)
+func(3.14); // 自动推导为调用 func<double>(3.14)
+
+如果参数类型的 auto 带有如 auto & 这样的修饰，则实际上等价于相应模板函数的 T &。
+// 自动推导为常引用
+void func(auto const &x) {
+ std::cout << x;
+}
+// 等价于:
+template <typename T>
+void func(T const &x) {
+ std::cout << x;
+}
+
+// 自动推导为万能引用
+void func(auto &&x) {
+ std::cout << x;
+}
+// 等价于:
+template <typename T>
+void func(T &&x) {
+ std::cout << x;
+}
+
+auto 在多态中的妙用
传统的，基于类型重载的：
int square(int x) {
return x * x;
@@ -343,7 +377,7 @@ 参数类型 auto
// 即使未来产生了 float 版的需求，也不用添加任何代码，因为是 square 是很方便的模板函数
}
-auto 推导为引用
+auto 推导为引用
TODO: 继续介绍 auto, auto const, auto &, auto const &, auto &&, decltype(auto), auto *, auto const *
diff --git a/index.html b/index.html
index b66af8c..e616745 100644
--- a/index.html
+++ b/index.html
@@ -292,7 +292,7 @@ 前言
本书还在持续更新中……要追番的话，可以在 GitHub 点一下右上角的 “Watch” 按钮，每当小彭老师提交新 commit，GitHub 会向你发送一封电子邮件，提醒你小彭老师更新了。
-更新时间：2024年11月01日 12:54:16 (UTC+08:00)
+更新时间：2024年11月09日 11:37:54 (UTC+08:00)
在 GitHub Pages 浏览本书 | 在小彭老师自己维护的镜像上浏览本书
格式约定
diff --git a/print_page/index.html b/print_page/index.html
index 220dfe1..ca2b960 100644
--- a/print_page/index.html
+++ b/print_page/index.html
@@ -421,7 +421,7 @@ 前言
本书还在持续更新中……要追番的话，可以在 GitHub 点一下右上角的 “Watch” 按钮，每当小彭老师提交新 commit，GitHub 会向你发送一封电子邮件，提醒你小彭老师更新了。
-更新时间：2024年11月01日 12:54:16 (UTC+08:00)
+更新时间：2024年11月09日 11:37:54 (UTC+08:00)
在 GitHub Pages 浏览本书 | 在小彭老师自己维护的镜像上浏览本书
格式约定
@@ -941,31 +941,31 @@ 返回类型 auto
闹了半天，还是要写返回类型，就只是挪到后面去好看一点……
当初引入后置返回类型实际的用途是 auto f(int x) -> decltype(x * x) { return x * x; } 这种情况，但很容易被接下来 C++14 引入的真正 auto 返回类型推导平替了。
-C++14 引入了函数返回类型推导，auto 才算真正意义上能用做函数返回类型，它会自动根据函数中的 return 表达式推导出函数的返回类型。
+但是 C++14 引入了函数返回类型推导，auto 才算真正意义上能用做函数返回类型，它会自动根据函数中的 return 表达式推导出函数的返回类型。
auto f(int x) {
- return x * x; // 表达式 `x * x` 的类型为 int，所以 auto 类型推导为 int
+ return x * x; // 表达式 `x * x` 的类型为 int，所以 auto 类型推导为 int
}
// 等价于：
int f() {
- return x * x;
+ return x * x;
}
如果函数中没有 return 语句，那么 auto 会被自动推导为 void，非常方便。
auto f() {
- std::println("hello");
+ std::println("hello");
}
// 等价于：
void f() {
- std::println("hello");
+ std::println("hello");
}
值得注意的是，返回类型用 auto 来推导的函数，如果有多条 return 语句，那么他们必须都返回相同的类型，否则报错。
auto f(int x) {
- if (x > 0) {
- return 1; // int
- } else {
- return 3.14; // double
- }
+ if (x > 0) {
+ return 1; // int
+ } else {
+ return 3.14; // double
+ }
} // 错误：有歧义，无法确定 auto 应该推导为 int 还是 double
auto 还有一个缺点是，无法用于“分离声明和定义”的情况。因为推导 auto 类型需要知道函数体，才能看到里面的 return 表达式是什么类型。所以当 auto 返回类型被用于函数的非定义声明时，会直接报错。
@@ -978,7 +978,41 @@ 返回类型 auto
因此，auto 通常只适用于头文件中“就地定义”的 inline 函数，不适合需要“分离 .cpp 文件”的函数。
参数类型 auto
C++20 引入了模板参数推导，可以让我们在函数参数中也使用 auto。
-TODO: 介绍
+在函数参数中也使用 auto 实际上等价于将该参数声明为模板参数，仅仅是一种更便捷的写法。
+void func(auto x) {
+ std::cout << x;
+}
+// 等价于:
+template <typename T>
+void func(T x) {
+ std::cout << x;
+}
+
+func(1); // 自动推导为调用 func<int>(1)
+func(3.14); // 自动推导为调用 func<double>(3.14)
+
+如果参数类型的 auto 带有如 auto & 这样的修饰，则实际上等价于相应模板函数的 T &。
+// 自动推导为常引用
+void func(auto const &x) {
+ std::cout << x;
+}
+// 等价于:
+template <typename T>
+void func(T const &x) {
+ std::cout << x;
+}
+
+// 自动推导为万能引用
+void func(auto &&x) {
+ std::cout << x;
+}
+// 等价于:
+template <typename T>
+void func(T &&x) {
+ std::cout << x;
+}
+
+auto 在多态中的妙用
传统的，基于类型重载的：
int square(int x) {
return x * x;
@@ -1005,7 +1039,7 @@ 参数类型 auto
// 即使未来产生了 float 版的需求，也不用添加任何代码，因为是 square 是很方便的模板函数
}
-auto 推导为引用
+auto 推导为引用
TODO: 继续介绍 auto, auto const, auto &, auto const &, auto &&, decltype(auto), auto *, auto const *
重新认识声明与定义（未完工）
diff --git a/search/search_index.json b/search/search_index.json
index a87424c..c656134 100644
--- a/search/search_index.json
+++ b/search/search_index.json
@@ -1 +1 @@
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\u7528\u8fd9\u79cd\u989c\u8272\u5b57\u4f53\u4e66\u5199\u7684\u5185\u5bb9\u662f\u7b11\u8bdd\u6216\u8da3\u5473\u5bd3\u8a00\u6545\u4e8b \u7528\u8fd9\u79cd\u989c\u8272\u4e66\u5199\u7684\u662f\u8865\u5145\u8bf4\u660e\u7684\u8bfe\u5916\u9605\u8bfb\uff0c\u770b\u4e0d\u61c2\u4e5f\u6ca1\u5173\u7cfb \u7528\u8fd9\u79cd\u989c\u8272\u5b57\u4f53\u4e66\u5199\u7684\u662f\u521d\u5b66\u8005\u53ef\u6682\u65f6\u4e0d\u7528\u7406\u89e3\u7684\u7ec6\u8282 \u672f\u8bed\u540d\u79f0: \u8fd9\u91cc\u662f\u672f\u8bed\u7684\u5b9a\u4e49\u3002 \u89c2\u524d\u987b\u77e5 \u4e0e\u5927\u591a\u6570\u73b0\u6709\u6559\u6750\u4e0d\u540c\u7684\u662f\uff0c\u672c\u8bfe\u7a0b\u5c06\u4f1a\u91c7\u7528\u201c\u5012\u53d9\u201d\u7684\u5f62\u5f0f\uff0c\u4ece\u6700\u65b0\u7684 C++23 \u8bb2\u8d77\uff01\u7136\u540e\u8bb2 C++20\u3001C++17\u3001C++14\u3001C++11\uff0c\u6162\u6162\u8bb2\u5230\u6700\u539f\u59cb\u7684 C++98\u3002 \u4e0d\u7528\u62c5\u5fc3\uff0c\u8d8a\u662f\u73b0\u4ee3\u7684 C++\uff0c\u5b66\u8d77\u6765\u53cd\u800c\u66f4\u5bb9\u6613\uff01\u53cd\u800c\u53e4\u4ee3 C++ \u624d \u53c8\u81ed\u53c8\u957f \u3002 \u5f88\u591a\u540c\u5b66\u60f3\u5f53\u7136\u5730\u8bef\u4ee5\u4e3a C++98 \u6700\u7b80\u5355\uff0c\u54fc\u54e7\u54fc\u54e7\u8d39\u8001\u5927\u52b2\u4ece C++98 \u5f00\u59cb\u5b66\uff0c\u624d\u662f\u9519\u8bef\u7684\u3002 \u4e3a\u4e86\u5e94\u4ed8\u7f3a\u80f3\u818a\u5c11\u817f\u7684 C++98\uff0c\u4eba\u4eec\u53d1\u660e\u4e86\u5404\u79cd \u7e41\u7410\u65e0\u8c13 \u7684\u5199\u6cd5\uff0c\u5728\u73b0\u4ee3 C++ \u4e2d\uff0c\u65e9\u5c31\u5df2\u7ecf\u88ab\u66f4 \u7b80\u6d01\u76f4\u89c2 \u7684\u5199\u6cd5\u66ff\u4ee3\u4e86\u3002 \u4f8b\u5982\u6240\u8c13\u7684 safe-bool idiom\uff0c\u5199\u8d77\u6765\u53c8\u81ed\u53c8\u957f\uff0cC++11 \u5f15\u5165\u4e00\u4e2a explicit \u5173\u952e\u5b57\u76f4\u63a5\u5c31\u79d2\u4e86\u3002\u7ed3\u679c\u8fd8\u6709\u4e00\u6279\u52b3\u4fdd\u6559\u6750\u5927\u5439\u7279\u5439 safe-bool idiom\uff0c\u5439\u5f97\u597d\u50cf\u662f\u4e2a\u4ec0\u4e48\u9ad8\u5927\u4e0a\u7684\u8bbe\u8ba1\u6a21\u5f0f\u4e00\u6837\uff0c\u4e0d\u8fc7\u662f\u4e2a\u5e94\u4ed8 C++98 \u8bed\u8a00\u7f3a\u9677\u7684\u8e69\u811a\u73a9\u610f\u3002 \u5c31\u597d\u6bd4\u4e00\u4e2a \u8001\u5916 \u60f3\u8981\u5b66\u4e60\u6c49\u8bed\uff0c\u4ed6\u9996\u5148\u80af\u5b9a\u662f\u4ece \u73b0\u4ee3\u6c49\u8bed \u5b66\u8d77\uff01\u800c\u4e0d\u662f\u4e0a\u6765\u5c31\u6559\u4ed6 \u6587\u8a00\u6587 \u3002 \u5373\u4f7f\u8fd9\u4e2a\u8001\u5916\u7684\u804c\u4e1a\u5c31\u662f\u201c\u8003\u53e4\u201d\uff0c\u6216\u8005\u4ed6\u5bf9\u201c\u53e4\u4ee3\u6587\u5b66\u201d\u611f\u5174\u8da3\uff0c\u4e5f\u4e0d\u53ef\u80fd\u81ea\u5b66\u6587\u8a00\u6587\u7684\u540c\u65f6\u5b8c\u5168\u8df3\u8fc7\u73b0\u4ee3\u6c49\u8bed\u3002 \u5f53\u6211\u4eec\u5b66\u4e60\u4e2d\u6587\u65f6\uff0c\u4f60\u80af\u5b9a\u5e0c\u671b\u5148\u5b66\u73b0\u4ee3\u6c49\u8bed\uff0c\u518d\u5b66\u6587\u8a00\u6587\uff0c\u518d\u5b66\u7532\u9aa8\u6587\uff0c\u518d\u5b66 brainf* * k\uff0c\u800c\u4e0d\u662f\u53cd\u8fc7\u6765\u3002 \u5bf9\u4e8e C++ \u521d\u5b66\u8005\u4e5f\u662f\u5982\u6b64\uff1a\u6211\u4eec\u9996\u5148\u5b66\u4f1a\u7b80\u5355\u660e\u4e86\u7684\uff0c\u7b26\u5408\u73b0\u4ee3\u4eba\u601d\u7ef4\u7684 C++23\uff0c\u518d\u9010\u6e10\u56de\u5230\u4e13\u4e3a\u4f3a\u5019\u201c\u53e4\u4ee3\u5f00\u53d1\u73af\u5883\u201d\u7684 C++98\u3002 \u4f60\u7684\u751f\u4ea7\u73af\u5883\u53ef\u80fd\u4e0d\u5141\u8bb8\u7528\u4e0a C++20 \u751a\u81f3 C++23 \u7684\u65b0\u6807\u51c6\u3002 \u522b\u62c5\u5fc3\uff0c\u5c0f\u5f6d\u8001\u5e08\u6559\u4f1a\u4f60 C++23 \u7684\u6b63\u5e38\u5199\u6cd5\u540e\uff0c\u4f1a\u8bb2\u89e3\u5982\u4f55\u5728 C++14\u3001C++98 \u4e2d\u5199\u51fa\u540c\u6837\u7684\u6548\u679c\u3002 \u8fd9\u6837\u4f60\u5b66\u4e60\u7684\u65f6\u5019\u601d\u8def\u6e05\u6670\uff0c\u4e0d\u7528\u88ab\u7e41\u7410\u7684 C++98 \u201c\u5947\u6280\u6deb\u5de7\u201d\u5e72\u6270\uff0c\u5b66\u8d77\u6765\u4e8b\u534a\u529f\u500d\uff1b\u4f46\u4e5f\u201c\u5403\u8fc7\u89c1\u8fc7\u201d\uff0c\u77e5\u9053\u53e4\u4ee3 C++98 \u7684\u5e94\u5bf9\u7b56\u7565\u3002 \u76ee\u524d\u4f01\u4e1a\u91cc\u4e3b\u6d41\u4f7f\u7528\u7684\u662f C++14 \u548c C++17\u3002\u4f8b\u5982\u8c37\u6b4c\u5c31\u660e\u786e\u89c4\u5b9a\u8981\u6c42 C++17\u3002 \u4e3e\u4e2a\u4f8b\u5b50 \u63a5\u4e0b\u6765\u7684\u4f8b\u5b50\u4f60\u53ef\u80fd\u770b\u4e0d\u61c2\uff0c\u4f46\u53ea\u9700\u8981\u8bb0\u4f4f\u8fd9\u4e2a\u4f8b\u5b50\u662f\u5411\u4f60\u8bf4\u660e\uff1a\u8d8a\u662f\u65b0\u7684 C++ \u6807\u51c6\uff0c\u53cd\u800c\u8d8a\u5bb9\u6613\u5b66\uff01 \u4f8b\u5982\uff0c\u5728\u6a21\u677f\u5143\u7f16\u7a0b\u4e2d\uff0c\u8981\u68c0\u6d4b\u4e00\u4e2a\u7c7b\u578b T \u662f\u5426\u62e5\u6709 foo() \u8fd9\u4e00\u6210\u5458\u51fd\u6570\u3002\u5982\u679c\u5b58\u5728\uff0c\u624d\u4f1a\u8c03\u7528\u3002 \u5728 C++20 \u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528\u5f88\u65b9\u4fbf\u7684 requires \u8bed\u6cd5\uff0c\u8f7b\u677e\u68c0\u6d4b\u4e00\u4e2a\u8868\u8fbe\u5f0f\u662f\u5426\u80fd\u5408\u6cd5\u901a\u8fc7\u7f16\u8bd1\u3002\u5982\u679c\u80fd\uff0c requires \u8bed\u53e5\u4f1a\u8fd4\u56de true \u3002\u7136\u540e\u7528\u4e00\u4e2a if constexpr \u8fdb\u884c\u7f16\u8bd1\u671f\u5206\u652f\u5224\u65ad\uff0c\u5373\u53ef\u5b9e\u73b0\u68c0\u6d4b\u5230\u5b58\u5728\u5219\u8c03\u7528\u3002 template void try_call_foo(T &t) { if constexpr (requires { t.foo(); }) { t.foo(); } } \u4f46\u4ec5\u4ec5\u662f\u56de\u5230 C++17\uff0c\u6ca1\u6709 requires \u8bed\u6cd5\uff0c\u6211\u4eec\u53ea\u80fd\u81ea\u5df1\u5b9a\u4e49\u4e00\u4e2a trait \u7c7b\uff0c\u5e76\u8fd0\u7528\u70e6\u4eba\u7684 SFINAE \u5c0f\u6280\u5de7\uff0c\u68c0\u6d4b\u8868\u8fbe\u5f0f\u662f\u5426\u7684\u5408\u6cd5\uff0c\u53c8\u81ed\u53c8\u957f\u3002 template struct has_foo { static constexpr bool value = false; }; template struct has_foo().foo())>> { static constexpr bool value = true; }; template void try_call_foo(T &t) { if constexpr (has_foo::value) { t.foo(); } } \u5982\u679c\u56de\u5230 C++14\uff0c\u60c5\u51b5\u5c31\u66f4\u7cdf\u7cd5\u4e86\uff01 if constexpr \u662f C++17 \u7684\u7279\u6027\uff0c\u6ca1\u6709\u4ed6\uff0c\u8981\u5b9e\u73b0\u7f16\u8bd1\u671f\u5206\u652f\uff0c\u6211\u4eec\u5c31\u5f97\u7528 enable_if_t \u7684 SFINAE \u5c0f\u6280\u5de7\uff0c\u9700\u8981\u5b9a\u4e49\u4e24\u4e2a try_call_foo \u51fd\u6570\uff0c\u4e92\u76f8\u91cd\u8f7d\uff0c\u624d\u80fd\u5b9e\u73b0\u540c\u6837\u7684\u6548\u679c\u3002 template struct has_foo { static constexpr bool value = false; }; template struct has_foo().foo())>> { static constexpr bool value = true; }; template ::value, int> = 0> void try_call_foo(T &t) { t.foo(); } template ::value, int> = 0> void try_call_foo(T &) { } \u5982\u679c\u56de\u5230 C++11\uff0c\u60c5\u51b5\u8fdb\u4e00\u6b65\u6076\u5316\uff01 enable_if_t \u8fd9\u4e2a\u65b9\u4fbf\u7684\u5c0f\u52a9\u624b\u5df2\u7ecf\u4e0d\u5b58\u5728\uff0c\u9700\u8981\u4f7f\u7528\u6bd4\u4ed6\u66f4\u5e95\u5c42\u7684 enable_if \u6a21\u677f\u7c7b\uff0c\u624b\u52a8\u53d6\u51fa ::type \uff0c\u5e76\u4e14\u9700\u8981 typename \u4fee\u9970\uff0c\u624d\u80fd\u7f16\u8bd1\u901a\u8fc7\uff01\u5e76\u4e14 void_t \u4e5f\u4e0d\u80fd\u7528\u4e86\uff0c\u8981\u7528\u9017\u53f7\u8868\u8fbe\u5f0f\u5c0f\u6280\u5de7\u624d\u80fd\u8ba9 decltype \u56fa\u5b9a\u8fd4\u56de void\u2026\u2026 template struct has_foo { static constexpr bool value = false; }; template struct has_foo().foo(), (void)0)> { static constexpr bool value = true; }; template ::value, int>::type = 0> void try_call_foo(T &t) { t.foo(); } template ::value, int>::type = 0> void try_call_foo(T &) { } \u5982\u679c\u56de\u5230 C++98\uff0c\u90a3\u53c8\u8981\u7f6a\u52a0\u4e00\u7b49\uff01 enable_if \u548c declval \u662f C++11 \u5f15\u5165\u7684 \u5934\u6587\u4ef6\u7684\u5e2e\u624b\u7c7b\u548c\u5e2e\u624b\u51fd\u6570\uff0c\u5728 C++98 \u4e2d\uff0c\u6211\u4eec\u9700\u8981\u81ea\u5df1\u5b9e\u73b0 enable_if \u2026\u2026 declval \u4e5f\u662f C++11 \u5f15\u5165\u7684 \u5934\u6587\u4ef6\u4e2d\u7684\u5e2e\u624b\u51fd\u6570\u2026\u2026\u5047\u8bbe\u4f60\u81ea\u5df1\u597d\u4e0d\u5bb9\u6613\u5b9e\u73b0\u51fa\u6765\u4e86 enable_if \u548c declval \uff0c\u8fd8\u6ca1\u5b8c\uff1a\u56e0\u4e3a constexpr \u5728 C++98 \u4e2d\u4e5f\u4e0d\u5b58\u5728\u4e86\uff01\u4f60\u65e0\u6cd5\u5b9a\u4e49 value \u6210\u5458\u53d8\u91cf\u4e3a\u7f16\u8bd1\u671f\u5e38\u91cf\uff0c\u6211\u4eec\u53ea\u597d\u53c8\u7528\u4e00\u4e2a\u62bd\u8c61\u7684\u679a\u4e3e\u5c0f\u6280\u5de7\u6765\u5b9e\u73b0\u5b9a\u4e49\u7c7b\u6210\u5458\u5e38\u91cf\u7684\u6548\u679c\u3002 template struct has_foo { enum { value = 0 }; }; template struct has_foo().foo(), (void)0)> { enum { value = 1 }; }; template ::value, int>::type = 0> void try_call_foo(T &t) { t.foo(); } template ::value, int>::type = 0> void try_call_foo(T &) { } \u5982\u6b64\u5197\u957f\u96be\u61c2\u7684\u62bd\u8c61 C++98 \u4ee3\u7801\uff0c\u4eff\u4f5b\u662f\u201c\u52a0\u5bc6\u201d\u8fc7\u7684\u4ee3\u7801\u4e00\u6837\uff0c\u4ec5\u4ec5\u662f\u4e3a\u4e86\u5b9e\u73b0\u68c0\u6d4b\u662f\u5426\u5b58\u5728\u6210\u5458\u51fd\u6570 foo\u2026\u2026 \u5982\u679c\u56de\u5230 C \u8bed\u8a00\uff0c\u90a3\u4e48\u4f60\u751a\u81f3\u90fd\u4e0d\u7528\u68c0\u6d4b\u4e86\u3002\u56e0\u4e3a\u4f1f\u5927\u7684 C \u8bed\u8a00\u8fde\u6210\u5458\u51fd\u6570\u90fd\u6ca1\u6709\uff0c\u4f55\u8c08\u201c\u68c0\u6d4b\u6210\u5458\u51fd\u6570\u662f\u5426\u5b58\u5728\u201d\uff1f \u53cd\u89c2 C++20 \u7684\u5199\u6cd5\uff0c\u4e00\u773c\u5c31\u770b\u660e\u767d\u4ee3\u7801\u7684\u903b\u8f91\u662f\u4ec0\u4e48\uff0c\u8868\u8fbe\u4f60\u8be5\u8868\u8fbe\u7684\uff0c\u800c\u4e0d\u662f\u8ff7\u5931\u4e8e\u4f3a\u5019\u5404\u79cd\u8bed\u8a00\u7f3a\u9677\uff0c\u5e72\u6270\u6211\u4eec\u5b66\u4e60\u3002 void try_call_foo(auto &t) { if constexpr (requires { t.foo(); }) { t.foo(); } } // \u4ece\u6b8b\u5e9f\u7684 C++98 \u5b66\u8d77\uff0c\u4f60\u7684\u601d\u7ef4\u5c31\u88ab\u8fd9\u4e9b\u65e0\u8c13\u7684\u201c\u5947\u6280\u6deb\u5de7\u201d\u626d\u66f2\u4e86\uff0c\u800c\u4f7f\u5f97\u771f\u6b63\u5e94\u8be5\u8868\u8fbe\u7684\u4ee3\u7801\u903b\u8f91\uff0c\u6df9\u6ca1\u5728\u53c8\u81ed\u53c8\u957f\u7684\u53e4\u4ee3\u6280\u5de7\u4e2d\u3002 // \u4ece\u73b0\u4ee3\u7684 C++23 \u5b66\u8d77\uff0c\u5148\u77e5\u9053\u6b63\u5e38\u7684\u5199\u6cd5\u201c\u7406\u5e94\u201d\u662f\u4ec0\u4e48\u6837\u3002\u5de5\u4f5c\u4e2d\u7528\u4e0d\u4e0a C++23\uff1f\u6211\u4f1a\u5411\u4f60\u4ecb\u7ecd\uff0c\u5982\u679c\u8981\u5012\u9000\u56de C++14\uff0c\u53e4\u4ee3\u4eba\u90fd\u662f\u7528\u4ec0\u4e48\u201c\u5947\u6280\u6deb\u5de7\u201d\u5b9e\u73b0\u540c\u6837\u7684\u6548\u679c\u3002 // \u8fd9\u6837\u4f60\u6700\u540e\u540c\u6837\u53ef\u4ee5\u9002\u5e94\u516c\u53f8\u8981\u6c42\u7684 C++14 \u73af\u5883\u3002\u4f46\u662f\u4ece C++23 \u5b66\u8d77\uff0c\u4f60\u7684\u601d\u7ef4\u53c8\u4e0d\u4f1a\u88ab\u5e94\u4ed8\u53e4\u4ee3\u8bed\u8a00\u7f3a\u9677\u7684\u201c\u5947\u6280\u6deb\u5de7\u201d\u6270\u4e71\uff0c\u5b66\u8d77\u6765\u5c31\u4e8b\u534a\u529f\u500d\u3002 \u65e2\u7136\u73b0\u4ee3 C++ \u8fd9\u4e48\u597d\uff0c\u4e3a\u4ec0\u4e48\u5b66\u6821\u4e0d\u4ece\u73b0\u4ee3 C++ \u6559\u8d77\uff0c\u6559\u8d77\u6765\u8fd8\u8f7b\u677e\uff1f\u56e0\u4e3a\u52b3\u4fdd\u8001\u5e08\u4fdd\uff0c\u61d2\u5f97\u63a5\u89e6\u65b0\u77e5\u8bc6\uff0c\u8ba4\u4e3a\u201c\u7956\u5b97\u4e4b\u6cd5\u4e0d\u53ef\u53d8\u201d\uff0c\u201c\u7248\u53f7\u7a33\u5b9a\u538b\u5012\u4e00\u5207\u201d\u3002","title":"\u524d\u8a00"},{"location":"#c","text":"\u5c0f\u5f6d\u5927\u5178\u662f\u4e00\u672c\u5173\u4e8e\u73b0\u4ee3 C++ \u7f16\u7a0b\u7684\u6743\u5a01\u6307\u5357\uff0c\u5b83\u6db5\u76d6\u4e86\u4ece\u57fa\u7840\u77e5\u8bc6\u5230\u9ad8\u7ea7\u6280\u5de7\u7684\u5185\u5bb9\uff0c\u9002\u5408\u521d\u5b66\u8005\u548c\u6709\u7ecf\u9a8c\u7684\u7a0b\u5e8f\u5458\u9605\u8bfb\u3002\u672c\u4e66\u7531\u5c0f\u5f6d\u8001\u5e08\u4eb2\u81ea\u7f16\u5199\uff0c\u901a\u8fc7\u7b80\u5355\u6613\u61c2\u7684\u8bed\u8a00\u548c\u4e30\u5bcc\u7684\u793a\u4f8b\uff0c\u5e2e\u52a9\u8bfb\u8005\u5feb\u901f\u638c\u63e1 C++ \u7684\u6838\u5fc3\u6982\u5ff5\uff0c\u5e76\u5b66\u4f1a\u5982\u4f55\u8fd0\u7528\u5b83\u4eec\u6765\u89e3\u51b3\u5b9e\u9645\u95ee\u9898\u3002 \u6562\u627f\u8bfa\uff1a\u571f\u6728\u8001\u54e5\u4e5f\u80fd\u770b\u61c2\uff01","title":"\u5c0f\u5f6d\u8001\u5e08\u73b0\u4ee3 C++ \u5927\u5178"},{"location":"#_1","text":"\u63a8\u8350\u7528\u624b\u673a\u6216\u5e73\u677f \u7ad6\u5c4f \u89c2\u770b\uff0c\u53ef\u4ee5\u5728\u5e8a\u6216\u6c99\u53d1\u4e0a\u8eba\u7740\u3002 \u7528\u7535\u8111\u770b\u7684\u8bdd\uff0c\u53ef\u4ee5\u6309 WIN + \u2190 \uff0c\u628a\u672c\u4e66\u7684\u6d4f\u89c8\u5668\u7a97\u53e3\u653e\u5728\u5c4f\u5e55\u5de6\u4fa7\uff0c\u53f3\u4fa7\u662f\u4f60\u7684 IDE\u3002\u4e00\u8fb9\u770b\u4e00\u8fb9\u81ea\u5df1\u52a8\u624b\u505a\u5b9e\u9a8c\u3002 \u8bf7\u5750\u548c\u653e\u5bbd\u3002 \u53ef\u4ee5\u6309\u987a\u5e8f\u9605\u8bfb\uff0c\u4e5f\u53ef\u4ee5\u5728\u672c\u9875\u9762\u4e0a\u65b9\u5bfc\u822a\u680f\u7684\u201c\u7ae0\u8282\u5217\u8868\u201d\u4e2d\uff0c\u9009\u62e9\u611f\u5174\u8da3\u7684\u7ae0\u8282\u9605\u8bfb\u3002 \u672c\u4e66\u5b8c\u5168\u5f00\u6e90\u548c\u514d\u8d39\uff0cGitHub \u4ed3\u5e93\uff1a https://github.com/parallel101/cppguidebook \u5982\u679c\u4f60\u662f\u5728\u4ed8\u8d39\u7fa4\u4e2d\u201c\u4e70\u201d\u5230\u672c\u4e66\uff0c\u6216\u8005\u6253\u7740\u5c0f\u5f6d\u8001\u5e08\u540d\u53f7\u5356\u8bfe\uff0c\u8bf4\u660e\u4f60\u53ef\u80fd\u662f\u79c1\u6709\u5236\u7684\u53d7\u5bb3\u8005\u3002\u56e0\u4e3a\u5c0f\u5f6d\u8001\u5e08\u4ece\u6765\u6ca1\u6709\u4ed8\u8d39\u624d\u80fd\u770b\u7684\u8bfe\u7a0b\uff0c\u6240\u6709\u5c0f\u5f6d\u8001\u5e08\u8bfe\u7a0b\u90fd\u5bf9\u5168\u7403\u4e92\u8054\u7f51\u5f00\u653e\u3002 \u5982\u9700\u79bb\u7ebf\u67e5\u770b\uff0c\u53ef\u4ee5\u524d\u5f80 GitHub Release \u9875\u9762 \u4e0b\u8f7d PDF \u6587\u4ef6\u3002 \u5982\u679c\u4f60\u5728\u9605\u8bfb\u8fc7\u7a0b\u4e2d\u9047\u5230\u4efb\u4f55\u95ee\u9898\uff0c\u53ef\u4ee5\u5728 GitHub Issues \u4e2d\u63d0\u51fa\uff0c\u5c0f\u5f6d\u8001\u5e08\u4f1a\u5c3d\u529b\u89e3\u7b54\u3002 \u4e5f\u53ef\u4ee5\u5728 B \u7ad9 \u53d1\u79c1\u4fe1\u7ed9\u5c0f\u5f6d\u8001\u5e08\u54e6\u3002 \u672c\u4e66\u8fd8\u5728\u6301\u7eed\u66f4\u65b0\u4e2d\u2026\u2026\u8981\u8ffd\u756a\u7684\u8bdd\uff0c\u53ef\u4ee5\u5728 GitHub \u70b9\u4e00\u4e0b\u53f3\u4e0a\u89d2\u7684 \u201cWatch\u201d \u6309\u94ae\uff0c\u6bcf\u5f53\u5c0f\u5f6d\u8001\u5e08\u63d0\u4ea4\u65b0 commit\uff0cGitHub \u4f1a\u5411\u4f60\u53d1\u9001\u4e00\u5c01\u7535\u5b50\u90ae\u4ef6\uff0c\u63d0\u9192\u4f60\u5c0f\u5f6d\u8001\u5e08\u66f4\u65b0\u4e86\u3002 \u66f4\u65b0\u65f6\u95f4\uff1a2024\u5e7411\u670801\u65e5 12:54:16 (UTC+08:00) \u5728 GitHub Pages \u6d4f\u89c8\u672c\u4e66 | \u5728\u5c0f\u5f6d\u8001\u5e08\u81ea\u5df1\u7ef4\u62a4\u7684\u955c\u50cf\u4e0a\u6d4f\u89c8\u672c\u4e66","title":"\u524d\u8a00"},{"location":"#_2","text":"\u7528\u8fd9\u79cd\u989c\u8272\u5b57\u4f53\u4e66\u5199\u7684\u5185\u5bb9\u662f\u6e29\u99a8\u63d0\u793a \u7528\u8fd9\u79cd\u989c\u8272\u5b57\u4f53\u4e66\u5199\u7684\u5185\u5bb9\u662f\u53ef\u80fd\u72af\u9519\u7684\u8b66\u544a \u7528\u8fd9\u79cd\u989c\u8272\u5b57\u4f53\u4e66\u5199\u7684\u5185\u5bb9\u662f\u7b11\u8bdd\u6216\u8da3\u5473\u5bd3\u8a00\u6545\u4e8b \u7528\u8fd9\u79cd\u989c\u8272\u4e66\u5199\u7684\u662f\u8865\u5145\u8bf4\u660e\u7684\u8bfe\u5916\u9605\u8bfb\uff0c\u770b\u4e0d\u61c2\u4e5f\u6ca1\u5173\u7cfb \u7528\u8fd9\u79cd\u989c\u8272\u5b57\u4f53\u4e66\u5199\u7684\u662f\u521d\u5b66\u8005\u53ef\u6682\u65f6\u4e0d\u7528\u7406\u89e3\u7684\u7ec6\u8282 \u672f\u8bed\u540d\u79f0: \u8fd9\u91cc\u662f\u672f\u8bed\u7684\u5b9a\u4e49\u3002","title":"\u683c\u5f0f\u7ea6\u5b9a"},{"location":"#_3","text":"\u4e0e\u5927\u591a\u6570\u73b0\u6709\u6559\u6750\u4e0d\u540c\u7684\u662f\uff0c\u672c\u8bfe\u7a0b\u5c06\u4f1a\u91c7\u7528\u201c\u5012\u53d9\u201d\u7684\u5f62\u5f0f\uff0c\u4ece\u6700\u65b0\u7684 C++23 \u8bb2\u8d77\uff01\u7136\u540e\u8bb2 C++20\u3001C++17\u3001C++14\u3001C++11\uff0c\u6162\u6162\u8bb2\u5230\u6700\u539f\u59cb\u7684 C++98\u3002 \u4e0d\u7528\u62c5\u5fc3\uff0c\u8d8a\u662f\u73b0\u4ee3\u7684 C++\uff0c\u5b66\u8d77\u6765\u53cd\u800c\u66f4\u5bb9\u6613\uff01\u53cd\u800c\u53e4\u4ee3 C++ \u624d \u53c8\u81ed\u53c8\u957f \u3002 \u5f88\u591a\u540c\u5b66\u60f3\u5f53\u7136\u5730\u8bef\u4ee5\u4e3a C++98 \u6700\u7b80\u5355\uff0c\u54fc\u54e7\u54fc\u54e7\u8d39\u8001\u5927\u52b2\u4ece C++98 \u5f00\u59cb\u5b66\uff0c\u624d\u662f\u9519\u8bef\u7684\u3002 \u4e3a\u4e86\u5e94\u4ed8\u7f3a\u80f3\u818a\u5c11\u817f\u7684 C++98\uff0c\u4eba\u4eec\u53d1\u660e\u4e86\u5404\u79cd \u7e41\u7410\u65e0\u8c13 \u7684\u5199\u6cd5\uff0c\u5728\u73b0\u4ee3 C++ \u4e2d\uff0c\u65e9\u5c31\u5df2\u7ecf\u88ab\u66f4 \u7b80\u6d01\u76f4\u89c2 \u7684\u5199\u6cd5\u66ff\u4ee3\u4e86\u3002 \u4f8b\u5982\u6240\u8c13\u7684 safe-bool idiom\uff0c\u5199\u8d77\u6765\u53c8\u81ed\u53c8\u957f\uff0cC++11 \u5f15\u5165\u4e00\u4e2a explicit \u5173\u952e\u5b57\u76f4\u63a5\u5c31\u79d2\u4e86\u3002\u7ed3\u679c\u8fd8\u6709\u4e00\u6279\u52b3\u4fdd\u6559\u6750\u5927\u5439\u7279\u5439 safe-bool idiom\uff0c\u5439\u5f97\u597d\u50cf\u662f\u4e2a\u4ec0\u4e48\u9ad8\u5927\u4e0a\u7684\u8bbe\u8ba1\u6a21\u5f0f\u4e00\u6837\uff0c\u4e0d\u8fc7\u662f\u4e2a\u5e94\u4ed8 C++98 \u8bed\u8a00\u7f3a\u9677\u7684\u8e69\u811a\u73a9\u610f\u3002 \u5c31\u597d\u6bd4\u4e00\u4e2a \u8001\u5916 \u60f3\u8981\u5b66\u4e60\u6c49\u8bed\uff0c\u4ed6\u9996\u5148\u80af\u5b9a\u662f\u4ece \u73b0\u4ee3\u6c49\u8bed \u5b66\u8d77\uff01\u800c\u4e0d\u662f\u4e0a\u6765\u5c31\u6559\u4ed6 \u6587\u8a00\u6587 \u3002 \u5373\u4f7f\u8fd9\u4e2a\u8001\u5916\u7684\u804c\u4e1a\u5c31\u662f\u201c\u8003\u53e4\u201d\uff0c\u6216\u8005\u4ed6\u5bf9\u201c\u53e4\u4ee3\u6587\u5b66\u201d\u611f\u5174\u8da3\uff0c\u4e5f\u4e0d\u53ef\u80fd\u81ea\u5b66\u6587\u8a00\u6587\u7684\u540c\u65f6\u5b8c\u5168\u8df3\u8fc7\u73b0\u4ee3\u6c49\u8bed\u3002 \u5f53\u6211\u4eec\u5b66\u4e60\u4e2d\u6587\u65f6\uff0c\u4f60\u80af\u5b9a\u5e0c\u671b\u5148\u5b66\u73b0\u4ee3\u6c49\u8bed\uff0c\u518d\u5b66\u6587\u8a00\u6587\uff0c\u518d\u5b66\u7532\u9aa8\u6587\uff0c\u518d\u5b66 brainf* * k\uff0c\u800c\u4e0d\u662f\u53cd\u8fc7\u6765\u3002 \u5bf9\u4e8e C++ \u521d\u5b66\u8005\u4e5f\u662f\u5982\u6b64\uff1a\u6211\u4eec\u9996\u5148\u5b66\u4f1a\u7b80\u5355\u660e\u4e86\u7684\uff0c\u7b26\u5408\u73b0\u4ee3\u4eba\u601d\u7ef4\u7684 C++23\uff0c\u518d\u9010\u6e10\u56de\u5230\u4e13\u4e3a\u4f3a\u5019\u201c\u53e4\u4ee3\u5f00\u53d1\u73af\u5883\u201d\u7684 C++98\u3002 \u4f60\u7684\u751f\u4ea7\u73af\u5883\u53ef\u80fd\u4e0d\u5141\u8bb8\u7528\u4e0a C++20 \u751a\u81f3 C++23 \u7684\u65b0\u6807\u51c6\u3002 \u522b\u62c5\u5fc3\uff0c\u5c0f\u5f6d\u8001\u5e08\u6559\u4f1a\u4f60 C++23 \u7684\u6b63\u5e38\u5199\u6cd5\u540e\uff0c\u4f1a\u8bb2\u89e3\u5982\u4f55\u5728 C++14\u3001C++98 \u4e2d\u5199\u51fa\u540c\u6837\u7684\u6548\u679c\u3002 \u8fd9\u6837\u4f60\u5b66\u4e60\u7684\u65f6\u5019\u601d\u8def\u6e05\u6670\uff0c\u4e0d\u7528\u88ab\u7e41\u7410\u7684 C++98 \u201c\u5947\u6280\u6deb\u5de7\u201d\u5e72\u6270\uff0c\u5b66\u8d77\u6765\u4e8b\u534a\u529f\u500d\uff1b\u4f46\u4e5f\u201c\u5403\u8fc7\u89c1\u8fc7\u201d\uff0c\u77e5\u9053\u53e4\u4ee3 C++98 \u7684\u5e94\u5bf9\u7b56\u7565\u3002 \u76ee\u524d\u4f01\u4e1a\u91cc\u4e3b\u6d41\u4f7f\u7528\u7684\u662f C++14 \u548c C++17\u3002\u4f8b\u5982\u8c37\u6b4c\u5c31\u660e\u786e\u89c4\u5b9a\u8981\u6c42 C++17\u3002","title":"\u89c2\u524d\u987b\u77e5"},{"location":"#_4","text":"\u63a5\u4e0b\u6765\u7684\u4f8b\u5b50\u4f60\u53ef\u80fd\u770b\u4e0d\u61c2\uff0c\u4f46\u53ea\u9700\u8981\u8bb0\u4f4f\u8fd9\u4e2a\u4f8b\u5b50\u662f\u5411\u4f60\u8bf4\u660e\uff1a\u8d8a\u662f\u65b0\u7684 C++ \u6807\u51c6\uff0c\u53cd\u800c\u8d8a\u5bb9\u6613\u5b66\uff01 \u4f8b\u5982\uff0c\u5728\u6a21\u677f\u5143\u7f16\u7a0b\u4e2d\uff0c\u8981\u68c0\u6d4b\u4e00\u4e2a\u7c7b\u578b T \u662f\u5426\u62e5\u6709 foo() \u8fd9\u4e00\u6210\u5458\u51fd\u6570\u3002\u5982\u679c\u5b58\u5728\uff0c\u624d\u4f1a\u8c03\u7528\u3002 \u5728 C++20 \u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528\u5f88\u65b9\u4fbf\u7684 requires \u8bed\u6cd5\uff0c\u8f7b\u677e\u68c0\u6d4b\u4e00\u4e2a\u8868\u8fbe\u5f0f\u662f\u5426\u80fd\u5408\u6cd5\u901a\u8fc7\u7f16\u8bd1\u3002\u5982\u679c\u80fd\uff0c requires \u8bed\u53e5\u4f1a\u8fd4\u56de true \u3002\u7136\u540e\u7528\u4e00\u4e2a if constexpr \u8fdb\u884c\u7f16\u8bd1\u671f\u5206\u652f\u5224\u65ad\uff0c\u5373\u53ef\u5b9e\u73b0\u68c0\u6d4b\u5230\u5b58\u5728\u5219\u8c03\u7528\u3002 template void try_call_foo(T &t) { if constexpr (requires { t.foo(); }) { t.foo(); } } \u4f46\u4ec5\u4ec5\u662f\u56de\u5230 C++17\uff0c\u6ca1\u6709 requires \u8bed\u6cd5\uff0c\u6211\u4eec\u53ea\u80fd\u81ea\u5df1\u5b9a\u4e49\u4e00\u4e2a trait \u7c7b\uff0c\u5e76\u8fd0\u7528\u70e6\u4eba\u7684 SFINAE \u5c0f\u6280\u5de7\uff0c\u68c0\u6d4b\u8868\u8fbe\u5f0f\u662f\u5426\u7684\u5408\u6cd5\uff0c\u53c8\u81ed\u53c8\u957f\u3002 template struct has_foo { static constexpr bool value = false; }; template struct has_foo().foo())>> { static constexpr bool value = true; }; template void try_call_foo(T &t) { if constexpr (has_foo::value) { t.foo(); } } \u5982\u679c\u56de\u5230 C++14\uff0c\u60c5\u51b5\u5c31\u66f4\u7cdf\u7cd5\u4e86\uff01 if constexpr \u662f C++17 \u7684\u7279\u6027\uff0c\u6ca1\u6709\u4ed6\uff0c\u8981\u5b9e\u73b0\u7f16\u8bd1\u671f\u5206\u652f\uff0c\u6211\u4eec\u5c31\u5f97\u7528 enable_if_t \u7684 SFINAE \u5c0f\u6280\u5de7\uff0c\u9700\u8981\u5b9a\u4e49\u4e24\u4e2a try_call_foo \u51fd\u6570\uff0c\u4e92\u76f8\u91cd\u8f7d\uff0c\u624d\u80fd\u5b9e\u73b0\u540c\u6837\u7684\u6548\u679c\u3002 template struct has_foo { static constexpr bool value = false; }; template struct has_foo().foo())>> { static constexpr bool value = true; }; template ::value, int> = 0> void try_call_foo(T &t) { t.foo(); } template ::value, int> = 0> void try_call_foo(T &) { } \u5982\u679c\u56de\u5230 C++11\uff0c\u60c5\u51b5\u8fdb\u4e00\u6b65\u6076\u5316\uff01 enable_if_t \u8fd9\u4e2a\u65b9\u4fbf\u7684\u5c0f\u52a9\u624b\u5df2\u7ecf\u4e0d\u5b58\u5728\uff0c\u9700\u8981\u4f7f\u7528\u6bd4\u4ed6\u66f4\u5e95\u5c42\u7684 enable_if \u6a21\u677f\u7c7b\uff0c\u624b\u52a8\u53d6\u51fa ::type \uff0c\u5e76\u4e14\u9700\u8981 typename \u4fee\u9970\uff0c\u624d\u80fd\u7f16\u8bd1\u901a\u8fc7\uff01\u5e76\u4e14 void_t \u4e5f\u4e0d\u80fd\u7528\u4e86\uff0c\u8981\u7528\u9017\u53f7\u8868\u8fbe\u5f0f\u5c0f\u6280\u5de7\u624d\u80fd\u8ba9 decltype \u56fa\u5b9a\u8fd4\u56de void\u2026\u2026 template struct has_foo { static constexpr bool value = false; }; template struct has_foo().foo(), (void)0)> { static constexpr bool value = true; }; template ::value, int>::type = 0> void try_call_foo(T &t) { t.foo(); } template ::value, int>::type = 0> void try_call_foo(T &) { } \u5982\u679c\u56de\u5230 C++98\uff0c\u90a3\u53c8\u8981\u7f6a\u52a0\u4e00\u7b49\uff01 enable_if \u548c declval \u662f C++11 \u5f15\u5165\u7684 \u5934\u6587\u4ef6\u7684\u5e2e\u624b\u7c7b\u548c\u5e2e\u624b\u51fd\u6570\uff0c\u5728 C++98 \u4e2d\uff0c\u6211\u4eec\u9700\u8981\u81ea\u5df1\u5b9e\u73b0 enable_if \u2026\u2026 declval \u4e5f\u662f C++11 \u5f15\u5165\u7684 \u5934\u6587\u4ef6\u4e2d\u7684\u5e2e\u624b\u51fd\u6570\u2026\u2026\u5047\u8bbe\u4f60\u81ea\u5df1\u597d\u4e0d\u5bb9\u6613\u5b9e\u73b0\u51fa\u6765\u4e86 enable_if \u548c declval \uff0c\u8fd8\u6ca1\u5b8c\uff1a\u56e0\u4e3a constexpr \u5728 C++98 \u4e2d\u4e5f\u4e0d\u5b58\u5728\u4e86\uff01\u4f60\u65e0\u6cd5\u5b9a\u4e49 value \u6210\u5458\u53d8\u91cf\u4e3a\u7f16\u8bd1\u671f\u5e38\u91cf\uff0c\u6211\u4eec\u53ea\u597d\u53c8\u7528\u4e00\u4e2a\u62bd\u8c61\u7684\u679a\u4e3e\u5c0f\u6280\u5de7\u6765\u5b9e\u73b0\u5b9a\u4e49\u7c7b\u6210\u5458\u5e38\u91cf\u7684\u6548\u679c\u3002 template struct has_foo { enum { value = 0 }; }; template struct has_foo().foo(), (void)0)> { enum { value = 1 }; }; template ::value, int>::type = 0> void try_call_foo(T &t) { t.foo(); } template ::value, int>::type = 0> void try_call_foo(T &) { } \u5982\u6b64\u5197\u957f\u96be\u61c2\u7684\u62bd\u8c61 C++98 \u4ee3\u7801\uff0c\u4eff\u4f5b\u662f\u201c\u52a0\u5bc6\u201d\u8fc7\u7684\u4ee3\u7801\u4e00\u6837\uff0c\u4ec5\u4ec5\u662f\u4e3a\u4e86\u5b9e\u73b0\u68c0\u6d4b\u662f\u5426\u5b58\u5728\u6210\u5458\u51fd\u6570 foo\u2026\u2026 \u5982\u679c\u56de\u5230 C \u8bed\u8a00\uff0c\u90a3\u4e48\u4f60\u751a\u81f3\u90fd\u4e0d\u7528\u68c0\u6d4b\u4e86\u3002\u56e0\u4e3a\u4f1f\u5927\u7684 C \u8bed\u8a00\u8fde\u6210\u5458\u51fd\u6570\u90fd\u6ca1\u6709\uff0c\u4f55\u8c08\u201c\u68c0\u6d4b\u6210\u5458\u51fd\u6570\u662f\u5426\u5b58\u5728\u201d\uff1f \u53cd\u89c2 C++20 \u7684\u5199\u6cd5\uff0c\u4e00\u773c\u5c31\u770b\u660e\u767d\u4ee3\u7801\u7684\u903b\u8f91\u662f\u4ec0\u4e48\uff0c\u8868\u8fbe\u4f60\u8be5\u8868\u8fbe\u7684\uff0c\u800c\u4e0d\u662f\u8ff7\u5931\u4e8e\u4f3a\u5019\u5404\u79cd\u8bed\u8a00\u7f3a\u9677\uff0c\u5e72\u6270\u6211\u4eec\u5b66\u4e60\u3002 void try_call_foo(auto &t) { if constexpr (requires { t.foo(); }) { t.foo(); } } // \u4ece\u6b8b\u5e9f\u7684 C++98 \u5b66\u8d77\uff0c\u4f60\u7684\u601d\u7ef4\u5c31\u88ab\u8fd9\u4e9b\u65e0\u8c13\u7684\u201c\u5947\u6280\u6deb\u5de7\u201d\u626d\u66f2\u4e86\uff0c\u800c\u4f7f\u5f97\u771f\u6b63\u5e94\u8be5\u8868\u8fbe\u7684\u4ee3\u7801\u903b\u8f91\uff0c\u6df9\u6ca1\u5728\u53c8\u81ed\u53c8\u957f\u7684\u53e4\u4ee3\u6280\u5de7\u4e2d\u3002 // \u4ece\u73b0\u4ee3\u7684 C++23 \u5b66\u8d77\uff0c\u5148\u77e5\u9053\u6b63\u5e38\u7684\u5199\u6cd5\u201c\u7406\u5e94\u201d\u662f\u4ec0\u4e48\u6837\u3002\u5de5\u4f5c\u4e2d\u7528\u4e0d\u4e0a C++23\uff1f\u6211\u4f1a\u5411\u4f60\u4ecb\u7ecd\uff0c\u5982\u679c\u8981\u5012\u9000\u56de C++14\uff0c\u53e4\u4ee3\u4eba\u90fd\u662f\u7528\u4ec0\u4e48\u201c\u5947\u6280\u6deb\u5de7\u201d\u5b9e\u73b0\u540c\u6837\u7684\u6548\u679c\u3002 // \u8fd9\u6837\u4f60\u6700\u540e\u540c\u6837\u53ef\u4ee5\u9002\u5e94\u516c\u53f8\u8981\u6c42\u7684 C++14 \u73af\u5883\u3002\u4f46\u662f\u4ece C++23 \u5b66\u8d77\uff0c\u4f60\u7684\u601d\u7ef4\u53c8\u4e0d\u4f1a\u88ab\u5e94\u4ed8\u53e4\u4ee3\u8bed\u8a00\u7f3a\u9677\u7684\u201c\u5947\u6280\u6deb\u5de7\u201d\u6270\u4e71\uff0c\u5b66\u8d77\u6765\u5c31\u4e8b\u534a\u529f\u500d\u3002 \u65e2\u7136\u73b0\u4ee3 C++ \u8fd9\u4e48\u597d\uff0c\u4e3a\u4ec0\u4e48\u5b66\u6821\u4e0d\u4ece\u73b0\u4ee3 C++ \u6559\u8d77\uff0c\u6559\u8d77\u6765\u8fd8\u8f7b\u677e\uff1f\u56e0\u4e3a\u52b3\u4fdd\u8001\u5e08\u4fdd\uff0c\u61d2\u5f97\u63a5\u89e6\u65b0\u77e5\u8bc6\uff0c\u8ba4\u4e3a\u201c\u7956\u5b97\u4e4b\u6cd5\u4e0d\u53ef\u53d8\u201d\uff0c\u201c\u7248\u53f7\u7a33\u5b9a\u538b\u5012\u4e00\u5207\u201d\u3002","title":"\u4e3e\u4e2a\u4f8b\u5b50"},{"location":"about/","text":"\u5173\u4e8e\u5c0f\u5f6d\u8001\u5e08 \u5c0f\u5f6d\u8001\u5e08\u662f\u4e00\u4f4d\u64c5\u957f\u9ad8\u6027\u80fd C++ \u7684\u7a0b\u5e8f\u5458\uff0c\u76ee\u524d\u4e3b\u8981\u4ece\u4e8b\u56fe\u5f62\u5b66\u9886\u57df\u7684\u5f15\u64ce\u5f00\u53d1\uff0c\u62e5\u6709\u591a\u5e74\u7684\u5f00\u53d1\u7ecf\u9a8c\u548c\u4e30\u5bcc\u7684\u77e5\u8bc6\u50a8\u5907\uff0c\u7cbe\u901a\u7ebf\u6027\u4ee3\u6570\u3001\u5fae\u79ef\u5206\u3001\u6982\u7387\u8bba\u3001\u5fae\u5206\u51e0\u4f55\u3001\u56fe\u5f62\u5b66\u3001\u6e38\u620f\u5f15\u64ce\u3001\u4e92\u8054\u7f51\u3001\u7f16\u8bd1\u539f\u7406\u3001\u8bbe\u8ba1\u6a21\u5f0f\u3001\u79bb\u7ebf\u6e32\u67d3\u3001\u73b0\u4ee3 C++\u3001\u73b0\u4ee3 CMake\u3001\u73b0\u4ee3 CUDA\u3001\u73b0\u4ee3 OpenGL\u3001\u591a\u7ebf\u7a0b\u5e76\u53d1\u3001\u534f\u7a0b\u3001\u5f02\u6b65 I/O\u3001SIMD\u3001\u5e76\u884c\u7f16\u7a0b\u3001\u6027\u80fd\u8c03\u4f18\u7b49\u591a\u4e2a\u9886\u57df\uff0c\u90fd\u80fd\u5bf9\u7b54\u5982\u6d41\u3002 \u4ed6\u64c5\u957f\u5e76\u884c\u7f16\u7a0b\u548c\u4f18\u5316\u6280\u672f\uff0c\u5bf9\u4e8e\u73b0\u4ee3 C++ \u548c\u8bbe\u8ba1\u6a21\u5f0f\u4e5f\u6709\u81ea\u5df1\u72ec\u5230\u7684\u89c1\u89e3\uff0c\u6df1\u53d7\u201c\u7ae5\u978b\u201d\u559c\u7231\u548c\u5c0a\u656c\u3002 \u5c0f\u5f6d\u8001\u5e08\u5728 B \u7ad9 \u64ad\u51fa\u7684\u300a\u9ad8\u6027\u80fd\u5e76\u884c\u7f16\u7a0b\u4e0e\u4f18\u5316\u300b\u7cfb\u5217\u516c\u5f00\u8bfe\uff0c\u4e00\u7ecf\u63a8\u51fa\uff0c\u7acb\u523b\u597d\u8bc4\u5982\u6f6e\uff01 \u5c0f\u5f6d\u8001\u5e08\u5c06\u81ea\u5df1\u4e30\u5bcc\u7684\u5f00\u53d1\u7ecf\u9a8c\u548c\u77e5\u8bc6\u50a8\u5907\u8f6c\u5316\u4e3a\u7ae5\u978b\u4eec\u7684\u751f\u4ea7\u529b\uff0c\u642d\u4e0a\u5c0f\u5f6d\u8001\u5e08\u6027\u80fd\u589e\u957f\u7684\u9ad8\u901f\u730e\u8f66\uff0c\u5f15\u9886\u7ae5\u978b\u9ad8\u5c31\u7684\u4f1f\u5927\u822a\u8def\u3002 \u4f1f\u5927\uff0c\u65e0\u9700\u591a\u8a00\u3002","title":"\u5173\u4e8e\u5c0f\u5f6d\u8001\u5e08"},{"location":"about/#_1","text":"\u5c0f\u5f6d\u8001\u5e08\u662f\u4e00\u4f4d\u64c5\u957f\u9ad8\u6027\u80fd C++ \u7684\u7a0b\u5e8f\u5458\uff0c\u76ee\u524d\u4e3b\u8981\u4ece\u4e8b\u56fe\u5f62\u5b66\u9886\u57df\u7684\u5f15\u64ce\u5f00\u53d1\uff0c\u62e5\u6709\u591a\u5e74\u7684\u5f00\u53d1\u7ecf\u9a8c\u548c\u4e30\u5bcc\u7684\u77e5\u8bc6\u50a8\u5907\uff0c\u7cbe\u901a\u7ebf\u6027\u4ee3\u6570\u3001\u5fae\u79ef\u5206\u3001\u6982\u7387\u8bba\u3001\u5fae\u5206\u51e0\u4f55\u3001\u56fe\u5f62\u5b66\u3001\u6e38\u620f\u5f15\u64ce\u3001\u4e92\u8054\u7f51\u3001\u7f16\u8bd1\u539f\u7406\u3001\u8bbe\u8ba1\u6a21\u5f0f\u3001\u79bb\u7ebf\u6e32\u67d3\u3001\u73b0\u4ee3 C++\u3001\u73b0\u4ee3 CMake\u3001\u73b0\u4ee3 CUDA\u3001\u73b0\u4ee3 OpenGL\u3001\u591a\u7ebf\u7a0b\u5e76\u53d1\u3001\u534f\u7a0b\u3001\u5f02\u6b65 I/O\u3001SIMD\u3001\u5e76\u884c\u7f16\u7a0b\u3001\u6027\u80fd\u8c03\u4f18\u7b49\u591a\u4e2a\u9886\u57df\uff0c\u90fd\u80fd\u5bf9\u7b54\u5982\u6d41\u3002 \u4ed6\u64c5\u957f\u5e76\u884c\u7f16\u7a0b\u548c\u4f18\u5316\u6280\u672f\uff0c\u5bf9\u4e8e\u73b0\u4ee3 C++ \u548c\u8bbe\u8ba1\u6a21\u5f0f\u4e5f\u6709\u81ea\u5df1\u72ec\u5230\u7684\u89c1\u89e3\uff0c\u6df1\u53d7\u201c\u7ae5\u978b\u201d\u559c\u7231\u548c\u5c0a\u656c\u3002 \u5c0f\u5f6d\u8001\u5e08\u5728 B \u7ad9 \u64ad\u51fa\u7684\u300a\u9ad8\u6027\u80fd\u5e76\u884c\u7f16\u7a0b\u4e0e\u4f18\u5316\u300b\u7cfb\u5217\u516c\u5f00\u8bfe\uff0c\u4e00\u7ecf\u63a8\u51fa\uff0c\u7acb\u523b\u597d\u8bc4\u5982\u6f6e\uff01 \u5c0f\u5f6d\u8001\u5e08\u5c06\u81ea\u5df1\u4e30\u5bcc\u7684\u5f00\u53d1\u7ecf\u9a8c\u548c\u77e5\u8bc6\u50a8\u5907\u8f6c\u5316\u4e3a\u7ae5\u978b\u4eec\u7684\u751f\u4ea7\u529b\uff0c\u642d\u4e0a\u5c0f\u5f6d\u8001\u5e08\u6027\u80fd\u589e\u957f\u7684\u9ad8\u901f\u730e\u8f66\uff0c\u5f15\u9886\u7ae5\u978b\u9ad8\u5c31\u7684\u4f1f\u5927\u822a\u8def\u3002 \u4f1f\u5927\uff0c\u65e0\u9700\u591a\u8a00\u3002","title":"\u5173\u4e8e\u5c0f\u5f6d\u8001\u5e08"},{"location":"auto/","text":"auto \u795e\u6559 (\u672a\u5b8c\u5de5) \u53d8\u91cf auto \u8fd4\u56de\u7c7b\u578b auto C++11 \u5f15\u5165\u7684 auto \u5173\u952e\u5b57\u53ef\u4ee5\u7528\u4f5c\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\uff0c\u4f46\u5b83\u53ea\u662f\u4e00\u4e2a\u201c\u5360\u4f4d\u201d\uff0c\u8ba9\u6211\u4eec\u5f97\u4ee5\u540e\u7f6e\u8fd4\u56de\u7c7b\u578b\uff0c\u5e76\u6ca1\u6709\u591a\u5927\u4f5c\u7528\uff0c\u975e\u5e38\u6b8b\u5e9f\u3002 auto f() -> int; // \u7b49\u4ef7\u4e8e\uff1a int f(); \u95f9\u4e86\u534a\u5929\uff0c\u8fd8\u662f\u8981\u5199\u8fd4\u56de\u7c7b\u578b\uff0c\u5c31\u53ea\u662f\u632a\u5230\u540e\u9762\u53bb\u597d\u770b\u4e00\u70b9\u2026\u2026 \u5f53\u521d\u5f15\u5165\u540e\u7f6e\u8fd4\u56de\u7c7b\u578b\u5b9e\u9645\u7684\u7528\u9014\u662f auto f(int x) -> decltype(x * x) { return x * x; } \u8fd9\u79cd\u60c5\u51b5\uff0c\u4f46\u5f88\u5bb9\u6613\u88ab\u63a5\u4e0b\u6765 C++14 \u5f15\u5165\u7684\u771f\u6b63 auto \u8fd4\u56de\u7c7b\u578b\u63a8\u5bfc\u5e73\u66ff\u4e86\u3002 C++14 \u5f15\u5165\u4e86\u51fd\u6570 \u8fd4\u56de\u7c7b\u578b\u63a8\u5bfc \uff0c auto \u624d\u7b97\u771f\u6b63\u610f\u4e49\u4e0a\u80fd\u7528\u505a\u51fd\u6570\u8fd4\u56de\u7c7b\u578b\uff0c\u5b83\u4f1a\u81ea\u52a8\u6839\u636e\u51fd\u6570\u4e2d\u7684 return \u8868\u8fbe\u5f0f\u63a8\u5bfc\u51fa\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\u3002 auto f(int x) { return x * x; // \u8868\u8fbe\u5f0f `x * x` \u7684\u7c7b\u578b\u4e3a int\uff0c\u6240\u4ee5 auto \u7c7b\u578b\u63a8\u5bfc\u4e3a int } // \u7b49\u4ef7\u4e8e\uff1a int f() { return x * x; } \u5982\u679c\u51fd\u6570\u4e2d\u6ca1\u6709 return \u8bed\u53e5\uff0c\u90a3\u4e48 auto \u4f1a\u88ab\u81ea\u52a8\u63a8\u5bfc\u4e3a void \uff0c\u975e\u5e38\u65b9\u4fbf\u3002 auto f() { std::println(\"hello\"); } // \u7b49\u4ef7\u4e8e\uff1a void f() { std::println(\"hello\"); } \u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u8fd4\u56de\u7c7b\u578b\u7528 auto \u6765\u63a8\u5bfc\u7684\u51fd\u6570\uff0c\u5982\u679c\u6709\u591a\u6761 return \u8bed\u53e5\uff0c\u90a3\u4e48\u4ed6\u4eec\u5fc5\u987b\u90fd\u8fd4\u56de\u76f8\u540c\u7684\u7c7b\u578b\uff0c\u5426\u5219\u62a5\u9519\u3002 auto f(int x) { if (x > 0) { return 1; // int } else { return 3.14; // double } } // \u9519\u8bef\uff1a\u6709\u6b67\u4e49\uff0c\u65e0\u6cd5\u786e\u5b9a auto \u5e94\u8be5\u63a8\u5bfc\u4e3a int \u8fd8\u662f double auto \u8fd8\u6709\u4e00\u4e2a\u7f3a\u70b9\u662f\uff0c\u65e0\u6cd5\u7528\u4e8e\u201c\u5206\u79bb\u58f0\u660e\u548c\u5b9a\u4e49\u201d\u7684\u60c5\u51b5\u3002\u56e0\u4e3a\u63a8\u5bfc auto \u7c7b\u578b\u9700\u8981\u77e5\u9053\u51fd\u6570\u4f53\uff0c\u624d\u80fd\u770b\u5230\u91cc\u9762\u7684 return \u8868\u8fbe\u5f0f\u662f\u4ec0\u4e48\u7c7b\u578b\u3002\u6240\u4ee5\u5f53 auto \u8fd4\u56de\u7c7b\u578b\u88ab\u7528\u4e8e\u51fd\u6570\u7684\u975e\u5b9a\u4e49\u58f0\u660e\u65f6\uff0c\u4f1a\u76f4\u63a5\u62a5\u9519\u3002 auto f(); // \u9519\u8bef\uff1a\u770b\u4e0d\u5230\u51fd\u6570\u4f53\uff0c\u65e0\u6cd5\u63a8\u5bfc\u8fd4\u56de\u7c7b\u578b auto f() { // \u7f16\u8bd1\u901a\u8fc7\uff1aauto \u63a8\u5bfc\u4e3a int return 1; // 1 \u662f int \u7c7b\u578b\u7684\u8868\u8fbe\u5f0f } \u56e0\u6b64\uff0c auto \u901a\u5e38\u53ea\u9002\u7528\u4e8e\u5934\u6587\u4ef6\u4e2d\u201c\u5c31\u5730\u5b9a\u4e49\u201d\u7684 inline \u51fd\u6570\uff0c\u4e0d\u9002\u5408\u9700\u8981\u201c\u5206\u79bb .cpp \u6587\u4ef6\u201d\u7684\u51fd\u6570\u3002 \u53c2\u6570\u7c7b\u578b auto C++20 \u5f15\u5165\u4e86 \u6a21\u677f\u53c2\u6570\u63a8\u5bfc \uff0c\u53ef\u4ee5\u8ba9\u6211\u4eec\u5728\u51fd\u6570\u53c2\u6570\u4e2d\u4e5f\u4f7f\u7528 auto \u3002 TODO: \u4ecb\u7ecd \u4f20\u7edf\u7684\uff0c\u57fa\u4e8e\u7c7b\u578b\u91cd\u8f7d\u7684\uff1a int square(int x) { return x * x; } double square(double x) { return x * x; } int main() { square(2); // 4\uff08\u8c03\u7528 int \u7248\u91cd\u8f7d\uff09 square(3.14); // 9.8596\uff08\u8c03\u7528 double \u7248\u91cd\u8f7d\uff09 // \u5982\u679c\u73b0\u5728\u53c8\u9700\u8981 float \u7248\u5462\uff1f\u53c8\u5f97\u5199\u4e00\u7248\u91cd\u8f7d\uff0c\u5185\u5bb9\u8fd8\u662f\u5b8c\u5168\u4e00\u6837\u7684\uff0c\u6d6a\u8d39\u65f6\u95f4 } \u57fa\u4e8e auto \u6a21\u677f\u53c2\u6570\u63a8\u5bfc\u7684\uff1a auto square(auto x) { return x * x; } int main() { square(2); // 4\uff08auto \u63a8\u5bfc\u4e3a int\uff09 square(3.14); // 9.8596\uff08auto \u63a8\u5bfc\u4e3a double\uff09 // \u5373\u4f7f\u672a\u6765\u4ea7\u751f\u4e86 float \u7248\u7684\u9700\u6c42\uff0c\u4e5f\u4e0d\u7528\u6dfb\u52a0\u4efb\u4f55\u4ee3\u7801\uff0c\u56e0\u4e3a\u662f square \u662f\u5f88\u65b9\u4fbf\u7684\u6a21\u677f\u51fd\u6570 } auto \u63a8\u5bfc\u4e3a\u5f15\u7528 TODO: \u7ee7\u7eed\u4ecb\u7ecd auto , auto const , auto & , auto const & , auto && , decltype(auto) , auto * , auto const *","title":"auto \u795e\u6559 (\u672a\u5b8c\u5de5)"},{"location":"auto/#auto","text":"","title":"auto \u795e\u6559 (\u672a\u5b8c\u5de5)"},{"location":"auto/#auto_1","text":"","title":"\u53d8\u91cf auto"},{"location":"auto/#auto_2","text":"C++11 \u5f15\u5165\u7684 auto \u5173\u952e\u5b57\u53ef\u4ee5\u7528\u4f5c\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\uff0c\u4f46\u5b83\u53ea\u662f\u4e00\u4e2a\u201c\u5360\u4f4d\u201d\uff0c\u8ba9\u6211\u4eec\u5f97\u4ee5\u540e\u7f6e\u8fd4\u56de\u7c7b\u578b\uff0c\u5e76\u6ca1\u6709\u591a\u5927\u4f5c\u7528\uff0c\u975e\u5e38\u6b8b\u5e9f\u3002 auto f() -> int; // \u7b49\u4ef7\u4e8e\uff1a int f(); \u95f9\u4e86\u534a\u5929\uff0c\u8fd8\u662f\u8981\u5199\u8fd4\u56de\u7c7b\u578b\uff0c\u5c31\u53ea\u662f\u632a\u5230\u540e\u9762\u53bb\u597d\u770b\u4e00\u70b9\u2026\u2026 \u5f53\u521d\u5f15\u5165\u540e\u7f6e\u8fd4\u56de\u7c7b\u578b\u5b9e\u9645\u7684\u7528\u9014\u662f auto f(int x) -> decltype(x * x) { return x * x; } \u8fd9\u79cd\u60c5\u51b5\uff0c\u4f46\u5f88\u5bb9\u6613\u88ab\u63a5\u4e0b\u6765 C++14 \u5f15\u5165\u7684\u771f\u6b63 auto \u8fd4\u56de\u7c7b\u578b\u63a8\u5bfc\u5e73\u66ff\u4e86\u3002 C++14 \u5f15\u5165\u4e86\u51fd\u6570 \u8fd4\u56de\u7c7b\u578b\u63a8\u5bfc \uff0c auto \u624d\u7b97\u771f\u6b63\u610f\u4e49\u4e0a\u80fd\u7528\u505a\u51fd\u6570\u8fd4\u56de\u7c7b\u578b\uff0c\u5b83\u4f1a\u81ea\u52a8\u6839\u636e\u51fd\u6570\u4e2d\u7684 return \u8868\u8fbe\u5f0f\u63a8\u5bfc\u51fa\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\u3002 auto f(int x) { return x * x; // \u8868\u8fbe\u5f0f `x * x` \u7684\u7c7b\u578b\u4e3a int\uff0c\u6240\u4ee5 auto \u7c7b\u578b\u63a8\u5bfc\u4e3a int } // \u7b49\u4ef7\u4e8e\uff1a int f() { return x * x; } \u5982\u679c\u51fd\u6570\u4e2d\u6ca1\u6709 return \u8bed\u53e5\uff0c\u90a3\u4e48 auto \u4f1a\u88ab\u81ea\u52a8\u63a8\u5bfc\u4e3a void \uff0c\u975e\u5e38\u65b9\u4fbf\u3002 auto f() { std::println(\"hello\"); } // \u7b49\u4ef7\u4e8e\uff1a void f() { std::println(\"hello\"); } \u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u8fd4\u56de\u7c7b\u578b\u7528 auto \u6765\u63a8\u5bfc\u7684\u51fd\u6570\uff0c\u5982\u679c\u6709\u591a\u6761 return \u8bed\u53e5\uff0c\u90a3\u4e48\u4ed6\u4eec\u5fc5\u987b\u90fd\u8fd4\u56de\u76f8\u540c\u7684\u7c7b\u578b\uff0c\u5426\u5219\u62a5\u9519\u3002 auto f(int x) { if (x > 0) { return 1; // int } else { return 3.14; // double } } // \u9519\u8bef\uff1a\u6709\u6b67\u4e49\uff0c\u65e0\u6cd5\u786e\u5b9a auto \u5e94\u8be5\u63a8\u5bfc\u4e3a int \u8fd8\u662f double auto \u8fd8\u6709\u4e00\u4e2a\u7f3a\u70b9\u662f\uff0c\u65e0\u6cd5\u7528\u4e8e\u201c\u5206\u79bb\u58f0\u660e\u548c\u5b9a\u4e49\u201d\u7684\u60c5\u51b5\u3002\u56e0\u4e3a\u63a8\u5bfc auto \u7c7b\u578b\u9700\u8981\u77e5\u9053\u51fd\u6570\u4f53\uff0c\u624d\u80fd\u770b\u5230\u91cc\u9762\u7684 return \u8868\u8fbe\u5f0f\u662f\u4ec0\u4e48\u7c7b\u578b\u3002\u6240\u4ee5\u5f53 auto \u8fd4\u56de\u7c7b\u578b\u88ab\u7528\u4e8e\u51fd\u6570\u7684\u975e\u5b9a\u4e49\u58f0\u660e\u65f6\uff0c\u4f1a\u76f4\u63a5\u62a5\u9519\u3002 auto f(); // \u9519\u8bef\uff1a\u770b\u4e0d\u5230\u51fd\u6570\u4f53\uff0c\u65e0\u6cd5\u63a8\u5bfc\u8fd4\u56de\u7c7b\u578b auto f() { // \u7f16\u8bd1\u901a\u8fc7\uff1aauto \u63a8\u5bfc\u4e3a int return 1; // 1 \u662f int \u7c7b\u578b\u7684\u8868\u8fbe\u5f0f } \u56e0\u6b64\uff0c auto \u901a\u5e38\u53ea\u9002\u7528\u4e8e\u5934\u6587\u4ef6\u4e2d\u201c\u5c31\u5730\u5b9a\u4e49\u201d\u7684 inline \u51fd\u6570\uff0c\u4e0d\u9002\u5408\u9700\u8981\u201c\u5206\u79bb .cpp \u6587\u4ef6\u201d\u7684\u51fd\u6570\u3002","title":"\u8fd4\u56de\u7c7b\u578b auto"},{"location":"auto/#auto_3","text":"C++20 \u5f15\u5165\u4e86 \u6a21\u677f\u53c2\u6570\u63a8\u5bfc \uff0c\u53ef\u4ee5\u8ba9\u6211\u4eec\u5728\u51fd\u6570\u53c2\u6570\u4e2d\u4e5f\u4f7f\u7528 auto \u3002 TODO: \u4ecb\u7ecd \u4f20\u7edf\u7684\uff0c\u57fa\u4e8e\u7c7b\u578b\u91cd\u8f7d\u7684\uff1a int square(int x) { return x * x; } double square(double x) { return x * x; } int main() { square(2); // 4\uff08\u8c03\u7528 int \u7248\u91cd\u8f7d\uff09 square(3.14); // 9.8596\uff08\u8c03\u7528 double \u7248\u91cd\u8f7d\uff09 // \u5982\u679c\u73b0\u5728\u53c8\u9700\u8981 float \u7248\u5462\uff1f\u53c8\u5f97\u5199\u4e00\u7248\u91cd\u8f7d\uff0c\u5185\u5bb9\u8fd8\u662f\u5b8c\u5168\u4e00\u6837\u7684\uff0c\u6d6a\u8d39\u65f6\u95f4 } \u57fa\u4e8e auto \u6a21\u677f\u53c2\u6570\u63a8\u5bfc\u7684\uff1a auto square(auto x) { return x * x; } int main() { square(2); // 4\uff08auto \u63a8\u5bfc\u4e3a int\uff09 square(3.14); // 9.8596\uff08auto \u63a8\u5bfc\u4e3a double\uff09 // \u5373\u4f7f\u672a\u6765\u4ea7\u751f\u4e86 float \u7248\u7684\u9700\u6c42\uff0c\u4e5f\u4e0d\u7528\u6dfb\u52a0\u4efb\u4f55\u4ee3\u7801\uff0c\u56e0\u4e3a\u662f square \u662f\u5f88\u65b9\u4fbf\u7684\u6a21\u677f\u51fd\u6570 }","title":"\u53c2\u6570\u7c7b\u578b auto"},{"location":"auto/#auto_4","text":"TODO: \u7ee7\u7eed\u4ecb\u7ecd auto , auto const , auto & , auto const & , auto && , decltype(auto) , auto * , auto const *","title":"auto \u63a8\u5bfc\u4e3a\u5f15\u7528"},{"location":"cmake_tutor/","text":"\u5b66\u73b0\u4ee3 C++ \u4ece\u73b0\u4ee3 CMake \u5b66\u8d77\uff08\u672a\u5b8c\u5de5\uff09 TODO","title":"\u5b66\u73b0\u4ee3 C++ \u4ece\u73b0\u4ee3 CMake \u5b66\u8d77\uff08\u672a\u5b8c\u5de5\uff09"},{"location":"cmake_tutor/#c-cmake","text":"TODO","title":"\u5b66\u73b0\u4ee3 C++ \u4ece\u73b0\u4ee3 CMake \u5b66\u8d77\uff08\u672a\u5b8c\u5de5\uff09"},{"location":"cpp_lifetime/","text":"\u6df1\u5165\u7406\u89e3\u6790\u6784\u51fd\u6570\u4e0e\u751f\u547d\u5468\u671f \u6df1\u5165\u7406\u89e3\u6790\u6784\u51fd\u6570\u4e0e\u751f\u547d\u5468\u671f C++ \u5bf9\u8c61\u751f\u547d\u5468\u671f \u4e09\u5927\u5b58\u50a8\u5468\u671f \u603b\u7ed3 \u6790\u6784\u51fd\u6570\u7684\u9006\u5929\u5927\u5751 \u865a\u7c7b\u7684\u6790\u6784\u51fd\u6570\u5fc5\u987b\u662f\u865a\u7684 \u4e34\u65f6\u53d8\u91cf\u7684\u751f\u547d\u5468\u671f\u662f\u4e00\u884c C++ \u5bf9\u8c61\u751f\u547d\u5468\u671f C++ \u4e2d\u4e00\u4e2a\u7c7b\u53ef\u4ee5\u5177\u6709\u6784\u9020\u51fd\u6570\u548c\u6790\u6784\u51fd\u6570\u3002 \u6784\u9020\u51fd\u6570\u56fa\u5b9a\u4e3a \u7c7b\u540d(\u6784\u9020\u51fd\u6570\u53c2\u6570\u5217\u8868) \u3002 \u6790\u6784\u51fd\u6570\u56fa\u5b9a\u4e3a ~\u7c7b\u540d() \u3002 \u6784\u9020\u51fd\u6570\u548c\u6790\u6784\u51fd\u6570\u90fd\u6ca1\u6709\u8fd4\u56de\u503c\u7c7b\u578b\u3002 \u6790\u6784\u51fd\u6570\u4e0d\u5f97\u62e5\u6709\u4efb\u4f55\u53c2\u6570\uff0c\u4f46\u6784\u9020\u51fd\u6570\u53ef\u4ee5\u6709\u3002 struct Class { Class() { puts(\"\u6784\u9020\u51fd\u6570\"); } ~Class() { puts(\"\u6790\u6784\u51fd\u6570\"); } }; int main() { puts(\"\u8fdb\u5165 main\"); Class c; puts(\"\u79bb\u5f00 main\"); } \u8fd0\u884c\u7ed3\u679c\uff1a \u8fdb\u5165 main \u6784\u9020\u51fd\u6570 \u79bb\u5f00 main \u6790\u6784\u51fd\u6570 \u8fd9\u662f C++ \u4e2d\u6700\u57fa\u672c\u7684\u73b0\u8c61\u3002\u6bcf\u5f53\u4e00\u4e2a\u5bf9\u8c61\u88ab\u521b\u5efa\u65f6\uff0c\u4f1a\u8c03\u7528\u6784\u9020\u51fd\u6570\uff0c\u6bcf\u5f53\u4e00\u4e2a\u5bf9\u8c61\u79bb\u5f00\u5b9a\u4e49\u4e86\u4ed6\u7684\u51fd\u6570\u4f53\u65f6\uff0c\u4f1a\u8c03\u7528\u6790\u6784\u51fd\u6570\u3002 \u51fd\u6570\u4f53\u6307\u7684\u662f\u4ece { \u5230 } \u4e4b\u95f4\u7684\u4ee3\u7801\u5757\u3002 \u5176\u4e2d\u6784\u9020\u51fd\u6570\u4e2d\u901a\u5e38\u8d1f\u8d23\u521b\u5efa\u8d44\u6e90\uff0c\u6790\u6784\u51fd\u6570\u4e2d\u901a\u5e38\u9500\u6bc1\u8d44\u6e90\u3002\u5bf9\u4e8e\u667a\u80fd\u6307\u9488\u548c vector \u800c\u8a00\uff0c\u8fd9\u4e2a\u8d44\u6e90\u5c31\u662f\u5185\u5b58\u3002 \u4e3a\u4ec0\u4e48\u8981\u53ca\u65f6\u9500\u6bc1\u4e0d\u7528\u7684\u8d44\u6e90\uff1f\u53ea\u5206\u914d\u4e0d\u91ca\u653e\uff0c\u4e00\u4e2a\u7a0b\u5e8f\u5360\u7528\u7684\u5185\u5b58\u548c\u5176\u4ed6\u5404\u79cd\u8d44\u6e90\u5c31\u4f1a\u8d8a\u6765\u8d8a\u591a\uff0c\u8fd9\u79cd\u7a0b\u5e8f\u5982\u679c\u957f\u671f\u8fd0\u884c\uff0c\u4f1a\u5403\u5149\u6574\u4e2a\u7cfb\u7edf\u7684\u6240\u6709\u8d44\u6e90\u7136\u540e\u88ab Linux \u5185\u6838\u89c6\u4e3a\u5371\u9669\u8fdb\u7a0b\u800c\u6740\u6b7b\u3002\u9664\u975e\u4f60\u7684\u7a0b\u5e8f\u53ea\u4f1a\u8fd0\u884c\u4e00\u4f1a\u4f1a\uff0c\u5982\u679c\u662f\u957f\u671f\u8fd0\u884c\u7684\u7a0b\u5e8f\uff0c\u4f8b\u5982\u670d\u52a1\u5668\uff0c\u5fc5\u987b\u4e25\u683c\u7ba1\u7406\u6240\u6709\u81ea\u5df1\u66fe\u7ecf\u5206\u914d\u8fc7\u7684\u5185\u5b58\uff0c\u4e0d\u7528\u65f6\u5c31\u7acb\u5373\u91ca\u653e\uff0c\u4e0d\u8981\u5360\u7740\u8305\u5751\u4e0d\u62c9\u53f2\u3002 } \u88ab\u8a89\u4e3a \u6700\u4f1f\u5927\u7684\u8fd0\u7b97\u7b26 \uff0c\u5c31\u662f\u56e0\u4e3a\u4ed6\u53ef\u4ee5\u89e6\u53d1\u6790\u6784\u51fd\u6570\uff0c\u5e2e\u4f60\u81ea\u52a8\u91ca\u653e\u6389\u8d44\u6e90\uff0c\u4f60\u5c31\u4e0d\u7528\u81ea\u5df1\u8d39\u5fc3\u624b\u52a8\u91ca\u653e\u5185\u5b58\uff0c\u548c\u5176\u4ed6\u5404\u79cd\u8d44\u6e90\u4e86\u3002 \u4e09\u5927\u5b58\u50a8\u5468\u671f \u5728\u8fdb\u4e00\u6b65\u6df1\u5165\u4e4b\u524d\uff0c\u6211\u4eec\u5fc5\u987b\u660e\u786e\u4ee5\u4e0b\u672f\u8bed\uff1a\u81ea\u52a8\u5b58\u50a8\u5468\u671f\u3001\u52a8\u6001\u5b58\u50a8\u5468\u671f\u3001\u9759\u6001\u5b58\u50a8\u5468\u671f\u3002 \u53d8\u91cf\u5b9a\u4e49\u5728\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u5176\u751f\u547d\u5468\u671f\uff08\u6784\u9020\u51fd\u6570\u548c\u6790\u6784\u51fd\u6570\u8c03\u7528\u7684\u65f6\u673a\uff09\u4f1a\u6709\u6240\u4e0d\u540c\u3002 \u6bd4\u5982\u4e00\u4e2a\u53d8\u91cf\u5b9a\u4e49\u5728\u51fd\u6570\u4f53\u5185\u3001\u7c7b\u4f53\u5185\u3001\u901a\u8fc7 new \u521b\u5efa\uff0c\u4e4b\u7c7b\u7684\u3002 \u81ea\u52a8\u5b58\u50a8\u5468\u671f\uff0c\u8fd9\u79cd\u53d8\u91cf\u76f4\u63a5\u5b9a\u4e49\u5728 \u51fd\u6570\u4f53 \u5185\u3002\u4fd7\u79f0\u201c\u6808\u4e0a\u201d\u6216\u201c\u5c40\u90e8\u53d8\u91cf\u201d void func() { Class a; // a \u662f\u81ea\u52a8\u5b58\u50a8\u5468\u671f } \u6784\u9020\u65f6\u673a\uff1a\u5f53\u53d8\u91cf\u5b9a\u4e49\u65f6\u88ab\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53\u53d8\u91cf\u6240\u5728\u7684 {} \u4ee3\u7801\u5757\u6267\u884c\u5230 } \u5904\u65f6\u8c03\u7528\u3002 \u52a8\u6001\u5b58\u50a8\u5468\u671f\uff0c\u8fd9\u79cd\u53d8\u91cf\u901a\u8fc7 new \u6765\u521b\u5efa\u3002\u4fd7\u79f0\u201c\u5806\u4e0a\u201d\u6216\u201c\u5806\u5bf9\u8c61\u201d void func() { Class *p = new Class; // *p \u662f\u52a8\u6001\u5b58\u50a8\u5468\u671f delete p; // \u91ca\u653e\u52a8\u6001\u5206\u914d\u7684\u5185\u5b58 } \u6784\u9020\u65f6\u673a\uff1a\u5f53\u53d8\u91cf\u901a\u8fc7 new \u521b\u5efa\u65f6\u88ab\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53 delete \u88ab\u8c03\u7528\u65f6\u88ab\u8c03\u7528\u3002 \u7279\u522b\u6ce8\u610f\uff0c p \u4f9d\u7136\u662f\u201c\u6808\u4e0a\u53d8\u91cf\u201d\uff0c p \u6307\u5411\u7684 *p \u624d\u662f\u201c\u5806\u4e0a\u53d8\u91cf\u201d\uff01 \u7528\u5f8b\u5e08\u8bed\u518d\u8bf4\u4e00\u904d\uff1a p \u662f\u81ea\u52a8\u5b58\u50a8\u5468\u671f\uff0c p \u6307\u5411\u7684 *p \u624d\u662f\u52a8\u6001\u5b58\u50a8\u5468\u671f\uff01\uff08\u767d\u5f8b\u5e08\u6700\u6ee1\u610f\u7684\u4e00\u96c6\uff09 \u6307\u9488\u672c\u8eab\uff0c\u548c\u6307\u9488\u6307\u5411\u7684\u5bf9\u8c61\uff0c\u662f\u4e24\u4e2a\u4e1c\u897f\uff0c\u4e0d\u8981\u6df7\u6dc6\u3002 p \u672c\u8eab\u4f1a\u968f\u7740 func \u7684 } \u800c\u6790\u6784\uff0c\u4f46\u662f *p \u7684\u7c7b\u578b\u662f Class * \uff0c\u662f\u4e00\u4e2a C \u8bed\u8a00\u539f\u59cb\u6307\u9488\uff0c\u539f\u59cb\u6307\u9488\u5c5e\u4e8e C \u8bed\u8a00\u539f\u59cb\u7c7b\u578b\uff0c\u6ca1\u6709\u6790\u6784\u51fd\u6570\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u62b5\u8fbe } \u65f6\uff0c p \u540d\u4e49\u4e0a\u4f1a\u6790\u6784\uff0c\u4f46\u662f\u4ed6\u6ca1\u6709\u6790\u6784\u51fd\u6570\uff0c\u5e76\u4e0d\u4f1a\u4ea7\u751f\u4efb\u4f55\u4f5c\u7528\u3002\u8fd9\u4e00\u5207\u548c p \u6307\u5411\u7684\u5bf9\u8c61 *p \u6ca1\u6709\u4efb\u4f55\u5173\u7cfb\uff0c\u4f60\u9700\u8981\u624b\u52a8 delete \u624d\u4f1a\u8c03\u7528\u5230 *p \u7684\u6790\u6784\u51fd\u6570\uff0c\u5e76\u91ca\u653e\u5206\u914d\u7684\u5185\u5b58\u3002 new \u5206\u4e3a\u4e24\u90e8\u5206\uff1a\u5185\u5b58\u5206\u914d + \u5bf9\u8c61\u6784\u9020 delete \u5206\u4e3a\u4e24\u90e8\u5206\uff1a \u5bf9\u8c61\u6790\u6784 + \u5185\u5b58\u91ca\u653e \u667a\u80fd\u6307\u9488\u7684\u4f18\u52bf\u5728\u4e8e\uff0c\u667a\u80fd\u6307\u9488\u662f\u4e2a C++ \u7c7b\uff0c\u5177\u6709\u5b9a\u5236\u7684\u6790\u6784\u51fd\u6570\u3002\u5f53 } \u62b5\u8fbe\uff0c \u667a\u80fd\u6307\u9488\u672c\u8eab \u7531\u4e8e\u81ea\u52a8\u5b58\u50a8\u5468\u671f\u7684\u89c4\u5219\u6790\u6784\u65f6\uff0c\u5176\u4f1a delete p \uff0c\u5229\u7528\u52a8\u6001\u5b58\u50a8\u5468\u671f\u7684\u89c4\u5219\uff0c\u89e6\u53d1 \u667a\u80fd\u6307\u9488\u6307\u5411\u5bf9\u8c61 \u7684\u6790\u6784\u51fd\u6570\uff0c\u4e5f\u5c31\u662f\u4ece\u800c\u8c03\u7528 *p \u7684\u6790\u6784\u51fd\u6570\u3002 \u9759\u6001\u5b58\u50a8\u5468\u671f\uff0c\u8fd9\u79cd\u53d8\u91cf\u53c8\u8981\u5177\u4f53\u5206\u4e09\u79cd\u60c5\u51b5\uff0c\u4fd7\u79f0\u201c\u5168\u5c40\u53d8\u91cf\u201d\u6216\u201c\u9759\u6001\u53d8\u91cf\u201d (1) \u5b9a\u4e49\u5728 \u540d\u5b57\u7a7a\u95f4 \u5185\uff0c\u4e0d\u8bba\u662f\u4e0d\u662f static \u6216 inline\uff08\u5728\u540d\u5b57\u7a7a\u95f4\u4e2d\uff0cstatic \u548c inline \u5f71\u54cd\u7684\u53ea\u662f\u201c\u7b26\u53f7\u53ef\u89c1\u6027\u201d\uff0c\u800c\u4e0d\u662f\u5b58\u50a8\u5468\u671f\uff09 namespace hello { Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f static Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f inline Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f } \u6784\u9020\u65f6\u673a\uff1a\u5f53\u7a0b\u5e8f\u542f\u52a8\u65f6\u8c03\u7528\uff08main \u51fd\u6570\u4e4b\u524d\uff09\uff1b\u5bf9 DLL \u6765\u8bf4\u5219\u662f DLL \u9996\u6b21\u52a0\u8f7d\u65f6\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53\u7a0b\u5e8f\u9000\u51fa\u65f6\u8c03\u7528\uff08main \u51fd\u6570\u4e4b\u540e\uff09\u3002 (2) \u6ce8\u610f\uff0c \u5168\u5c40\u540d\u5b57\u7a7a\u95f4 \u662f\u4e00\u4e2a\u7279\u6b8a\u7684 \u540d\u5b57\u7a7a\u95f4 \uff0c\u5916\u9762\u6ca1\u6709\u5305\u88f9\u4efb\u4f55 namespace \u65f6\u5c31\u5c5e\u4e8e\u8fd9\u79cd\u60c5\u51b5\uff0c\u4fd7\u79f0\u201c\u5168\u5c40\u53d8\u91cf\u201d\u3002\u6240\u4ee5\u4e0b\u9762\u8fd9\u79cd\u4e5f\u5c5e\u4e8e\u201c\u5728 (\u5168\u5c40) \u540d\u5b57\u7a7a\u95f4\u5185\u201d\uff1a Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f static Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f inline Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f (3) \u5b9a\u4e49\u5728\u7c7b\u5185\u7684\u9759\u6001\u6210\u5458\u53d8\u91cf\uff0c\u4e5f\u5c31\u662f\u901a\u8fc7 static \u4fee\u9970\u8fc7\u7684\u6210\u5458\u53d8\u91cf\uff08\u5728\u7c7b\u5185\uff0cstatic \u5c31\u5f71\u54cd\u5b58\u50a8\u5468\u671f\u4e86\uff0cinline \u7ee7\u7eed\u53ea\u5f71\u54cd\u201c\u7b26\u53f7\u53ef\u89c1\u6027\u201d\uff09 struct Other { static Class s; }; Class Other::s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f struct Other { inline static Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f }; struct Other { Class a; // a \u4e0d\u662f\u9759\u6001\u5b58\u50a8\u5468\u671f\uff0c\u800c\u662f\u8ddf\u968f\u5176\u6240\u5c5e\u7684 Other \u7ed3\u6784\u4f53\u7684\u5b58\u50a8\u5468\u671f }; \u5b9a\u4e49\u5728\u7c7b\u5185\u7684\u6210\u5458\u53d8\u91cf\uff08\u6ca1\u6709 static \u7684\uff09\uff0c\u8ddf\u968f\u6240\u5c5e\u7c7b\u7684\u5b58\u50a8\u5468\u671f struct Other { Class a; // a \u8ddf\u968f Other \u7ed3\u6784\u4f53\u7684\u5b58\u50a8\u5468\u671f }; Other o; // o.a \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f int main() { Other o; // o.a \u662f\u81ea\u52a8\u5b58\u50a8\u5468\u671f Other *p; // p->a \u662f\u52a8\u6001\u5b58\u50a8\u5468\u671f } \u6784\u9020\u65f6\u673a\uff1a\u5f53 Other \u7ed3\u6784\u4f53\u6784\u9020\u65f6\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53 Other \u7ed3\u6784\u4f53\u6790\u6784\u65f6\u8c03\u7528\u3002 \u603b\u7ed3 \u81ea\u52a8\u5b58\u50a8\u5468\u671f - \u51fd\u6570\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u81ea\u52a8\u6790\u6784 \u52a8\u6001\u5b58\u50a8\u5468\u671f - \u901a\u8fc7 new \u521b\u5efa\u7684\uff0cdelete \u65f6\u6790\u6784 \u9759\u6001\u5b58\u50a8\u5468\u671f - \u5168\u5c40\u53d8\u91cf\uff0c\u7a0b\u5e8f\u7ed3\u675f\u65f6\u6790\u6784 \u6790\u6784\u51fd\u6570\u7684\u9006\u5929\u5927\u5751 \u5b9a\u4e49\u4e86\u6790\u6784\u51fd\u6570\uff0c\u5c31 \u5fc5\u987b\u5220\u9664\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3001\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\u3001\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3001\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570 \uff01 \u539f\u56e0\u5f88\u590d\u6742\uff0c\u6574\u4e2a\u6545\u4e8b\u8981\u4ece boost \u5f53\u5e74\u5982\u4f55\u8bbe\u8ba1\u51fa\u53f3\u503c\u5f15\u7528\u5230\u56fe\u7075\u7684\u505c\u673a\u95ee\u9898\u8bb2\u8d77\uff0c\u8bb2\u4e86\u4f60\u4e5f\u8bb0\u4e0d\u4f4f\uff0c\u53ea\u9700\u8981\u8bb0\u4f4f\u7ed3\u8bba\uff1a \u5982\u679c\u4f60\u8981\u5b9a\u4e49\u6790\u6784\u51fd\u6570\uff0c\u5c31 \u5fc5\u987b\u5220\u9664\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3001\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\u3001\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3001\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570 \uff01 \u865a\u7c7b\u7684\u6790\u6784\u51fd\u6570\u5fc5\u987b\u662f\u865a\u7684 -Wnon-virtual-dtor -Wdelete-non-virtual-dtor TODO: \u4ecb\u7ecd \u4e34\u65f6\u53d8\u91cf\u7684\u751f\u547d\u5468\u671f\u662f\u4e00\u884c TODO int main() { std::string const &s = std::string(\"hello\"); std::cout << s; // OK } std::string const &identity(std::string const &s) { return s; } int main() { std::string const &s = identity(std::string(\"hello\")); std::cout << s; // BOOM! }","title":"\u6df1\u5165\u7406\u89e3\u6790\u6784\u51fd\u6570\u4e0e\u751f\u547d\u5468\u671f"},{"location":"cpp_lifetime/#_1","text":"\u6df1\u5165\u7406\u89e3\u6790\u6784\u51fd\u6570\u4e0e\u751f\u547d\u5468\u671f C++ \u5bf9\u8c61\u751f\u547d\u5468\u671f \u4e09\u5927\u5b58\u50a8\u5468\u671f \u603b\u7ed3 \u6790\u6784\u51fd\u6570\u7684\u9006\u5929\u5927\u5751 \u865a\u7c7b\u7684\u6790\u6784\u51fd\u6570\u5fc5\u987b\u662f\u865a\u7684 \u4e34\u65f6\u53d8\u91cf\u7684\u751f\u547d\u5468\u671f\u662f\u4e00\u884c","title":"\u6df1\u5165\u7406\u89e3\u6790\u6784\u51fd\u6570\u4e0e\u751f\u547d\u5468\u671f"},{"location":"cpp_lifetime/#c","text":"C++ \u4e2d\u4e00\u4e2a\u7c7b\u53ef\u4ee5\u5177\u6709\u6784\u9020\u51fd\u6570\u548c\u6790\u6784\u51fd\u6570\u3002 \u6784\u9020\u51fd\u6570\u56fa\u5b9a\u4e3a \u7c7b\u540d(\u6784\u9020\u51fd\u6570\u53c2\u6570\u5217\u8868) \u3002 \u6790\u6784\u51fd\u6570\u56fa\u5b9a\u4e3a ~\u7c7b\u540d() \u3002 \u6784\u9020\u51fd\u6570\u548c\u6790\u6784\u51fd\u6570\u90fd\u6ca1\u6709\u8fd4\u56de\u503c\u7c7b\u578b\u3002 \u6790\u6784\u51fd\u6570\u4e0d\u5f97\u62e5\u6709\u4efb\u4f55\u53c2\u6570\uff0c\u4f46\u6784\u9020\u51fd\u6570\u53ef\u4ee5\u6709\u3002 struct Class { Class() { puts(\"\u6784\u9020\u51fd\u6570\"); } ~Class() { puts(\"\u6790\u6784\u51fd\u6570\"); } }; int main() { puts(\"\u8fdb\u5165 main\"); Class c; puts(\"\u79bb\u5f00 main\"); } \u8fd0\u884c\u7ed3\u679c\uff1a \u8fdb\u5165 main \u6784\u9020\u51fd\u6570 \u79bb\u5f00 main \u6790\u6784\u51fd\u6570 \u8fd9\u662f C++ \u4e2d\u6700\u57fa\u672c\u7684\u73b0\u8c61\u3002\u6bcf\u5f53\u4e00\u4e2a\u5bf9\u8c61\u88ab\u521b\u5efa\u65f6\uff0c\u4f1a\u8c03\u7528\u6784\u9020\u51fd\u6570\uff0c\u6bcf\u5f53\u4e00\u4e2a\u5bf9\u8c61\u79bb\u5f00\u5b9a\u4e49\u4e86\u4ed6\u7684\u51fd\u6570\u4f53\u65f6\uff0c\u4f1a\u8c03\u7528\u6790\u6784\u51fd\u6570\u3002 \u51fd\u6570\u4f53\u6307\u7684\u662f\u4ece { \u5230 } \u4e4b\u95f4\u7684\u4ee3\u7801\u5757\u3002 \u5176\u4e2d\u6784\u9020\u51fd\u6570\u4e2d\u901a\u5e38\u8d1f\u8d23\u521b\u5efa\u8d44\u6e90\uff0c\u6790\u6784\u51fd\u6570\u4e2d\u901a\u5e38\u9500\u6bc1\u8d44\u6e90\u3002\u5bf9\u4e8e\u667a\u80fd\u6307\u9488\u548c vector \u800c\u8a00\uff0c\u8fd9\u4e2a\u8d44\u6e90\u5c31\u662f\u5185\u5b58\u3002 \u4e3a\u4ec0\u4e48\u8981\u53ca\u65f6\u9500\u6bc1\u4e0d\u7528\u7684\u8d44\u6e90\uff1f\u53ea\u5206\u914d\u4e0d\u91ca\u653e\uff0c\u4e00\u4e2a\u7a0b\u5e8f\u5360\u7528\u7684\u5185\u5b58\u548c\u5176\u4ed6\u5404\u79cd\u8d44\u6e90\u5c31\u4f1a\u8d8a\u6765\u8d8a\u591a\uff0c\u8fd9\u79cd\u7a0b\u5e8f\u5982\u679c\u957f\u671f\u8fd0\u884c\uff0c\u4f1a\u5403\u5149\u6574\u4e2a\u7cfb\u7edf\u7684\u6240\u6709\u8d44\u6e90\u7136\u540e\u88ab Linux \u5185\u6838\u89c6\u4e3a\u5371\u9669\u8fdb\u7a0b\u800c\u6740\u6b7b\u3002\u9664\u975e\u4f60\u7684\u7a0b\u5e8f\u53ea\u4f1a\u8fd0\u884c\u4e00\u4f1a\u4f1a\uff0c\u5982\u679c\u662f\u957f\u671f\u8fd0\u884c\u7684\u7a0b\u5e8f\uff0c\u4f8b\u5982\u670d\u52a1\u5668\uff0c\u5fc5\u987b\u4e25\u683c\u7ba1\u7406\u6240\u6709\u81ea\u5df1\u66fe\u7ecf\u5206\u914d\u8fc7\u7684\u5185\u5b58\uff0c\u4e0d\u7528\u65f6\u5c31\u7acb\u5373\u91ca\u653e\uff0c\u4e0d\u8981\u5360\u7740\u8305\u5751\u4e0d\u62c9\u53f2\u3002 } \u88ab\u8a89\u4e3a \u6700\u4f1f\u5927\u7684\u8fd0\u7b97\u7b26 \uff0c\u5c31\u662f\u56e0\u4e3a\u4ed6\u53ef\u4ee5\u89e6\u53d1\u6790\u6784\u51fd\u6570\uff0c\u5e2e\u4f60\u81ea\u52a8\u91ca\u653e\u6389\u8d44\u6e90\uff0c\u4f60\u5c31\u4e0d\u7528\u81ea\u5df1\u8d39\u5fc3\u624b\u52a8\u91ca\u653e\u5185\u5b58\uff0c\u548c\u5176\u4ed6\u5404\u79cd\u8d44\u6e90\u4e86\u3002","title":"C++ \u5bf9\u8c61\u751f\u547d\u5468\u671f"},{"location":"cpp_lifetime/#_2","text":"\u5728\u8fdb\u4e00\u6b65\u6df1\u5165\u4e4b\u524d\uff0c\u6211\u4eec\u5fc5\u987b\u660e\u786e\u4ee5\u4e0b\u672f\u8bed\uff1a\u81ea\u52a8\u5b58\u50a8\u5468\u671f\u3001\u52a8\u6001\u5b58\u50a8\u5468\u671f\u3001\u9759\u6001\u5b58\u50a8\u5468\u671f\u3002 \u53d8\u91cf\u5b9a\u4e49\u5728\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u5176\u751f\u547d\u5468\u671f\uff08\u6784\u9020\u51fd\u6570\u548c\u6790\u6784\u51fd\u6570\u8c03\u7528\u7684\u65f6\u673a\uff09\u4f1a\u6709\u6240\u4e0d\u540c\u3002 \u6bd4\u5982\u4e00\u4e2a\u53d8\u91cf\u5b9a\u4e49\u5728\u51fd\u6570\u4f53\u5185\u3001\u7c7b\u4f53\u5185\u3001\u901a\u8fc7 new \u521b\u5efa\uff0c\u4e4b\u7c7b\u7684\u3002 \u81ea\u52a8\u5b58\u50a8\u5468\u671f\uff0c\u8fd9\u79cd\u53d8\u91cf\u76f4\u63a5\u5b9a\u4e49\u5728 \u51fd\u6570\u4f53 \u5185\u3002\u4fd7\u79f0\u201c\u6808\u4e0a\u201d\u6216\u201c\u5c40\u90e8\u53d8\u91cf\u201d void func() { Class a; // a \u662f\u81ea\u52a8\u5b58\u50a8\u5468\u671f } \u6784\u9020\u65f6\u673a\uff1a\u5f53\u53d8\u91cf\u5b9a\u4e49\u65f6\u88ab\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53\u53d8\u91cf\u6240\u5728\u7684 {} \u4ee3\u7801\u5757\u6267\u884c\u5230 } \u5904\u65f6\u8c03\u7528\u3002 \u52a8\u6001\u5b58\u50a8\u5468\u671f\uff0c\u8fd9\u79cd\u53d8\u91cf\u901a\u8fc7 new \u6765\u521b\u5efa\u3002\u4fd7\u79f0\u201c\u5806\u4e0a\u201d\u6216\u201c\u5806\u5bf9\u8c61\u201d void func() { Class *p = new Class; // *p \u662f\u52a8\u6001\u5b58\u50a8\u5468\u671f delete p; // \u91ca\u653e\u52a8\u6001\u5206\u914d\u7684\u5185\u5b58 } \u6784\u9020\u65f6\u673a\uff1a\u5f53\u53d8\u91cf\u901a\u8fc7 new \u521b\u5efa\u65f6\u88ab\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53 delete \u88ab\u8c03\u7528\u65f6\u88ab\u8c03\u7528\u3002 \u7279\u522b\u6ce8\u610f\uff0c p \u4f9d\u7136\u662f\u201c\u6808\u4e0a\u53d8\u91cf\u201d\uff0c p \u6307\u5411\u7684 *p \u624d\u662f\u201c\u5806\u4e0a\u53d8\u91cf\u201d\uff01 \u7528\u5f8b\u5e08\u8bed\u518d\u8bf4\u4e00\u904d\uff1a p \u662f\u81ea\u52a8\u5b58\u50a8\u5468\u671f\uff0c p \u6307\u5411\u7684 *p \u624d\u662f\u52a8\u6001\u5b58\u50a8\u5468\u671f\uff01\uff08\u767d\u5f8b\u5e08\u6700\u6ee1\u610f\u7684\u4e00\u96c6\uff09 \u6307\u9488\u672c\u8eab\uff0c\u548c\u6307\u9488\u6307\u5411\u7684\u5bf9\u8c61\uff0c\u662f\u4e24\u4e2a\u4e1c\u897f\uff0c\u4e0d\u8981\u6df7\u6dc6\u3002 p \u672c\u8eab\u4f1a\u968f\u7740 func \u7684 } \u800c\u6790\u6784\uff0c\u4f46\u662f *p \u7684\u7c7b\u578b\u662f Class * \uff0c\u662f\u4e00\u4e2a C \u8bed\u8a00\u539f\u59cb\u6307\u9488\uff0c\u539f\u59cb\u6307\u9488\u5c5e\u4e8e C \u8bed\u8a00\u539f\u59cb\u7c7b\u578b\uff0c\u6ca1\u6709\u6790\u6784\u51fd\u6570\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u62b5\u8fbe } \u65f6\uff0c p \u540d\u4e49\u4e0a\u4f1a\u6790\u6784\uff0c\u4f46\u662f\u4ed6\u6ca1\u6709\u6790\u6784\u51fd\u6570\uff0c\u5e76\u4e0d\u4f1a\u4ea7\u751f\u4efb\u4f55\u4f5c\u7528\u3002\u8fd9\u4e00\u5207\u548c p \u6307\u5411\u7684\u5bf9\u8c61 *p \u6ca1\u6709\u4efb\u4f55\u5173\u7cfb\uff0c\u4f60\u9700\u8981\u624b\u52a8 delete \u624d\u4f1a\u8c03\u7528\u5230 *p \u7684\u6790\u6784\u51fd\u6570\uff0c\u5e76\u91ca\u653e\u5206\u914d\u7684\u5185\u5b58\u3002 new \u5206\u4e3a\u4e24\u90e8\u5206\uff1a\u5185\u5b58\u5206\u914d + \u5bf9\u8c61\u6784\u9020 delete \u5206\u4e3a\u4e24\u90e8\u5206\uff1a \u5bf9\u8c61\u6790\u6784 + \u5185\u5b58\u91ca\u653e \u667a\u80fd\u6307\u9488\u7684\u4f18\u52bf\u5728\u4e8e\uff0c\u667a\u80fd\u6307\u9488\u662f\u4e2a C++ \u7c7b\uff0c\u5177\u6709\u5b9a\u5236\u7684\u6790\u6784\u51fd\u6570\u3002\u5f53 } \u62b5\u8fbe\uff0c \u667a\u80fd\u6307\u9488\u672c\u8eab \u7531\u4e8e\u81ea\u52a8\u5b58\u50a8\u5468\u671f\u7684\u89c4\u5219\u6790\u6784\u65f6\uff0c\u5176\u4f1a delete p \uff0c\u5229\u7528\u52a8\u6001\u5b58\u50a8\u5468\u671f\u7684\u89c4\u5219\uff0c\u89e6\u53d1 \u667a\u80fd\u6307\u9488\u6307\u5411\u5bf9\u8c61 \u7684\u6790\u6784\u51fd\u6570\uff0c\u4e5f\u5c31\u662f\u4ece\u800c\u8c03\u7528 *p \u7684\u6790\u6784\u51fd\u6570\u3002 \u9759\u6001\u5b58\u50a8\u5468\u671f\uff0c\u8fd9\u79cd\u53d8\u91cf\u53c8\u8981\u5177\u4f53\u5206\u4e09\u79cd\u60c5\u51b5\uff0c\u4fd7\u79f0\u201c\u5168\u5c40\u53d8\u91cf\u201d\u6216\u201c\u9759\u6001\u53d8\u91cf\u201d (1) \u5b9a\u4e49\u5728 \u540d\u5b57\u7a7a\u95f4 \u5185\uff0c\u4e0d\u8bba\u662f\u4e0d\u662f static \u6216 inline\uff08\u5728\u540d\u5b57\u7a7a\u95f4\u4e2d\uff0cstatic \u548c inline \u5f71\u54cd\u7684\u53ea\u662f\u201c\u7b26\u53f7\u53ef\u89c1\u6027\u201d\uff0c\u800c\u4e0d\u662f\u5b58\u50a8\u5468\u671f\uff09 namespace hello { Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f static Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f inline Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f } \u6784\u9020\u65f6\u673a\uff1a\u5f53\u7a0b\u5e8f\u542f\u52a8\u65f6\u8c03\u7528\uff08main \u51fd\u6570\u4e4b\u524d\uff09\uff1b\u5bf9 DLL \u6765\u8bf4\u5219\u662f DLL \u9996\u6b21\u52a0\u8f7d\u65f6\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53\u7a0b\u5e8f\u9000\u51fa\u65f6\u8c03\u7528\uff08main \u51fd\u6570\u4e4b\u540e\uff09\u3002 (2) \u6ce8\u610f\uff0c \u5168\u5c40\u540d\u5b57\u7a7a\u95f4 \u662f\u4e00\u4e2a\u7279\u6b8a\u7684 \u540d\u5b57\u7a7a\u95f4 \uff0c\u5916\u9762\u6ca1\u6709\u5305\u88f9\u4efb\u4f55 namespace \u65f6\u5c31\u5c5e\u4e8e\u8fd9\u79cd\u60c5\u51b5\uff0c\u4fd7\u79f0\u201c\u5168\u5c40\u53d8\u91cf\u201d\u3002\u6240\u4ee5\u4e0b\u9762\u8fd9\u79cd\u4e5f\u5c5e\u4e8e\u201c\u5728 (\u5168\u5c40) \u540d\u5b57\u7a7a\u95f4\u5185\u201d\uff1a Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f static Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f inline Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f (3) \u5b9a\u4e49\u5728\u7c7b\u5185\u7684\u9759\u6001\u6210\u5458\u53d8\u91cf\uff0c\u4e5f\u5c31\u662f\u901a\u8fc7 static \u4fee\u9970\u8fc7\u7684\u6210\u5458\u53d8\u91cf\uff08\u5728\u7c7b\u5185\uff0cstatic \u5c31\u5f71\u54cd\u5b58\u50a8\u5468\u671f\u4e86\uff0cinline \u7ee7\u7eed\u53ea\u5f71\u54cd\u201c\u7b26\u53f7\u53ef\u89c1\u6027\u201d\uff09 struct Other { static Class s; }; Class Other::s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f struct Other { inline static Class s; // s \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f }; struct Other { Class a; // a \u4e0d\u662f\u9759\u6001\u5b58\u50a8\u5468\u671f\uff0c\u800c\u662f\u8ddf\u968f\u5176\u6240\u5c5e\u7684 Other \u7ed3\u6784\u4f53\u7684\u5b58\u50a8\u5468\u671f }; \u5b9a\u4e49\u5728\u7c7b\u5185\u7684\u6210\u5458\u53d8\u91cf\uff08\u6ca1\u6709 static \u7684\uff09\uff0c\u8ddf\u968f\u6240\u5c5e\u7c7b\u7684\u5b58\u50a8\u5468\u671f struct Other { Class a; // a \u8ddf\u968f Other \u7ed3\u6784\u4f53\u7684\u5b58\u50a8\u5468\u671f }; Other o; // o.a \u662f\u9759\u6001\u5b58\u50a8\u5468\u671f int main() { Other o; // o.a \u662f\u81ea\u52a8\u5b58\u50a8\u5468\u671f Other *p; // p->a \u662f\u52a8\u6001\u5b58\u50a8\u5468\u671f } \u6784\u9020\u65f6\u673a\uff1a\u5f53 Other \u7ed3\u6784\u4f53\u6784\u9020\u65f6\u8c03\u7528\u3002 \u6790\u6784\u65f6\u673a\uff1a\u5f53 Other \u7ed3\u6784\u4f53\u6790\u6784\u65f6\u8c03\u7528\u3002","title":"\u4e09\u5927\u5b58\u50a8\u5468\u671f"},{"location":"cpp_lifetime/#_3","text":"\u81ea\u52a8\u5b58\u50a8\u5468\u671f - \u51fd\u6570\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u81ea\u52a8\u6790\u6784 \u52a8\u6001\u5b58\u50a8\u5468\u671f - \u901a\u8fc7 new \u521b\u5efa\u7684\uff0cdelete \u65f6\u6790\u6784 \u9759\u6001\u5b58\u50a8\u5468\u671f - \u5168\u5c40\u53d8\u91cf\uff0c\u7a0b\u5e8f\u7ed3\u675f\u65f6\u6790\u6784","title":"\u603b\u7ed3"},{"location":"cpp_lifetime/#_4","text":"\u5b9a\u4e49\u4e86\u6790\u6784\u51fd\u6570\uff0c\u5c31 \u5fc5\u987b\u5220\u9664\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3001\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\u3001\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3001\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570 \uff01 \u539f\u56e0\u5f88\u590d\u6742\uff0c\u6574\u4e2a\u6545\u4e8b\u8981\u4ece boost \u5f53\u5e74\u5982\u4f55\u8bbe\u8ba1\u51fa\u53f3\u503c\u5f15\u7528\u5230\u56fe\u7075\u7684\u505c\u673a\u95ee\u9898\u8bb2\u8d77\uff0c\u8bb2\u4e86\u4f60\u4e5f\u8bb0\u4e0d\u4f4f\uff0c\u53ea\u9700\u8981\u8bb0\u4f4f\u7ed3\u8bba\uff1a \u5982\u679c\u4f60\u8981\u5b9a\u4e49\u6790\u6784\u51fd\u6570\uff0c\u5c31 \u5fc5\u987b\u5220\u9664\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3001\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\u3001\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3001\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570 \uff01","title":"\u6790\u6784\u51fd\u6570\u7684\u9006\u5929\u5927\u5751"},{"location":"cpp_lifetime/#_5","text":"-Wnon-virtual-dtor -Wdelete-non-virtual-dtor TODO: \u4ecb\u7ecd","title":"\u865a\u7c7b\u7684\u6790\u6784\u51fd\u6570\u5fc5\u987b\u662f\u865a\u7684"},{"location":"cpp_lifetime/#_6","text":"TODO int main() { std::string const &s = std::string(\"hello\"); std::cout << s; // OK } std::string const &identity(std::string const &s) { return s; } int main() { std::string const &s = identity(std::string(\"hello\")); std::cout << s; // BOOM! }","title":"\u4e34\u65f6\u53d8\u91cf\u7684\u751f\u547d\u5468\u671f\u662f\u4e00\u884c"},{"location":"cpp_memory/","text":"\u771f\u6b63\u7684 C++ \u5185\u5b58\u6a21\u578b\uff01 (\u672a\u5b8c\u5de5) void modify(int *pa) { int *pb = pa + 1; *pb = 9; } int func() { int a = 4; int b = 5; modify(&a); return b; // 5 \u8fd8\u662f 9\uff1f }","title":"\u771f\u6b63\u7684 C++ \u5185\u5b58\u6a21\u578b\uff01 (\u672a\u5b8c\u5de5)"},{"location":"cpp_memory/#c","text":"void modify(int *pa) { int *pb = pa + 1; *pb = 9; } int func() { int a = 4; int b = 5; modify(&a); return b; // 5 \u8fd8\u662f 9\uff1f }","title":"\u771f\u6b63\u7684 C++ \u5185\u5b58\u6a21\u578b\uff01 (\u672a\u5b8c\u5de5)"},{"location":"cpp_tricks/","text":"\u5e94\u77e5\u5e94\u4f1a C++ \u5c0f\u6280\u5de7 \u5e94\u77e5\u5e94\u4f1a C++ \u5c0f\u6280\u5de7 \u4ea4\u6362\u4e24\u4e2a\u53d8\u91cf \u5b89\u5168\u5730\u5206\u914d\u4e00\u6bb5\u5185\u5b58\u7a7a\u95f4 \u5730\u677f\u9664\u4e0e\u5929\u82b1\u677f\u9664 \u522b\u518d [] \u5566\uff01 \u522b\u518d\u5199\u6784\u9020\u51fd\u6570\u5566\uff01 \u522b\u518d\u5199\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u5566\uff01 \u7ee7\u627f\u6784\u9020\u51fd\u6570 \u63d0\u524d\u8fd4\u56de \u7acb\u5373\u8c03\u7528\u7684 Lambda Lambda \u590d\u7528\u4ee3\u7801 \u7c7b\u5185\u9759\u6001\u6210\u5458 inline \u522b\u518d make_pair \u5566\uff01 insert \u4e0d\u4f1a\u66ff\u6362\u73b0\u6709\u503c\u54e6 \u4e00\u8fb9\u904d\u5386 map\uff0c\u4e00\u8fb9\u5220\u9664\uff1f \u9ad8\u6548\u5220\u9664\u5355\u4e2a vector \u5143\u7d20 \u6279\u91cf\u5220\u9664\u90e8\u5206 vector \u5143\u7d20 \u4fdd\u6301\u6709\u5e8f\u7684 vector \u7528\u4e8e\u4e8c\u5206\u6cd5 C++ \u968f\u673a\u6570\u7684\u6b63\u786e\u751f\u6210\u65b9\u5f0f const \u5c45\u7136\u5e94\u8be5\u540e\u7f6e\u2026 \u51fd\u6570\u53c2\u6570\u4e5f\u53ef\u4ee5 auto \u8bfb\u53d6\u6574\u4e2a\u6587\u4ef6\u5230\u5b57\u7b26\u4e32 \u9010\u884c\u8bfb\u53d6\u6587\u672c\u6587\u4ef6 \u5b57\u7b26\u4e32\u5207\u7247 cout \u4e0d\u9700\u8981 endl \u591a\u7ebf\u7a0b\u4e2d cout \u51fa\u73b0\u4e71\u5e8f\uff1f cerr \u4e0e cout \u7684\u6289\u62e9 \u667a\u80fd\u6307\u9488\u9632\u6b62\u5927\u5bf9\u8c61\u79fb\u52a8 optional \u5b9e\u73b0\u5ef6\u8fdf\u521d\u59cb\u5316 if-auto \u4e0e while-auto bind \u662f\u5386\u53f2\u7cdf\u7c95\uff0c\u5e94\u8be5\u7531 Lambda \u8868\u8fbe\u5f0f\u53d6\u4ee3 bind \u7684\u5386\u53f2 thread \u819d\u76d6\u4e2d\u7bad \u4e3e\u4e2a\u7ed1\u5b9a\u968f\u673a\u6570\u751f\u6210\u5668\u4f8b\u5b50 forward \u8ff7\u60d1\u6027\u5730\u4e0d\u597d\u7528\uff0c\u5efa\u8bae\u6539\u7528 FWD \u5b8f bind \u7ed1\u5b9a\u6210\u5458\u51fd\u6570\u662f\u964b\u4e60\uff0c\u6539\u7528 lambda \u6216 bind_front \u6551\u547d\uff01\u4e3a\u4ec0\u4e48\u6211\u7684\u5168\u5c40\u51fd\u6570\u4e0d\u80fd\u4f5c\u4e3a\u51fd\u6570\u5bf9\u8c61\uff1f map + any \u5916\u6302\u5c5e\u6027 \u81ea\u5b9a\u4e49 shared_ptr \u7684 deleter CHECK_CUDA \u7c7b\u9519\u8bef\u68c0\u6d4b\u5b8f \u51fd\u6570\u9ed8\u8ba4\u53c2\u6570\u6c42\u503c\u7684\u4f4d\u7f6e\u662f\u8c03\u7528\u8005 \u8bbe\u7f6e locale \u4e3a .utf8 \u82b1\u62ec\u53f7\u5b9e\u73b0\u5b89\u5168\u7684\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5 \u6210\u5458\u51fd\u6570\u9488\u5bf9 this \u7684\u79fb\u52a8\u91cd\u8f7d CHECK_CUDA \u7c7b\u9519\u8bef\u68c0\u6d4b\u5b8f \u51fd\u6570\u9ed8\u8ba4\u53c2\u6570\u6c42\u503c\u7684\u4f4d\u7f6e\u662f\u8c03\u7528\u8005 \u82b1\u62ec\u53f7\u5b9e\u73b0\u5b89\u5168\u7684\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5 \u4e34\u65f6\u53f3\u503c\u8f6c\u5de6\u503c ostringstream \u683c\u5f0f\u5316\u5b57\u7b26\u4e32 ADL \u673a\u5236\u5b9e\u73b0\u9759\u6001\u591a\u6001 shared_from_this requires \u8bed\u6cd5\u68c0\u6d4b\u662f\u5426\u5b58\u5728\u6307\u5b9a\u6210\u5458\u51fd\u6570 \u8bbe\u7f6e locale \u4e3a .utf8 \u89e3\u51b3 Windows \u7f16\u7801\u96be\u95ee\u9898 \u6210\u5458\u51fd\u6570\u9488\u5bf9 this \u7684\u79fb\u52a8\u91cd\u8f7d \u4f4d\u57df\uff08bit-field\uff09 vector + unordered_map = LRU cache Lambda \u6355\u83b7 unique_ptr \u5bfc\u81f4 function \u62a5\u9519\u600e\u4e48\u529e \u591a\u7ebf\u7a0b\u901a\u4fe1\u5e94\u57fa\u4e8e\u961f\u5217\uff0c\u800c\u4e0d\u662f\u5171\u4eab\u5168\u5c40\u53d8\u91cf RAII \u7684 finally \u5e2e\u624b\u7c7b swap \u7f29\u5c0f mutex \u533a\u95f4\u4ee3\u4ef7 namespace \u522b\u540d \u4ea4\u6362\u4e24\u4e2a\u53d8\u91cf int a = 42; int b = 58; \u73b0\u5728\u4f60\u60f3\u4ea4\u6362\u8fd9\u4e24\u4e2a\u53d8\u91cf\u3002 int tmp = a; a = b; b = tmp; \u4f46\u662f\u6807\u51c6\u5e93\u63d0\u4f9b\u4e86\u66f4\u597d\u7684\u65b9\u6cd5\uff1a std::swap(a, b); \u8fd9\u4e2a\u65b9\u6cd5\u53ef\u4ee5\u4ea4\u6362\u4efb\u610f\u4e24\u4e2a\u540c\u7c7b\u578b\u7684\u503c\uff0c\u5305\u62ec\u7ed3\u6784\u4f53\u3001\u6570\u7ec4\u3001\u5bb9\u5668\u7b49\u3002 \u53ea\u9700\u8981 #include \u5c31\u53ef\u4ee5\u4f7f\u7528\uff01 \u5b89\u5168\u5730\u5206\u914d\u4e00\u6bb5\u5185\u5b58\u7a7a\u95f4 \u5c0f\u5f6d\u8001\u5e08\uff1a\u4e0d\u8981\u51fa\u73b0 new \u548c delete\uff0c\u4e0d\u5b89\u5168\u3002 \u540c\u5b66\uff1a\u6211\u60f3\u8981 \u5206\u914d\u4e00\u6bb5\u5185\u5b58\u7a7a\u95f4 \uff0c\u4f60\u4e0d\u8ba9\u6211 new\uff0c\u6211\u8fd8\u80fd\u600e\u4e48\u529e\u5462\uff1f char *mem = new char[1024]; // \u540c\u5b66\u60f3\u8981 1024 \u5b57\u8282\u7684\u7f13\u51b2\u533a read(1, mem, 1024); // \u7528\u4e8e\u4f9b C \u8bed\u8a00\u7684\u8bfb\u6587\u4ef6\u51fd\u6570\u4f7f\u7528 delete[] mem; // \u9700\u8981\u624b\u52a8 delete \u53ef\u4ee5\u770b\u5230\uff0c\u4ed6\u6240\u8c13\u7684\u201c\u5185\u5b58\u7a7a\u95f4\u201d\u5b9e\u9645\u4e0a\u5c31\u662f\u4e00\u4e2a\u201cchar \u6570\u7ec4\u201d\u3002 \u5c0f\u5f6d\u8001\u5e08\uff1a\u6709\u6ca1\u6709\u4e00\u79cd\u53ef\u80fd\uff0cvector \u5c31\u53ef\u4ee5\u5206\u914d\u5185\u5b58\u7a7a\u95f4\u3002 vector mem(1024); read(1, mem.data(), mem.size()); vector \u4e00\u6837\u7b26\u5408 RAII \u601d\u60f3\uff0c\u6784\u9020\u65f6\u81ea\u52a8\u7533\u8bf7\u5185\u5b58\uff0c\u79bb\u5f00\u4f5c\u7528\u57df\u65f6\u81ea\u52a8\u91ca\u653e\u3002 \u53ea\u9700\u5728\u8c03\u7528 C \u8bed\u8a00\u63a5\u53e3\u65f6\uff0c\u53d6\u51fa\u539f\u59cb\u6307\u9488\uff1a \u7528 data() \u5373\u53ef\u83b7\u53d6\u51fa\u9996\u4e2a char \u5143\u7d20\u7684\u6307\u9488\uff0c\u7528\u4e8e\u4f20\u9012\u7ed9 C \u8bed\u8a00\u51fd\u6570\u4f7f\u7528\u3002 \u7528 size() \u53d6\u51fa\u6570\u7ec4\u7684\u957f\u5ea6\uff0c\u5373\u662f\u5185\u5b58\u7a7a\u95f4\u7684\u5b57\u8282\u6570\uff0c\u56e0\u4e3a\u6211\u4eec\u7684\u5143\u7d20\u7c7b\u578b\u662f char\uff0cchar \u521a\u597d\u5c31\u662f 1 \u5b57\u8282\u7684\uff0csize() \u521a\u597d\u5c31\u662f\u5b57\u8282\u7684\u6570\u91cf\u3002 \u6b64\u5904 read \u51fd\u6570\u8bfb\u5b8c\u540e\uff0c\u6570\u636e\u5c31\u76f4\u63a5\u8fdb\u5165\u4e86 vector \u4e2d\uff0c\u6839\u672c\u4e0d\u9700\u8981\u4ec0\u4e48 new\u3002 \u66f4\u73b0\u4ee3\u7684 C++ \u601d\u60f3\u5bb6\u8fd8\u4f1a\u7528 vector \uff0c\u660e\u786e\u533a\u5206\u8fd9\u662f\u201c\u5b57\u8282\u201d\u4e0d\u662f\u201c\u5b57\u7b26\u201d\u3002\u5982\u679c\u4f60\u8bfb\u51fa\u6765\u7684\u76ee\u7684\u662f\u5f53\u4f5c\u5b57\u7b26\u4e32\uff0c\u53ef\u4ee5\u7528 std::string \u3002 \u6ce8\u610f\uff1a\u4e00\u4e9b\u611a\u8822\u7684\u6559\u6750\u4e2d\uff0c\u7528 shared_ptr \u548c unique_ptr \u6765\u7ba1\u7406\u6570\u7ec4\uff0c\u8fd9\u662f\u9519\u8bef\u7684\u3002 shared_ptr \u548c unique_ptr \u667a\u80fd\u6307\u9488\u4e3b\u8981\u662f\u7528\u4e8e\u7ba1\u7406\u201c\u5355\u4e2a\u5bf9\u8c61\u201d\u7684\uff0c\u4e0d\u662f\u7ba1\u7406\u201c\u6570\u7ec4\u201d\u7684\u3002 vector \u4e00\u76f4\u90fd\u662f\u6570\u7ec4\u7684\u7ba1\u7406\u65b9\u5f0f\uff0c\u4e14\u4ece C++98 \u5c31\u6709\u3002\u4e0d\u8981\u770b\u5230 \u201cnew \u7684\u66ff\u4ee3\u54c1\u201d \u53ea\u60f3\u5230\u667a\u80fd\u6307\u9488\u554a\uff01\u201cnew [] \u7684\u66ff\u4ee3\u54c1\u201d \u662f vector \u554a\uff01 \u6b64\u5904\u653e\u51fa\u4e00\u4e2a\u5229\u7528 std::wstring \u5206\u914d wchar_t * \u5185\u5b58\u7684\u6848\u4f8b\uff1a std::wstring utf8_to_wstring(std::string const &s) { int len = MultiByteToWideChar(CP_UTF8, 0, s.data(), s.size(), nullptr, 0); // \u5148\u786e\u5b9a\u957f\u5ea6 std::wstring ws(len, 0); MultiByteToWideChar(CP_UTF8, 0, s.data(), s.size(), ws.data(), ws.size()); // \u518d\u8bfb\u51fa\u6570\u636e return ws; } \u5730\u677f\u9664\u4e0e\u5929\u82b1\u677f\u9664 \u4f17\u6240\u5468\u77e5\uff0cC\u8bed\u8a00\u4e2d int \u76f8\u9664 / \uff0c\u5f97\u5230\u7684\u7ed3\u679c\u4e5f\u662f int \uff0c\u5982\u679c\u9664\u6cd5\u4ea7\u751f\u4e86\u4f59\u6570\uff0c\u90a3\u4e48\u53ea\u4f1a\u4fdd\u7559\u6574\u6570\u90e8\u5206\u3002 \u4f8b\u5982 14 / 5 \uff0c\u672c\u6765\u5e94\u8be5\u5f97\u5230 2.8\u3002\u4f46\u662f\u56e0\u4e3a C \u8bed\u8a00\u7684\u9664\u6cd5\u8fd4\u56de int \uff0c\u7ed3\u679c\u4f1a\u81ea\u52a8\u5411\u4e0b\u53d6\u6574\uff0c\u5bfc\u81f4\u5f97\u5230 2\u3002 int a = 14, b = 5; int c = a / b; // c = 14 / 5 = 2 \u7b49\u4ef7\u4e8e int c = floor((float)a / b); // c = floor(2.8) = 2 \u5982\u679c a \u9664\u4ee5 b \u9664\u4e0d\u5c3d\uff0c\u90a3\u4e48\u4f1a\u627e\u5230\u6bd4\u4ed6\u5927\u7684\u7b2c\u4e00\u4e2a\u6574\u6570\u4f5c\u4e3a\u7ed3\u679c\uff0c\u8fd9\u5c31\u662f \u5730\u677f\u9664 (floor div) \u3002 C \u8bed\u8a00\u9ed8\u8ba4\u7684\u5c31\u662f\u5730\u677f\u9664\u3002 \u5982\u679c\u6211\u60f3\u8981\u7684\u662f\u5411\u4e0a\u53d6\u6574\uff0c\u8be5\u600e\u4e48\u5199\uff1f \u6700\u539f\u59cb\u7684\u5199\u6cd5\u662f\u5148\u8f6c\u6210\u6d6e\u70b9\u6570\u6765\u9664\uff0c\u7136\u540eceil\u51fd\u6570\u5411\u4e0a\u53d6\u6574\uff1a int c = ceil((float)a / b); \u4f46\u662f\u6d6e\u70b9\u6570\u4e0d\u4ec5\u4f4e\u6548\uff0c\u8fd8\u6709\u7cdf\u7cd5\u7684\u6d6e\u70b9\u6570\u7cbe\u5ea6\u8bef\u5dee\uff01\u5bf9\u4e8e\u5f88\u5927\u7684\u6574\u6570\uff08\u5927\u4e8e 2^{23} 2^{23} \uff09\u4f1a\u4ea7\u751f\u9519\u8bef\u7684\u7ed3\u679c\u3002 \u66f4\u5408\u7406\u7684\u5199\u6cd5\u662f\u5148\u628a a \u52a0\u4e0a b - 1 \uff0c\u7136\u540e\u518d\u4e0b\u53d6\u6574\u5730\u9664\u4ee5 b \uff1a int c = (a + b - 1) / b; \u8fd9\u6837\u5c31\u80fd\u4ea7\u751f\u4e00\u4e2a\u5411\u4e0a\u53d6\u6574\u7684\u9664\u6cd5\u4e86\u3002 \u5982\u679c a \u9664\u4ee5 b \u9664\u4e0d\u5c3d\uff0c\u90a3\u4e48\u4f1a\u627e\u5230\u6bd4\u4ed6\u5927\u7684\u7b2c\u4e00\u4e2a\u6574\u6570\u4f5c\u4e3a\u7ed3\u679c\uff0c\u8fd9\u5c31\u662f \u5929\u82b1\u677f\u9664 (ceil div) \u3002 \u8bd5\u8bd5\u770b\uff1a14 \u9664\u4ee5 5\uff0c\u5e94\u8be5\u5f97\u5230 2.8\uff1b\u5982\u679c\u7528\u5730\u677f\u9664\uff0c\u4f1a\u5f97\u5230 2\uff1b\u5982\u679c\u7528\u5929\u82b1\u677f\u9664\uff0c\u4f1a\u5f97\u5230 3\u3002 14 / 5 = 2 (14 + 5 - 1) / 5 = (14 + 4) / 5 = 18 / 5 = 3 \u8bd5\u8bd5\u770b\uff1a10 \u9664\u4ee5 5\uff0c\u5e94\u8be5\u5f97\u5230 2\uff1b\u90a3\u4e48\u65e0\u8bba\u662f\u5730\u677f\u9664\u8fd8\u662f\u5929\u82b1\u677f\u9664\uff0c\u90fd\u5e94\u8be5\u5f97\u5230 2\u3002 10 / 5 = 2 (10 + 5 - 1) / 5 = (10 + 4) / 5 = 14 / 5 = 2 \u8fd9\u5c31\u662f C \u8bed\u8a00\u4e2d\u5b9e\u73b0\u5929\u82b1\u677f\u9664\u7684\u4e1a\u754c\u516c\u8ba4\u65b9\u5f0f\u3002 \u522b\u518d [] \u5566\uff01 \u4f60\u77e5\u9053\u5417\uff1f\u5728 map \u4e2d\u4f7f\u7528 [] \u67e5\u627e\u5143\u7d20\uff0c\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u4f1a\u81ea\u52a8\u521b\u5efa\u4e00\u4e2a\u9ed8\u8ba4\u503c\u3002\u8fd9\u4e2a\u7279\u6027\u6709\u65f6\u5f88\u65b9\u4fbf\uff0c\u4f46\u5982\u679c\u4f60\u4e0d\u5c0f\u5fc3\u5199\u9519\u4e86\uff0c\u5c31\u4f1a\u5728 map \u4e2d\u521b\u5efa\u4e00\u4e2a\u591a\u4f59\u7684\u9ed8\u8ba4\u5143\u7d20\u3002 map table; table[\"\u5c0f\u5f6d\u8001\u5e08\"] = 24; cout << table[\"\u4faf\u6377\u8001\u5e08\"]; table \u4e2d\u660e\u660e\u6ca1\u6709 \u201c\u4faf\u6377\u8001\u5e08\u201d \u8fd9\u4e2a\u5143\u7d20\uff0c\u4f46\u7531\u4e8e [] \u7684\u7279\u6027\uff0c\u4ed6\u4f1a\u9ed8\u8ba4\u8fd4\u56de\u4e00\u4e2a 0\uff0c\u4e0d\u4f1a\u7206\u4efb\u4f55\u9519\u8bef\uff01 \u6539\u7528\u66f4\u5b89\u5168\u7684 at() \u51fd\u6570\uff0c\u5f53\u67e5\u8be2\u7684\u5143\u7d20\u4e0d\u5b58\u5728\u65f6\uff0c\u4f1a\u629b\u51fa\u5f02\u5e38\uff0c\u65b9\u4fbf\u4f60\u8c03\u8bd5\uff1a map table; table.at(\"\u5c0f\u5f6d\u8001\u5e08\") = 24; cout << table.at(\"\u4faf\u6377\u8001\u5e08\"); // \u629b\u51fa\u5f02\u5e38 [] \u771f\u6b63\u7684\u7528\u9014\u662f\u201c\u5199\u5165\u65b0\u5143\u7d20\u201d\u65f6\uff0c\u5982\u679c\u5143\u7d20\u4e0d\u5b58\u5728\uff0c\u4ed6\u53ef\u4ee5\u81ea\u52a8\u5e2e\u4f60\u521b\u5efa\u4e00\u4e2a\u9ed8\u8ba4\u503c\uff0c\u4f9b\u4f60\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u8d4b\u503c\u8fdb\u53bb\u3002 \u68c0\u6d4b\u5143\u7d20\u662f\u5426\u5b58\u5728\u53ef\u4ee5\u7528 count \uff1a if (table.count(\"\u5c0f\u5f6d\u8001\u5e08\")) { return table.at(\"\u5c0f\u5f6d\u8001\u5e08\"); } else { return 0; } \u5373\u4f7f\u4f60\u60f3\u8981\u9ed8\u8ba4\u503c 0 \u8fd9\u4e00\u7279\u6027\uff0c count + at \u4e5f\u6bd4 [] \u66f4\u597d\uff0c\u56e0\u4e3a [] \u7684\u9ed8\u8ba4\u503c\u662f\u4f1a\u5bf9 table \u505a\u7834\u574f\u6027\u4fee\u6539\u7684\uff0c\u8fd9\u5bfc\u81f4 [] \u9700\u8981 map \u7684\u58f0\u660e\u4e0d\u4e3a const \uff1a map table; return table[\"\u5c0f\u5f6d\u8001\u5e08\"]; // \u5982\u679c\"\u5c0f\u5f6d\u8001\u5e08\"\u8fd9\u4e00\u952e\u4e0d\u5b58\u5728\uff0c\u4f1a\u521b\u5efa\"\u5c0f\u5f6d\u8001\u5e08\"\u5e76\u8bbe\u4e3a\u9ed8\u8ba4\u503c 0 const map table; return table[\"\u5c0f\u5f6d\u8001\u5e08\"]; // \u7f16\u8bd1\u5931\u8d25\uff01[] \u9700\u8981\u975e const \u7684 map \u5bf9\u8c61\uff0c\u56e0\u4e3a\u4ed6\u4f1a\u7834\u574f\u6027\u4fee\u6539 \u66f4\u591a map \u77e5\u8bc6\u8bf7\u770b\u6211\u4eec\u7684 map \u4e13\u9898\u8bfe \u3002 \u522b\u518d\u5199\u6784\u9020\u51fd\u6570\u5566\uff01 // C++98 struct Student { string name; int age; int id; Student(string name_, int age_, int id_) : name(name_), age(age_), id(id_) {} }; Student stu(\"\u4faf\u6377\u8001\u5e08\", 42, 123); C++98 \u9700\u8981\u624b\u52a8\u4e66\u5199\u6784\u9020\u51fd\u6570\uff0c\u975e\u5e38\u9ebb\u70e6\uff01\u800c\u4e14\u51e0\u4e4e\u90fd\u662f\u91cd\u590d\u7684\u3002 C++11 \u4e2d\uff0c\u5e73\u51e1\u7684\u7ed3\u6784\u4f53\u7c7b\u578b\u4e0d\u9700\u8981\u518d\u5199\u6784\u9020\u51fd\u6570\u4e86\uff0c\u53ea\u9700\u7528 {} \u5c31\u80fd\u5bf9\u6210\u5458\u4f9d\u6b21\u521d\u59cb\u5316\uff1a // C++11 struct Student { string name; int age; int id; }; Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24, 123}; \u8fd9\u88ab\u79f0\u4e3a \u805a\u5408\u521d\u59cb\u5316 (aggregate initialize)\u3002\u53ea\u8981\u4f60\u7684\u7c7b\u6ca1\u6709\u81ea\u5b9a\u4e49\u6784\u9020\u51fd\u6570\uff0c\u6ca1\u6709 private \u6210\u5458\uff0c\u90fd\u53ef\u4ee5\u7528 {} \u805a\u5408\u521d\u59cb\u5316\u3002 \u597d\u6d88\u606f\uff1aC++20 \u4e2d\uff0c\u805a\u5408\u521d\u59cb\u5316\u4e5f\u652f\u6301 () \u4e86\uff0c\u7528\u8d77\u6765\u5c31\u548c\u4f20\u7edf\u7684 C++98 \u6784\u9020\u51fd\u6570\u4e00\u6837\uff01 // C++20 Student stu(\"\u5c0f\u5f6d\u8001\u5e08\", 24, 123); \u805a\u5408\u521d\u59cb\u5316\u8fd8\u53ef\u4ee5\u6307\u5b9a\u9ed8\u8ba4\u503c\uff1a // C++11 struct Student { string name; int age; int id = 9999; }; Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24}; // \u7b49\u4ef7\u4e8e\uff1a Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24, 9999}; C++20 \u5f00\u59cb\uff0c {} \u805a\u5408\u521d\u59cb\u5316\u8fd8\u53ef\u4ee5\u6839\u636e\u6bcf\u4e2a\u6210\u5458\u7684\u540d\u5b57\u6765\u6307\u5b9a\u503c\uff1a Student stu{.name = \"\u5c0f\u5f6d\u8001\u5e08\", .age = 24, .id = 9999}; // \u7b49\u4ef7\u4e8e\uff1a Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24, 9999}; \u597d\u5904\u662f\uff0c\u5373\u4f7f\u4e0d\u614e\u5199\u9519\u53c2\u6570\u987a\u5e8f\u4e5f\u4e0d\u7528\u62c5\u5fc3\u3002 Student stu{.name = \"\u5c0f\u5f6d\u8001\u5e08\", .age = 24, .id = 9999}; Student stu{.name = \"\u5c0f\u5f6d\u8001\u5e08\", .id = 9999, .age = 24}; \u522b\u518d\u5199\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u5566\uff01 \u53ea\u6709\u5f53\u4f60\u9700\u8981\u6709\u201c\u81ea\u5b9a\u4e49\u94a9\u5b50\u903b\u8f91\u201d\u7684\u65f6\u5019\uff0c\u624d\u9700\u8981\u81ea\u5b9a\u4e49\u6784\u9020\u51fd\u6570\u3002 struct Student { string name; int age; int id; Student(string name_, int age_, int id_) : name(name_), age(age_), id(id_) {} Student(Student const &other) : name(other.name), age(other.age), id(other.id) { std::cout << \"\u62f7\u8d1d\u6784\u9020\\n\"; } Student &operator=(Student const &other) { name = other.name; age = other.age; id = other.id; std::cout << \"\u62f7\u8d1d\u8d4b\u503c\\n\"; return *this; } }; Student stu1(\"\u4faf\u6377\u8001\u5e08\", 42, 123); Student stu2 = stu1; // \u62f7\u8d1d\u6784\u9020 stu2 = stu1; // \u62f7\u8d1d\u8d4b\u503c \u5982\u679c\u4f60\u4e0d\u9700\u8981\u8fd9\u4e2a std::cout \uff0c\u53ea\u662f\u5e73\u51e1\u5730\u62f7\u8d1d\u6240\u6709\u6210\u5458\uff0c\u5b8c\u5168\u53ef\u4ee5\u4e0d\u5199\uff0c\u8ba9\u7f16\u8bd1\u5668\u81ea\u52a8\u751f\u6210\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3001\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570\u3001\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3001\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\uff1a struct Student { string name; int age; int id; Student(string name_, int age_, int id_) : name(name_), age(age_), id(id_) {} // \u7f16\u8bd1\u5668\u81ea\u52a8\u751f\u6210 Student(Student const &other) // \u7f16\u8bd1\u5668\u81ea\u52a8\u751f\u6210 Student &operator=(Student const &other) }; Student stu1(\"\u4faf\u6377\u8001\u5e08\", 42, 123); Student stu2 = stu1; // \u62f7\u8d1d\u6784\u9020 stu2 = stu1; // \u62f7\u8d1d\u8d4b\u503c assert(stu2.name == \"\u4faf\u6377\u8001\u5e08\"); \u603b\u4e4b\uff0c\u5f88\u591a C++ \u6559\u6750\u628a\u62f7\u8d1d/\u79fb\u52a8\u6784\u9020\u51fd\u6570\u8fc7\u4e8e\u5938\u5927\uff0c\u641e\u5f97\u597d\u50cf\u6bcf\u4e2a\u7c7b\u90fd\u9700\u8981\u81ea\u5df1\u5b9a\u4e49\u4e00\u6837\u3002 \u5b9e\u9645\u4e0a\uff0c\u53ea\u6709\u5728\u201c\u81ea\u5df1\u5b9e\u73b0\u5bb9\u5668\u201d\u7684\u60c5\u51b5\u4e0b\uff0c\u624d\u9700\u8981\u81ea\u5b9a\u4e49\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3002\u53ef\u662f\u8c01\u4f1a\u6574\u5929\u624b\u6413\u5bb9\u5668\uff1f \u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u6211\u4eec\u53ea\u9700\u8981\u5728\u7c7b\u91cc\u9762\u5b58 vector\u3001string \u7b49\u5c01\u88c5\u597d\u7684\u5bb9\u5668\uff0c\u7f16\u8bd1\u5668\u9ed8\u8ba4\u751f\u6210\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u4f1a\u81ea\u52a8\u8c03\u7528\u4ed6\u4eec\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\uff0c\u7528\u6237\u53ea\u9700\u4e13\u6ce8\u4e8e\u4e1a\u52a1\u903b\u8f91\u5373\u53ef\uff0c\u4e0d\u9700\u8981\u64cd\u5fc3\u5e95\u5c42\u7ec6\u8282\u3002 \u5bf9\u4e8e\u6301\u6709\u8d44\u6e90\u7684 RAII \u7c7b\uff0c\u6211\u4eec\u90fd\u4f1a\u76f4\u63a5\u5220\u9664\u5176\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u548c\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570\uff1a struct RAIIHandle { int handle; RAIIHandle() { handle = CreateObject(); } RAIIHandle(RAIIHandle const &) = delete; RAIIHandle &operator=(RAIIHandle const &) = delete; RAIIHandle() { DeleteObject(handle); } }; \u7ee7\u627f\u6784\u9020\u51fd\u6570 C++ \u7279\u8272\uff1a\u5b50\u7c7b\u4e0d\u4f1a\u81ea\u52a8\u7ee7\u627f\u7236\u7c7b\u7684\u6784\u9020\u51fd\u6570\uff01\uff08\u9664\u975e\u7236\u7c7b\u7684\u6784\u9020\u51fd\u6570\u662f\u6ca1\u6709\u53c2\u6570\u7684\u9ed8\u8ba4\u6784\u9020\u51fd\u6570\uff09 struct Parent { Parent(int age, const char *name) { ... } void parent_func() { ... } }; struct Child : Parent { void child_func() { ... } }; Child child(23, \"peng\"); // \u9519\u8bef\uff01Child \u6ca1\u6709\u6784\u9020\u51fd\u6570\uff01 C++11 \u4e2d\u53ef\u4ee5\u5728\u5b50\u7c7b\u91cc\u9762\u5199 using \u7236\u7c7b::\u7236\u7c7b \uff0c\u5c31\u80fd\u81ea\u52a8\u7ee7\u627f\u7236\u7c7b\u6240\u6709\u7684\u6784\u9020\u51fd\u6570\u4e86\u3002 struct Parent { Parent(int age, const char *name) { ... } void parent_func() { ... } }; struct Child : Parent { using Parent::Parent; // \u52a0\u4e0a\u8fd9\u4e00\u884c\uff01 void child_func() { ... } }; Child child(23, \"peng\"); // \u7f16\u8bd1\u901a\u8fc7\uff0c\u81ea\u52a8\u8c03\u7528\u5230\u7236\u7c7b\u7684\u6784\u9020\u51fd\u6570 Parent(int, const char *) \u5728 C++98 \u4e2d\uff0c\u6ca1\u6709 using \u7684\u8fd9\u4e2a\u8bed\u6cd5\uff0c\u53ea\u80fd\u81ea\u5df1\u5b9a\u4e49\u4e00\u4e2a\u6784\u9020\u51fd\u6570\uff0c\u7136\u540e\u4f7f\u7528\u201c\u59d4\u4efb\u6784\u9020\u201d\u7684\u8bed\u6cd5\u8f6c\u53d1\u6240\u6709\u53c2\u6570\u7ed9\u7236\u7c7b\uff0c\u975e\u5e38\u7e41\u7410\u3002 struct Parent { Parent(int age, const char *name) { ... } void parent_func() { ... } }; struct Child : Parent { Child(int age, const char *name) : Parent(age, name) { ... } void child_func() { ... } }; Child child(23, \"peng\"); // \u7f16\u8bd1\u901a\u8fc7\uff0c\u8c03\u7528\u5230\u5b50\u7c7b\u7684\u6784\u9020\u51fd\u6570\u540e\u8f6c\u53d1\u5230\u7236\u7c7b \u63d0\u524d\u8fd4\u56de void babysitter(Baby *baby) { if (!baby->is_alive()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u53bb\u4e16\u4e86\"); } else { puts(\"\u6b63\u5728\u68c0\u67e5\u5b9d\u5b9d\u5582\u98df\u60c5\u51b5...\"); if (baby->is_feeded()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u5582\u98df\u8fc7\u4e86\"); } else { puts(\"\u6b63\u5728\u5582\u98df\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u8c03\u6559\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u5b89\u629a\u5b9d\u5b9d...\"); } } } \u8fd9\u4e2a\u51fd\u6570\u6709\u5f88\u591a\u5c42\u5d4c\u5957\uff0c\u5f88\u4e0d\u7f8e\u89c2\u3002\u7528 \u63d0\u524d\u8fd4\u56de \u7684\u5199\u6cd5\u6765\u4f18\u5316\uff1a void babysitter(Baby *baby) { if (!baby->is_alive()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u53bb\u4e16\u4e86\"); return; } puts(\"\u6b63\u5728\u68c0\u67e5\u5b9d\u5b9d\u5582\u98df\u60c5\u51b5...\"); if (baby->is_feeded()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u5582\u98df\u8fc7\u4e86\"); return; } puts(\"\u6b63\u5728\u5582\u98df\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u8c03\u6559\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u5b89\u629a\u5b9d\u5b9d...\"); } \u7acb\u5373\u8c03\u7528\u7684 Lambda \u6709\u65f6\uff0c\u9700\u8981\u5728\u4e00\u4e2a\u5217\u8868\u91cc\u5faa\u73af\u67e5\u627e\u67d0\u6837\u4e1c\u897f\uff0c\u4e5f\u53ef\u4ee5\u7528\u63d0\u524d\u8fd4\u56de\u7684\u5199\u6cd5\u4f18\u5316\uff1a bool find(const vector &v, int target) { for (int i = 0; i < v.size(); ++i) { if (v[i] == target) { return true; } } return false; } \u53ef\u4ee5\u5305\u88f9\u4e00\u4e2a\u7acb\u5373\u8c03\u7528\u7684 Lambda \u5757 [&] { ... } () \uff0c\u9650\u5236\u63d0\u524d\u8fd4\u56de\u7684\u8303\u56f4\uff1a void find(const vector &v, int target) { bool found = [&] { for (int i = 0; i < v.size(); ++i) { if (v[i] == target) { return true; } } return false; } (); if (found) { ... } } Lambda \u590d\u7528\u4ee3\u7801 vector spilt(string str) { vector list; string last; for (char c: str) { if (c == ' ') { list.push_back(last); last.clear(); } else { last.push_back(c); } } list.push_back(last); return list; } \u4e0a\u9762\u7684\u4ee3\u7801\u53ef\u4ee5\u7528 Lambda \u590d\u7528\uff1a vector spilt(string str) { vector list; string last; auto push = [&] { list.push_back(last); last.clear(); }; for (char c: str) { if (c == ' ') { push(); } else { last.push_back(c); } } push(); return list; } \u7c7b\u5185\u9759\u6001\u6210\u5458 inline \u5728\u5934\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7ed3\u6784\u4f53\u7684 static \u6210\u5458\u65f6\uff1a struct Class { static int member; }; \u4f1a\u62a5\u9519 undefined reference to 'Class::member' \u3002\u8fd9\u662f\u8bf4\u7684\u4f60\u9700\u8981\u627e\u4e2a .cpp \u6587\u4ef6\uff0c\u5199\u51fa int Class::member \u624d\u80fd\u6d88\u9664\u8be5\u9519\u8bef\u3002 C++17 \u4e2d\uff0c\u53ea\u9700\u52a0\u4e2a inline \u5c31\u80fd\u89e3\u51b3\uff01 struct Class { inline static int member; }; \u522b\u518d make_pair \u5566\uff01 map table; table.insert(pair(\"\u4faf\u6377\u8001\u5e08\", 42)); \u4e3a\u907f\u514d\u5199\u51fa\u7c7b\u578b\u540d\u7684\u9ebb\u70e6\uff0c\u5f88\u591a\u8001\u5e08\u90fd\u4f1a\u8ba9\u4f60\u5199 make_pair\uff1a map table; table.insert(make_pair(\"\u4faf\u6377\u8001\u5e08\", 42)); \u7136\u800c C++11 \u63d0\u4f9b\u4e86\u66f4\u597d\u7684\u5199\u6cd5\uff0c\u90a3\u5c31\u662f\u901a\u8fc7 {} \u9690\u5f0f\u6784\u9020\uff0c\u4e0d\u7528\u5199\u51fa\u7c7b\u578b\u540d\u6216 make_pair\uff1a map table; table.insert({\"\u4faf\u6377\u8001\u5e08\", 42}); \u5373\u4f7f\u4f60\u51fa\u4e8e\u67d0\u79cd\u201c\u6296m\u201d\u60c5\u8282\uff0c\u8fd8\u60f3\u5199\u51fa\u7c7b\u578b\u540d\uff0c\u4e5f\u53ef\u4ee5\u7528 C++17 \u7684 CTAD \u8bed\u6cd5\uff0c\u514d\u53bb\u6a21\u677f\u53c2\u6570\uff1a map table; table.insert(pair(\"\u4faf\u6377\u8001\u5e08\", 42)); // tuple \u4e5f\u652f\u6301 CTAD\uff1a auto t = tuple(\"\u4faf\u6377\u8001\u5e08\", 42, string(\"\u5c0f\u5f6d\u8001\u5e08\")); // \u7b49\u4ef7\u4e8e\uff1a auto t = make_tuple(\"\u4faf\u6377\u8001\u5e08\", 42, string(\"\u5c0f\u5f6d\u8001\u5e08\")); println(\"{}\", typeid(t).name()); // tuple insert \u4e0d\u4f1a\u66ff\u6362\u73b0\u6709\u503c\u54e6 map table; table.insert({\"\u5c0f\u5f6d\u8001\u5e08\", 24}); table.insert({\"\u5c0f\u5f6d\u8001\u5e08\", 42}); \u8fd9\u65f6\uff0c table[\"\u5c0f\u5f6d\u8001\u5e08\"] \u4ecd\u7136\u4f1a\u662f 24\uff0c\u800c\u4e0d\u662f 42\u3002\u56e0\u4e3a insert \u4e0d\u4f1a\u66ff\u6362 map \u91cc\u5df2\u7ecf\u5b58\u5728\u7684\u503c\u3002 \u5982\u679c\u5e0c\u671b\u5982\u679c\u5df2\u7ecf\u5b58\u5728\u65f6\uff0c\u66ff\u6362\u73b0\u6709\u5143\u7d20\uff0c\u53ef\u4ee5\u4f7f\u7528 [] \u8fd0\u7b97\u7b26\uff1a map table; table[\"\u5c0f\u5f6d\u8001\u5e08\"] = 24; table[\"\u5c0f\u5f6d\u8001\u5e08\"] = 42; C++17 \u63d0\u4f9b\u4e86\u6bd4 [] \u8fd0\u7b97\u7b26\u66f4\u9002\u5408\u8986\u76d6\u6027\u63d2\u5165\u7684 insert_or_assign \u51fd\u6570\uff1a map table; table.insert_or_assign(\"\u5c0f\u5f6d\u8001\u5e08\", 24); table.insert_or_assign(\"\u5c0f\u5f6d\u8001\u5e08\", 42); \u597d\u5904\uff1a insert_or_assign \u4e0d\u9700\u8981\u503c\u7c7b\u578b\u652f\u6301\u9ed8\u8ba4\u6784\u9020\uff0c\u53ef\u4ee5\u907f\u514d\u4e00\u6b21\u9ed8\u8ba4\u6784\u9020\u51fd\u6570 + \u4e00\u6b21\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\u7684\u5f00\u9500\u3002 \u5efa\u8bae\u628a insert_or_assign \u6539\u540d\u6210 set \uff0c at \u6539\u540d\u6210 get \uff1b\u53ea\u662f\u7531\u4e8e\u5386\u53f2\u539f\u56e0\u540d\u5b57\u8ff7\u60d1\u4e86\u3002 \u4e00\u8fb9\u904d\u5386 map\uff0c\u4e00\u8fb9\u5220\u9664\uff1f map table; for (auto it = table.begin(); it != table.end(); ++it) { if (it->second < 0) { table.erase(it); } } \u4f1a\u53d1\u751f\u5d29\u6e83\uff01\u770b\u6765 map \u4f3c\u4e4e\u4e0d\u5141\u8bb8\u5728\u904d\u5386\u7684\u8fc7\u7a0b\u4e2d\u5220\u9664\uff1f\u4e0d\uff0c\u53ea\u662f\u4f60\u7684\u5199\u6cd5\u6709\u9519\u8bef\uff1a map table; for (auto it = table.begin(); it != table.end(); ) { if (it->second < 0) { it = table.erase(it); } else { ++it; } } C++20 \u5f15\u5165\u4e86\u66f4\u597d\u7684 erase_if \u5168\u5c40\u51fd\u6570\uff0c\u4e0d\u7528\u624b\u5199\u4e0a\u9762\u8fd9\u4e48\u9ebb\u70e6\u7684\u4ee3\u7801\uff1a map table; erase_if(table, [](pair it) { return it.second < 0; }); \u9ad8\u6548\u5220\u9664\u5355\u4e2a vector \u5143\u7d20 vector v = {48, 23, 76, 11, 88, 63, 45, 28, 59}; \u4f17\u6240\u5468\u77e5\uff0c\u5728 vector \u4e2d\u5220\u9664\u5143\u7d20\uff0c\u4f1a\u5bfc\u81f4\u540e\u9762\u7684\u6240\u6709\u5143\u7d20\u5411\u524d\u79fb\u52a8\uff0c\u5341\u5206\u4f4e\u6548\u3002\u590d\u6742\u5ea6\uff1a O(n) O(n) // \u76f4\u63a5\u5220\u9664 v[3] v.erase(v.begin() + 3); \u5982\u679c\u4e0d\u5728\u4e4e\u5143\u7d20\u7684\u987a\u5e8f\uff0c\u53ef\u4ee5\u628a\u8981\u5220\u9664\u7684\u5143\u7d20\u548c\u6700\u540e\u4e00\u4e2a\u5143\u7d20 swap\uff0c\u7136\u540e pop_back\u3002\u590d\u6742\u5ea6\uff1a O(1) O(1) // \u628a v[3] \u548c v[v.size() - 1] \u4f4d\u7f6e\u5bf9\u8c03 swap(v[3], v[v.size() - 1]); // \u7136\u540e\u5220\u9664 v[v.size() - 1] v.pop_back(); \u8fd9\u6837\u5c31\u4e0d\u7528\u79fb\u52a8\u4e00\u5927\u5806\u5143\u7d20\u4e86\u3002\u8fd9\u88ab\u79f0\u4e3a back-swap-erase\u3002 \u6279\u91cf\u5220\u9664\u90e8\u5206 vector \u5143\u7d20 vector \u4e2d\u53ea\u5220\u9664\u4e00\u4e2a\u5143\u7d20\u9700\u8981 O(n) O(n) \u3002\u5982\u679c\u4e00\u8fb9\u904d\u5386\uff0c\u4e00\u8fb9\u5220\u9664\u591a\u4e2a\u7b26\u5408\u6761\u4ef6\u7684\u5143\u7d20\uff0c\u5c31\u9700\u8981\u590d\u6742\u5ea6 O(n^2) O(n^2) \u4e86\u3002 \u6807\u51c6\u5e93\u63d0\u4f9b\u4e86 remove \u548c remove_if \u51fd\u6570\uff0c\u5176\u5185\u90e8\u91c7\u7528\u7c7b\u4f3c back-swap-erase \u7684\u65b9\u6cd5\uff0c\u5148\u628a\u8981\u5220\u9664\u7684\u5143\u7d20\u79fb\u52a8\u5230\u672b\u5c3e\u3002\u7136\u540e\u4e00\u6b21\u6027 erase \u6389\u672b\u5c3e\u540c\u6837\u6570\u91cf\u7684\u5143\u7d20\u3002 \u4e14\u4ed6\u4eec\u90fd\u80fd\u4fdd\u6301\u987a\u5e8f\u4e0d\u53d8\u3002 \u5220\u9664\u6240\u6709\u503c\u4e3a 42 \u7684\u5143\u7d20\uff1a vector v; v.erase(remove(v.begin(), v.end(), 42), v.end()); \u5220\u9664\u6240\u6709\u503c\u5927\u4e8e 0 \u7684\u5143\u7d20\uff1a vector v; v.erase(remove_if(v.begin(), v.end(), [](int x) { return x > 0; }), v.end()); \u73b0\u5728 C++20 \u4e5f\u5f15\u5165\u4e86\u5168\u5c40\u51fd\u6570 erase \u548c erase_if\uff0c\u4f7f\u7528\u8d77\u6765\u66f4\u52a0\u76f4\u89c2\uff1a vector v; erase(v, 42); // \u5220\u9664\u6240\u6709\u503c\u4e3a 42 \u7684\u5143\u7d20 erase_if(v, [](int x) { return x > 0; // \u5220\u9664\u6240\u6709\u503c\u5927\u4e8e 0 \u7684\u5143\u7d20 }); \u4fdd\u6301\u6709\u5e8f\u7684 vector \u7528\u4e8e\u4e8c\u5206\u6cd5 \u5982\u679c\u4f60\u60f3\u8981\u7ef4\u62a4\u4e00\u4e2a\u6709\u5e8f\u7684\u6570\u7ec4\uff0c\u7528 lower_bound \u6216 upper_bound \u6765\u63d2\u5165\u5143\u7d20\uff0c\u4fdd\u8bc1\u63d2\u5165\u540e\u4ecd\u4fdd\u6301\u6709\u5e8f\uff1a vector s; s.push_back(1); s.push_back(2); s.push_back(4); s.push_back(6); // s = { 1, 2, 4, 6 } s.insert(lower_bound(s.begin(), s.end(), 3), 3); // s = { 1, 2, 3, 4, 6 } s.insert(lower_bound(s.begin(), s.end(), 5), 5); // s = { 1, 2, 3, 4, 5, 6 } \u6709\u5e8f\u6570\u7ec4\u4e2d\uff0c\u53ef\u4ee5\u5229\u7528 lower_bound \u6216 upper_bound \u5feb\u901f\u4e8c\u5206\u67e5\u627e\u5230\u60f3\u8981\u7684\u503c\uff1a vector s; s.push_back(1); s.push_back(2); s.push_back(4); s.push_back(6); // s = { 1, 2, 4, 6 } lower_bound(s.begin(), s.end(), 3); // s.begin() + 2; lower_bound(s.begin(), s.end(), 5); // s.begin() + 3; \u6709\u5e8f vector \u5e94\u7528\u6848\u4f8b\uff1a\u5229\u7528 CDF \u79ef\u5206 + \u4e8c\u5206\u6cd5\u53ef\u4ee5\u5b9e\u73b0\u751f\u6210\u4efb\u610f\u6307\u5b9a\u5206\u5e03\u7684\u968f\u673a\u6570\u3002 \u4f8b\u5982\u6570\u503c\u7b56\u5212\u8981\u6c42\u7684\u62bd\u5361\u6982\u7387\u5206\u5e03\u662f\uff1a 2% \u51fa\u91d1\u5361 10% \u51fa\u84dd\u5361 80% \u51fa\u767d\u5361 8% \u51fa\u7b54\u8fa9 \u90a3\u4e48\u4f60\u8f6c\u6362\u4e00\u4e0b\u4efb\u52a1\u3002\u53d8\u6210\u968f\u673a\u751f\u6210\u4e00\u4e2a 0 \u5230 1 \u7684\u6d6e\u70b9\u6570\uff0c\u7136\u540e\u5224\u65ad\uff1a \u5c0f\u4e8e 0.02 \u65f6\uff0c\u51fa\u91d1\u5361 \u5c0f\u4e8e 0.12 \u65f6\uff0c\u51fa\u84dd\u5361 \u5c0f\u4e8e 0.92 \u65f6\uff0c\u51fa\u767d\u5361 \u5c0f\u4e8e 1.00 \u65f6\uff0c\u51fa\u7b54\u8fa9 \u8fd9\u4e2a\u8f6c\u6362\u8fc7\u7a0b\u5c31\u662f CDF \u79ef\u5206\u3002\u5982\u679c\u4f60\u628a\u8fd9 4 \u4e2a\u6570\u6309\u7167\u987a\u5e8f\u6392\u5217\uff0c\u5c31\u662f\u4e00\u4e2a\u6709\u5e8f vector\u3002 \u6807\u51c6\u5e93\u63d0\u4f9b\u4e86 std::partial_sum \uff08\u4e0d\u7cbe\u51c6\uff09\u6216 std::inclusive_scan \uff08\u66f4\u7cbe\u51c6\uff0cC++17 \u5f15\u5165\uff09\u90fd\u53ef\u4ee5\u8ba1\u7b97\u4e00\u4e2a\u6570\u7ec4\u7684 CDF \u79bb\u6563\u79ef\u5206\u3002 vector probs = {0.02, 0.1, 0.8, 0.08}; vector cdf; // \u8ba1\u7b97 probs \u7684 CDF \u79ef\u5206\uff0c\u5b58\u5165 cdf \u6570\u7ec4 std::inclusive_scan(probs.begin(), probs.end(), std::back_inserter(cdf)); // cdf = {0.02, 0.12, 0.92, 1.00} \u662f\u4e00\u4e2a\u6709\u5e8f vector\uff0c\u53ef\u4ee5\u8fd0\u7528\u4e8c\u5206\u6cd5\u5b9a\u4f4d vector result = {\"\u91d1\u5361\", \"\u84dd\u5361\", \"\u767d\u5361\", \"\u7b54\u8fa9\"}; // \u751f\u6210 100 \u4e2a\u968f\u673a\u6570\uff1a for (int i = 0; i < 100; ++i) { double r = rand() / (RAND_MAX + 1.0); int index = lower_bound(cdf.begin(), cdf.end(), r) - cdf.begin(); cout << \"\u4f60\u62bd\u5230\u4e86\" << result[index] << endl; } \u987a\u4fbf\u4e00\u63d0\uff0cCDF \u79ef\u5206\u7684\u9006\u8fd0\u7b97\u662f\u79bb\u6563\u5fae\u5206\uff1a std::adjacent_difference \uff0c\u53ef\u4ee5\u4ece cdf \u6570\u7ec4\u590d\u539f\u51fa probs \u6570\u7ec4\u3002 C++ \u968f\u673a\u6570\u7684\u6b63\u786e\u751f\u6210\u65b9\u5f0f // \u9519\u8bef\u7684\u5199\u6cd5\uff1a int r = rand() % 10; // \u8fd9\u6837\u5199\u662f\u9519\u8bef\u7684\uff01 rand() \u7684\u8fd4\u56de\u503c\u8303\u56f4\u662f [0, RAND_MAX]\uff0cRAND_MAX \u5728\u4e0d\u540c\u5e73\u53f0\u4e0b\u4e0d\u540c\uff0c\u5728 Windows \u5e73\u53f0\u7684\u662f 32767\uff0c\u5373 rand() \u53ea\u80fd\u751f\u6210 0\uff5e32767 \u4e4b\u95f4\u7684\u968f\u673a\u6570\u3002 \u5982\u679c\u60f3\u8981\u751f\u6210 0\uff5e9 \u4e4b\u95f4\u7684\u968f\u673a\u6570\uff0c\u6700\u7b80\u5355\u7684\u529e\u6cd5\u662f\uff1a int r = rand() % 10; \u7136\u800c\u8fd9\u79cd\u65b9\u6cd5\u6709\u4e2a\u81f4\u547d\u7684\u95ee\u9898\uff1a\u4e0d\u540c\u7684\u968f\u673a\u6570\u751f\u6210\u6982\u7387\u4e0d\u4e00\u6837\u3002 \u4f8b\u5982\u628a [0, RAND_MAX] \u5747\u5300\u5730\u5206\u6210 10 \u4efd\uff0c\u6bcf\u4efd 3276.7\u3002\u90a3\u4e48 0\uff5e6 \u4e4b\u95f4\u7684\u6570\u5b57\u51fa\u73b0\u7684\u6982\u7387\u662f 3276.7 / 32767 = 10.0003%\uff0c\u800c 7\uff5e9 \u4e4b\u95f4\u7684\u6570\u5b57\u51fa\u73b0\u7684\u6982\u7387\u662f 3276.7 / 32767 = 9.997%\u3002 \u8fd9\u6837\u5c31\u4e0d\u662f\u771f\u6b63\u7684\u5747\u5300\u5206\u5e03\uff0c\u8fd9\u53ef\u80fd\u4f1a\u5f71\u54cd\u7a0b\u5e8f\u7684\u6b63\u786e\u6027\u3002 \u5f53\u6a21\u6570\u5927\u7684\u65f6\u5019\u4e0d\u5747\u5300\u6027\u4f1a\u53d8\u5f97\u7279\u522b\u660e\u663e\uff0c\u4f8b\u5982 rand() % 10000 \u3002 RAND_MAX \u5728\u4e0d\u540c\u5e73\u53f0\u4e0d\u540c\u7684\u7279\u6027\u4e5f\u8ba9\u8de8\u5e73\u53f0\u5f00\u53d1\u8005\u5f88\u5934\u5927\u3002 rand \u4f7f\u7528\u5168\u5c40\u53d8\u91cf\u5b58\u50a8\u79cd\u5b50\uff0c\u5bf9\u591a\u7ebf\u7a0b\u4e0d\u53cb\u597d\u3002 \u65e0\u6cd5\u72ec\u7acb\u7684\u4e3a\u591a\u4e2a\u751f\u6210\u5e8f\u5217\u8bbe\u5b9a\u72ec\u7acb\u7684\u79cd\u5b50\uff0c\u4e00\u4e9b\u6e38\u620f\u53ef\u80fd\u9700\u8981\u7528\u5230\u591a\u4e2a\u968f\u673a\u5e8f\u5217\uff0c\u5404\u81ea\u6709\u72ec\u7acb\u7684\u79cd\u5b50\u3002 \u53ea\u80fd\u751f\u6210\u5747\u5300\u5206\u5e03\u7684\u6574\u6570\uff0c\u4e0d\u80fd\u751f\u6210\u5e42\u7387\u5206\u5e03\u3001\u6b63\u592a\u5206\u5e03\u7b49\uff0c\u751f\u6210\u6d6e\u70b9\u6570\u4e5f\u6bd4\u8f83\u9ebb\u70e6\u3002 \u4f7f\u7528 srand(time(NULL)) \u65e0\u6cd5\u5b89\u5168\u5730\u751f\u6210\u968f\u673a\u6570\u7684\u521d\u59cb\u79cd\u5b50\uff0c\u5bb9\u6613\u88ab\u9ed1\u5ba2\u9884\u6d4b\u5e76\u653b\u51fb\u3002 rand \u7684\u7b97\u6cd5\u5b9e\u73b0\u6ca1\u6709\u5b98\u65b9\u89c4\u5b9a\uff0c\u5728\u4e0d\u540c\u5e73\u53f0\u5404\u6709\u4e0d\u540c\uff0c\u4ea7\u751f\u7684\u968f\u673a\u6570\u5e8f\u5217\u53ef\u80fd\u4e0d\u540c\u3002 \u4e3a\u6b64\uff0cC++ \u63d0\u51fa\u4e86\u66f4\u52a0\u4e13\u4e1a\u7684\u968f\u673a\u6570\u751f\u6210\u5668\uff1a \u5e93\u3002 // \u4f7f\u7528 \u5e93\u751f\u6210 0\uff5e9 \u4e4b\u95f4\u7684\u968f\u673a\u6570\uff1a #include #include int main() { uint64_t seed = std::random_device()(); std::mt19937 gen(seed); std::uniform_int_distribution dis(0, 9); for (int i = 0; i < 100; ++i) { int r = dis(gen); std::cout << r << \" \"; } } \u8fd9\u6837\u5c31\u53ef\u4ee5\u751f\u6210 0\uff5e9 \u4e4b\u95f4\u7684\u5747\u5300\u5206\u5e03\u7684\u968f\u673a\u6570\u4e86\u3002 std::random_device \u662f\u4e00\u4e2a\u968f\u673a\u6570\u79cd\u5b50\u751f\u6210\u5668\uff0c\u5b83\u4f1a\u5229\u7528\u7cfb\u7edf\u7684\u968f\u673a\u8bbe\u5907\uff08\u5982\u679c\u6709\u7684\u8bdd\uff0c\u5426\u5219\u4f1a\u629b\u51fa\u5f02\u5e38\uff09\u751f\u6210\u4e00\u4e2a\u5b89\u5168\u7684\u968f\u673a\u6570\u79cd\u5b50\uff0c\u9ed1\u5ba2\u65e0\u6cd5\u9884\u6d4b\u3002 std::mt19937 \u662f\u4e00\u4e2a\u968f\u673a\u6570\u751f\u6210\u5668\uff0c\u5b83\u4f1a\u5229\u7528\u521d\u59cb\u79cd\u5b50\u751f\u6210\u4e00\u4e2a\u968f\u673a\u6570\u5e8f\u5217\u3002\u5e76\u4e14\u5fc5\u5b9a\u662f MT19937 \u8fd9\u4e2a\u9ad8\u5f3a\u5ea6\u7684\u968f\u673a\u7b97\u6cd5\uff0c\u6240\u6709\u5e73\u53f0\u90fd\u4e00\u6837\u3002 std::uniform_int_distribution \u662f\u4e00\u4e2a\u5206\u5e03\u5668\uff0c\u5b83\u53ef\u4ee5\u628a\u5747\u5300\u5206\u5e03\u7684\u968f\u673a\u6570\u6620\u5c04\u5230\u6211\u4eec\u60f3\u8981\u7684\u4e0a\u4e0b\u754c\u4e2d\u3002\u91cc\u9762\u7684\u5b9e\u73b0\u7c7b\u4f3c\u4e8e gen() % 10 \uff0c\u4f46\u901a\u8fc7\u6570\u5b66\u673a\u5236\u4fdd\u8bc1\u4e86\u7edd\u5bf9\u5747\u5300\u6027\u3002 \u7c7b\u4f3c\u7684\u8fd8\u6709 std::uniform_real_distribution \u7528\u4e8e\u751f\u6210\u6d6e\u70b9\u6570\uff0c std::normal_distribution \u7528\u4e8e\u751f\u6210\u6b63\u592a\u5206\u5e03\u7684\u968f\u673a\u6570\uff0c std::poisson_distribution \u7528\u4e8e\u751f\u6210\u6cca\u677e\u5206\u5e03\u7684\u968f\u673a\u6570\uff0c\u7b49\u7b49\u3002 \u5982\u679c\u559c\u6b22\u8001\u5f0f\u7684\u51fd\u6570\u8c03\u7528\u98ce\u683c\u63a5\u53e3\uff0c\u53ef\u4ee5\u5c01\u88c5\u4e00\u4e2a\u65b0\u7684 C++ \u91cd\u7f6e\u7248\u5b89\u5168 rand \uff1a thread_local std::mt19937 gen(std::random_device{}()); // \u6bcf\u7ebf\u7a0b\u4e00\u4e2a\uff0c\u4e92\u4e0d\u51b2\u7a81 int randint(int min, int max) { return std::uniform_int_distribution(min, max)(gen); } float randfloat(float min, float max) { return std::uniform_real_distribution(min, max)(gen); } const \u5c45\u7136\u5e94\u8be5\u540e\u7f6e\u2026 \u4f17\u6240\u5468\u77e5\uff0c const \u5728\u6307\u9488\u7b26\u53f7 * \u7684\u524d\u540e\uff0c\u6548\u679c\u662f\u4e0d\u540c\u7684\u3002 const int *p; int *const p; \u4f60\u80fd\u770b\u51fa\u6765\u4e0a\u9762\u8fd9\u4e2a const \u5206\u522b\u4fee\u9970\u7684\u662f\u8c01\u5417\uff1f const int *p; // \u6307\u9488\u6307\u5411\u7684 int \u4e0d\u53ef\u53d8 int *const p; // \u6307\u9488\u672c\u8eab\u4e0d\u53ef\u6539\u53d8\u6307\u5411 \u4e3a\u4e86\u770b\u8d77\u6765\u66f4\u52a0\u660e\u786e\uff0c\u6211\u901a\u5e38\u90fd\u4f1a\u540e\u7f6e\u6240\u6709\u7684 const \u4fee\u9970\u3002 int const *p; // \u6307\u9488\u6307\u5411\u7684 int \u4e0d\u53ef\u53d8 int *const p; // \u6307\u9488\u672c\u8eab\u4e0d\u53ef\u6539\u53d8\u6307\u5411 \u8fd9\u6837\u5c31\u4e00\u76ee\u4e86\u7136\uff0cconst \u603b\u662f\u5728\u4fee\u9970\u4ed6\u524d\u9762\u7684\u4e1c\u897f\uff0c\u800c\u4e0d\u662f\u540e\u9762\u3002 \u4e3a\u4ec0\u4e48 int *const \u4fee\u9970\u7684\u662f int * \u4e5f\u5c31\u5f88\u5bb9\u6613\u7406\u89e3\u4e86\u3002 int const i; int const *p; int *const q; int const &r; \u4e3e\u4e2a\u4f8b\u5b50\uff1a int i, j; int *const p = &i; *p = 1; // OK\uff1ap \u6307\u5411\u7684\u5bf9\u8c61\u53ef\u53d8 p = &j; // \u9519\u8bef\uff1ap \u672c\u8eab\u4e0d\u53ef\u53d8\uff0c\u4e0d\u80fd\u6539\u53d8\u6307\u5411 int i, j; int const *p = &i; *p = 1; // \u9519\u8bef\uff1ap \u6307\u5411\u7684\u5bf9\u8c61\u4e0d\u53ef\u53d8 p = &j; // OK\uff1ap \u672c\u8eab\u53ef\u53d8\uff0c\u53ef\u4ee5\u6539\u53d8\u6307\u5411 int i, j; int const *const p = &i; *p = 1; // \u9519\u8bef\uff1ap \u6307\u5411\u7684\u5bf9\u8c61\u4e0d\u53ef\u53d8 p = &j; // \u9519\u8bef\uff1ap \u672c\u8eab\u4e5f\u4e0d\u53ef\u53d8\uff0c\u4e0d\u80fd\u6539\u53d8\u6307\u5411 int const * \u548c const int * \u7b49\u4ef7\uff01\u53ea\u6709 int *const \u662f\u4e0d\u540c\u7684\u3002 \u51fd\u6570\u53c2\u6570\u4e5f\u53ef\u4ee5 auto \u5927\u5bb6\u90fd\u77e5\u9053\uff0c\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\u53ef\u4ee5\u58f0\u660e\u4e3a auto \uff0c\u8ba9\u5176\u81ea\u52a8\u63a8\u5bfc\u3002 auto square() { // int square(); return 1; } \u4f46\u4f60\u77e5\u9053\u4ece C++20 \u5f00\u59cb\uff0c\u53c2\u6570\u4e5f\u53ef\u4ee5\u58f0\u660e\u4e3a auto \u4e86\u5417\uff1f auto square(auto x) { // T square(T x); return x * x; } square(1); // square(int) square(3.14); // square(double) \u7b49\u4ef7\u4e8e\u4ee5\u4e0b\u201c\u6a21\u677f\u51fd\u6570\u201d\u7684\u4f20\u7edf\u5199\u6cd5\uff1a template T square(T x) { return x * x; } square(1); // square(int) square(3.14); // square(double) \u56e0\u4e3a\u662f\u6a21\u677f\u51fd\u6570\uff0c\u6240\u4ee5\u4e5f\u5f88\u96be\u5206\u79bb\u58f0\u660e\u548c\u5b9a\u4e49\uff0c\u53ea\u9002\u7528\u4e8e\u5934\u6587\u4ef6\u4e2d\u5c31\u5730\u5b9a\u4e49\u51fd\u6570\u7684\u60c5\u51b5\u3002 auto \u53c2\u6570\u8fd8\u53ef\u4ee5\u5e26\u6709\u5f15\u7528\uff1a auto square(auto const &x) { // T square(T const &x); return x * x; } square(1); // square(int const &) square(3.14); // square(double const &) \u7b49\u4ef7\u4e8e\uff1a template T square(T const &x) { return x * x; } auto \u53c2\u6570\u6700\u597d\u7684\u914d\u5408\u83ab\u8fc7\u4e8e\u662f\u4e0e\u540c\u6837 C++20 \u5f15\u5165\u7684 concept\uff1a auto square(std::integral auto x) { // T square(T x) requires std::integral return x * x; } square(1); // square(int) square(3.14); // \u9519\u8bef\uff1adouble \u4e0d\u662f\u6574\u6570\u7c7b\u578b \u7b49\u4ef7\u4e8e\uff1a template requires std::integral T square(T x) { return x * x; } \u6216\u8005\uff1a template T square(T x) { return x * x; } \u8bfb\u53d6\u6574\u4e2a\u6587\u4ef6\u5230\u5b57\u7b26\u4e32 std::string file_get_content(std::string const &filename) { std::ifstream ifs(filename, std::ios::in | std::ios::binary); std::istreambuf_iterator iit(ifs), iite; std::string content(iit, iite); return content; } void file_put_content(std::string const &filename, std::string const &content) { std::ofstream ofs(filename, std::ios::out | std::ios::binary); ofs << content; } \u8fd9\u6837\u5c31\u53ef\u4ee5\u628a\u6574\u4e2a\u6587\u4ef6\u8bfb\u53d6\u5230\u5185\u5b58\u4e2d\uff0c\u5f88\u65b9\u4fbf\u5730\u8fdb\u884c\u5904\u7406\u540e\u518d\u5199\u56de\u6587\u4ef6\u3002 \u63a8\u8350\u7528 std::ios::binary \u9009\u9879\u6253\u5f00\u4e8c\u8fdb\u5236\u6587\u4ef6\uff0c\u5426\u5219\u5b57\u7b26\u4e32\u4e2d\u51fa\u73b0 '\\n' \u65f6\uff0c\u4f1a\u88ab MSVC \u6807\u51c6\u5e93\u81ea\u52a8\u8f6c\u6362\u6210 '\\r\\n' \u6765\u5199\u5165\uff0c\u59a8\u788d\u6211\u4eec\u8de8\u5e73\u53f0\u3002 \u9010\u884c\u8bfb\u53d6\u6587\u672c\u6587\u4ef6 std::ifstream fin(\"test.txt\"); std::string line; while (std::getline(fin, line)) { std::cout << \"\u8bfb\u53d6\u5230\u4e00\u884c\uff1a\" << line << '\\n'; } \u5b57\u7b26\u4e32\u5207\u7247 #include #include #include std::vector split_str(std::string const &str, char ch) { std::stringstream ss(str); std::string line; std::vector res; while (std::getline(ss, line, ch)) { res.push_back(std::move(line)); } return res; } auto res = split_str(\"hello world\", ' '); // res = {\"hello\", \"world\"} cout \u4e0d\u9700\u8981 endl int a = 42; printf(\"%d\\n\", a); \u4e07\u4e00\u4f60\u5199\u9519\u4e86 % \u540e\u9762\u7684\u7c7b\u578b\uff0c\u7f16\u8bd1\u5668\u4e0d\u4f1a\u6709\u4efb\u4f55\u62a5\u9519\uff0c\u7559\u4e0b\u9690\u60a3\u3002 int a = 42; printf(\"%s\\n\", a); // \u7f16\u8bd1\u5668\u4e0d\u62a5\u9519\uff0c\u4f46\u662f\u8fd0\u884c\u65f6\u4f1a\u5d29\u6e83\uff01 C++ \u4e2d\u6709\u66f4\u5b89\u5168\u7684\u8f93\u51fa\u65b9\u5f0f cout \uff0c\u901a\u8fc7 C++ \u7684\u91cd\u8f7d\u673a\u5236\uff0c\u65e0\u9700\u624b\u52a8\u6307\u5b9a % \uff0c\u81ea\u52a8\u5c31\u80fd\u63a8\u5bfc\u7c7b\u578b\u3002 int a = 42; cout << a << endl; double d = 3.14; cout << d << endl; cout << \"Hello, World!\" << endl; endl \u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u6d41\u64cd\u4f5c\u7b26\uff0c\u4f5c\u7528\u7b49\u4ef7\u4e8e\u5148\u8f93\u51fa\u4e00\u4e2a '\\n' \u7136\u540e flush \u3002 cout << \"Hello, World!\" << '\\n'; cout.flush(); \u4f46\u5b9e\u9645\u4e0a\uff0c\u8f93\u51fa\u6d41 cout \u9ed8\u8ba4\u7684\u8bbe\u7f6e\u5c31\u662f\u201c\u884c\u5237\u65b0\u7f13\u5b58\u201d\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u68c0\u6d4b\u5230 '\\n' \u65f6\uff0c\u5c31\u4f1a\u81ea\u52a8\u5237\u65b0\u4e00\u6b21\uff0c\u6839\u672c\u4e0d\u9700\u8981\u6211\u4eec\u624b\u52a8\u5237\u65b0\uff01 \u5982\u679c\u8fd8\u7528 endl \u7684\u8bdd\uff0c\u5c31\u76f8\u5f53\u4e8e\u5237\u65b0\u4e86\u4e24\u6b21\uff0c\u6d6a\u8d39\u6027\u80fd\u3002 \u53ef\u89c1\uff0cendl \u662f\u4e00\u4e2a\u88ab\u5f88\u591a\u65e0\u8111\u6559\u6750\u9519\u8bef\u5ba3\u4f20\uff0c\u5b9e\u9645\u4e0a\u6839\u672c\u591a\u6b64\u4e00\u4e3e\u7684\u4e1c\u897f\u3002 \u6211\u4eec\u53ea\u9700\u8981\u8f93\u51fa '\\n' \u5c31\u53ef\u4ee5\u4e86\uff0c\u6bcf\u6b21\u6362\u884c\u65f6 cout \u90fd\u4f1a\u81ea\u52a8\u5237\u65b0\u3002 cout << \"Hello, World!\" << '\\n'; endl \u662f\u4e00\u4e2a\u5178\u578b\u7684\u4ee5\u8bb9\u4f20\u8bb9\u9519\u8bef\u5199\u6cd5\uff0c\u53ea\u6709\u5f53\u4f60\u7684\u8f93\u51fa\u662f\u6307\u5411\u53e6\u4e00\u4e2a\u8fdb\u7a0b\u7684\u7ba1\u9053\u65f6\uff0c\u5176\u9644\u5e26\u7684\u5237\u65b0\u529f\u80fd\u624d\u6709\u4f5c\u7528\u3002 \u5f53\u8f93\u51fa\u662f\u7ba1\u9053\u6216\u6587\u4ef6\u65f6\uff0c cout \u9700\u8981 endl \u624d\u80fd\u5237\u65b0\u3002 \u5f53\u8f93\u51fa\u662f\u666e\u901a\u63a7\u5236\u53f0\u65f6\uff0c cout \u53ea\u9700 '\\n' \u5c31\u80fd\u5237\u65b0\u4e86\uff0c\u6839\u672c\u7528\u4e0d\u7740 endl \u3002 \u800c\u4e14\uff0c\u7ba1\u9053\u6216\u6587\u4ef6\u5b9e\u9645\u4e0a\u4e5f\u4e0d\u5b58\u5728\u9891\u7e41\u5237\u65b0\u7684\u9700\u6c42\uff0c\u53cd\u6b63 ifstream \u6790\u6784\u65f6\u603b\u662f\u4f1a\u81ea\u52a8\u5237\u65b0\u5199\u5165\u78c1\u76d8\u3002 \u56e0\u6b64\uff0c endl \u64cd\u7eb5\u7b26\u5927\u591a\u65f6\u5019\u90fd\u662f\u5197\u4f59\u7684\uff1a\u63a7\u5236\u53f0\u8f93\u51fa\u7684 cout \u53ea\u9700\u8981\u5b57\u7b26\u6216\u5b57\u7b26\u4e32\u4e2d\u542b\u6709 '\\n' \u5c31\u5237\u65b0\u4e86\uff0c\u5373\u4f7f\u662f\u6587\u4ef6\u8bfb\u5199\u4e5f\u5f88\u5c11\u4f1a\u4f7f\u7528 endl \u3002 \u5982\u679c\u786e\u5b9e\u9700\u8981\u5f3a\u5236\u5237\u65b0\uff0c\u4e5f\u53ef\u4ee5\u7528 flush \u8fd9\u79cd\u66f4\u52a0\u53ef\u8bfb\u7684\u5199\u6cd5\uff1a int num; cout << \"please input the number: \" << flush; cin >> num; ofstream fout(\"log.txt\"); fout << \"immediate write 1\\n\" << flush; sleep(1); fout << \"immediate write 2\\n\" << flush; fout.close(); // \u5173\u95ed\u6587\u4ef6\u65f6\u603b\u662f\u81ea\u52a8 flush\uff0c\u4e0d\u4f1a\u6709\u6b8b\u7559\u672a\u5199\u5165\u7684\u5b57\u7b26 \u591a\u7ebf\u7a0b\u4e2d cout \u51fa\u73b0\u4e71\u5e8f\uff1f \u540c\u5b66\uff1a\u5c0f\u5f6d\u8001\u5e08\uff0c\u6211\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e2d\u4f7f\u7528\uff1a cout << \"the answer is \" << 42 << '\\n'; \u53d1\u73b0\u8f93\u51fa\u4e71\u5957\u4e86\uff01\u8fd9\u662f\u4e0d\u662f\u8bf4\u660e cout \u4e0d\u662f \u591a\u7ebf\u7a0b\u5b89\u5168 \u7684\u5462\uff1f \u5c0f\u5f6d\u8001\u5e08\uff1acout \u662f\u4e00\u4e2a\u201c\u540c\u6b65\u6d41\u201d\uff0c\u662f \u591a\u7ebf\u7a0b\u5b89\u5168 \u7684\uff0c\u9519\u8bef\u7684\u662f\u4f60\u7684\u4f7f\u7528\u65b9\u5f0f\u3002 \u5982\u679c\u4ed6\u4e0d\u591a\u7ebf\u7a0b\u5b89\u5168\uff0c\u90a3\u591a\u7ebf\u7a0b\u5730\u8c03\u7528\u4ed6\u5c31\u4e0d\u662f\u8f93\u51fa\u4e71\u5e8f\uff0c\u800c\u662f\u7a0b\u5e8f\u5d29\u6e83\u4e86\u3002 \u4f46\u662f\uff0ccout \u7684\u7ebf\u7a0b\u5b89\u5168\uff0c\u53ea\u80fd\u4fdd\u8bc1\u6bcf\u4e00\u6b21 operator<< \u90fd\u662f\u539f\u5b50\u7684\uff0c\u6bcf\u4e00\u6b21\u5355\u72ec\u7684 operator<< \u4e0d\u4f1a\u88ab\u5176\u4ed6\u4eba\u6253\u65ad\u3002 \u4f46\u4f17\u6240\u5468\u77e5\uff0ccout \u4e3a\u4e86\u652f\u6301\u7ea7\u8054\u8c03\u7528\uff0c\u4ed6\u7684 operator<< \u90fd\u662f\u8fd4\u56de\u81ea\u5df1\u7684\uff0c\u4e0a\u9762\u7684\u4ee3\u7801\u5b9e\u9645\u4e0a\u7b49\u4ef7\u4e8e\u5206\u522b\u4e09\u6b21\u8c03\u7528 cout \u7684 operator<< \u3002 cout << \"the answer is \" << 42 << '\\n'; // \u7b49\u4ef7\u4e8e\uff1a cout << \"the answer is \"; cout << 42; cout << '\\n'; \u53d8\u6210\u4e86\u4e09\u6b21 operator<< \uff0c\u6bcf\u4e00\u6b21\u90fd\u662f\u201c\u5404\u81ea\u201d\u539f\u5b50\u7684\uff0c\u4f46\u4e09\u4e2a\u539f\u5b50\u52a0\u5728\u4e00\u8d77\u5c31\u4e0d\u662f\u539f\u5b50\u4e86\u3002 \u800c\u662f\u5206\u5b50\u4e86 :) \u4ed6\u4eec\u4e2d\u95f4\u53ef\u80fd\u7a7f\u63d2\u4e86\u5176\u4ed6\u7ebf\u7a0b\u7684 cout\uff0c\u4ece\u800c\u5bfc\u81f4\u4f60 \"the answer is\" \u6253\u5370\u5b8c\u540e\uff0c\u88ab\u5176\u4ed6\u7ebf\u7a0b\u7684 '\\n' \u63d2\u5165\u8fdb\u6765\uff0c\u5bfc\u81f4\u6362\u884c\u6df7\u4e71\u3002 std::cout \u7684 operator<< \u8c03\u7528\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u4e0d\u4f1a\u88ab\u6253\u65ad\uff0c\u4f46\u591a\u4e2a operator<< \u7684\u8c03\u7528\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e2d\u53ef\u80fd\u4f1a \u4ea4\u9519 \uff0c\u5bfc\u81f4\u8f93\u51fa\u7ed3\u679c\u6df7\u4e71\u3002 \u66f4\u591a\u7ec6\u8282\u8bf7\u770b\u6211\u4eec\u7684 \u591a\u7ebf\u7a0b\u4e13\u9898 \u3002 \u89e3\u51b3\u65b9\u6cd5\u662f\uff0c\u5148\u521b\u5efa\u4e00\u4e2a\u53ea\u5c5e\u4e8e\u5f53\u524d\u7ebf\u7a0b\u7684 ostringstream \uff0c\u6700\u540e\u4e00\u6b21\u6027\u8c03\u7528\u4e00\u6b21 cout \u7684 operator<< \uff0c\u8ba9\u201c\u539f\u5b50\u201d\u7684\u5355\u4f4d\u53d8\u6210\u201c\u4e00\u884c\u201d\u800c\u4e0d\u662f\u4e00\u4e2a\u5b57\u7b26\u4e32\u3002 ostringstream oss; oss << \"the answer is \" << 42 << '\\n'; cout << oss.str(); \u6216\u8005\uff0c\u4f7f\u7528 std::format \uff1a cout << std::format(\"the answer is {}\\n\", 42); \u603b\u4e4b\uff0c\u5c31\u662f\u8981\u8ba9 operator<< \u53ea\u6709\u4e00\u6b21\uff0c\u81ea\u7136\u5c31\u662f\u6ca1\u6709\u4ea4\u9519\u3002 \u5728 C++20 \u4e2d\uff0c\u53ef\u4ee5\u6539\u7528 std::osyncstream(std::cout) \u4ee3\u66ff std::cout : std::osyncstream(std::cout) << \"the answer is \" << 42 << '\\n'; std::osyncstream \u53ef\u4ee5\u4fdd\u8bc1\uff1a1. \u4e0d\u4f1a\u4ea7\u751f\u6570\u636e\u7ade\u4e89\uff1b2. \u4e0d\u4f1a\u53d1\u751f\u7a7f\u63d2\u548c\u622a\u65ad\u3002\u53ef\u4ee5\u7406\u89e3\u4e3a std::osyncstream \u5728\u6784\u9020\u65f6\u5bf9\u7f13\u51b2\u533a\u4e0a\u9501\uff0c\u5728\u6790\u6784\u65f6\u89e3\u9501\u3002 \u5982\u679c\u4f60\u7684\u6807\u51c6\u5e93\u652f\u6301 C++23\uff0c\u8fd8\u53ef\u4ee5\u7528 std::println \uff0c\u8fd9\u4e2a\u51fd\u6570\u7684\u8f93\u51fa\u4e5f\u662f\u539f\u5b50\u7684\uff08\u7b2c\u4e09\u65b9\u5e93\u5982 fmt::println \u4ea6\u53ef\uff09\uff1a std::println(\"the answer is {}\", 42); cerr \u4e0e cout \u7684\u6289\u62e9 \u5982\u679c\u4f60\u7684\u76ee\u7684\u662f\u8c03\u8bd5\u548c\u62a5\u9519\uff0c\u53ef\u4ee5\u8003\u8651\u7528 cerr \uff01 \u4ed6\u4f1a\u5728\u6bcf\u6b21 << \u65f6\u5237\u65b0\uff0c cerr \u624d\u662f\u6700\u9002\u5408\u6253\u5370\u9519\u8bef\u548c\u8c03\u8bd5\u4fe1\u606f\u7684\u6d41\u3002 cout \u7684\u4f18\u70b9\u662f\u4e0d\u9700\u8981\u65f6\u523b\u5237\u65b0\uff0c\u6709\u66f4\u597d\u7684\u6027\u80fd\u3002 cout << \"hello\\n\"; cout << \"the answer is \"; cout << 42; *(int *)1 = 1; // \u5d29\u6e83\uff01 cout << \"!\\n\"; // \u56e0\u4e3a\u8fd8\u6ca1\u6709\u62b5\u8fbe \\n \u4ea7\u751f\u5237\u65b0\u5c31\u5d29\u6e83\uff0c\u5bfc\u81f4\u4e4b\u524d\u5c1a\u672a\u5237\u65b0\u7684 the answer is 42 \u4e22\u5931 \u53ef\u80fd\u7684\u8f93\u51fa\uff1a hello[\u6362\u884c] cerr << \"hello\\n\"; cerr << \"the answer is \"; cerr << 42; *(int *)1 = 1; // \u5d29\u6e83\uff01 cerr << \"!\\n\"; \u8f93\u51fa\uff1a hello[\u6362\u884c] the answer is 42 \u8fd8\u6709\u4e00\u4e2a\u7279\u70b9\uff1a cout \u8f93\u51fa\u5230\u201c\u6807\u51c6\u8f93\u51fa\u6d41\u201d\uff0c\u53ef\u4ee5\u88ab\u8f93\u51fa\u91cd\u5b9a\u5411\u5230\u6587\u4ef6\u7ba1\u9053\u3002\u800c cerr \u8f93\u51fa\u5230\u201c\u6807\u51c6\u9519\u8bef\u6d41\u201d\uff0c\u901a\u5e38\u4e0d\u4f1a\u88ab\u91cd\u5b9a\u5411\u5230\u6587\u4ef6\u6216\u7ba1\u9053\u3002 \u4f8b\u5982\uff0c\u53ef\u4ee5\u628a\u7a0b\u5e8f\u9884\u8ba2\u7684\u8ba1\u7b97\u7ed3\u679c\u5199\u5230 cout \uff0c\u628a\u8c03\u8bd5\u548c\u62a5\u9519\u4fe1\u606f\u5199\u5230 cerr \uff0c\u8fd9\u6837\u7528\u6237\u5c31\u53ef\u4ee5\u901a\u8fc7 > \u91cd\u5b9a\u5411\u8ba1\u7b97\u7ed3\u679c\uff0c\u800c\u8c03\u8bd5\u548c\u62a5\u9519\u4fe1\u606f\u5219\u6b63\u5e38\u8f93\u51fa\u5230\u5c4f\u5e55\u4e0a\uff0c\u4e0d\u53d7\u91cd\u5b9a\u5411\u5f71\u54cd\u3002 cout << \"1 3 5 7\\n\"; cerr << \"ERROR: this is an error message!\\n\"; cout << \"11 13 17 19\\n\"; $ g++ prime.cpp -o prime $ ./prime 1 3 5 7 ERROR: this is an error message! 11 13 17 19 $ ./prime > output.txt ERROR: this is an error message! $ cat output.txt 1 3 5 7 11 13 17 19 \u667a\u80fd\u6307\u9488\u9632\u6b62\u5927\u5bf9\u8c61\u79fb\u52a8 \u6211\u4eec\u8bf4\u4e00\u4e2a\u7c7b\u578b\u5927\uff0c\u6709\u4e24\u79cd\u60c5\u51b5\u3002 \u7c7b\u672c\u8eab\u5f88\u5927\uff1a\u4f8b\u5982 array \u7c7b\u672c\u8eab\u4e0d\u5927\uff0c\u4f46\u5176\u6307\u5411\u7684\u5bf9\u8c61\u5927\uff0c\u4e14\u8be5\u7c7b\u662f\u6df1\u62f7\u8d1d\uff0c\u5bf9\u8be5\u7c7b\u7684\u62f7\u8d1d\u4f1a\u5f15\u8d77\u5176\u6307\u5411\u5bf9\u8c61\u7684\u62f7\u8d1d\uff1a\u4f8b\u5982 vector sizeof(array); // \u672c\u8eab 4000 \u5b57\u8282 sizeof(vector); // \u672c\u8eab 24 \u5b57\u8282\uff08\u6210\u5458\u662f 3 \u4e2a\u6307\u9488\uff09\uff0c\u6307\u5411\u7684\u6570\u7ec4\u53ef\u4ee5\u65e0\u9650\u589e\u5927 sizeof(vector) \u4e3a 24 \u5b57\u8282\u4ec5\u4e3a x86_64-pc-linux-gnu \u5e73\u53f0 libstdc++ \u5e93\u7684\u5b9e\u6d4b\u7ed3\u679c\uff0c\u5728 32 \u4f4d\u7cfb\u7edf\u4ee5\u53ca MSVC \u7684 Debug \u6a21\u5f0f STL \u4e0b\u53ef\u80fd\u5f97\u51fa\u4e0d\u540c\u7684\u7ed3\u679c\uff0c\u4e0d\u53ef\u4ee5\u4f9d\u8d56\u8fd9\u4e2a\u5e73\u53f0\u76f8\u5173\u7684\u7ed3\u679c\u6765\u7f16\u7a0b\u3002 \u5bf9\u4e8e vector\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 std::move \u79fb\u52a8\u8bed\u4e49\uff0c\u53ea\u62f7\u8d1d\u8be5\u7c7b\u672c\u8eab\u7684\u4e09\u4e2a\u6307\u9488\u6210\u5458\uff0c\u800c\u4e0d\u5bf9\u5176\u6307\u5411\u7684 4000 \u5b57\u8282\u6570\u7ec4\u8fdb\u884c\u6df1\u62f7\u8d1d\u3002 \u5bf9\u4e8e array\uff0c\u5219 std::move \u79fb\u52a8\u8bed\u4e49\u4e0e\u666e\u901a\u7684\u62f7\u8d1d\u6ca1\u6709\u533a\u522b\uff1aarray \u4f5c\u4e3a\u9759\u6001\u6570\u7ec4\u5bb9\u5668\uff0c\u4e0d\u662f\u901a\u8fc7\u201c\u6307\u9488\u6210\u5458\u201d\u6765\u4fdd\u5b58\u6570\u7ec4\u7684\uff0c\u800c\u662f\u76f4\u63a5\u628a\u6570\u7ec4\u5b58\u5728\u4ed6\u7684\u4f53\u5185\uff0c\u5bf9 array \u7684\u79fb\u52a8\u548c\u62f7\u8d1d\u662f\u5b8c\u5168\u4e00\u6837\u7684\uff01 \u603b\u4e4b\uff0c\u79fb\u52a8\u8bed\u4e49\u7684\u52a0\u901f\u6548\u679c\uff0c\u53ea\u5bf9\u91c7\u7528\u4e86\u201c\u6307\u9488\u95f4\u63a5\u5b58\u50a8\u52a8\u6001\u6570\u636e\u201d\u7684\u7c7b\u578b\uff08\u5982 vector\u3001map\u3001set\u3001string\uff09\u6709\u6548\u3002\u5bf9\u201c\u76f4\u63a5\u5b58\u50a8\u9759\u6001\u5927\u5c0f\u6570\u636e\u201d\u7684\u7c7b\u578b\uff08array\u3001tuple\u3001variant\u3001\u6210\u529f\u201c\u5c0f\u5b57\u7b26\u4e32\u4f18\u5316\u201d\u7684 string\uff09\u65e0\u6548\u3002 \u6240\u4ee5\uff0c\u8ba9\u5f88\u591a\u201c\u79fb\u52a8\u8bed\u4e49\u201d\u5b5d\u5b50\u5931\u671b\u4e86\uff1a\u201c\u672c\u8eab\u5f88\u5927\u201d\u7684\u7c7b\uff0c\u79fb\u52a8\u548c\u62f7\u8d1d\u4e00\u6837\u6162\uff01 \u90a3\u4e48\u73b0\u5728\u6211\u4eec\u6709\u4e2a\u8d85\u5927\u7684\u7c7b\uff1a using BigType = array; // 4000 \u5b57\u8282\u5927\u5c0f\u7684\u5e73\u5766\u7c7b\u578b vector arr; void func(BigType x) { arr.push_back(std::move(x)); // \u62f7\u8d1d 4000 \u5b57\u8282\uff0c\u8d85\u6162\uff0cmove \u4e5f\u6ca1\u7528 } int main() { BigType x; func(std::move(x)); // \u62f7\u8d1d 4000 \u5b57\u8282\uff0c\u8d85\u6162\uff0cmove \u4e5f\u6ca1\u7528 } \u5982\u4f55\u52a0\u901f\u8fd9\u79cd\u672c\u8eab\u8d85\u5927\u7684\u53d8\u91cf\u8f6c\u79fb\uff1f\u4f7f\u7528 const \u5f15\u7528\uff1a void func(BigType const &x) \u4f3c\u4e4e\u53ef\u4ee5\u907f\u514d\u4f20\u53c2\u65f6\u7684\u62f7\u8d1d\uff0c\u4f46\u662f\u4f9d\u7136\u4e0d\u80fd\u907f\u514d push_back \u63a8\u5165 vector \u65f6\u6240\u4e0d\u5f97\u5df2\u7684\u62f7\u8d1d\u3002 \u5c0f\u6280\u5de7\uff1a\u6539\u7528 unique_ptr using BigType = array; // 4000 \u5b57\u8282\u5927\u5c0f\u7684\u5e73\u5766\u7c7b\u578b using BigTypePtr = unique_ptr; vector arr; void func(BigTypePtr x) { arr.push_back(std::move(x)); // \u53ea\u62f7\u8d1d 8 \u5b57\u8282\u7684\u6307\u9488\uff0c\u5176\u6307\u5411\u7684 4000 \u5b57\u8282\u4e0d\u7528\u6df1\u62f7\u8d1d\u4e86\uff0c\u76f4\u63a5\u79fb\u52a8\u6240\u6709\u6743\u7ed9 vector \u91cc\u7684 BigTypePtr \u667a\u80fd\u6307\u9488 // \u7531\u4e8e\u79fb\u8d70\u4e86\u6240\u6709\u6743\uff0cx \u6b64\u65f6\u5df2\u7ecf\u4e3a nullptr } int main() { BigTypePtr x = make_unique(); // \u6ce8\u610f\uff1a\u7528\u667a\u80fd\u6307\u9488\u7684\u8bdd\uff0c\u9700\u8981\u7528 make_unique \u624d\u80fd\u521b\u5efa\u5bf9\u8c61\u4e86 func(std::move(x)); // \u53ea\u62f7\u8d1d 8 \u5b57\u8282\u7684\u6307\u9488 // \u7531\u4e8e\u79fb\u8d70\u4e86\u6240\u6709\u6743\uff0cx \u6b64\u65f6\u5df2\u7ecf\u4e3a nullptr } \u4e0a\u9762\u6574\u4e2a\u7a0b\u5e8f\u4e2d\uff0c\u4e00\u5f00\u59cb\u901a\u8fc7 make_unique \u521b\u5efa\u7684\u8d85\u5927\u5bf9\u8c61\uff0c\u5168\u7a0b\u6ca1\u6709\u53d1\u751f\u4efb\u4f55\u79fb\u52a8\uff0c\u907f\u514d\u4e86\u65e0\u8c13\u7684\u6df1\u62f7\u8d1d\u3002 \u5bf9\u4e8e\u4e0d\u652f\u6301\u79fb\u52a8\u6784\u9020\u51fd\u6570\u7684\u7c7b\u578b\u6765\u8bf4\uff0c\u4e5f\u53ef\u4ee5\u7528\u8fd9\u4e2a\u65b9\u6cd5\uff0c\u5c31\u80fd\u5728\u51fd\u6570\u4e4b\u95f4\u7a7f\u68ad\u81ea\u5982\u4e86\u3002 // \u70ed\u77e5\u8bc6\uff1astd::mutex \u4e0d\u652f\u6301\u79fb\u52a8 void func(std::mutex lock); int main() { std::mutex lock; func(std::move(lock)); // \u9519\u8bef\uff1amutex(mutex &&) = delete } void func(std::unique_ptr lock); int main() { std::unique_ptr lock = std::make_unique(); func(std::move(lock)); // OK\uff1a\u8c03\u7528\u7684\u662f unique_ptr(unique_ptr &&)\uff0c\u4e0d\u5173 mutex \u4ec0\u4e48\u4e8b } \u66f4\u597d\u7684\u662f shared_ptr \uff0c\u8fde std::move \u90fd\u4e0d\u7528\u5199\uff0c\u66f4\u7701\u5fc3\u3002 void func(std::shared_ptr lock); int main() { std::shared_ptr lock = std::make_shared(); func(lock); // OK\uff1a\u8c03\u7528\u7684\u662f shared_ptr(shared_ptr const &)\uff0c\u4e0d\u5173 mutex \u4ec0\u4e48\u4e8b func(lock); // OK\uff1ashared_ptr \u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u662f\u6d45\u62f7\u8d1d\uff0c\u5373\u4f7f\u6d45\u62f7\u8d1d\u53d1\u751f\u591a\u6b21\uff0c\u6307\u5411\u7684\u5bf9\u8c61\u4e5f\u4e0d\u4f1a\u88ab\u62f7\u8d1d\u6216\u79fb\u52a8 } optional \u5b9e\u73b0\u5ef6\u8fdf\u521d\u59cb\u5316 \u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a\u7c7b\uff0c\u5177\u6709\u81ea\u5b9a\u4e49\u7684\u6784\u9020\u51fd\u6570\uff0c\u4e14\u6ca1\u6709\u9ed8\u8ba4\u6784\u9020\u51fd\u6570\uff1a struct SomeClass { int m_i; int m_j; SomeClass(int i, int j) : m_i(i), m_j(j) {} }; \u5f53\u6211\u4eec\u9700\u8981\u201c\u5ef6\u8fdf\u521d\u59cb\u5316\u201d\u65f6\u600e\u4e48\u529e\uff1f SomeClass c; if (test()) { c = SomeClass(1, 2); } else { c = SomeClass(2, 3); } do_something(c); \u53ef\u4ee5\u5229\u7528 optional \u9ed8\u8ba4\u521d\u59cb\u5316\u4e3a\u201c\u7a7a\u201d\u7684\u7279\u6027\uff0c\u5b9e\u73b0\u5ef6\u8fdf\u8d4b\u503c\uff1a std::optional c; if (test()) { c = SomeClass(1, 2); } else { c = SomeClass(2, 3); } do_something(c.value()); // \u5982\u679c\u62b5\u8fbe\u6b64\u5904\u524d\uff0cc \u6ca1\u6709\u521d\u59cb\u5316\uff0c\u5c31\u4f1a\u62a5\u9519\uff0c\u4ece\u800c\u628a\u7f16\u8bd1\u671f\u7684\u672a\u521d\u59cb\u5316\u8f6c\u6362\u4e3a\u8fd0\u884c\u65f6\u5f02\u5e38 \u5c31\u7c7b\u4f3c\u4e8e Python \u4e2d\u5148\u7ed9\u53d8\u91cf\u8d4b\u503c\u4e3a None\uff0c\u7136\u540e\u5728\u5faa\u73af\u6216 if \u91cc\u6761\u4ef6\u6027\u5730\u8d4b\u503c\u4e00\u6837\u3002 \u5982\u679c\u8981\u8fdb\u4e00\u6b65\u907f\u514d c = \u65f6\uff0c\u79fb\u52a8\u6784\u9020\u7684\u5f00\u9500\uff0c\u4e5f\u53ef\u4ee5\u7528 unique_ptr \u6216 shared_ptr \uff1a std::shared_ptr c; if (test()) { c = std::make_shared(1, 2); } else { c = std::make_shared(2, 3); } do_something(c); // \u5982\u679c\u62b5\u8fbe\u6b64\u5904\u524d\uff0cc \u6ca1\u6709\u521d\u59cb\u5316\uff0c\u90a3\u4e48\u4f20\u5165\u7684\u5c31\u662f\u4e00\u4e2a nullptr\uff0cdo_something \u5185\u90e8\u9700\u8981\u8d1f\u8d23\u68c0\u6d4b\u6307\u9488\u662f\u5426\u4e3a nullptr \u5982\u679c do_something \u53c2\u6570\u9700\u8981\u7684\u662f\u539f\u59cb\u6307\u9488\uff0c\u53ef\u4ee5\u7528 .get() \u83b7\u53d6\u51fa\u6765\uff1a do_something(c.get()); // .get() \u53ef\u4ee5\u628a\u667a\u80fd\u6307\u9488\u8f6c\u6362\u56de\u539f\u59cb\u6307\u9488\uff0c\u4f46\u8bf7\u6ce8\u610f\u539f\u59cb\u6307\u9488\u4e0d\u6301\u6709\u5f15\u7528\uff0c\u4e0d\u4f1a\u5ef6\u4f38\u6307\u5411\u5bf9\u8c61\u7684\u751f\u547d\u5468\u671f \u5b9e\u9645\u4e0a\uff0cJava\u3001Python \u4e2d\u7684\u4e00\u5207\u5bf9\u8c61\uff08\u9664 int\u3001str \u7b49\u201c\u94a6\u5b9a\u201d\u7684\u57fa\u7840\u7c7b\u578b\u5916\uff09\u90fd\u662f\u5f15\u7528\u8ba1\u6570\u7684\u667a\u80fd\u6307\u9488 shared_ptr \uff0c\u53ea\u4e0d\u8fc7\u56e0\u4e3a\u4e00\u5207\u7686\u6307\u9488\u4e86\uff0c\u6240\u4ee5\u770b\u8d77\u6765\u597d\u50cf\u6ca1\u6709\u6307\u9488\u4e86\u3002 if-auto \u4e0e while-auto \u9700\u8981\u5148\u5b9a\u4e49\u4e00\u4e2a\u53d8\u91cf\uff0c\u7136\u540e\u5224\u65ad\u67d0\u4e9b\u6761\u4ef6\u7684\u60c5\u51b5\uff0c\u975e\u5e38\u5e38\u89c1\uff1a extern std::optional some_func(); auto opt = some_func(); if (opt.has_value()) { std::cout << opt.value(); } C++17 \u5f15\u5165\u7684 if-auto \u8bed\u6cd5\uff0c\u53ef\u4ee5\u5c31\u5730\u4e66\u5199\u53d8\u91cf\u5b9a\u4e49\u548c\u5224\u65ad\u6761\u4ef6\uff1a extern std::optional some_func(); if (auto opt = some_func(); opt.has_value()) { std::cout << opt.value(); } \u5bf9\u4e8e\u652f\u6301 (bool)opt \u7684 optional \u7c7b\u578b\u6765\u8bf4\uff0c\u540e\u9762\u7684\u6761\u4ef6\u4e5f\u53ef\u4ee5\u7701\u7565\uff1a extern std::optional some_func(); if (auto opt = some_func()) { std::cout << opt.value(); } // \u7b49\u4ef7\u4e8e\uff1a auto opt = some_func(); if (opt) { std::cout << opt.value(); } \u7c7b\u4f3c\u7684\u8fd8\u6709 while-auto\uff1a extern std::optional some_func(); while (auto opt = some_func()) { std::cout << opt.value(); } // \u7b49\u4ef7\u4e8e\uff1a while (true) { auto opt = some_func(); if (!opt) break; std::cout << opt.value(); } if-auto \u6700\u5e38\u89c1\u7684\u914d\u5408\u83ab\u8fc7\u4e8e map.find\uff1a std::map table; int key = 42; if (auto it = table.find(key); it != table.end()) { std::cout << it->second << '\\n'; } else { std::cout << \"not found\\n\"; } bind \u662f\u5386\u53f2\u7cdf\u7c95\uff0c\u5e94\u8be5\u7531 Lambda \u8868\u8fbe\u5f0f\u53d6\u4ee3 \u4f17\u6240\u5468\u77e5\uff0c std::bind \u53ef\u4ee5\u4e3a\u51fd\u6570\u7ed1\u5b9a\u4e00\u90e8\u5206\u53c2\u6570\uff0c\u5f62\u6210\u4e00\u4e2a\u65b0\u7684\u51fd\u6570\uff08\u5bf9\u8c61\uff09\u3002 int func(int x, int y) { printf(\"func(%d, %d)\\n\", x, y); return x + y; } auto new_func = std::bind(func, 1, std::placeholders::_1); new_func(2); // \u8c03\u7528 new_func(2) \u65f6\uff0c\u5b9e\u9645\u4e0a\u8c03\u7528\u7684\u662f func(1, 2) } \u8f93\u51fa\uff1a func(1, 2) \u5f53\u6211\u4eec\u7ed1\u5b9a\u51fa\u6765\u7684\u51fd\u6570\u5bf9\u8c61\u8fd8\u9700\u8981\u63a5\u53d7\u53c2\u6570\u65f6\uff0c\u5c31\u53d8\u5f97\u5c24\u4e3a\u590d\u6742\uff1a\u9700\u8981\u4f7f\u7528\u5360\u4f4d\u7b26\uff08placeholder\uff09\u3002 int func(int x, int y, int z, int &w); int w = rand(); auto bound = std::bind(func, std::placeholders::_2, 1, std::placeholders::_1, std::ref(w)); // int res = bound(5, 6); // \u7b49\u4ef7\u4e8e func(6, 1, 5, w); \u8fd9\u662f\u4e00\u4e2a\u7ed1\u5b9a\u5668\uff0c\u628a func \u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u548c\u7b2c\u56db\u4e2a\u53c2\u6570\u56fa\u5b9a\u4e0b\u6765\uff0c\u5f62\u6210\u4e00\u4e2a\u65b0\u7684\u51fd\u6570\u5bf9\u8c61\uff0c\u7136\u540e\u53ea\u9700\u8981\u4f20\u5165\u524d\u9762\u4e24\u4e2a\u53c2\u6570\u5c31\u53ef\u4ee5\u8c03\u7528\u539f\u6765\u7684\u51fd\u6570\u4e86\u3002 \u8fd9\u662f\u4e00\u4e2a\u975e\u5e38\u65e7\u7684\u6280\u672f\uff0cC++98 \u65f6\u4ee3\u5c31\u6709\u4e86\u3002\u4f46\u662f\uff0c\u73b0\u5728\u6709\u4e86 Lambda \u8868\u8fbe\u5f0f\uff0c\u53ef\u4ee5\u66f4\u7b80\u6d01\u5730\u5b9e\u73b0\uff1a int func(int x, int y, int z, int &w); int w = rand(); auto lambda = [&w](int x, int y) { return func(y, 1, x, w); }; int res = lambda(5, 6); Lambda \u8868\u8fbe\u5f0f\u6709\u8bb8\u591a\u4f18\u52bf\uff1a \u7b80\u6d01\uff1a\u4e0d\u9700\u8981\u5199\u4e00\u5927\u5806\u770b\u4e0d\u61c2\u7684 std::placeholders::_1 \uff0c\u76f4\u63a5\u5199\u53d8\u91cf\u540d\u5c31\u53ef\u4ee5\u4e86\u3002 \u7075\u6d3b\uff1a\u53ef\u4ee5\u5728 Lambda \u4e2d\u4f7f\u7528\u4efb\u610f\u591a\u7684\u53d8\u91cf\uff0c\u8c03\u6574\u987a\u5e8f\uff0c\u800c\u4e0d\u4ec5\u4ec5\u662f std::placeholders::_1 \u3002 \u6613\u61c2\uff1a\u5199\u8d77\u6765\u548c\u666e\u901a\u51fd\u6570\u8c03\u7528\u4e00\u6837\uff0c\u6240\u6709\u4eba\u90fd\u5bb9\u6613\u770b\u61c2\u3002 \u6355\u83b7\u5f15\u7528\uff1a std::bind \u4e0d\u652f\u6301\u6355\u83b7\u5f15\u7528\uff0c\u603b\u662f\u62f7\u8d1d\u53c2\u6570\uff0c\u5fc5\u987b\u914d\u5408 std::ref \u624d\u80fd\u6355\u83b7\u5230\u5f15\u7528\u3002\u800c Lambda \u53ef\u4ee5\u968f\u610f\u6355\u83b7\u4e0d\u540c\u7c7b\u578b\u7684\u53d8\u91cf\uff0c\u6309\u503c\uff08 [x] \uff09\u6216\u6309\u5f15\u7528\uff08 [&x] \uff09\uff0c\u8fd8\u53ef\u4ee5\u79fb\u52a8\u6355\u83b7\uff08 [x = move(x)] \uff09\uff0c\u751a\u81f3\u6355\u83b7 this\uff08 [this] \uff09\u3002 \u5939\u5e26\u79c1\u8d27\uff1a\u53ef\u4ee5\u5728 lambda \u4f53\u5185\u5f88\u65b9\u4fbf\u5730\u5939\u5e26\u5176\u4ed6\u989d\u5916\u8f6c\u6362\u64cd\u4f5c\uff0c\u6bd4\u5982\uff1a auto lambda = [&w](int x, int y) { return func(y + 8, 1, x * x, ++w) * 2; }; bind \u7684\u5386\u53f2 \u4e3a\u4ec0\u4e48 C++11 \u6709\u4e86 Lambda \u8868\u8fbe\u5f0f\uff0c\u8fd8\u8981\u63d0\u51fa std::bind \u5462\uff1f \u867d\u7136 bind \u548c lambda \u770b\u4f3c\u90fd\u662f\u5728 C++11 \u5f15\u5165\u7684\uff0c\u5b9e\u9645\u4e0a bind \u7684\u63d0\u51fa\u8fdc\u8fdc\u65e9\u4e8e lambda\u3002 \u6807\u51c6\u59d4\u5458\u4f1a\uff1a\u6211\u4eec\u4e0d\u751f\u4ea7\u5e93\uff0c\u6211\u4eec\u53ea\u662f boost \u7684\u642c\u8fd0\u5de5\u3002 \u5f53\u65f6\u8fd8\u662f C++98\uff0c\u7531\u4e8e\u6ca1\u6709 lambda\uff0c\u96be\u4ee5\u521b\u5efa\u51fd\u6570\u5bf9\u8c61\uff0c\u201c\u6355\u83b7\u53c2\u6570\u201d\u975e\u5e38\u56f0\u96be\u3002 \u4e3a\u4e86\u89e3\u51b3\u201c\u6355\u83b7\u96be\u201d\u95ee\u9898\uff0c\u5728\u7b2c\u4e09\u65b9\u5e93 boost \u4e2d\u63d0\u51fa\u4e86 boost::bind \uff0c\u7531\u4e8e\u5f53\u65f6\u53ea\u6709 C++98\uff0c\u5f88\u591a\u6709\u76ca\u4e8e\u51fd\u6570\u5f0f\u7f16\u7a0b\u7684\u7279\u6027\u90fd\u6ca1\u6709\uff0c\u6240\u4ee5\u5b9e\u73b0\u7684\u975e\u5e38\u4e11\u964b\u3002 \u4f8b\u5982\uff0c\u56e0\u4e3a C++98 \u6ca1\u6709\u53d8\u957f\u6a21\u677f\u53c2\u6570\uff0c\u65e0\u6cd5\u5b9e\u73b0 \u3002\u6240\u4ee5\u5b9e\u9645\u4e0a\u5f53\u65f6 boost \u6240\u6709\u652f\u6301\u591a\u53c2\u6570\u7684\u51fd\u6570\uff0c\u5b9e\u9645\u4e0a\u90fd\u662f\u901a\u8fc7\uff1a void some_func(); void some_func(int i1); void some_func(int i1, int i2); void some_func(int i1, int i2, int i3); void some_func(int i1, int i2, int i3, int i4); // ... \u8fd9\u6837\u66b4\u529b\u91cd\u8f7d\u51e0\u5341\u4e2a\u51fd\u6570\u6765\u5b9e\u73b0\u7684\uff0c\u800c\u4e14\u53c2\u6570\u6570\u91cf\u6709\u4e0a\u9650\u3002\u901a\u5e38\u4f1a\u5b9e\u73b0 0 \u5230 20 \u4e2a\u53c2\u6570\u7684\u91cd\u8f7d\uff0c\u66f4\u591a\u5c31\u4e0d\u652f\u6301\u4e86\u3002 \u4f8b\u5982\uff0c\u6211\u4eec\u77e5\u9053\u73b0\u5728 bind \u9700\u8981\u914d\u5408\u5404\u79cd std::placeholders::_1 \u4f7f\u7528\uff0c\u6709\u6ca1\u6709\u60f3\u8fc7\u8fd9\u5957\u4e11\u964b\u7684\u5360\u4f4d\u7b26\u662f\u4e3a\u4ec0\u4e48\uff1f\u4e3a\u4ec0\u4e48\u4e0d\u7528 std::placeholder<1> \uff0c\u8fd9\u6837\u4e0d\u662f\u66f4\u53ef\u6269\u5c55\u5417\uff1f \u6ca1\u9519\uff0c\u5f53\u65f6 boost::bind \u5c31\u662f\u7528\u66b4\u529b\u91cd\u8f7d\u51e0\u5341\u4e2a\u53c2\u6570\u6570\u91cf\u4e0d\u7b49\u7684\u51fd\u6570\uff0c\u6392\u5217\u7ec4\u5408\uff0c\u55ef\u662f\u6392\u51fa\u6765\u7684\uff0c\u6240\u4ee5\u6211\u4eec\u4f1a\u770b\u5230 boost::placeholders \u53ea\u6709\u6709\u9650\u4e2a\u6570\u7684\u5360\u4f4d\u7b26\u6570\u91cf\u3002 \u7cdf\u7cd5\u7684\u662f\uff0c\u6807\u51c6\u5e93\u7684 std::bind \u628a boost::bind \u539f\u5c01\u4e0d\u52a8\u642c\u4e86\u8fc7\u6765\uff0c\u751a\u81f3 placeholders \u7684\u66b4\u529b\u7ec4\u5408\u4e5f\u6ca1\u6709\u53d8\uff0c\u9020\u6210\u4e86 std::bind \u5982\u4eca\u4e11\u964b\u7684\u63a5\u53e3\u3002 \u4eba\u5bb6 boost::bind \u662f\u56e0\u4e3a\u4e0d\u80fd\u4fee\u6539\u8bed\u8a00\u8bed\u6cd5\uff0c\u624d\u53ea\u80fd\u90a3\u6837\u618b\u5c48\u7684\u554a\uff1f\u53ef\u73b0\u5728\u4f60\u7801\u662f\u6807\u51c6\u59d4\u5458\u4f1a\u554a\uff0c\u4f60\u53ef\u4ee5\u4fee\u6539\u8bed\u8a00\u8bed\u6cd5\u554a\uff1f \u7136\u800c\uff0cC++ \u6807\u51c6\u7684\u66f4\u65b0\u662f\u4ee5\u201c\u63d0\u6848\u201d\u7684\u65b9\u5f0f\uff0c\u9010\u6b65\u201c\u589e\u91cf\u201d\u66f4\u65b0\u8fdb\u5165\u8bed\u8a00\u6807\u51c6\u7684\u3002\u5373\u4f7f\u662f\u5728 C++98 \u5230 C++11 \u8fd9\u6bb5\u65f6\u95f4\u5185\uff0c\u5185\u90e8\u4e5f\u662f\u6709\u4e00\u4e2a\u5f88\u957f\u7684\u6d88\u5316\u6d41\u7a0b\u7684\uff0c\u4e5f\u5c31\u662f\u8bf4\u6709\u5f88\u591a\u5b50\u7248\u672c\uff0c\u53ea\u662f\u5bf9\u5916\u770b\u8d77\u6765\u597d\u50cf\u53ea\u6709\u4e00\u4e2a C++11\u3002 \u6bd4\u65b9\u8bf4\uff0c\u6211 2001 \u5e74\u63d0\u51fa std::bind \u63d0\u6848\uff0c2005 \u5e74\u88ab\u6279\u51c6\u8fdb\u5165\u672a\u6765\u5c06\u8981\u53d1\u5e03\u7684 C++11 \u6807\u51c6\u3002\u7136\u540e\u53c8\u4e00\u4e2a\u4eba\u5728 2006 \u5e74\u63d0\u51fa\u5176\u5b9e\u4e0d\u9700\u8981 bind\uff0c\u5b8c\u5168\u53ef\u4ee5\u7528\u66f4\u597d\u7684 lambda \u8bed\u6cd5\u6765\u4ee3\u66ff bind\uff0c\u7136\u540e\u7b49\u5230\u4e86 2008 \u5e74\u624d\u6279\u51c6\u8fdb\u5165\u5373\u5c06\u53d1\u5e03\u7684 C++11 \u6807\u51c6\u3002\u4f46\u662f\u5df2\u7ecf\u8fdb\u5165\u6807\u51c6\u7684\u4e1c\u897f\u5c31\u4e0d\u4f1a\u518d\u9000\u51fa\u4e86\uff0c\u54ea\u6015\u8fd8\u6ca1\u6709\u53d1\u5e03\u3002\u5c31\u8fd9\u6837 bind \u548c lambda \u540c\u65f6\u8fdb\u5165\u4e86\u6807\u51c6\u3002 \u6240\u4ee5\u95f9\u4e86\u534a\u5929\uff0clambda \u5b9e\u9645\u4e0a\u662f bind \u7684\u4e0a\u4f4d\u66ff\u4ee3\uff0c\u6709\u4e86 lambda \u6839\u672c\u4e0d\u9700\u8981 bind \u7684\u3002\u53ea\u4e0d\u8fc7\u662f\u7531\u4e8e C++ \u59d4\u5458\u4f1a\u524d\u540e\u626f\u76ae\u7684\u201c\u5236\u5ea6\u4f18\u52bf\u201d\uff0c\u5bfc\u81f4 bind \u548c\u4ed6\u7684\u4e0a\u4f4d\u66ff\u4ee3 lambda \u540c\u65f6\u8fdb\u5165\u4e86 C++11 \u6807\u51c6\u4e00\u8d77\u53d1\u5e03\u3002 \u8fd9\u4e0b\u770b\u61c2\u4e86\u3002 \u5f88\u591a\u540c\u5b66\u5c31\u4e0d\u7406\u89e3\uff0c\u5c0f\u5f6d\u8001\u5e08\u8bf4\u201clambda \u662f bind \u7684\u4e0a\u4f4d\u66ff\u4ee3\u201d\uff0c\u4ed6\u5c31\u8d28\u7591\u201c\u53ef\u4ed6\u4eec\u4e0d\u90fd\u662f C++11 \u63d0\u51fa\u7684\u5417\uff1f\u201d \u6709\u6ca1\u6709\u4e00\u79cd\u53ef\u80fd\uff0cC++11 \u548c C++98 \u4e4b\u95f4\u4e3a\u4ec0\u4e48\u5e74\u4ee3\u5dee\u4e86\u90a3\u4e48\u4e45\u8fdc\uff0c\u5c31\u662f\u56e0\u4e3a\u4e00\u4e2a\u6807\u51c6\u4e00\u62d6\u518d\u62d6\uff0c\u5185\u90e8\u5b9e\u9645\u4e0a\u5df2\u7ecf\u8fed\u4ee3\u4e86\u597d\u51e0\u4e2a\u5c0f\u7248\u672c\u4e86\uff0c\u624d\u53d1\u5e03\u51fa\u6765\u3002 \u518d\u4e3e\u4e2a\u4f8b\u5b50\uff0cCTAD \u548c optional \u90fd\u662f C++17 \u5f15\u5165\u7684\uff0c\u4e3a\u4ec0\u4e48\u8fd8\u8981 make_optional \u8fd9\u4e2a\u5e2e\u624b\u51fd\u6570\uff1f\u4e0d\u662f\u8bf4 CTAD \u662f make_xxx \u7684\u4e0a\u4f4d\u66ff\u4ee3\u5417\uff1f\u53ef\u89c1\uff0cC++ \u6807\u51c6\u4e2d\u8fd9\u79cd\u201c\u540c\u4e00\u4e2a\u7248\u672c\u5185\u201d\u81ea\u5df1\u6253\u81ea\u5df1\u8033\u5149\u7684\u73b0\u8c61\u6bd4\u6bd4\u7686\u662f\u3002 \u6240\u4ee5\uff0c\u73b0\u5728\u8fd8\u575a\u6301\u7528 bind \u7684\uff0c\u90fd\u662f\u4e9b 2005 \u5e74\u524d\u540e\u5728\u8c61\u7259\u5854\u63a5\u53d7 C++ \u6559\u80b2\uff0c\u4f46\u53c8\u4e0d\u80af\u201c\u7ec8\u8eab\u5b66\u4e60\u201d\u7684\u52b3\u4fdd\u3002\u8fd9\u6279\u52b3\u4fdd\u53c8\u53bb\u201c\u4e0a\u5cb8\u201d\u5f53\u201c\u6559\u5e08\u201d\uff0c\u7ee7\u7eed\u590d\u5236 2005 \u5e74\u7684\u9519\u8bef\u6bd2\u5bb3\u9752\u5c11\u5e74\uff0c\u5b9e\u73b0\u4e86\u52b3\u4fdd\u7684\u518d\u751f\u4ea7\u3002 thread \u819d\u76d6\u4e2d\u7bad \u7cdf\u7cd5\u7684\u662f\uff0cbind \u7684\u8fd9\u79cd\u837c\u6bd2\uff0c\u751a\u81f3\u5f71\u54cd\u5230\u4e86\u7ebf\u7a0b\u5e93\uff1a std::thread \u7684\u6784\u9020\u51fd\u6570\u5c31\u662f\u57fa\u4e8e std::bind \u7684\uff01 \u8fd9\u5bfc\u81f4\u4e86 std::thread \u548c std::bind \u4e00\u6837\uff0c\u65e0\u6cd5\u6355\u83b7\u5f15\u7528\u3002 void thread_func(int &x) { x = 42; } int x = 0; std::thread t(thread_func, x); t.join(); printf(\"%d\\n\", x); // 0 \u4e3a\u4e86\u907f\u514d\u8e29\u5230 bind \u7684\u5751\uff0c\u6211\u5efa\u8bae\u6240\u6709\u540c\u5b66\uff0c\u6784\u9020 std::thread \u65f6\uff0c\u7edf\u4e00\u53ea\u6307\u5b9a\u201c\u5355\u4e2a\u53c2\u6570\u201d\uff0c\u4e5f\u5c31\u662f\u51fd\u6570\u672c\u8eab\u3002\u5982\u679c\u9700\u8981\u6355\u83b7\u53c2\u6570\uff0c\u8bf7\u4f7f\u7528 lambda\u3002\u56e0\u4e3a lambda \u4e2d\uff0c\u6355\u83b7\u4e86\u54ea\u4e9b\u53d8\u91cf\uff0c\u53c2\u6570\u7684\u987a\u5e8f\u662f\u4ec0\u4e48\uff0c\u54ea\u4e9b\u6355\u83b7\u662f\u5f15\u7528\uff0c\u54ea\u4e9b\u6355\u83b7\u662f\u62f7\u8d1d\uff0c\u975e\u5e38\u6e05\u6670\u3002 void thread_func(int &x) { x = 42; } int x = 0; std::thread t([&x] { // [&x] \u8868\u793a\u6309\u5f15\u7528\u6355\u83b7 x\uff1b\u5982\u679c\u5199\u4f5c [x]\uff0c\u90a3\u5c31\u662f\u62f7\u8d1d\u6355\u83b7 thread_func(x); }); t.join(); printf(\"%d\\n\", x); // 42 \u4e3e\u4e2a\u7ed1\u5b9a\u968f\u673a\u6570\u751f\u6210\u5668\u4f8b\u5b50 bind \u5199\u6cd5\uff1a std::mt19937 gen(seed); std::uniform_real_distribution uni(0, 1); auto frand = std::bind(uni, std::ref(gen)); double x = frand(); double y = frand(); \u6539\u7528 lambda\uff1a std::mt19937 gen(seed); std::uniform_real_distribution uni(0, 1); auto frand = [uni, &gen] { return uni(gen); }; double x = frand(); double y = frand(); forward \u8ff7\u60d1\u6027\u5730\u4e0d\u597d\u7528\uff0c\u5efa\u8bae\u6539\u7528 FWD \u5b8f \u4f17\u6240\u5468\u77e5\uff0c\u5f53\u4f60\u5728\u8f6c\u53d1\u4e00\u4e2a\u201c\u4e07\u80fd\u5f15\u7528\u201d\u53c2\u6570\u65f6\uff1a template void some_func(Arg &&arg) { other_func(arg); } \u5982\u679c\u6b64\u5904 arg \u4f20\u5165\u7684\u662f\u53f3\u503c\u5f15\u7528\uff0c\u90a3\u4e48\u4f20\u5165 other_func \u5c31\u4f1a\u53d8\u56de\u5de6\u503c\u5f15\u7528\u4e86\uff0c\u4e0d\u7b26\u5408\u5b8c\u7f8e\u8f6c\u53d1\u7684\u8981\u6c42\u3002 \u56e0\u6b64\u5f15\u5165\u4e86 forward \uff0c\u4ed6\u4f1a\u68c0\u6d4b arg \u662f\u5426\u4e3a\u201c\u53f3\u503c\u201d\uff1a\u5982\u679c\u662f\uff0c\u5219 forward \u7b49\u4ef7\u4e8e move \uff1b\u5982\u679c\u4e0d\u662f\uff0c\u5219 forward \u4ec0\u4e48\u90fd\u4e0d\u505a\uff08\u9ed8\u8ba4\u5c31\u662f\u5de6\u503c\u5f15\u7528\uff09\u3002 \u8fd9\u5f04\u5f97 forward \u7684\u5916\u89c2\u975e\u5e38\u5177\u6709\u8ff7\u60d1\u6027\uff0c\u53c8\u662f\u5c16\u62ec\u53f7\u53c8\u662f\u5706\u62ec\u53f7\u7684\u3002 template void some_func(Arg &&arg) { other_func(std::forward(arg)); } \u5b9e\u9645\u4e0a\uff0cforward \u7684\u7528\u6cd5\u975e\u5e38\u5355\u4e00\uff1a\u6c38\u8fdc\u662f forward(t) \u7684\u5f62\u5f0f\uff0c\u5176\u4e2d T \u662f t \u53d8\u91cf\u7684\u7c7b\u578b\u3002 \u53c8\u662f\u52b3\u4fdd\u7684\u9b45\u529b\uff0c\u5229\u7528\u540c\u6837\u662f C++11 \u7684 decltype \u5c31\u80fd\u83b7\u5f97 t \u5b9a\u4e49\u65f6\u7684 T \u3002 void some_func(auto &&arg) { other_func(std::forward(arg)); } \u6240\u4ee5 std::forward(arg) \u5b9e\u9645\u624d\u662f forward \u7684\u6b63\u786e\u7528\u6cd5\uff0c\u53ea\u4e0d\u8fc7\u56e0\u4e3a\u5927\u591a\u6570\u65f6\u5019\u4f60\u662f\u6a21\u677f\u53c2\u6570 Arg && \uff0c\u6709\u7684\u4eba\u5077\u61d2\uff0c\u5c31\u628a decltype(arg) \u66ff\u6362\u6210\u5df2\u7ecf\u5339\u914d\u597d\u7684\u6a21\u677f\u53c2\u6570 Arg \u4e86\uff0c\u5b9e\u9645\u4e0a\u662f\u7b49\u4ef7\u7684\u3002 \u8fd9\u91cc\u9700\u8981\u590d\u8bfb arg \u592a\u7eb1\u5e01\u4e86\u3002\u5b9e\u9645\u4e0a\uff0c\u6211\u4eec\u53ef\u4ee5\u5b9a\u4e49\u4e00\u4e2a\u5b8f\uff1a #define FWD(arg) std::forward(arg) \u8fd9\u6837\u5c31\u53ef\u4ee5\u7b80\u5316\u4e3a\uff1a void some_func(auto &&arg) { other_func(FWD(arg)); } \u5c11\u4e86\u70e6\u4eba\u7684\u5c16\u62ec\u53f7\uff0c\u770b\u8d77\u6765\u5bb9\u6613\u61c2\u591a\u4e86\u3002 \u4f46\u662f\uff0c\u6211\u4eec\u540c\u5b66\u6709\u4e00\u4e2a\u95ee\u9898\uff0c\u4e3a\u4ec0\u4e48 std::forward \u8981\u5199\u6210 std::forward \u7684\u5f62\u5f0f\u5462\uff1f\u4e3a\u4ec0\u4e48\u4e0d\u662f std::forward(t) \u5462\uff1f\u56e0\u4e3a\u8fd9\u6837\u5199\u7684\u8bdd\uff0c forward \u4e5f\u6ca1\u6cd5\u77e5\u9053\u4f60\u7684 t \u662f\u5de6\u662f\u53f3\u4e86\uff08\u51fd\u6570\u53c2\u6570\u59cb\u7ec8\u4f1a\u9ed8\u8ba4\u63a8\u5bfc\u4e3a\u5de6\uff0c\u5373\u4f7f\u5b9a\u4e49\u7684 t \u662f\u53f3\uff09\u56e0\u6b64\u5fc5\u987b\u544a\u8bc9 forward \uff0c t \u7684\u5b9a\u4e49\u7c7b\u578b\uff0c\u4e5f\u5c31\u662f T \uff0c\u6216\u8005\u901a\u8fc7 decltype(t) \u6765\u83b7\u5f97 T \u3002 \u603b\u4e4b\uff0c\u5982\u679c\u4f60\u7528\u7684\u662f auto && \u53c2\u6570\uff0c\u90a3\u4e48 FWD \u4f1a\u5f88\u65b9\u4fbf\uff08\u81ea\u52a8\u5e2e\u4f60 decltype \uff09\u3002\u4f46\u662f\u5982\u679c\u4f60\u7528\u7684\u662f\u6a21\u677f\u53c2\u6570 T && \uff0c\u90a3\u4e48 FWD \u4e5f\u53ef\u4ee5\u7528\uff0c\u56e0\u4e3a decltype(t) \u603b\u662f\u5f97\u5230 T \u3002 bind \u7ed1\u5b9a\u6210\u5458\u51fd\u6570\u662f\u964b\u4e60\uff0c\u6539\u7528 lambda \u6216 bind_front \u4f7f\u7528\u201c\u6210\u5458\u51fd\u6570\u6307\u9488\u201d\u8bed\u6cd5\uff08\u8fd9\u4e00\u5947\u8469\u8bed\u6cd5\u5728 C++98 \u5c31\u6709\uff09\u914d\u5408 std::bind \uff0c\u53ef\u4ee5\u5b9e\u73b0\u7ed1\u5b9a\u4e00\u4e2a\u7c7b\u578b\u7684\u6210\u5458\u51fd\u6570\uff1a struct Class { void world() { puts(\"world!\"); } void hello() { auto memfn = std::bind(&Class::world, this); // \u5c06 this->world \u7ed1\u5b9a\u6210\u4e00\u4e2a\u53ef\u4ee5\u5ef6\u540e\u8c03\u7528\u7684\u51fd\u6570\u5bf9\u8c61 memfn(); memfn(); } } \u4e0d\u5c31\u662f\u6355\u83b7 this \u5417\uff1f\u6211\u4eec lambda \u4e5f\u53ef\u4ee5\u8f7b\u6613\u505a\u5230\uff01\u4e14\u65e0\u9700\u7e41\u7410\u5730\u5199\u51fa this \u7c7b\u7684\u5b8c\u6574\u7c7b\u540d\uff0c\u8fd8\u5199\u4e2a\u8111\u762b &:: \u5f3a\u78b1\u4f60\u7684\u952e\u76d8\u3002 struct Class { void world() { puts(\"world!\"); } void hello() { auto memfn = [this] { world(); // \u7b49\u4ef7\u4e8e this->world() }; memfn(); memfn(); } } bind \u7684\u7f3a\u70b9\u662f\uff0c\u5f53\u6211\u4eec\u7684\u6210\u5458\u51fd\u6570\u542b\u6709\u591a\u4e2a\u53c2\u6570\u65f6\uff0cbind \u5c31\u975e\u5e38\u9ebb\u70e6\u4e86\uff1a\u9700\u8981\u4e00\u4e2a\u4e2a\u5199\u51fa placeholder\uff0c\u800c\u4e14\u6570\u91cf\u5fc5\u987b\u548c world \u7684\u53c2\u6570\u6570\u91cf\u4e00\u81f4\u3002\u6bcf\u6b21 world \u8981\u65b0\u589e\u53c2\u6570\u65f6\uff0c\u6240\u6709 bind \u7684\u5730\u65b9\u90fd\u9700\u8981\u52a0\u4e00\u4e0b placeholder\uff0c\u975e\u5e38\u6c99\u96d5\u3002 struct Class { void world(int x, int y) { printf(\"world(%d, %d)\\n\"); } void hello() { auto memfn = std::bind(&Class::world, this, std::placeholders::_1, std::placeholders::_2); memfn(1, 2); memfn(3, 4); } } \u800c\u4e14\uff0c\u5982\u679c\u6709\u8981\u7ed1\u5b9a\u7684\u76ee\u6807\u51fd\u6570\u6709\u591a\u4e2a\u53c2\u6570\u6570\u91cf\u4e0d\u540c\u7684\u91cd\u8f7d\uff0c\u90a3 bind \u5c31\u5b8c\u5168\u4e0d\u80fd\u5de5\u4f5c\u4e86\uff01 struct Class { void world(int x, int y) { printf(\"world(%d, %d)\\n\"); } void world(double x) { printf(\"world(%d)\\n\"); } void hello() { auto memfn = std::bind(&Class::world, this, std::placeholders::_1, std::placeholders::_2); memfn(1, 2); memfn(3.14); // \u7f16\u8bd1\u51fa\u9519\uff01\u6b7b\u6263\u5360\u4f4d\u7b26\u7684 bind \u5fc5\u987b\u8981\u6c42\u4e24\u4e2a\u53c2\u6570\uff0c\u5373\u4f7f world \u660e\u660e\u6709\u5355\u53c2\u6570\u7684\u91cd\u8f7d auto memfn_1arg = std::bind(&Class::world, this, std::placeholders::_1); memfn_1arg(3.14); // \u5fc5\u987b\u91cd\u65b0\u7ed1\u5b9a\u4e00\u4e2a\u201c\u5355\u53c2\u6570\u7248\u201d\u624d OK } } \u800c C++14 \u8d77 lambda \u652f\u6301\u4e86\u53d8\u957f\u53c2\u6570\uff0c\u5c31\u4e0d\u7528\u8fd9\u4e48\u6b7b\u677f\uff1a struct Class { void world(int x, int y) { printf(\"world(%d, %d)\\n\"); } void world(double x) { printf(\"world(%d)\\n\"); } void hello() { auto memfn = [this] (auto ...args) { // \u8ba9 lambda \u63a5\u53d7\u4efb\u610f\u53c2\u6570 world(args...); // \u62f7\u8d1d\u8f6c\u53d1\u6240\u6709\u53c2\u6570\u7ed9 world }; memfn(1, 2); // \u53cc\u53c2\u6570\uff1aOK memfn(3.14); // \u5355\u53c2\u6570\uff1aOK } } \u66f4\u597d\u7684\u662f\u914d\u5408\u4e0a\u6587\u63d0\u5230\u7684 FWD \u5b8f\u5b9e\u73b0\u53c2\u6570\u7684\u5b8c\u7f8e\u8f6c\u53d1\uff1a struct Class { void world(int &x, int &&y) { printf(\"world(%d, %d)\\n\"); ++x; } void world(double const &x) { printf(\"world(%d)\\n\"); } void hello() { auto memfn = [this] (auto &&...args) { // \u8ba9 lambda \u63a5\u53d7\u4e07\u80fd\u5f15\u7528\u505a\u53c2\u6570 world(FWD(args)...); // \u901a\u8fc7 FWD \u5b8c\u7f8e\u8f6c\u53d1\u7ed9 world\uff0c\u907f\u514d\u5f15\u7528\u9000\u5316 }; int x = 1; memfn(x, 2); // \u53cc\u53c2\u6570\uff1aOK memfn(3.14); // \u5355\u53c2\u6570\uff1aOK } } \u540c\u6837\u53ef\u4ee5\u5b9a\u4e49\u4e00\u4e2a\u79f0\u624b\u7684\u5b8f\uff1a #define BIND(func, ...) [__VA_ARGS__] (auto &&..._args) { func(FWD(_args)...); } \u8fd9\u91cc\u4f7f\u7528\u4e86\u5b8f\u53c2\u6570\u5305\uff0c\u6b64\u5904 __VA_ARGS__ \u5c31\u662f\u5b8f\u7684 ... \u4e2d\u7684\u5185\u5bb9\u3002\u6ce8\u610f\u533a\u5206\u5b8f\u7684 ... \u548c C++ \u53d8\u957f\u6a21\u677f\u7684 ... \u662f\u4e92\u76f8\u72ec\u7acb\u7684\u3002 struct Class { void world(int &x, int &&y) { printf(\"world(%d, %d)\\n\"); ++x; } void world(double const &x) { printf(\"world(%d)\\n\"); } void hello() { auto memfn = BIND(world, this); int x = 1; memfn(x, 2); memfn(3.14); } } int main() { // \u6355\u83b7\u975e this \u7684\u6210\u5458\u51fd\u6570\u4e5f OK\uff1a Class c; auto memfn = BIND(c.world, &c); // [&c] \u6309\u5f15\u7528\u6355\u83b7 c \u53d8\u91cf // \u5c55\u5f00\u4e3a\uff1a auto memfn = [&c] (auto &&..._args) { c.world(std::forward(_args)...); } memfn(3.14); } BIND \u8fd9\u4e2a\u540d\u5b57\u662f\u968f\u4fbf\u53d6\u7684\uff0c\u53d6\u8fd9\u4e2a\u540d\u5b57\u662f\u4e3a\u4e86\u8fb1 std::bind \u3002 \u4e3a\u4e86\u89e3\u51b3 bind \u4e0d\u80fd\u6355\u83b7\u591a\u53c2\u6570\u91cd\u8f7d\u7684\u60c5\u51b5\uff0cC++17 \u8fd8\u5f15\u5165\u4e86 std::bind_front \u548c std::bind_back \uff0c\u4ed6\u4eec\u4e0d\u9700\u8981 placeholder\uff0c\u4f46\u53ea\u80fd\u7528\u4e8e\u8981\u7ed1\u5b9a\u7684\u53c2\u6570\u5728\u6700\u524d\u6216\u8005\u6700\u540e\u7684\u7279\u6b8a\u60c5\u51b5\u3002 \u5176\u4e2d std::bind_front \u5bf9\u4e8e\u6211\u4eec\u53ea\u9700\u8981\u628a\u7b2c\u4e00\u4e2a\u53c2\u6570\u7ed1\u5b9a\u4e3a this \uff0c\u5176\u4ed6\u53c2\u6570\u5982\u6570\u8f6c\u53d1\u7684\u573a\u666f\uff0c\u7b80\u76f4\u662f\u96ea\u4e2d\u9001\u70ad\uff01 struct Class { void world(int x, int y) { printf(\"world(%d, %d)\\n\"); } void world(double x) { printf(\"world(%d)\\n\"); } void hello() { auto memfn = std::bind_front(&Class::world, this); memfn(1, 2); memfn(3.14); // OK\uff01 } } auto memfn = std::bind_front(&Class::world, this); // C++17 \u7684 bind \u5b5d\u5b50\u8865\u6551\u63aa\u65bd auto memfn = BIND(world, this); // \u5c0f\u5f6d\u8001\u5e08\u7684 BIND \u5b8f\uff0cC++14 \u8d77\u53ef\u7528 \u4f60\u66f4\u559c\u6b22\u54ea\u4e00\u79cd\u5462\uff1f \u6551\u547d\uff01\u4e3a\u4ec0\u4e48\u6211\u7684\u5168\u5c40\u51fd\u6570\u4e0d\u80fd\u4f5c\u4e3a\u51fd\u6570\u5bf9\u8c61\uff1f \u5f53\u4f60\u7684\u5168\u5c40\u51fd\u6570\u662f\u6a21\u677f\u51fd\u6570\uff0c\u6216\u5e26\u6709\u91cd\u8f7d\u7684\u51fd\u6570\u65f6\uff1a template T square(T const t) { return t * t; } template void do_something(Fn &&fn) { fn(2); fn(3.14); } int main() { do_something(square); // \u7f16\u8bd1\u9519\u8bef\uff1a\u6709\u6b67\u4e49\u7684\u91cd\u8f7d } \u5c31\u4f1a\u51fa\u73b0\u8fd9\u6837\u607c\u4eba\u7684\u7f16\u8bd1\u9519\u8bef\uff1a test.cpp: In instantiation of 'void do_something(Fn&&) [with Fn = T (*)(T) [with T = double]]': test.cpp:18:21: required from here test.cpp:14:9: error: no matching function for call to 'do_something()' do_something(square); ^~~~~~~~~~~~~ test.cpp:7:3: note: candidate: 'template void do_something(Fn&&) [with Fn = T (*)(T) [with T = double]]' void do_something(Fn &&fn) { ^~~~~~~~~~~~~ test.cpp:7:3: note: template argument deduction/substitution failed: test.cpp:14:21: note: couldn't deduce template parameter 'Fn' do_something(square); ~~~~~~~~~~~~~^~~~~~ \u8fd9\u662f\u56e0\u4e3a\uff0c\u6a21\u677f\u51fd\u6570\u548c\u6709\u91cd\u8f7d\u7684\u51fd\u6570\uff0c\u662f\u201c\u591a\u4e2a\u51fd\u6570\u5bf9\u8c61\u201d\u7684\u201c\u5e7b\u60f3\u8054\u5408\u4f53\u201d\uff0c\u800c do_something \u7684 Fn \u9700\u8981\u201c\u5355\u4e2a\u201d\u5177\u4f53\u7684\u51fd\u6570\u5bf9\u8c61\u3002 \u4e00\u822c\u6765\u8bf4\u662f\u9700\u8981 square \u548c square \u624d\u80fd\u53d8\u6210\u201c\u5177\u4f53\u201d\u7684\u201c\u5355\u4e2a\u201d\u51fd\u6570\u5bf9\u8c61\uff0c\u4f20\u5165 do_something \u7684 Fn \u6a21\u677f\u53c2\u6570\u3002 \u4f46\u662f\u5728\u201c\u51fd\u6570\u8c03\u7528\u201d\u7684\u8bed\u5883\u4e0b\uff0c\u56e0\u4e3a\u5df2\u77e5\u53c2\u6570\u7684\u7c7b\u578b\uff0c\u5f97\u76ca\u4e8e C++ \u7684\u201c\u91cd\u8f7d\u201d\u673a\u5236\uff0c\u5e26\u6709\u6a21\u677f\u53c2\u6570\u7684\u51fd\u6570\uff0c\u53ef\u4ee5\u81ea\u52a8\u5339\u914d\u90a3\u4e2a\u6a21\u677f\u53c2\u6570\u4e3a\u4f60\u53c2\u6570\u7684\u7c7b\u578b\u3002 \u4f46\u73b0\u5728\u4f60\u5e76\u6ca1\u6709\u6307\u5b9a\u8c03\u7528\u53c2\u6570\uff0c\u800c\u53ea\u662f\u6307\u5b9a\u4e86\u4e00\u4e2a\u51fd\u6570\u540d square \uff0c\u90a3 C++ \u201c\u91cd\u8f7d\u201d\u673a\u5236\u65e0\u6cd5\u786e\u5b9a\u4f60\u9700\u8981\u7684\u662f square \u8fd8\u662f square \u4e2d\u7684\u54ea\u4e00\u4e2a\u51fd\u6570\u6307\u9488\uff0c\u4ed6\u4eec\u7684\u7c7b\u578b\u90fd\u4e0d\u540c\uff0c\u5c31\u65e0\u6cd5\u5177\u8c61\u82b1\u51fa\u4e00\u4e2a\u51fd\u6570\u5bf9\u8c61\u7c7b\u578b Fn \u6765\uff0c\u5bfc\u81f4 \u9519\u8bef\u3002 \u6709\u8da3\u7684\u662f\uff0c\u53ea\u9700\u8981\u5957\u4e00\u5c42 lambda \u5c31\u80fd\u89e3\u51b3\uff1a do_something([] (auto x) { return square(x); }); // \u7f16\u8bd1\u901a\u8fc7 \u6216\u8005\u7528\u6211\u4eec\u4e0a\u9762\u63a8\u8350\u7684 BIND \u5b8f\uff1a #define FWD(arg) std::forward(arg) #define BIND(func, ...) [__VA_ARGS__] (auto &&..._args) { func(FWD(_args)...); } do_something(BIND(square)); // \u7f16\u8bd1\u901a\u8fc7 \u6709\u65f6\u5019\uff0c\u5982\u679c\u4f60\u60f3\u4f20\u9012 this \u7684\u6210\u5458\u51fd\u6570\u4e3a\u51fd\u6570\u5bf9\u8c61\uff0c\u4e5f\u4f1a\u51fa\u73b0\u8fd9\u79cd\u607c\u4eba\u7684\u9519\u8bef\uff1a struct Class { int func(int x) { return x + 1; } void test() { do_something(this->func); // \u8fd9\u91cc\u53c8\u4f1a\u4ea7\u751f\u70e6\u4eba\u7684 unresolved overload \u9519\u8bef\uff01 } }; \u540c\u6837\u53ef\u4ee5\u5305\u4e00\u5c42 lambda\uff0c\u6216\u8005\u7528\u5c0f\u5f6d\u8001\u5e08\u63d0\u4f9b\u7684 BIND \u5b8f\uff0c\u9ebb\u75f9\u7684\u7f16\u8bd1\u5668\u5c31\u4e0d\u72d7\u53eb\u4e86\uff1a #define FWD(arg) std::forward(arg) #define BIND(func, ...) [__VA_ARGS__] (auto &&..._args) { func(FWD(_args)...); } void test() { do_something(BIND(func, this)); // \u641e\u5b9a } \u5efa\u8bae\u4fee\u6539\u6807\u51c6\u5e93\uff0c\u628a\u5c0f\u5f6d\u8001\u5e08\u8fd9\u4e24\u4e2a\u771f\u6b63\u597d\u7528\u7684\u5b8f\u585e\u5230 \u548c \u91cc\uff0c\u4f5c\u4e3a C++26 \u6807\u51c6\u7684\u4e00\u90e8\u5206\u3002 map + any \u5916\u6302\u5c5e\u6027 TODO \u81ea\u5b9a\u4e49 shared_ptr \u7684 deleter CHECK_CUDA \u7c7b\u9519\u8bef\u68c0\u6d4b\u5b8f \u51fd\u6570\u9ed8\u8ba4\u53c2\u6570\u6c42\u503c\u7684\u4f4d\u7f6e\u662f\u8c03\u7528\u8005 \u8bbe\u7f6e locale \u4e3a .utf8 \u82b1\u62ec\u53f7\u5b9e\u73b0\u5b89\u5168\u7684\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5 \u6210\u5458\u51fd\u6570\u9488\u5bf9 this \u7684\u79fb\u52a8\u91cd\u8f7d CHECK_CUDA \u7c7b\u9519\u8bef\u68c0\u6d4b\u5b8f \u51fd\u6570\u9ed8\u8ba4\u53c2\u6570\u6c42\u503c\u7684\u4f4d\u7f6e\u662f\u8c03\u7528\u8005 \u82b1\u62ec\u53f7\u5b9e\u73b0\u5b89\u5168\u7684\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5 \u4e34\u65f6\u53f3\u503c\u8f6c\u5de6\u503c C++ \u6709\u4e2a\u7279\u6027\uff1a\u652f\u6301\u7eaf\u53f3\u503c(prvalue)\u9690\u5f0f\u8f6c\u6362\u6210 const \u7684\u5de6\u503c\u5f15\u7528\u3002 \u7ffb\u8bd1\uff1a int && \u53ef\u4ee5\u81ea\u52a8\u8f6c\u6362\u6210 int const & \u3002 void func(int const &i); func(1); // OK\uff1a\u81ea\u52a8\u521b\u5efa\u4e00\u4e2a\u53d8\u91cf\u4fdd\u5b58 1\uff0c\u7136\u540e\u4f5c\u4e3a int const & \u53c2\u6570\u4f20\u5165 \u5b9e\u9645\u4e0a\u5c31\u7b49\u4ef7\u4e8e\uff1a const int tmp = 1; func(tmp); \u4f46\u662f\uff0c int && \u5374\u4e0d\u80fd\u81ea\u52a8\u8f6c\u6362\u6210 int & \u3002 void func(int &i); func(1); // \u9519\u8bef\uff1a\u65e0\u6cd5\u4ece int && \u81ea\u52a8\u8f6c\u6362\u6210 int & C++ \u5b98\u65b9\u8bbe\u7f6e\u8fd9\u4e2a\u9650\u5236\uff0c\u662f\u51fa\u4e8e\u8bed\u4e49\u5b89\u5168\u6027\u8003\u8651\uff0c\u56e0\u4e3a\u53c2\u6570\u63a5\u53d7 int & \u7684\uff0c\u4e00\u822c\u90fd\u610f\u5473\u7740\u8fd9\u4e2a\u662f\u7528\u4f5c\u8fd4\u56de\u503c\uff0c\u800c\u5982\u679c func \u7684\u53c2\u6570\u662f\uff0c func(1) \u3002 \u4e3a\u4e86\u7ed5\u5f00\u8fd9\u4e2a\u89c4\u5219\uff0c\u6211\u4eec\u53ef\u4ee5\u5b9a\u4e49\u4e00\u4e2a\u5e2e\u624b\u51fd\u6570\uff1a T &temporary(T const &t) { return const_cast(t); } // \u6216\u8005\uff1a T &temporary(T &&t) { return const_cast(t); } \u7136\u540e\uff0c\u5c31\u53ef\u4ee5\u5feb\u4e50\u5730\u8f6c\u6362\u7eaf\u53f3\u503c\u4e3a\u975e const \u5de6\u503c\u4e86\uff1a void func(int &i); func(temporary(1)); \u5728 Libreoffice \u6e90\u7801\u4e2d\u5c31\u6709\u5e94\u7528\u8fd9\u4e2a\u5e2e\u624b\u51fd\u6570\u3002 \u4e34\u65f6\u53d8\u91cf\u7684\u751f\u547d\u5468\u671f\u662f\u4e00\u884c ostringstream \u683c\u5f0f\u5316\u5b57\u7b26\u4e32 std::string name = \"\u4f60\u597d\"; int answer = 42; auto str = std::format(\"\u4f60\u597d\uff0c{}\uff01\u7b54\u6848\u662f {}\uff0c\u5341\u516d\u8fdb\u5236\uff1a0x{:02x}\\n\", name, answer, answer); \u6ca1\u6709 C++20 \u4e4b\u524d\uff0c\u8981\u4e48\u4f7f\u7528\u7b2c\u4e09\u65b9\u7684 fmt::format \uff0c\u8981\u4e48\u53ea\u80fd\u4f7f\u7528\u5b57\u7b26\u4e32\u7684 + \u8fd0\u7b97\u7b26\u62d9\u52a3\u5730\u62fc\u63a5\uff1a auto str = std::string(\"\u4f60\u597d\uff0c\") + name + \"\uff01\u7b54\u6848\u662f \" + std::to_string(answer) + \"\uff0c\u5341\u516d\u8fdb\u5236\uff1a0x\" + std::to_string(answer) + \"\\n\"; \u8fd9\u6837\u505a\u6548\u7387\u4f4e\u4e0b\uff0c\u4e14\u4e0d\u6613\u9605\u8bfb\u3002\u800c\u4e14\u4e5f\u65e0\u6cd5\u5b9e\u73b0\u6570\u5b57\u6309\u201c\u5341\u516d\u8fdb\u5236\u201d\u8f6c\u5b57\u7b26\u4e32\u3002 \u53ef\u4ee5\u7528 std::ostringstream \uff0c\u5176\u7528\u6cd5\u4e0e std::cout \u76f8\u540c\u3002\u53ea\u4e0d\u8fc7\u4f1a\u628a\u7ed3\u679c\u5199\u5165\u4e00\u4e2a\u5b57\u7b26\u4e32\uff08\u800c\u4e0d\u662f\u76f4\u63a5\u8f93\u51fa\uff09\uff0c\u53ef\u4ee5\u7528 .str() \u53d6\u51fa\u90a3\u4e2a\u5b57\u7b26\u4e32\u3002 #include std::ostringstream oss; oss << \"\u4f60\u597d\uff0c\" << name << \"\uff01\u7b54\u6848\u662f \" << answer << \"\uff0c\u5341\u516d\u8fdb\u5236\uff1a0x\" << std::hex << std::setfill('0') << std::setw(2) << answer << \"\\n\"; auto str = oss.str(); \u5229\u7528\u4e34\u65f6\u53d8\u91cf\u8bed\u6cd5\uff0c\u53ef\u4ee5\u6d53\u7f29\u5199\u5728\u4e00\u884c\u91cc\uff0c\u505a\u4e2a format \u62d9\u52a3\u7684\u6a21\u4eff\u8005\uff1a auto str = (std::ostringstream() << \"\u4f60\u597d\uff0c\" << name << \"\uff01\u7b54\u6848\u662f \" << answer << \"\uff0c\u5341\u516d\u8fdb\u5236\uff1a0x\" << std::hex << std::setfill('0') << std::setw(2) << answer << \"\\n\").str(); ADL \u673a\u5236\u5b9e\u73b0\u9759\u6001\u591a\u6001 TODO shared_from_this requires \u8bed\u6cd5\u68c0\u6d4b\u662f\u5426\u5b58\u5728\u6307\u5b9a\u6210\u5458\u51fd\u6570 \u8bbe\u7f6e locale \u4e3a .utf8 \u89e3\u51b3 Windows \u7f16\u7801\u96be\u95ee\u9898 system(\"chcp 65001\"); setlocale(\"LC_ALL\", \".utf-8\"); \u8be6\u89c1 Unicode \u4e13\u9898\u7ae0\u8282 \u3002 \u6210\u5458\u51fd\u6570\u9488\u5bf9 this \u7684\u79fb\u52a8\u91cd\u8f7d \u4f4d\u57df\uff08bit-field\uff09 \u5728\u4e92\u8054\u7f51\u7f16\u7a0b\u548c\u5404\u79cd\u4e0e\u786c\u76d8\u3001\u5e8f\u5217\u5316\u6253\u4ea4\u9053\u7684\u573a\u666f\u4e2d\uff0c\u5e38\u5e38\u9700\u8981\u6309\u4f4d\u62c6\u5206\u5355\u4e2a\u5b57\u8282\u3002 C \u8bed\u8a00\u6709\u4e13\u95e8\u7167\u987e\u6b64\u7c7b\u5de5\u4f5c\u7684\u8bed\u6cd5\u7cd6\uff1a\u4f4d\u57df\u3002 \u4f4d\u57df\u662f\u4e00\u79cd\u7279\u6b8a\u7684\u7ed3\u6784\u4f53\u6210\u5458\uff0c\u53ef\u4ee5\u5bf9\u4f4d\u8fdb\u884c\u5206\u7ec4\uff0c\u65b9\u4fbf\u8bfb\u53d6\u3002\u4f8b\u5982\uff0c\u6211\u4eec\u60f3\u8981\u4ece\u4e00\u4e2a\u5b57\u8282\u4e2d\u8bfb\u53d6\u4e09\u4e2a\u72b6\u6001\u4f4d\uff1a struct Flag { uint8_t a : 4; // \u4f4e 4 \u4f4d uint8_t b : 4; // \u9ad8 4 \u4f4d }; sizeof(Flag); // 1 \u5b57\u8282\u5927\u5c0f\uff08\u5171 8 \u4f4d\uff09 Flag f = std::bit_cast(0x21); f.a; // 0x1 f.b; // 0x2 \u4ee5\u4e0a\u7684\u4ee3\u7801\u7b49\u4ef7\u4e8e\uff1a uint8_t f = 0x21; int a = f & 0xF; // 0x1 int b = f >> 4; // 0x2 vector + unordered_map = LRU cache Lambda \u6355\u83b7 unique_ptr \u5bfc\u81f4 function \u62a5\u9519\u600e\u4e48\u529e \u591a\u7ebf\u7a0b\u901a\u4fe1\u5e94\u57fa\u4e8e\u961f\u5217\uff0c\u800c\u4e0d\u662f\u5171\u4eab\u5168\u5c40\u53d8\u91cf RAII \u7684 finally \u5e2e\u624b\u7c7b swap \u7f29\u5c0f mutex \u533a\u95f4\u4ee3\u4ef7 namespace \u522b\u540d \u6709\u4e9b\u5d4c\u5957\u5f88\u6df1\u7684\u540d\u5b57\u7a7a\u95f4\u6bcf\u6b21\u90fd\u8981\u590d\u8bfb\u975e\u5e38\u5570\u55e6\u3002 #include int main() { std::filesystem::path p = \"/var/www/html\"; ... } \u5982\u679c using namespace \u7684\u8bdd\uff0c\u53c8\u89c9\u5f97\u6c61\u67d3\u5168\u5c40\u540d\u5b57\u7a7a\u95f4\u4e86\u3002 #include using namespace std::filesystem; int main() { std::filesystem::path p = \"/var/www/html\"; ... } \u53ef\u4ee5\u7528 C++11 \u7684 namespace = \u8bed\u6cd5\uff0c\u7ed9\u540d\u5b57\u7a7a\u95f4\u53d6\u4e2a\u522b\u540d\u3002 #include namespace fs = std::filesystem; int main() { fs::path p = \"/var/www/html\"; ... } \u8fd9\u6837\u4ee5\u540e\u5c31\u53ef\u4ee5 fs \u8fd9\u4e2a\u7b80\u79f0\u8bbf\u95ee\u4e86\u3002","title":"\u5e94\u77e5\u5e94\u4f1a C++ \u5c0f\u6280\u5de7"},{"location":"cpp_tricks/#c","text":"\u5e94\u77e5\u5e94\u4f1a C++ \u5c0f\u6280\u5de7 \u4ea4\u6362\u4e24\u4e2a\u53d8\u91cf \u5b89\u5168\u5730\u5206\u914d\u4e00\u6bb5\u5185\u5b58\u7a7a\u95f4 \u5730\u677f\u9664\u4e0e\u5929\u82b1\u677f\u9664 \u522b\u518d [] \u5566\uff01 \u522b\u518d\u5199\u6784\u9020\u51fd\u6570\u5566\uff01 \u522b\u518d\u5199\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u5566\uff01 \u7ee7\u627f\u6784\u9020\u51fd\u6570 \u63d0\u524d\u8fd4\u56de \u7acb\u5373\u8c03\u7528\u7684 Lambda Lambda \u590d\u7528\u4ee3\u7801 \u7c7b\u5185\u9759\u6001\u6210\u5458 inline \u522b\u518d make_pair \u5566\uff01 insert \u4e0d\u4f1a\u66ff\u6362\u73b0\u6709\u503c\u54e6 \u4e00\u8fb9\u904d\u5386 map\uff0c\u4e00\u8fb9\u5220\u9664\uff1f \u9ad8\u6548\u5220\u9664\u5355\u4e2a vector \u5143\u7d20 \u6279\u91cf\u5220\u9664\u90e8\u5206 vector \u5143\u7d20 \u4fdd\u6301\u6709\u5e8f\u7684 vector \u7528\u4e8e\u4e8c\u5206\u6cd5 C++ \u968f\u673a\u6570\u7684\u6b63\u786e\u751f\u6210\u65b9\u5f0f const \u5c45\u7136\u5e94\u8be5\u540e\u7f6e\u2026 \u51fd\u6570\u53c2\u6570\u4e5f\u53ef\u4ee5 auto \u8bfb\u53d6\u6574\u4e2a\u6587\u4ef6\u5230\u5b57\u7b26\u4e32 \u9010\u884c\u8bfb\u53d6\u6587\u672c\u6587\u4ef6 \u5b57\u7b26\u4e32\u5207\u7247 cout \u4e0d\u9700\u8981 endl \u591a\u7ebf\u7a0b\u4e2d cout \u51fa\u73b0\u4e71\u5e8f\uff1f cerr \u4e0e cout \u7684\u6289\u62e9 \u667a\u80fd\u6307\u9488\u9632\u6b62\u5927\u5bf9\u8c61\u79fb\u52a8 optional \u5b9e\u73b0\u5ef6\u8fdf\u521d\u59cb\u5316 if-auto \u4e0e while-auto bind \u662f\u5386\u53f2\u7cdf\u7c95\uff0c\u5e94\u8be5\u7531 Lambda \u8868\u8fbe\u5f0f\u53d6\u4ee3 bind \u7684\u5386\u53f2 thread \u819d\u76d6\u4e2d\u7bad \u4e3e\u4e2a\u7ed1\u5b9a\u968f\u673a\u6570\u751f\u6210\u5668\u4f8b\u5b50 forward \u8ff7\u60d1\u6027\u5730\u4e0d\u597d\u7528\uff0c\u5efa\u8bae\u6539\u7528 FWD \u5b8f bind \u7ed1\u5b9a\u6210\u5458\u51fd\u6570\u662f\u964b\u4e60\uff0c\u6539\u7528 lambda \u6216 bind_front \u6551\u547d\uff01\u4e3a\u4ec0\u4e48\u6211\u7684\u5168\u5c40\u51fd\u6570\u4e0d\u80fd\u4f5c\u4e3a\u51fd\u6570\u5bf9\u8c61\uff1f map + any \u5916\u6302\u5c5e\u6027 \u81ea\u5b9a\u4e49 shared_ptr \u7684 deleter CHECK_CUDA \u7c7b\u9519\u8bef\u68c0\u6d4b\u5b8f \u51fd\u6570\u9ed8\u8ba4\u53c2\u6570\u6c42\u503c\u7684\u4f4d\u7f6e\u662f\u8c03\u7528\u8005 \u8bbe\u7f6e locale \u4e3a .utf8 \u82b1\u62ec\u53f7\u5b9e\u73b0\u5b89\u5168\u7684\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5 \u6210\u5458\u51fd\u6570\u9488\u5bf9 this \u7684\u79fb\u52a8\u91cd\u8f7d CHECK_CUDA \u7c7b\u9519\u8bef\u68c0\u6d4b\u5b8f \u51fd\u6570\u9ed8\u8ba4\u53c2\u6570\u6c42\u503c\u7684\u4f4d\u7f6e\u662f\u8c03\u7528\u8005 \u82b1\u62ec\u53f7\u5b9e\u73b0\u5b89\u5168\u7684\u7c7b\u578b\u8f6c\u6362\u68c0\u67e5 \u4e34\u65f6\u53f3\u503c\u8f6c\u5de6\u503c ostringstream \u683c\u5f0f\u5316\u5b57\u7b26\u4e32 ADL \u673a\u5236\u5b9e\u73b0\u9759\u6001\u591a\u6001 shared_from_this requires \u8bed\u6cd5\u68c0\u6d4b\u662f\u5426\u5b58\u5728\u6307\u5b9a\u6210\u5458\u51fd\u6570 \u8bbe\u7f6e locale \u4e3a .utf8 \u89e3\u51b3 Windows \u7f16\u7801\u96be\u95ee\u9898 \u6210\u5458\u51fd\u6570\u9488\u5bf9 this \u7684\u79fb\u52a8\u91cd\u8f7d \u4f4d\u57df\uff08bit-field\uff09 vector + unordered_map = LRU cache Lambda \u6355\u83b7 unique_ptr \u5bfc\u81f4 function \u62a5\u9519\u600e\u4e48\u529e \u591a\u7ebf\u7a0b\u901a\u4fe1\u5e94\u57fa\u4e8e\u961f\u5217\uff0c\u800c\u4e0d\u662f\u5171\u4eab\u5168\u5c40\u53d8\u91cf RAII \u7684 finally \u5e2e\u624b\u7c7b swap \u7f29\u5c0f mutex \u533a\u95f4\u4ee3\u4ef7 namespace \u522b\u540d","title":"\u5e94\u77e5\u5e94\u4f1a C++ \u5c0f\u6280\u5de7"},{"location":"cpp_tricks/#_1","text":"int a = 42; int b = 58; \u73b0\u5728\u4f60\u60f3\u4ea4\u6362\u8fd9\u4e24\u4e2a\u53d8\u91cf\u3002 int tmp = a; a = b; b = tmp; \u4f46\u662f\u6807\u51c6\u5e93\u63d0\u4f9b\u4e86\u66f4\u597d\u7684\u65b9\u6cd5\uff1a std::swap(a, b); \u8fd9\u4e2a\u65b9\u6cd5\u53ef\u4ee5\u4ea4\u6362\u4efb\u610f\u4e24\u4e2a\u540c\u7c7b\u578b\u7684\u503c\uff0c\u5305\u62ec\u7ed3\u6784\u4f53\u3001\u6570\u7ec4\u3001\u5bb9\u5668\u7b49\u3002 \u53ea\u9700\u8981 #include \u5c31\u53ef\u4ee5\u4f7f\u7528\uff01","title":"\u4ea4\u6362\u4e24\u4e2a\u53d8\u91cf"},{"location":"cpp_tricks/#_2","text":"\u5c0f\u5f6d\u8001\u5e08\uff1a\u4e0d\u8981\u51fa\u73b0 new \u548c delete\uff0c\u4e0d\u5b89\u5168\u3002 \u540c\u5b66\uff1a\u6211\u60f3\u8981 \u5206\u914d\u4e00\u6bb5\u5185\u5b58\u7a7a\u95f4 \uff0c\u4f60\u4e0d\u8ba9\u6211 new\uff0c\u6211\u8fd8\u80fd\u600e\u4e48\u529e\u5462\uff1f char *mem = new char[1024]; // \u540c\u5b66\u60f3\u8981 1024 \u5b57\u8282\u7684\u7f13\u51b2\u533a read(1, mem, 1024); // \u7528\u4e8e\u4f9b C \u8bed\u8a00\u7684\u8bfb\u6587\u4ef6\u51fd\u6570\u4f7f\u7528 delete[] mem; // \u9700\u8981\u624b\u52a8 delete \u53ef\u4ee5\u770b\u5230\uff0c\u4ed6\u6240\u8c13\u7684\u201c\u5185\u5b58\u7a7a\u95f4\u201d\u5b9e\u9645\u4e0a\u5c31\u662f\u4e00\u4e2a\u201cchar \u6570\u7ec4\u201d\u3002 \u5c0f\u5f6d\u8001\u5e08\uff1a\u6709\u6ca1\u6709\u4e00\u79cd\u53ef\u80fd\uff0cvector \u5c31\u53ef\u4ee5\u5206\u914d\u5185\u5b58\u7a7a\u95f4\u3002 vector mem(1024); read(1, mem.data(), mem.size()); vector \u4e00\u6837\u7b26\u5408 RAII \u601d\u60f3\uff0c\u6784\u9020\u65f6\u81ea\u52a8\u7533\u8bf7\u5185\u5b58\uff0c\u79bb\u5f00\u4f5c\u7528\u57df\u65f6\u81ea\u52a8\u91ca\u653e\u3002 \u53ea\u9700\u5728\u8c03\u7528 C \u8bed\u8a00\u63a5\u53e3\u65f6\uff0c\u53d6\u51fa\u539f\u59cb\u6307\u9488\uff1a \u7528 data() \u5373\u53ef\u83b7\u53d6\u51fa\u9996\u4e2a char \u5143\u7d20\u7684\u6307\u9488\uff0c\u7528\u4e8e\u4f20\u9012\u7ed9 C \u8bed\u8a00\u51fd\u6570\u4f7f\u7528\u3002 \u7528 size() \u53d6\u51fa\u6570\u7ec4\u7684\u957f\u5ea6\uff0c\u5373\u662f\u5185\u5b58\u7a7a\u95f4\u7684\u5b57\u8282\u6570\uff0c\u56e0\u4e3a\u6211\u4eec\u7684\u5143\u7d20\u7c7b\u578b\u662f char\uff0cchar \u521a\u597d\u5c31\u662f 1 \u5b57\u8282\u7684\uff0csize() \u521a\u597d\u5c31\u662f\u5b57\u8282\u7684\u6570\u91cf\u3002 \u6b64\u5904 read \u51fd\u6570\u8bfb\u5b8c\u540e\uff0c\u6570\u636e\u5c31\u76f4\u63a5\u8fdb\u5165\u4e86 vector \u4e2d\uff0c\u6839\u672c\u4e0d\u9700\u8981\u4ec0\u4e48 new\u3002 \u66f4\u73b0\u4ee3\u7684 C++ \u601d\u60f3\u5bb6\u8fd8\u4f1a\u7528 vector \uff0c\u660e\u786e\u533a\u5206\u8fd9\u662f\u201c\u5b57\u8282\u201d\u4e0d\u662f\u201c\u5b57\u7b26\u201d\u3002\u5982\u679c\u4f60\u8bfb\u51fa\u6765\u7684\u76ee\u7684\u662f\u5f53\u4f5c\u5b57\u7b26\u4e32\uff0c\u53ef\u4ee5\u7528 std::string \u3002 \u6ce8\u610f\uff1a\u4e00\u4e9b\u611a\u8822\u7684\u6559\u6750\u4e2d\uff0c\u7528 shared_ptr \u548c unique_ptr \u6765\u7ba1\u7406\u6570\u7ec4\uff0c\u8fd9\u662f\u9519\u8bef\u7684\u3002 shared_ptr \u548c unique_ptr \u667a\u80fd\u6307\u9488\u4e3b\u8981\u662f\u7528\u4e8e\u7ba1\u7406\u201c\u5355\u4e2a\u5bf9\u8c61\u201d\u7684\uff0c\u4e0d\u662f\u7ba1\u7406\u201c\u6570\u7ec4\u201d\u7684\u3002 vector \u4e00\u76f4\u90fd\u662f\u6570\u7ec4\u7684\u7ba1\u7406\u65b9\u5f0f\uff0c\u4e14\u4ece C++98 \u5c31\u6709\u3002\u4e0d\u8981\u770b\u5230 \u201cnew \u7684\u66ff\u4ee3\u54c1\u201d \u53ea\u60f3\u5230\u667a\u80fd\u6307\u9488\u554a\uff01\u201cnew [] \u7684\u66ff\u4ee3\u54c1\u201d \u662f vector \u554a\uff01 \u6b64\u5904\u653e\u51fa\u4e00\u4e2a\u5229\u7528 std::wstring \u5206\u914d wchar_t * \u5185\u5b58\u7684\u6848\u4f8b\uff1a std::wstring utf8_to_wstring(std::string const &s) { int len = MultiByteToWideChar(CP_UTF8, 0, s.data(), s.size(), nullptr, 0); // \u5148\u786e\u5b9a\u957f\u5ea6 std::wstring ws(len, 0); MultiByteToWideChar(CP_UTF8, 0, s.data(), s.size(), ws.data(), ws.size()); // \u518d\u8bfb\u51fa\u6570\u636e return ws; }","title":"\u5b89\u5168\u5730\u5206\u914d\u4e00\u6bb5\u5185\u5b58\u7a7a\u95f4"},{"location":"cpp_tricks/#_3","text":"\u4f17\u6240\u5468\u77e5\uff0cC\u8bed\u8a00\u4e2d int \u76f8\u9664 / \uff0c\u5f97\u5230\u7684\u7ed3\u679c\u4e5f\u662f int \uff0c\u5982\u679c\u9664\u6cd5\u4ea7\u751f\u4e86\u4f59\u6570\uff0c\u90a3\u4e48\u53ea\u4f1a\u4fdd\u7559\u6574\u6570\u90e8\u5206\u3002 \u4f8b\u5982 14 / 5 \uff0c\u672c\u6765\u5e94\u8be5\u5f97\u5230 2.8\u3002\u4f46\u662f\u56e0\u4e3a C \u8bed\u8a00\u7684\u9664\u6cd5\u8fd4\u56de int \uff0c\u7ed3\u679c\u4f1a\u81ea\u52a8\u5411\u4e0b\u53d6\u6574\uff0c\u5bfc\u81f4\u5f97\u5230 2\u3002 int a = 14, b = 5; int c = a / b; // c = 14 / 5 = 2 \u7b49\u4ef7\u4e8e int c = floor((float)a / b); // c = floor(2.8) = 2 \u5982\u679c a \u9664\u4ee5 b \u9664\u4e0d\u5c3d\uff0c\u90a3\u4e48\u4f1a\u627e\u5230\u6bd4\u4ed6\u5927\u7684\u7b2c\u4e00\u4e2a\u6574\u6570\u4f5c\u4e3a\u7ed3\u679c\uff0c\u8fd9\u5c31\u662f \u5730\u677f\u9664 (floor div) \u3002 C \u8bed\u8a00\u9ed8\u8ba4\u7684\u5c31\u662f\u5730\u677f\u9664\u3002 \u5982\u679c\u6211\u60f3\u8981\u7684\u662f\u5411\u4e0a\u53d6\u6574\uff0c\u8be5\u600e\u4e48\u5199\uff1f \u6700\u539f\u59cb\u7684\u5199\u6cd5\u662f\u5148\u8f6c\u6210\u6d6e\u70b9\u6570\u6765\u9664\uff0c\u7136\u540eceil\u51fd\u6570\u5411\u4e0a\u53d6\u6574\uff1a int c = ceil((float)a / b); \u4f46\u662f\u6d6e\u70b9\u6570\u4e0d\u4ec5\u4f4e\u6548\uff0c\u8fd8\u6709\u7cdf\u7cd5\u7684\u6d6e\u70b9\u6570\u7cbe\u5ea6\u8bef\u5dee\uff01\u5bf9\u4e8e\u5f88\u5927\u7684\u6574\u6570\uff08\u5927\u4e8e 2^{23} 2^{23} \uff09\u4f1a\u4ea7\u751f\u9519\u8bef\u7684\u7ed3\u679c\u3002 \u66f4\u5408\u7406\u7684\u5199\u6cd5\u662f\u5148\u628a a \u52a0\u4e0a b - 1 \uff0c\u7136\u540e\u518d\u4e0b\u53d6\u6574\u5730\u9664\u4ee5 b \uff1a int c = (a + b - 1) / b; \u8fd9\u6837\u5c31\u80fd\u4ea7\u751f\u4e00\u4e2a\u5411\u4e0a\u53d6\u6574\u7684\u9664\u6cd5\u4e86\u3002 \u5982\u679c a \u9664\u4ee5 b \u9664\u4e0d\u5c3d\uff0c\u90a3\u4e48\u4f1a\u627e\u5230\u6bd4\u4ed6\u5927\u7684\u7b2c\u4e00\u4e2a\u6574\u6570\u4f5c\u4e3a\u7ed3\u679c\uff0c\u8fd9\u5c31\u662f \u5929\u82b1\u677f\u9664 (ceil div) \u3002 \u8bd5\u8bd5\u770b\uff1a14 \u9664\u4ee5 5\uff0c\u5e94\u8be5\u5f97\u5230 2.8\uff1b\u5982\u679c\u7528\u5730\u677f\u9664\uff0c\u4f1a\u5f97\u5230 2\uff1b\u5982\u679c\u7528\u5929\u82b1\u677f\u9664\uff0c\u4f1a\u5f97\u5230 3\u3002 14 / 5 = 2 (14 + 5 - 1) / 5 = (14 + 4) / 5 = 18 / 5 = 3 \u8bd5\u8bd5\u770b\uff1a10 \u9664\u4ee5 5\uff0c\u5e94\u8be5\u5f97\u5230 2\uff1b\u90a3\u4e48\u65e0\u8bba\u662f\u5730\u677f\u9664\u8fd8\u662f\u5929\u82b1\u677f\u9664\uff0c\u90fd\u5e94\u8be5\u5f97\u5230 2\u3002 10 / 5 = 2 (10 + 5 - 1) / 5 = (10 + 4) / 5 = 14 / 5 = 2 \u8fd9\u5c31\u662f C \u8bed\u8a00\u4e2d\u5b9e\u73b0\u5929\u82b1\u677f\u9664\u7684\u4e1a\u754c\u516c\u8ba4\u65b9\u5f0f\u3002","title":"\u5730\u677f\u9664\u4e0e\u5929\u82b1\u677f\u9664"},{"location":"cpp_tricks/#_4","text":"\u4f60\u77e5\u9053\u5417\uff1f\u5728 map \u4e2d\u4f7f\u7528 [] \u67e5\u627e\u5143\u7d20\uff0c\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u4f1a\u81ea\u52a8\u521b\u5efa\u4e00\u4e2a\u9ed8\u8ba4\u503c\u3002\u8fd9\u4e2a\u7279\u6027\u6709\u65f6\u5f88\u65b9\u4fbf\uff0c\u4f46\u5982\u679c\u4f60\u4e0d\u5c0f\u5fc3\u5199\u9519\u4e86\uff0c\u5c31\u4f1a\u5728 map \u4e2d\u521b\u5efa\u4e00\u4e2a\u591a\u4f59\u7684\u9ed8\u8ba4\u5143\u7d20\u3002 map table; table[\"\u5c0f\u5f6d\u8001\u5e08\"] = 24; cout << table[\"\u4faf\u6377\u8001\u5e08\"]; table \u4e2d\u660e\u660e\u6ca1\u6709 \u201c\u4faf\u6377\u8001\u5e08\u201d \u8fd9\u4e2a\u5143\u7d20\uff0c\u4f46\u7531\u4e8e [] \u7684\u7279\u6027\uff0c\u4ed6\u4f1a\u9ed8\u8ba4\u8fd4\u56de\u4e00\u4e2a 0\uff0c\u4e0d\u4f1a\u7206\u4efb\u4f55\u9519\u8bef\uff01 \u6539\u7528\u66f4\u5b89\u5168\u7684 at() \u51fd\u6570\uff0c\u5f53\u67e5\u8be2\u7684\u5143\u7d20\u4e0d\u5b58\u5728\u65f6\uff0c\u4f1a\u629b\u51fa\u5f02\u5e38\uff0c\u65b9\u4fbf\u4f60\u8c03\u8bd5\uff1a map table; table.at(\"\u5c0f\u5f6d\u8001\u5e08\") = 24; cout << table.at(\"\u4faf\u6377\u8001\u5e08\"); // \u629b\u51fa\u5f02\u5e38 [] \u771f\u6b63\u7684\u7528\u9014\u662f\u201c\u5199\u5165\u65b0\u5143\u7d20\u201d\u65f6\uff0c\u5982\u679c\u5143\u7d20\u4e0d\u5b58\u5728\uff0c\u4ed6\u53ef\u4ee5\u81ea\u52a8\u5e2e\u4f60\u521b\u5efa\u4e00\u4e2a\u9ed8\u8ba4\u503c\uff0c\u4f9b\u4f60\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u8d4b\u503c\u8fdb\u53bb\u3002 \u68c0\u6d4b\u5143\u7d20\u662f\u5426\u5b58\u5728\u53ef\u4ee5\u7528 count \uff1a if (table.count(\"\u5c0f\u5f6d\u8001\u5e08\")) { return table.at(\"\u5c0f\u5f6d\u8001\u5e08\"); } else { return 0; } \u5373\u4f7f\u4f60\u60f3\u8981\u9ed8\u8ba4\u503c 0 \u8fd9\u4e00\u7279\u6027\uff0c count + at \u4e5f\u6bd4 [] \u66f4\u597d\uff0c\u56e0\u4e3a [] \u7684\u9ed8\u8ba4\u503c\u662f\u4f1a\u5bf9 table \u505a\u7834\u574f\u6027\u4fee\u6539\u7684\uff0c\u8fd9\u5bfc\u81f4 [] \u9700\u8981 map \u7684\u58f0\u660e\u4e0d\u4e3a const \uff1a map table; return table[\"\u5c0f\u5f6d\u8001\u5e08\"]; // \u5982\u679c\"\u5c0f\u5f6d\u8001\u5e08\"\u8fd9\u4e00\u952e\u4e0d\u5b58\u5728\uff0c\u4f1a\u521b\u5efa\"\u5c0f\u5f6d\u8001\u5e08\"\u5e76\u8bbe\u4e3a\u9ed8\u8ba4\u503c 0 const map table; return table[\"\u5c0f\u5f6d\u8001\u5e08\"]; // \u7f16\u8bd1\u5931\u8d25\uff01[] \u9700\u8981\u975e const \u7684 map \u5bf9\u8c61\uff0c\u56e0\u4e3a\u4ed6\u4f1a\u7834\u574f\u6027\u4fee\u6539 \u66f4\u591a map \u77e5\u8bc6\u8bf7\u770b\u6211\u4eec\u7684 map \u4e13\u9898\u8bfe \u3002","title":"\u522b\u518d [] \u5566\uff01"},{"location":"cpp_tricks/#_5","text":"// C++98 struct Student { string name; int age; int id; Student(string name_, int age_, int id_) : name(name_), age(age_), id(id_) {} }; Student stu(\"\u4faf\u6377\u8001\u5e08\", 42, 123); C++98 \u9700\u8981\u624b\u52a8\u4e66\u5199\u6784\u9020\u51fd\u6570\uff0c\u975e\u5e38\u9ebb\u70e6\uff01\u800c\u4e14\u51e0\u4e4e\u90fd\u662f\u91cd\u590d\u7684\u3002 C++11 \u4e2d\uff0c\u5e73\u51e1\u7684\u7ed3\u6784\u4f53\u7c7b\u578b\u4e0d\u9700\u8981\u518d\u5199\u6784\u9020\u51fd\u6570\u4e86\uff0c\u53ea\u9700\u7528 {} \u5c31\u80fd\u5bf9\u6210\u5458\u4f9d\u6b21\u521d\u59cb\u5316\uff1a // C++11 struct Student { string name; int age; int id; }; Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24, 123}; \u8fd9\u88ab\u79f0\u4e3a \u805a\u5408\u521d\u59cb\u5316 (aggregate initialize)\u3002\u53ea\u8981\u4f60\u7684\u7c7b\u6ca1\u6709\u81ea\u5b9a\u4e49\u6784\u9020\u51fd\u6570\uff0c\u6ca1\u6709 private \u6210\u5458\uff0c\u90fd\u53ef\u4ee5\u7528 {} \u805a\u5408\u521d\u59cb\u5316\u3002 \u597d\u6d88\u606f\uff1aC++20 \u4e2d\uff0c\u805a\u5408\u521d\u59cb\u5316\u4e5f\u652f\u6301 () \u4e86\uff0c\u7528\u8d77\u6765\u5c31\u548c\u4f20\u7edf\u7684 C++98 \u6784\u9020\u51fd\u6570\u4e00\u6837\uff01 // C++20 Student stu(\"\u5c0f\u5f6d\u8001\u5e08\", 24, 123); \u805a\u5408\u521d\u59cb\u5316\u8fd8\u53ef\u4ee5\u6307\u5b9a\u9ed8\u8ba4\u503c\uff1a // C++11 struct Student { string name; int age; int id = 9999; }; Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24}; // \u7b49\u4ef7\u4e8e\uff1a Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24, 9999}; C++20 \u5f00\u59cb\uff0c {} \u805a\u5408\u521d\u59cb\u5316\u8fd8\u53ef\u4ee5\u6839\u636e\u6bcf\u4e2a\u6210\u5458\u7684\u540d\u5b57\u6765\u6307\u5b9a\u503c\uff1a Student stu{.name = \"\u5c0f\u5f6d\u8001\u5e08\", .age = 24, .id = 9999}; // \u7b49\u4ef7\u4e8e\uff1a Student stu{\"\u5c0f\u5f6d\u8001\u5e08\", 24, 9999}; \u597d\u5904\u662f\uff0c\u5373\u4f7f\u4e0d\u614e\u5199\u9519\u53c2\u6570\u987a\u5e8f\u4e5f\u4e0d\u7528\u62c5\u5fc3\u3002 Student stu{.name = \"\u5c0f\u5f6d\u8001\u5e08\", .age = 24, .id = 9999}; Student stu{.name = \"\u5c0f\u5f6d\u8001\u5e08\", .id = 9999, .age = 24};","title":"\u522b\u518d\u5199\u6784\u9020\u51fd\u6570\u5566\uff01"},{"location":"cpp_tricks/#_6","text":"\u53ea\u6709\u5f53\u4f60\u9700\u8981\u6709\u201c\u81ea\u5b9a\u4e49\u94a9\u5b50\u903b\u8f91\u201d\u7684\u65f6\u5019\uff0c\u624d\u9700\u8981\u81ea\u5b9a\u4e49\u6784\u9020\u51fd\u6570\u3002 struct Student { string name; int age; int id; Student(string name_, int age_, int id_) : name(name_), age(age_), id(id_) {} Student(Student const &other) : name(other.name), age(other.age), id(other.id) { std::cout << \"\u62f7\u8d1d\u6784\u9020\\n\"; } Student &operator=(Student const &other) { name = other.name; age = other.age; id = other.id; std::cout << \"\u62f7\u8d1d\u8d4b\u503c\\n\"; return *this; } }; Student stu1(\"\u4faf\u6377\u8001\u5e08\", 42, 123); Student stu2 = stu1; // \u62f7\u8d1d\u6784\u9020 stu2 = stu1; // \u62f7\u8d1d\u8d4b\u503c \u5982\u679c\u4f60\u4e0d\u9700\u8981\u8fd9\u4e2a std::cout \uff0c\u53ea\u662f\u5e73\u51e1\u5730\u62f7\u8d1d\u6240\u6709\u6210\u5458\uff0c\u5b8c\u5168\u53ef\u4ee5\u4e0d\u5199\uff0c\u8ba9\u7f16\u8bd1\u5668\u81ea\u52a8\u751f\u6210\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3001\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570\u3001\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3001\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\uff1a struct Student { string name; int age; int id; Student(string name_, int age_, int id_) : name(name_), age(age_), id(id_) {} // \u7f16\u8bd1\u5668\u81ea\u52a8\u751f\u6210 Student(Student const &other) // \u7f16\u8bd1\u5668\u81ea\u52a8\u751f\u6210 Student &operator=(Student const &other) }; Student stu1(\"\u4faf\u6377\u8001\u5e08\", 42, 123); Student stu2 = stu1; // \u62f7\u8d1d\u6784\u9020 stu2 = stu1; // \u62f7\u8d1d\u8d4b\u503c assert(stu2.name == \"\u4faf\u6377\u8001\u5e08\"); \u603b\u4e4b\uff0c\u5f88\u591a C++ \u6559\u6750\u628a\u62f7\u8d1d/\u79fb\u52a8\u6784\u9020\u51fd\u6570\u8fc7\u4e8e\u5938\u5927\uff0c\u641e\u5f97\u597d\u50cf\u6bcf\u4e2a\u7c7b\u90fd\u9700\u8981\u81ea\u5df1\u5b9a\u4e49\u4e00\u6837\u3002 \u5b9e\u9645\u4e0a\uff0c\u53ea\u6709\u5728\u201c\u81ea\u5df1\u5b9e\u73b0\u5bb9\u5668\u201d\u7684\u60c5\u51b5\u4e0b\uff0c\u624d\u9700\u8981\u81ea\u5b9a\u4e49\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u3002\u53ef\u662f\u8c01\u4f1a\u6574\u5929\u624b\u6413\u5bb9\u5668\uff1f \u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u6211\u4eec\u53ea\u9700\u8981\u5728\u7c7b\u91cc\u9762\u5b58 vector\u3001string \u7b49\u5c01\u88c5\u597d\u7684\u5bb9\u5668\uff0c\u7f16\u8bd1\u5668\u9ed8\u8ba4\u751f\u6210\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u4f1a\u81ea\u52a8\u8c03\u7528\u4ed6\u4eec\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\uff0c\u7528\u6237\u53ea\u9700\u4e13\u6ce8\u4e8e\u4e1a\u52a1\u903b\u8f91\u5373\u53ef\uff0c\u4e0d\u9700\u8981\u64cd\u5fc3\u5e95\u5c42\u7ec6\u8282\u3002 \u5bf9\u4e8e\u6301\u6709\u8d44\u6e90\u7684 RAII \u7c7b\uff0c\u6211\u4eec\u90fd\u4f1a\u76f4\u63a5\u5220\u9664\u5176\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u548c\u62f7\u8d1d\u8d4b\u503c\u51fd\u6570\uff1a struct RAIIHandle { int handle; RAIIHandle() { handle = CreateObject(); } RAIIHandle(RAIIHandle const &) = delete; RAIIHandle &operator=(RAIIHandle const &) = delete; RAIIHandle() { DeleteObject(handle); } };","title":"\u522b\u518d\u5199\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u5566\uff01"},{"location":"cpp_tricks/#_7","text":"C++ \u7279\u8272\uff1a\u5b50\u7c7b\u4e0d\u4f1a\u81ea\u52a8\u7ee7\u627f\u7236\u7c7b\u7684\u6784\u9020\u51fd\u6570\uff01\uff08\u9664\u975e\u7236\u7c7b\u7684\u6784\u9020\u51fd\u6570\u662f\u6ca1\u6709\u53c2\u6570\u7684\u9ed8\u8ba4\u6784\u9020\u51fd\u6570\uff09 struct Parent { Parent(int age, const char *name) { ... } void parent_func() { ... } }; struct Child : Parent { void child_func() { ... } }; Child child(23, \"peng\"); // \u9519\u8bef\uff01Child \u6ca1\u6709\u6784\u9020\u51fd\u6570\uff01 C++11 \u4e2d\u53ef\u4ee5\u5728\u5b50\u7c7b\u91cc\u9762\u5199 using \u7236\u7c7b::\u7236\u7c7b \uff0c\u5c31\u80fd\u81ea\u52a8\u7ee7\u627f\u7236\u7c7b\u6240\u6709\u7684\u6784\u9020\u51fd\u6570\u4e86\u3002 struct Parent { Parent(int age, const char *name) { ... } void parent_func() { ... } }; struct Child : Parent { using Parent::Parent; // \u52a0\u4e0a\u8fd9\u4e00\u884c\uff01 void child_func() { ... } }; Child child(23, \"peng\"); // \u7f16\u8bd1\u901a\u8fc7\uff0c\u81ea\u52a8\u8c03\u7528\u5230\u7236\u7c7b\u7684\u6784\u9020\u51fd\u6570 Parent(int, const char *) \u5728 C++98 \u4e2d\uff0c\u6ca1\u6709 using \u7684\u8fd9\u4e2a\u8bed\u6cd5\uff0c\u53ea\u80fd\u81ea\u5df1\u5b9a\u4e49\u4e00\u4e2a\u6784\u9020\u51fd\u6570\uff0c\u7136\u540e\u4f7f\u7528\u201c\u59d4\u4efb\u6784\u9020\u201d\u7684\u8bed\u6cd5\u8f6c\u53d1\u6240\u6709\u53c2\u6570\u7ed9\u7236\u7c7b\uff0c\u975e\u5e38\u7e41\u7410\u3002 struct Parent { Parent(int age, const char *name) { ... } void parent_func() { ... } }; struct Child : Parent { Child(int age, const char *name) : Parent(age, name) { ... } void child_func() { ... } }; Child child(23, \"peng\"); // \u7f16\u8bd1\u901a\u8fc7\uff0c\u8c03\u7528\u5230\u5b50\u7c7b\u7684\u6784\u9020\u51fd\u6570\u540e\u8f6c\u53d1\u5230\u7236\u7c7b","title":"\u7ee7\u627f\u6784\u9020\u51fd\u6570"},{"location":"cpp_tricks/#_8","text":"void babysitter(Baby *baby) { if (!baby->is_alive()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u53bb\u4e16\u4e86\"); } else { puts(\"\u6b63\u5728\u68c0\u67e5\u5b9d\u5b9d\u5582\u98df\u60c5\u51b5...\"); if (baby->is_feeded()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u5582\u98df\u8fc7\u4e86\"); } else { puts(\"\u6b63\u5728\u5582\u98df\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u8c03\u6559\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u5b89\u629a\u5b9d\u5b9d...\"); } } } \u8fd9\u4e2a\u51fd\u6570\u6709\u5f88\u591a\u5c42\u5d4c\u5957\uff0c\u5f88\u4e0d\u7f8e\u89c2\u3002\u7528 \u63d0\u524d\u8fd4\u56de \u7684\u5199\u6cd5\u6765\u4f18\u5316\uff1a void babysitter(Baby *baby) { if (!baby->is_alive()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u53bb\u4e16\u4e86\"); return; } puts(\"\u6b63\u5728\u68c0\u67e5\u5b9d\u5b9d\u5582\u98df\u60c5\u51b5...\"); if (baby->is_feeded()) { puts(\"\u5b9d\u5b9d\u5df2\u7ecf\u5582\u98df\u8fc7\u4e86\"); return; } puts(\"\u6b63\u5728\u5582\u98df\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u8c03\u6559\u5b9d\u5b9d...\"); puts(\"\u6b63\u5728\u5b89\u629a\u5b9d\u5b9d...\"); }","title":"\u63d0\u524d\u8fd4\u56de"},{"location":"cpp_tricks/#lambda","text":"\u6709\u65f6\uff0c\u9700\u8981\u5728\u4e00\u4e2a\u5217\u8868\u91cc\u5faa\u73af\u67e5\u627e\u67d0\u6837\u4e1c\u897f\uff0c\u4e5f\u53ef\u4ee5\u7528\u63d0\u524d\u8fd4\u56de\u7684\u5199\u6cd5\u4f18\u5316\uff1a bool find(const vector &v, int target) { for (int i = 0; i < v.size(); ++i) { if (v[i] == target) { return true; } } return false; } \u53ef\u4ee5\u5305\u88f9\u4e00\u4e2a\u7acb\u5373\u8c03\u7528\u7684 Lambda \u5757 [&] { ... } () \uff0c\u9650\u5236\u63d0\u524d\u8fd4\u56de\u7684\u8303\u56f4\uff1a void find(const vector &v, int target) { bool found = [&] { for (int i = 0; i < v.size(); ++i) { if (v[i] == target) { return true; } } return false; } (); if (found) { ... } }","title":"\u7acb\u5373\u8c03\u7528\u7684 Lambda"},{"location":"cpp_tricks/#lambda_1","text":"vector spilt(string str) { vector list; string last; for (char c: str) { if (c == ' ') { list.push_back(last); last.clear(); } else { last.push_back(c); } } list.push_back(last); return list; } \u4e0a\u9762\u7684\u4ee3\u7801\u53ef\u4ee5\u7528 Lambda \u590d\u7528\uff1a vector spilt(string str) { vector list; string last; auto push = [&] { list.push_back(last); last.clear(); }; for (char c: str) { if (c == ' ') { push(); } else { last.push_back(c); } } push(); return list; }","title":"Lambda \u590d\u7528\u4ee3\u7801"},{"location":"cpp_tricks/#inline","text":"\u5728\u5934\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7ed3\u6784\u4f53\u7684 static \u6210\u5458\u65f6\uff1a struct Class { static int member; }; \u4f1a\u62a5\u9519 undefined reference to 'Class::member' \u3002\u8fd9\u662f\u8bf4\u7684\u4f60\u9700\u8981\u627e\u4e2a .cpp \u6587\u4ef6\uff0c\u5199\u51fa int Class::member \u624d\u80fd\u6d88\u9664\u8be5\u9519\u8bef\u3002 C++17 \u4e2d\uff0c\u53ea\u9700\u52a0\u4e2a inline \u5c31\u80fd\u89e3\u51b3\uff01 struct Class { inline static int member; };","title":"\u7c7b\u5185\u9759\u6001\u6210\u5458 inline"},{"location":"cpp_tricks/#make_pair","text":"map table; table.insert(pair(\"\u4faf\u6377\u8001\u5e08\", 42)); \u4e3a\u907f\u514d\u5199\u51fa\u7c7b\u578b\u540d\u7684\u9ebb\u70e6\uff0c\u5f88\u591a\u8001\u5e08\u90fd\u4f1a\u8ba9\u4f60\u5199 make_pair\uff1a map table; table.insert(make_pair(\"\u4faf\u6377\u8001\u5e08\", 42)); \u7136\u800c C++11 \u63d0\u4f9b\u4e86\u66f4\u597d\u7684\u5199\u6cd5\uff0c\u90a3\u5c31\u662f\u901a\u8fc7 {} \u9690\u5f0f\u6784\u9020\uff0c\u4e0d\u7528\u5199\u51fa\u7c7b\u578b\u540d\u6216 make_pair\uff1a map table; table.insert({\"\u4faf\u6377\u8001\u5e08\", 42}); \u5373\u4f7f\u4f60\u51fa\u4e8e\u67d0\u79cd\u201c\u6296m\u201d\u60c5\u8282\uff0c\u8fd8\u60f3\u5199\u51fa\u7c7b\u578b\u540d\uff0c\u4e5f\u53ef\u4ee5\u7528 C++17 \u7684 CTAD \u8bed\u6cd5\uff0c\u514d\u53bb\u6a21\u677f\u53c2\u6570\uff1a map table; table.insert(pair(\"\u4faf\u6377\u8001\u5e08\", 42)); // tuple \u4e5f\u652f\u6301 CTAD\uff1a auto t = tuple(\"\u4faf\u6377\u8001\u5e08\", 42, string(\"\u5c0f\u5f6d\u8001\u5e08\")); // \u7b49\u4ef7\u4e8e\uff1a auto t = make_tuple(\"\u4faf\u6377\u8001\u5e08\", 42, string(\"\u5c0f\u5f6d\u8001\u5e08\")); println(\"{}\", typeid(t).name()); // tuple","title":"\u522b\u518d make_pair \u5566\uff01"},{"location":"cpp_tricks/#insert","text":"map table; table.insert({\"\u5c0f\u5f6d\u8001\u5e08\", 24}); table.insert({\"\u5c0f\u5f6d\u8001\u5e08\", 42}); \u8fd9\u65f6\uff0c table[\"\u5c0f\u5f6d\u8001\u5e08\"] \u4ecd\u7136\u4f1a\u662f 24\uff0c\u800c\u4e0d\u662f 42\u3002\u56e0\u4e3a insert \u4e0d\u4f1a\u66ff\u6362 map \u91cc\u5df2\u7ecf\u5b58\u5728\u7684\u503c\u3002 \u5982\u679c\u5e0c\u671b\u5982\u679c\u5df2\u7ecf\u5b58\u5728\u65f6\uff0c\u66ff\u6362\u73b0\u6709\u5143\u7d20\uff0c\u53ef\u4ee5\u4f7f\u7528 [] \u8fd0\u7b97\u7b26\uff1a map table; table[\"\u5c0f\u5f6d\u8001\u5e08\"] = 24; table[\"\u5c0f\u5f6d\u8001\u5e08\"] = 42; C++17 \u63d0\u4f9b\u4e86\u6bd4 [] \u8fd0\u7b97\u7b26\u66f4\u9002\u5408\u8986\u76d6\u6027\u63d2\u5165\u7684 insert_or_assign \u51fd\u6570\uff1a map table; table.insert_or_assign(\"\u5c0f\u5f6d\u8001\u5e08\", 24); table.insert_or_assign(\"\u5c0f\u5f6d\u8001\u5e08\", 42); \u597d\u5904\uff1a insert_or_assign \u4e0d\u9700\u8981\u503c\u7c7b\u578b\u652f\u6301\u9ed8\u8ba4\u6784\u9020\uff0c\u53ef\u4ee5\u907f\u514d\u4e00\u6b21\u9ed8\u8ba4\u6784\u9020\u51fd\u6570 + \u4e00\u6b21\u79fb\u52a8\u8d4b\u503c\u51fd\u6570\u7684\u5f00\u9500\u3002 \u5efa\u8bae\u628a insert_or_assign \u6539\u540d\u6210 set \uff0c at \u6539\u540d\u6210 get \uff1b\u53ea\u662f\u7531\u4e8e\u5386\u53f2\u539f\u56e0\u540d\u5b57\u8ff7\u60d1\u4e86\u3002","title":"insert \u4e0d\u4f1a\u66ff\u6362\u73b0\u6709\u503c\u54e6"},{"location":"cpp_tricks/#map","text":"map table; for (auto it = table.begin(); it != table.end(); ++it) { if (it->second < 0) { table.erase(it); } } \u4f1a\u53d1\u751f\u5d29\u6e83\uff01\u770b\u6765 map \u4f3c\u4e4e\u4e0d\u5141\u8bb8\u5728\u904d\u5386\u7684\u8fc7\u7a0b\u4e2d\u5220\u9664\uff1f\u4e0d\uff0c\u53ea\u662f\u4f60\u7684\u5199\u6cd5\u6709\u9519\u8bef\uff1a map table; for (auto it = table.begin(); it != table.end(); ) { if (it->second < 0) { it = table.erase(it); } else { ++it; } } C++20 \u5f15\u5165\u4e86\u66f4\u597d\u7684 erase_if \u5168\u5c40\u51fd\u6570\uff0c\u4e0d\u7528\u624b\u5199\u4e0a\u9762\u8fd9\u4e48\u9ebb\u70e6\u7684\u4ee3\u7801\uff1a map table; erase_if(table, [](pair it) { return it.second < 0; });","title":"\u4e00\u8fb9\u904d\u5386 map\uff0c\u4e00\u8fb9\u5220\u9664\uff1f"},{"location":"cpp_tricks/#vector","text":"vector v = {48, 23, 76, 11, 88, 63, 45, 28, 59}; \u4f17\u6240\u5468\u77e5\uff0c\u5728 vector \u4e2d\u5220\u9664\u5143\u7d20\uff0c\u4f1a\u5bfc\u81f4\u540e\u9762\u7684\u6240\u6709\u5143\u7d20\u5411\u524d\u79fb\u52a8\uff0c\u5341\u5206\u4f4e\u6548\u3002\u590d\u6742\u5ea6\uff1a O(n) O(n) // \u76f4\u63a5\u5220\u9664 v[3] v.erase(v.begin() + 3); \u5982\u679c\u4e0d\u5728\u4e4e\u5143\u7d20\u7684\u987a\u5e8f\uff0c\u53ef\u4ee5\u628a\u8981\u5220\u9664\u7684\u5143\u7d20\u548c\u6700\u540e\u4e00\u4e2a\u5143\u7d20 swap\uff0c\u7136\u540e pop_back\u3002\u590d\u6742\u5ea6\uff1a O(1) O(1) // \u628a v[3] \u548c v[v.size() - 1] \u4f4d\u7f6e\u5bf9\u8c03 swap(v[3], v[v.size() - 1]); // \u7136\u540e\u5220\u9664 v[v.size() - 1] v.pop_back(); \u8fd9\u6837\u5c31\u4e0d\u7528\u79fb\u52a8\u4e00\u5927\u5806\u5143\u7d20\u4e86\u3002\u8fd9\u88ab\u79f0\u4e3a back-swap-erase\u3002","title":"\u9ad8\u6548\u5220\u9664\u5355\u4e2a vector \u5143\u7d20"},{"location":"cpp_tricks/#vector_1","text":"vector \u4e2d\u53ea\u5220\u9664\u4e00\u4e2a\u5143\u7d20\u9700\u8981 O(n) O(n) \u3002\u5982\u679c\u4e00\u8fb9\u904d\u5386\uff0c\u4e00\u8fb9\u5220\u9664\u591a\u4e2a\u7b26\u5408\u6761\u4ef6\u7684\u5143\u7d20\uff0c\u5c31\u9700\u8981\u590d\u6742\u5ea6 O(n^2) O(n^2) \u4e86\u3002 \u6807\u51c6\u5e93\u63d0\u4f9b\u4e86 remove \u548c remove_if \u51fd\u6570\uff0c\u5176\u5185\u90e8\u91c7\u7528\u7c7b\u4f3c back-swap-erase \u7684\u65b9\u6cd5\uff0c\u5148\u628a\u8981\u5220\u9664\u7684\u5143\u7d20\u79fb\u52a8\u5230\u672b\u5c3e\u3002\u7136\u540e\u4e00\u6b21\u6027 erase \u6389\u672b\u5c3e\u540c\u6837\u6570\u91cf\u7684\u5143\u7d20\u3002 \u4e14\u4ed6\u4eec\u90fd\u80fd\u4fdd\u6301\u987a\u5e8f\u4e0d\u53d8\u3002 \u5220\u9664\u6240\u6709\u503c\u4e3a 42 \u7684\u5143\u7d20\uff1a vector v; v.erase(remove(v.begin(), v.end(), 42), v.end()); \u5220\u9664\u6240\u6709\u503c\u5927\u4e8e 0 \u7684\u5143\u7d20\uff1a vector v; v.erase(remove_if(v.begin(), v.end(), [](int x) { return x > 0; }), v.end()); \u73b0\u5728 C++20 \u4e5f\u5f15\u5165\u4e86\u5168\u5c40\u51fd\u6570 erase \u548c erase_if\uff0c\u4f7f\u7528\u8d77\u6765\u66f4\u52a0\u76f4\u89c2\uff1a vector v; erase(v, 42); // \u5220\u9664\u6240\u6709\u503c\u4e3a 42 \u7684\u5143\u7d20 erase_if(v, [](int x) { return x > 0; // \u5220\u9664\u6240\u6709\u503c\u5927\u4e8e 0 \u7684\u5143\u7d20 });","title":"\u6279\u91cf\u5220\u9664\u90e8\u5206 vector \u5143\u7d20"},{"location":"cpp_tricks/#vector_2","text":"\u5982\u679c\u4f60\u60f3\u8981\u7ef4\u62a4\u4e00\u4e2a\u6709\u5e8f\u7684\u6570\u7ec4\uff0c\u7528 lower_bound \u6216 upper_bound \u6765\u63d2\u5165\u5143\u7d20\uff0c\u4fdd\u8bc1\u63d2\u5165\u540e\u4ecd\u4fdd\u6301\u6709\u5e8f\uff1a vector s; s.push_back(1); s.push_back(2); s.push_back(4); s.push_back(6); // s = { 1, 2, 4, 6 } s.insert(lower_bound(s.begin(), s.end(), 3), 3); // s = { 1, 2, 3, 4, 6 } s.insert(lower_bound(s.begin(), s.end(), 5), 5); // s = { 1, 2, 3, 4, 5, 6 } \u6709\u5e8f\u6570\u7ec4\u4e2d\uff0c\u53ef\u4ee5\u5229\u7528 lower_bound \u6216 upper_bound \u5feb\u901f\u4e8c\u5206\u67e5\u627e\u5230\u60f3\u8981\u7684\u503c\uff1a vector s; s.push_back(1); s.push_back(2); s.push_back(4); s.push_back(6); // s = { 1, 2, 4, 6 } lower_bound(s.begin(), s.end(), 3); // s.begin() + 2; lower_bound(s.begin(), s.end(), 5); // s.begin() + 3; \u6709\u5e8f vector \u5e94\u7528\u6848\u4f8b\uff1a\u5229\u7528 CDF \u79ef\u5206 + \u4e8c\u5206\u6cd5\u53ef\u4ee5\u5b9e\u73b0\u751f\u6210\u4efb\u610f\u6307\u5b9a\u5206\u5e03\u7684\u968f\u673a\u6570\u3002 \u4f8b\u5982\u6570\u503c\u7b56\u5212\u8981\u6c42\u7684\u62bd\u5361\u6982\u7387\u5206\u5e03\u662f\uff1a 2% \u51fa\u91d1\u5361 10% \u51fa\u84dd\u5361 80% \u51fa\u767d\u5361 8% \u51fa\u7b54\u8fa9 \u90a3\u4e48\u4f60\u8f6c\u6362\u4e00\u4e0b\u4efb\u52a1\u3002\u53d8\u6210\u968f\u673a\u751f\u6210\u4e00\u4e2a 0 \u5230 1 \u7684\u6d6e\u70b9\u6570\uff0c\u7136\u540e\u5224\u65ad\uff1a \u5c0f\u4e8e 0.02 \u65f6\uff0c\u51fa\u91d1\u5361 \u5c0f\u4e8e 0.12 \u65f6\uff0c\u51fa\u84dd\u5361 \u5c0f\u4e8e 0.92 \u65f6\uff0c\u51fa\u767d\u5361 \u5c0f\u4e8e 1.00 \u65f6\uff0c\u51fa\u7b54\u8fa9 \u8fd9\u4e2a\u8f6c\u6362\u8fc7\u7a0b\u5c31\u662f CDF \u79ef\u5206\u3002\u5982\u679c\u4f60\u628a\u8fd9 4 \u4e2a\u6570\u6309\u7167\u987a\u5e8f\u6392\u5217\uff0c\u5c31\u662f\u4e00\u4e2a\u6709\u5e8f vector\u3002 \u6807\u51c6\u5e93\u63d0\u4f9b\u4e86 std::partial_sum \uff08\u4e0d\u7cbe\u51c6\uff09\u6216 std::inclusive_scan \uff08\u66f4\u7cbe\u51c6\uff0cC++17 \u5f15\u5165\uff09\u90fd\u53ef\u4ee5\u8ba1\u7b97\u4e00\u4e2a\u6570\u7ec4\u7684 CDF \u79bb\u6563\u79ef\u5206\u3002 vector probs = {0.02, 0.1, 0.8, 0.08}; vector cdf; // \u8ba1\u7b97 probs \u7684 CDF \u79ef\u5206\uff0c\u5b58\u5165 cdf \u6570\u7ec4 std::inclusive_scan(probs.begin(), probs.end(), std::back_inserter(cdf)); // cdf = {0.02, 0.12, 0.92, 1.00} \u662f\u4e00\u4e2a\u6709\u5e8f vector\uff0c\u53ef\u4ee5\u8fd0\u7528\u4e8c\u5206\u6cd5\u5b9a\u4f4d vector result = {\"\u91d1\u5361\", \"\u84dd\u5361\", \"\u767d\u5361\", \"\u7b54\u8fa9\"}; // \u751f\u6210 100 \u4e2a\u968f\u673a\u6570\uff1a for (int i = 0; i < 100; ++i) { double r = rand() / (RAND_MAX + 1.0); int index = lower_bound(cdf.begin(), cdf.end(), r) - cdf.begin(); cout << \"\u4f60\u62bd\u5230\u4e86\" << result[index] << endl; } \u987a\u4fbf\u4e00\u63d0\uff0cCDF \u79ef\u5206\u7684\u9006\u8fd0\u7b97\u662f\u79bb\u6563\u5fae\u5206\uff1a std::adjacent_difference \uff0c\u53ef\u4ee5\u4ece cdf \u6570\u7ec4\u590d\u539f\u51fa probs \u6570\u7ec4\u3002","title":"\u4fdd\u6301\u6709\u5e8f\u7684 vector \u7528\u4e8e\u4e8c\u5206\u6cd5"},{"location":"cpp_tricks/#c_1","text":"// \u9519\u8bef\u7684\u5199\u6cd5\uff1a int r = rand() % 10; // \u8fd9\u6837\u5199\u662f\u9519\u8bef\u7684\uff01 rand() \u7684\u8fd4\u56de\u503c\u8303\u56f4\u662f [0, RAND_MAX]\uff0cRAND_MAX \u5728\u4e0d\u540c\u5e73\u53f0\u4e0b\u4e0d\u540c\uff0c\u5728 Windows \u5e73\u53f0\u7684\u662f 32767\uff0c\u5373 rand() \u53ea\u80fd\u751f\u6210 0\uff5e32767 \u4e4b\u95f4\u7684\u968f\u673a\u6570\u3002 \u5982\u679c\u60f3\u8981\u751f\u6210 0\uff5e9 \u4e4b\u95f4\u7684\u968f\u673a\u6570\uff0c\u6700\u7b80\u5355\u7684\u529e\u6cd5\u662f\uff1a int r = rand() % 10; \u7136\u800c\u8fd9\u79cd\u65b9\u6cd5\u6709\u4e2a\u81f4\u547d\u7684\u95ee\u9898\uff1a\u4e0d\u540c\u7684\u968f\u673a\u6570\u751f\u6210\u6982\u7387\u4e0d\u4e00\u6837\u3002 \u4f8b\u5982\u628a [0, RAND_MAX] \u5747\u5300\u5730\u5206\u6210 10 \u4efd\uff0c\u6bcf\u4efd 3276.7\u3002\u90a3\u4e48 0\uff5e6 \u4e4b\u95f4\u7684\u6570\u5b57\u51fa\u73b0\u7684\u6982\u7387\u662f 3276.7 / 32767 = 10.0003%\uff0c\u800c 7\uff5e9 \u4e4b\u95f4\u7684\u6570\u5b57\u51fa\u73b0\u7684\u6982\u7387\u662f 3276.7 / 32767 = 9.997%\u3002 \u8fd9\u6837\u5c31\u4e0d\u662f\u771f\u6b63\u7684\u5747\u5300\u5206\u5e03\uff0c\u8fd9\u53ef\u80fd\u4f1a\u5f71\u54cd\u7a0b\u5e8f\u7684\u6b63\u786e\u6027\u3002 \u5f53\u6a21\u6570\u5927\u7684\u65f6\u5019\u4e0d\u5747\u5300\u6027\u4f1a\u53d8\u5f97\u7279\u522b\u660e\u663e\uff0c\u4f8b\u5982 rand() % 10000 \u3002 RAND_MAX \u5728\u4e0d\u540c\u5e73\u53f0\u4e0d\u540c\u7684\u7279\u6027\u4e5f\u8ba9\u8de8\u5e73\u53f0\u5f00\u53d1\u8005\u5f88\u5934\u5927\u3002 rand \u4f7f\u7528\u5168\u5c40\u53d8\u91cf\u5b58\u50a8\u79cd\u5b50\uff0c\u5bf9\u591a\u7ebf\u7a0b\u4e0d\u53cb\u597d\u3002 \u65e0\u6cd5\u72ec\u7acb\u7684\u4e3a\u591a\u4e2a\u751f\u6210\u5e8f\u5217\u8bbe\u5b9a\u72ec\u7acb\u7684\u79cd\u5b50\uff0c\u4e00\u4e9b\u6e38\u620f\u53ef\u80fd\u9700\u8981\u7528\u5230\u591a\u4e2a\u968f\u673a\u5e8f\u5217\uff0c\u5404\u81ea\u6709\u72ec\u7acb\u7684\u79cd\u5b50\u3002 \u53ea\u80fd\u751f\u6210\u5747\u5300\u5206\u5e03\u7684\u6574\u6570\uff0c\u4e0d\u80fd\u751f\u6210\u5e42\u7387\u5206\u5e03\u3001\u6b63\u592a\u5206\u5e03\u7b49\uff0c\u751f\u6210\u6d6e\u70b9\u6570\u4e5f\u6bd4\u8f83\u9ebb\u70e6\u3002 \u4f7f\u7528 srand(time(NULL)) \u65e0\u6cd5\u5b89\u5168\u5730\u751f\u6210\u968f\u673a\u6570\u7684\u521d\u59cb\u79cd\u5b50\uff0c\u5bb9\u6613\u88ab\u9ed1\u5ba2\u9884\u6d4b\u5e76\u653b\u51fb\u3002 rand \u7684\u7b97\u6cd5\u5b9e\u73b0\u6ca1\u6709\u5b98\u65b9\u89c4\u5b9a\uff0c\u5728\u4e0d\u540c\u5e73\u53f0\u5404\u6709\u4e0d\u540c\uff0c\u4ea7\u751f\u7684\u968f\u673a\u6570\u5e8f\u5217\u53ef\u80fd\u4e0d\u540c\u3002 \u4e3a\u6b64\uff0cC++ \u63d0\u51fa\u4e86\u66f4\u52a0\u4e13\u4e1a\u7684\u968f\u673a\u6570\u751f\u6210\u5668\uff1a \u5e93\u3002 // \u4f7f\u7528 \u5e93\u751f\u6210 0\uff5e9 \u4e4b\u95f4\u7684\u968f\u673a\u6570\uff1a #include #include int main() { uint64_t seed = std::random_device()(); std::mt19937 gen(seed); std::uniform_int_distribution dis(0, 9); for (int i = 0; i < 100; ++i) { int r = dis(gen); std::cout << r << \" \"; } } \u8fd9\u6837\u5c31\u53ef\u4ee5\u751f\u6210 0\uff5e9 \u4e4b\u95f4\u7684\u5747\u5300\u5206\u5e03\u7684\u968f\u673a\u6570\u4e86\u3002 std::random_device \u662f\u4e00\u4e2a\u968f\u673a\u6570\u79cd\u5b50\u751f\u6210\u5668\uff0c\u5b83\u4f1a\u5229\u7528\u7cfb\u7edf\u7684\u968f\u673a\u8bbe\u5907\uff08\u5982\u679c\u6709\u7684\u8bdd\uff0c\u5426\u5219\u4f1a\u629b\u51fa\u5f02\u5e38\uff09\u751f\u6210\u4e00\u4e2a\u5b89\u5168\u7684\u968f\u673a\u6570\u79cd\u5b50\uff0c\u9ed1\u5ba2\u65e0\u6cd5\u9884\u6d4b\u3002 std::mt19937 \u662f\u4e00\u4e2a\u968f\u673a\u6570\u751f\u6210\u5668\uff0c\u5b83\u4f1a\u5229\u7528\u521d\u59cb\u79cd\u5b50\u751f\u6210\u4e00\u4e2a\u968f\u673a\u6570\u5e8f\u5217\u3002\u5e76\u4e14\u5fc5\u5b9a\u662f MT19937 \u8fd9\u4e2a\u9ad8\u5f3a\u5ea6\u7684\u968f\u673a\u7b97\u6cd5\uff0c\u6240\u6709\u5e73\u53f0\u90fd\u4e00\u6837\u3002 std::uniform_int_distribution \u662f\u4e00\u4e2a\u5206\u5e03\u5668\uff0c\u5b83\u53ef\u4ee5\u628a\u5747\u5300\u5206\u5e03\u7684\u968f\u673a\u6570\u6620\u5c04\u5230\u6211\u4eec\u60f3\u8981\u7684\u4e0a\u4e0b\u754c\u4e2d\u3002\u91cc\u9762\u7684\u5b9e\u73b0\u7c7b\u4f3c\u4e8e gen() % 10 \uff0c\u4f46\u901a\u8fc7\u6570\u5b66\u673a\u5236\u4fdd\u8bc1\u4e86\u7edd\u5bf9\u5747\u5300\u6027\u3002 \u7c7b\u4f3c\u7684\u8fd8\u6709 std::uniform_real_distribution \u7528\u4e8e\u751f\u6210\u6d6e\u70b9\u6570\uff0c std::normal_distribution \u7528\u4e8e\u751f\u6210\u6b63\u592a\u5206\u5e03\u7684\u968f\u673a\u6570\uff0c std::poisson_distribution \u7528\u4e8e\u751f\u6210\u6cca\u677e\u5206\u5e03\u7684\u968f\u673a\u6570\uff0c\u7b49\u7b49\u3002 \u5982\u679c\u559c\u6b22\u8001\u5f0f\u7684\u51fd\u6570\u8c03\u7528\u98ce\u683c\u63a5\u53e3\uff0c\u53ef\u4ee5\u5c01\u88c5\u4e00\u4e2a\u65b0\u7684 C++ \u91cd\u7f6e\u7248\u5b89\u5168 rand \uff1a thread_local std::mt19937 gen(std::random_device{}()); // \u6bcf\u7ebf\u7a0b\u4e00\u4e2a\uff0c\u4e92\u4e0d\u51b2\u7a81 int randint(int min, int max) { return std::uniform_int_distribution(min, max)(gen); } float randfloat(float min, float max) { return std::uniform_real_distribution(min, max)(gen); }","title":"C++ \u968f\u673a\u6570\u7684\u6b63\u786e\u751f\u6210\u65b9\u5f0f"},{"location":"cpp_tricks/#const","text":"\u4f17\u6240\u5468\u77e5\uff0c const \u5728\u6307\u9488\u7b26\u53f7 * \u7684\u524d\u540e\uff0c\u6548\u679c\u662f\u4e0d\u540c\u7684\u3002 const int *p; int *const p; \u4f60\u80fd\u770b\u51fa\u6765\u4e0a\u9762\u8fd9\u4e2a const \u5206\u522b\u4fee\u9970\u7684\u662f\u8c01\u5417\uff1f const int *p; // \u6307\u9488\u6307\u5411\u7684 int \u4e0d\u53ef\u53d8 int *const p; // \u6307\u9488\u672c\u8eab\u4e0d\u53ef\u6539\u53d8\u6307\u5411 \u4e3a\u4e86\u770b\u8d77\u6765\u66f4\u52a0\u660e\u786e\uff0c\u6211\u901a\u5e38\u90fd\u4f1a\u540e\u7f6e\u6240\u6709\u7684 const \u4fee\u9970\u3002 int const *p; // \u6307\u9488\u6307\u5411\u7684 int \u4e0d\u53ef\u53d8 int *const p; // \u6307\u9488\u672c\u8eab\u4e0d\u53ef\u6539\u53d8\u6307\u5411 \u8fd9\u6837\u5c31\u4e00\u76ee\u4e86\u7136\uff0cconst \u603b\u662f\u5728\u4fee\u9970\u4ed6\u524d\u9762\u7684\u4e1c\u897f\uff0c\u800c\u4e0d\u662f\u540e\u9762\u3002 \u4e3a\u4ec0\u4e48 int *const \u4fee\u9970\u7684\u662f int * \u4e5f\u5c31\u5f88\u5bb9\u6613\u7406\u89e3\u4e86\u3002 int const i; int const *p; int *const q; int const &r; \u4e3e\u4e2a\u4f8b\u5b50\uff1a int i, j; int *const p = &i; *p = 1; // OK\uff1ap \u6307\u5411\u7684\u5bf9\u8c61\u53ef\u53d8 p = &j; // \u9519\u8bef\uff1ap \u672c\u8eab\u4e0d\u53ef\u53d8\uff0c\u4e0d\u80fd\u6539\u53d8\u6307\u5411 int i, j; int const *p = &i; *p = 1; // \u9519\u8bef\uff1ap \u6307\u5411\u7684\u5bf9\u8c61\u4e0d\u53ef\u53d8 p = &j; // OK\uff1ap \u672c\u8eab\u53ef\u53d8\uff0c\u53ef\u4ee5\u6539\u53d8\u6307\u5411 int i, j; int const *const p = &i; *p = 1; // \u9519\u8bef\uff1ap \u6307\u5411\u7684\u5bf9\u8c61\u4e0d\u53ef\u53d8 p = &j; // \u9519\u8bef\uff1ap \u672c\u8eab\u4e5f\u4e0d\u53ef\u53d8\uff0c\u4e0d\u80fd\u6539\u53d8\u6307\u5411 int const * \u548c const int * \u7b49\u4ef7\uff01\u53ea\u6709 int *const \u662f\u4e0d\u540c\u7684\u3002","title":"const \u5c45\u7136\u5e94\u8be5\u540e\u7f6e…"},{"location":"cpp_tricks/#auto","text":"\u5927\u5bb6\u90fd\u77e5\u9053\uff0c\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\u53ef\u4ee5\u58f0\u660e\u4e3a auto \uff0c\u8ba9\u5176\u81ea\u52a8\u63a8\u5bfc\u3002 auto square() { // int square(); return 1; } \u4f46\u4f60\u77e5\u9053\u4ece C++20 \u5f00\u59cb\uff0c\u53c2\u6570\u4e5f\u53ef\u4ee5\u58f0\u660e\u4e3a auto \u4e86\u5417\uff1f auto square(auto x) { // T square(T x); return x * x; } square(1); // square(int) square(3.14); // square(double) \u7b49\u4ef7\u4e8e\u4ee5\u4e0b\u201c\u6a21\u677f\u51fd\u6570\u201d\u7684\u4f20\u7edf\u5199\u6cd5\uff1a template T square(T x) { return x * x; } square(1); // square(int) square(3.14); // square(double) \u56e0\u4e3a\u662f\u6a21\u677f\u51fd\u6570\uff0c\u6240\u4ee5\u4e5f\u5f88\u96be\u5206\u79bb\u58f0\u660e\u548c\u5b9a\u4e49\uff0c\u53ea\u9002\u7528\u4e8e\u5934\u6587\u4ef6\u4e2d\u5c31\u5730\u5b9a\u4e49\u51fd\u6570\u7684\u60c5\u51b5\u3002 auto \u53c2\u6570\u8fd8\u53ef\u4ee5\u5e26\u6709\u5f15\u7528\uff1a auto square(auto const &x) { // T square(T const &x); return x * x; } square(1); // square(int const &) square(3.14); // square(double const &) \u7b49\u4ef7\u4e8e\uff1a template T square(T const &x) { return x * x; } auto \u53c2\u6570\u6700\u597d\u7684\u914d\u5408\u83ab\u8fc7\u4e8e\u662f\u4e0e\u540c\u6837 C++20 \u5f15\u5165\u7684 concept\uff1a auto square(std::integral auto x) { // T square(T x) requires std::integral return x * x; } square(1); // square(int) square(3.14); // \u9519\u8bef\uff1adouble \u4e0d\u662f\u6574\u6570\u7c7b\u578b \u7b49\u4ef7\u4e8e\uff1a template requires std::integral T square(T x) { return x * x; } \u6216\u8005\uff1a template T square(T x) { return x * x; }","title":"\u51fd\u6570\u53c2\u6570\u4e5f\u53ef\u4ee5 auto"},{"location":"cpp_tricks/#_9","text":"std::string file_get_content(std::string const &filename) { std::ifstream ifs(filename, std::ios::in | std::ios::binary); std::istreambuf_iterator iit(ifs), iite; std::string content(iit, iite); return content; } void file_put_content(std::string const &filename, std::string const &content) { std::ofstream ofs(filename, std::ios::out | std::ios::binary); ofs << content; } \u8fd9\u6837\u5c31\u53ef\u4ee5\u628a\u6574\u4e2a\u6587\u4ef6\u8bfb\u53d6\u5230\u5185\u5b58\u4e2d\uff0c\u5f88\u65b9\u4fbf\u5730\u8fdb\u884c\u5904\u7406\u540e\u518d\u5199\u56de\u6587\u4ef6\u3002 \u63a8\u8350\u7528 std::ios::binary \u9009\u9879\u6253\u5f00\u4e8c\u8fdb\u5236\u6587\u4ef6\uff0c\u5426\u5219\u5b57\u7b26\u4e32\u4e2d\u51fa\u73b0 '\\n' \u65f6\uff0c\u4f1a\u88ab MSVC \u6807\u51c6\u5e93\u81ea\u52a8\u8f6c\u6362\u6210 '\\r\\n' \u6765\u5199\u5165\uff0c\u59a8\u788d\u6211\u4eec\u8de8\u5e73\u53f0\u3002","title":"\u8bfb\u53d6\u6574\u4e2a\u6587\u4ef6\u5230\u5b57\u7b26\u4e32"},{"location":"cpp_tricks/#_10","text":"std::ifstream fin(\"test.txt\"); std::string line; while (std::getline(fin, line)) { std::cout << \"\u8bfb\u53d6\u5230\u4e00\u884c\uff1a\" << line << '\\n'; }","title":"\u9010\u884c\u8bfb\u53d6\u6587\u672c\u6587\u4ef6"},{"location":"cpp_tricks/#_11","text":"#include #include #include std::vector split_str(std::string const &str, char ch) { std::stringstream ss(str); std::string line; std::vector res; while (std::getline(ss, line, ch)) { res.push_back(std::move(line)); } return res; } auto res = split_str(\"hello world\", ' '); // res = {\"hello\", \"world\"}","title":"\u5b57\u7b26\u4e32\u5207\u7247"},{"location":"cpp_tricks/#cout-endl","text":"int a = 42; printf(\"%d\\n\", a); \u4e07\u4e00\u4f60\u5199\u9519\u4e86 % \u540e\u9762\u7684\u7c7b\u578b\uff0c\u7f16\u8bd1\u5668\u4e0d\u4f1a\u6709\u4efb\u4f55\u62a5\u9519\uff0c\u7559\u4e0b\u9690\u60a3\u3002 int a = 42; printf(\"%s\\n\", a); // \u7f16\u8bd1\u5668\u4e0d\u62a5\u9519\uff0c\u4f46\u662f\u8fd0\u884c\u65f6\u4f1a\u5d29\u6e83\uff01 C++ \u4e2d\u6709\u66f4\u5b89\u5168\u7684\u8f93\u51fa\u65b9\u5f0f cout \uff0c\u901a\u8fc7 C++ \u7684\u91cd\u8f7d\u673a\u5236\uff0c\u65e0\u9700\u624b\u52a8\u6307\u5b9a % \uff0c\u81ea\u52a8\u5c31\u80fd\u63a8\u5bfc\u7c7b\u578b\u3002 int a = 42; cout << a << endl; double d = 3.14; cout << d << endl; cout << \"Hello, World!\" << endl; endl \u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u6d41\u64cd\u4f5c\u7b26\uff0c\u4f5c\u7528\u7b49\u4ef7\u4e8e\u5148\u8f93\u51fa\u4e00\u4e2a '\\n' \u7136\u540e flush \u3002 cout << \"Hello, World!\" << '\\n'; cout.flush(); \u4f46\u5b9e\u9645\u4e0a\uff0c\u8f93\u51fa\u6d41 cout \u9ed8\u8ba4\u7684\u8bbe\u7f6e\u5c31\u662f\u201c\u884c\u5237\u65b0\u7f13\u5b58\u201d\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u68c0\u6d4b\u5230 '\\n' \u65f6\uff0c\u5c31\u4f1a\u81ea\u52a8\u5237\u65b0\u4e00\u6b21\uff0c\u6839\u672c\u4e0d\u9700\u8981\u6211\u4eec\u624b\u52a8\u5237\u65b0\uff01 \u5982\u679c\u8fd8\u7528 endl \u7684\u8bdd\uff0c\u5c31\u76f8\u5f53\u4e8e\u5237\u65b0\u4e86\u4e24\u6b21\uff0c\u6d6a\u8d39\u6027\u80fd\u3002 \u53ef\u89c1\uff0cendl \u662f\u4e00\u4e2a\u88ab\u5f88\u591a\u65e0\u8111\u6559\u6750\u9519\u8bef\u5ba3\u4f20\uff0c\u5b9e\u9645\u4e0a\u6839\u672c\u591a\u6b64\u4e00\u4e3e\u7684\u4e1c\u897f\u3002 \u6211\u4eec\u53ea\u9700\u8981\u8f93\u51fa '\\n' \u5c31\u53ef\u4ee5\u4e86\uff0c\u6bcf\u6b21\u6362\u884c\u65f6 cout \u90fd\u4f1a\u81ea\u52a8\u5237\u65b0\u3002 cout << \"Hello, World!\" << '\\n'; endl \u662f\u4e00\u4e2a\u5178\u578b\u7684\u4ee5\u8bb9\u4f20\u8bb9\u9519\u8bef\u5199\u6cd5\uff0c\u53ea\u6709\u5f53\u4f60\u7684\u8f93\u51fa\u662f\u6307\u5411\u53e6\u4e00\u4e2a\u8fdb\u7a0b\u7684\u7ba1\u9053\u65f6\uff0c\u5176\u9644\u5e26\u7684\u5237\u65b0\u529f\u80fd\u624d\u6709\u4f5c\u7528\u3002 \u5f53\u8f93\u51fa\u662f\u7ba1\u9053\u6216\u6587\u4ef6\u65f6\uff0c cout \u9700\u8981 endl \u624d\u80fd\u5237\u65b0\u3002 \u5f53\u8f93\u51fa\u662f\u666e\u901a\u63a7\u5236\u53f0\u65f6\uff0c cout \u53ea\u9700 '\\n' \u5c31\u80fd\u5237\u65b0\u4e86\uff0c\u6839\u672c\u7528\u4e0d\u7740 endl \u3002 \u800c\u4e14\uff0c\u7ba1\u9053\u6216\u6587\u4ef6\u5b9e\u9645\u4e0a\u4e5f\u4e0d\u5b58\u5728\u9891\u7e41\u5237\u65b0\u7684\u9700\u6c42\uff0c\u53cd\u6b63 ifstream \u6790\u6784\u65f6\u603b\u662f\u4f1a\u81ea\u52a8\u5237\u65b0\u5199\u5165\u78c1\u76d8\u3002 \u56e0\u6b64\uff0c endl \u64cd\u7eb5\u7b26\u5927\u591a\u65f6\u5019\u90fd\u662f\u5197\u4f59\u7684\uff1a\u63a7\u5236\u53f0\u8f93\u51fa\u7684 cout \u53ea\u9700\u8981\u5b57\u7b26\u6216\u5b57\u7b26\u4e32\u4e2d\u542b\u6709 '\\n' \u5c31\u5237\u65b0\u4e86\uff0c\u5373\u4f7f\u662f\u6587\u4ef6\u8bfb\u5199\u4e5f\u5f88\u5c11\u4f1a\u4f7f\u7528 endl \u3002 \u5982\u679c\u786e\u5b9e\u9700\u8981\u5f3a\u5236\u5237\u65b0\uff0c\u4e5f\u53ef\u4ee5\u7528 flush \u8fd9\u79cd\u66f4\u52a0\u53ef\u8bfb\u7684\u5199\u6cd5\uff1a int num; cout << \"please input the number: \" << flush; cin >> num; ofstream fout(\"log.txt\"); fout << \"immediate write 1\\n\" << flush; sleep(1); fout << \"immediate write 2\\n\" << flush; fout.close(); // \u5173\u95ed\u6587\u4ef6\u65f6\u603b\u662f\u81ea\u52a8 flush\uff0c\u4e0d\u4f1a\u6709\u6b8b\u7559\u672a\u5199\u5165\u7684\u5b57\u7b26","title":"cout \u4e0d\u9700\u8981 endl"},{"location":"cpp_tricks/#cout","text":"\u540c\u5b66\uff1a\u5c0f\u5f6d\u8001\u5e08\uff0c\u6211\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e2d\u4f7f\u7528\uff1a cout << \"the answer is \" << 42 << '\\n'; \u53d1\u73b0\u8f93\u51fa\u4e71\u5957\u4e86\uff01\u8fd9\u662f\u4e0d\u662f\u8bf4\u660e cout \u4e0d\u662f \u591a\u7ebf\u7a0b\u5b89\u5168 \u7684\u5462\uff1f \u5c0f\u5f6d\u8001\u5e08\uff1acout \u662f\u4e00\u4e2a\u201c\u540c\u6b65\u6d41\u201d\uff0c\u662f \u591a\u7ebf\u7a0b\u5b89\u5168 \u7684\uff0c\u9519\u8bef\u7684\u662f\u4f60\u7684\u4f7f\u7528\u65b9\u5f0f\u3002 \u5982\u679c\u4ed6\u4e0d\u591a\u7ebf\u7a0b\u5b89\u5168\uff0c\u90a3\u591a\u7ebf\u7a0b\u5730\u8c03\u7528\u4ed6\u5c31\u4e0d\u662f\u8f93\u51fa\u4e71\u5e8f\uff0c\u800c\u662f\u7a0b\u5e8f\u5d29\u6e83\u4e86\u3002 \u4f46\u662f\uff0ccout \u7684\u7ebf\u7a0b\u5b89\u5168\uff0c\u53ea\u80fd\u4fdd\u8bc1\u6bcf\u4e00\u6b21 operator<< \u90fd\u662f\u539f\u5b50\u7684\uff0c\u6bcf\u4e00\u6b21\u5355\u72ec\u7684 operator<< \u4e0d\u4f1a\u88ab\u5176\u4ed6\u4eba\u6253\u65ad\u3002 \u4f46\u4f17\u6240\u5468\u77e5\uff0ccout \u4e3a\u4e86\u652f\u6301\u7ea7\u8054\u8c03\u7528\uff0c\u4ed6\u7684 operator<< \u90fd\u662f\u8fd4\u56de\u81ea\u5df1\u7684\uff0c\u4e0a\u9762\u7684\u4ee3\u7801\u5b9e\u9645\u4e0a\u7b49\u4ef7\u4e8e\u5206\u522b\u4e09\u6b21\u8c03\u7528 cout \u7684 operator<< \u3002 cout << \"the answer is \" << 42 << '\\n'; // \u7b49\u4ef7\u4e8e\uff1a cout << \"the answer is \"; cout << 42; cout << '\\n'; \u53d8\u6210\u4e86\u4e09\u6b21 operator<< \uff0c\u6bcf\u4e00\u6b21\u90fd\u662f\u201c\u5404\u81ea\u201d\u539f\u5b50\u7684\uff0c\u4f46\u4e09\u4e2a\u539f\u5b50\u52a0\u5728\u4e00\u8d77\u5c31\u4e0d\u662f\u539f\u5b50\u4e86\u3002 \u800c\u662f\u5206\u5b50\u4e86 :) \u4ed6\u4eec\u4e2d\u95f4\u53ef\u80fd\u7a7f\u63d2\u4e86\u5176\u4ed6\u7ebf\u7a0b\u7684 cout\uff0c\u4ece\u800c\u5bfc\u81f4\u4f60 \"the answer is\" \u6253\u5370\u5b8c\u540e\uff0c\u88ab\u5176\u4ed6\u7ebf\u7a0b\u7684 '\\n' \u63d2\u5165\u8fdb\u6765\uff0c\u5bfc\u81f4\u6362\u884c\u6df7\u4e71\u3002 std::cout \u7684 operator<< \u8c03\u7528\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u4e0d\u4f1a\u88ab\u6253\u65ad\uff0c\u4f46\u591a\u4e2a operator<< \u7684\u8c03\u7528\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e2d\u53ef\u80fd\u4f1a \u4ea4\u9519 \uff0c\u5bfc\u81f4\u8f93\u51fa\u7ed3\u679c\u6df7\u4e71\u3002 \u66f4\u591a\u7ec6\u8282\u8bf7\u770b\u6211\u4eec\u7684 \u591a\u7ebf\u7a0b\u4e13\u9898 \u3002 \u89e3\u51b3\u65b9\u6cd5\u662f\uff0c\u5148\u521b\u5efa\u4e00\u4e2a\u53ea\u5c5e\u4e8e\u5f53\u524d\u7ebf\u7a0b\u7684 ostringstream \uff0c\u6700\u540e\u4e00\u6b21\u6027\u8c03\u7528\u4e00\u6b21 cout \u7684 operator<< \uff0c\u8ba9\u201c\u539f\u5b50\u201d\u7684\u5355\u4f4d\u53d8\u6210\u201c\u4e00\u884c\u201d\u800c\u4e0d\u662f\u4e00\u4e2a\u5b57\u7b26\u4e32\u3002 ostringstream oss; oss << \"the answer is \" << 42 << '\\n'; cout << oss.str(); \u6216\u8005\uff0c\u4f7f\u7528 std::format \uff1a cout << std::format(\"the answer is {}\\n\", 42); \u603b\u4e4b\uff0c\u5c31\u662f\u8981\u8ba9 operator<< \u53ea\u6709\u4e00\u6b21\uff0c\u81ea\u7136\u5c31\u662f\u6ca1\u6709\u4ea4\u9519\u3002 \u5728 C++20 \u4e2d\uff0c\u53ef\u4ee5\u6539\u7528 std::osyncstream(std::cout) \u4ee3\u66ff std::cout : std::osyncstream(std::cout) << \"the answer is \" << 42 << '\\n'; std::osyncstream \u53ef\u4ee5\u4fdd\u8bc1\uff1a1. \u4e0d\u4f1a\u4ea7\u751f\u6570\u636e\u7ade\u4e89\uff1b2. \u4e0d\u4f1a\u53d1\u751f\u7a7f\u63d2\u548c\u622a\u65ad\u3002\u53ef\u4ee5\u7406\u89e3\u4e3a std::osyncstream \u5728\u6784\u9020\u65f6\u5bf9\u7f13\u51b2\u533a\u4e0a\u9501\uff0c\u5728\u6790\u6784\u65f6\u89e3\u9501\u3002 \u5982\u679c\u4f60\u7684\u6807\u51c6\u5e93\u652f\u6301 C++23\uff0c\u8fd8\u53ef\u4ee5\u7528 std::println \uff0c\u8fd9\u4e2a\u51fd\u6570\u7684\u8f93\u51fa\u4e5f\u662f\u539f\u5b50\u7684\uff08\u7b2c\u4e09\u65b9\u5e93\u5982 fmt::println \u4ea6\u53ef\uff09\uff1a std::println(\"the answer is {}\", 42);","title":"\u591a\u7ebf\u7a0b\u4e2d cout \u51fa\u73b0\u4e71\u5e8f\uff1f"},{"location":"cpp_tricks/#cerr-cout","text":"\u5982\u679c\u4f60\u7684\u76ee\u7684\u662f\u8c03\u8bd5\u548c\u62a5\u9519\uff0c\u53ef\u4ee5\u8003\u8651\u7528 cerr \uff01 \u4ed6\u4f1a\u5728\u6bcf\u6b21 << \u65f6\u5237\u65b0\uff0c cerr \u624d\u662f\u6700\u9002\u5408\u6253\u5370\u9519\u8bef\u548c\u8c03\u8bd5\u4fe1\u606f\u7684\u6d41\u3002 cout \u7684\u4f18\u70b9\u662f\u4e0d\u9700\u8981\u65f6\u523b\u5237\u65b0\uff0c\u6709\u66f4\u597d\u7684\u6027\u80fd\u3002 cout << \"hello\\n\"; cout << \"the answer is \"; cout << 42; *(int *)1 = 1; // \u5d29\u6e83\uff01 cout << \"!\\n\"; // \u56e0\u4e3a\u8fd8\u6ca1\u6709\u62b5\u8fbe \\n \u4ea7\u751f\u5237\u65b0\u5c31\u5d29\u6e83\uff0c\u5bfc\u81f4\u4e4b\u524d\u5c1a\u672a\u5237\u65b0\u7684 the answer is 42 \u4e22\u5931 \u53ef\u80fd\u7684\u8f93\u51fa\uff1a hello[\u6362\u884c] cerr << \"hello\\n\"; cerr << \"the answer is \"; cerr << 42; *(int *)1 = 1; // \u5d29\u6e83\uff01 cerr << \"!\\n\"; \u8f93\u51fa\uff1a hello[\u6362\u884c] the answer is 42 \u8fd8\u6709\u4e00\u4e2a\u7279\u70b9\uff1a cout \u8f93\u51fa\u5230\u201c\u6807\u51c6\u8f93\u51fa\u6d41\u201d\uff0c\u53ef\u4ee5\u88ab\u8f93\u51fa\u91cd\u5b9a\u5411\u5230\u6587\u4ef6\u7ba1\u9053\u3002\u800c cerr \u8f93\u51fa\u5230\u201c\u6807\u51c6\u9519\u8bef\u6d41\u201d\uff0c\u901a\u5e38\u4e0d\u4f1a\u88ab\u91cd\u5b9a\u5411\u5230\u6587\u4ef6\u6216\u7ba1\u9053\u3002 \u4f8b\u5982\uff0c\u53ef\u4ee5\u628a\u7a0b\u5e8f\u9884\u8ba2\u7684\u8ba1\u7b97\u7ed3\u679c\u5199\u5230 cout \uff0c\u628a\u8c03\u8bd5\u548c\u62a5\u9519\u4fe1\u606f\u5199\u5230 cerr \uff0c\u8fd9\u6837\u7528\u6237\u5c31\u53ef\u4ee5\u901a\u8fc7 > \u91cd\u5b9a\u5411\u8ba1\u7b97\u7ed3\u679c\uff0c\u800c\u8c03\u8bd5\u548c\u62a5\u9519\u4fe1\u606f\u5219\u6b63\u5e38\u8f93\u51fa\u5230\u5c4f\u5e55\u4e0a\uff0c\u4e0d\u53d7\u91cd\u5b9a\u5411\u5f71\u54cd\u3002 cout << \"1 3 5 7\\n\"; cerr << \"ERROR: this is an error message!\\n\"; cout << \"11 13 17 19\\n\"; $ g++ prime.cpp -o prime $ ./prime 1 3 5 7 ERROR: this is an error message! 11 13 17 19 $ ./prime > output.txt ERROR: this is an error message! $ cat output.txt 1 3 5 7 11 13 17 19","title":"cerr \u4e0e cout \u7684\u6289\u62e9"},{"location":"cpp_tricks/#_12","text":"\u6211\u4eec\u8bf4\u4e00\u4e2a\u7c7b\u578b\u5927\uff0c\u6709\u4e24\u79cd\u60c5\u51b5\u3002 \u7c7b\u672c\u8eab\u5f88\u5927\uff1a\u4f8b\u5982 array \u7c7b\u672c\u8eab\u4e0d\u5927\uff0c\u4f46\u5176\u6307\u5411\u7684\u5bf9\u8c61\u5927\uff0c\u4e14\u8be5\u7c7b\u662f\u6df1\u62f7\u8d1d\uff0c\u5bf9\u8be5\u7c7b\u7684\u62f7\u8d1d\u4f1a\u5f15\u8d77\u5176\u6307\u5411\u5bf9\u8c61\u7684\u62f7\u8d1d\uff1a\u4f8b\u5982 vector sizeof(array); // \u672c\u8eab 4000 \u5b57\u8282 sizeof(vector); // \u672c\u8eab 24 \u5b57\u8282\uff08\u6210\u5458\u662f 3 \u4e2a\u6307\u9488\uff09\uff0c\u6307\u5411\u7684\u6570\u7ec4\u53ef\u4ee5\u65e0\u9650\u589e\u5927 sizeof(vector) \u4e3a 24 \u5b57\u8282\u4ec5\u4e3a x86_64-pc-linux-gnu \u5e73\u53f0 libstdc++ \u5e93\u7684\u5b9e\u6d4b\u7ed3\u679c\uff0c\u5728 32 \u4f4d\u7cfb\u7edf\u4ee5\u53ca MSVC \u7684 Debug \u6a21\u5f0f STL \u4e0b\u53ef\u80fd\u5f97\u51fa\u4e0d\u540c\u7684\u7ed3\u679c\uff0c\u4e0d\u53ef\u4ee5\u4f9d\u8d56\u8fd9\u4e2a\u5e73\u53f0\u76f8\u5173\u7684\u7ed3\u679c\u6765\u7f16\u7a0b\u3002 \u5bf9\u4e8e vector\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 std::move \u79fb\u52a8\u8bed\u4e49\uff0c\u53ea\u62f7\u8d1d\u8be5\u7c7b\u672c\u8eab\u7684\u4e09\u4e2a\u6307\u9488\u6210\u5458\uff0c\u800c\u4e0d\u5bf9\u5176\u6307\u5411\u7684 4000 \u5b57\u8282\u6570\u7ec4\u8fdb\u884c\u6df1\u62f7\u8d1d\u3002 \u5bf9\u4e8e array\uff0c\u5219 std::move \u79fb\u52a8\u8bed\u4e49\u4e0e\u666e\u901a\u7684\u62f7\u8d1d\u6ca1\u6709\u533a\u522b\uff1aarray \u4f5c\u4e3a\u9759\u6001\u6570\u7ec4\u5bb9\u5668\uff0c\u4e0d\u662f\u901a\u8fc7\u201c\u6307\u9488\u6210\u5458\u201d\u6765\u4fdd\u5b58\u6570\u7ec4\u7684\uff0c\u800c\u662f\u76f4\u63a5\u628a\u6570\u7ec4\u5b58\u5728\u4ed6\u7684\u4f53\u5185\uff0c\u5bf9 array \u7684\u79fb\u52a8\u548c\u62f7\u8d1d\u662f\u5b8c\u5168\u4e00\u6837\u7684\uff01 \u603b\u4e4b\uff0c\u79fb\u52a8\u8bed\u4e49\u7684\u52a0\u901f\u6548\u679c\uff0c\u53ea\u5bf9\u91c7\u7528\u4e86\u201c\u6307\u9488\u95f4\u63a5\u5b58\u50a8\u52a8\u6001\u6570\u636e\u201d\u7684\u7c7b\u578b\uff08\u5982 vector\u3001map\u3001set\u3001string\uff09\u6709\u6548\u3002\u5bf9\u201c\u76f4\u63a5\u5b58\u50a8\u9759\u6001\u5927\u5c0f\u6570\u636e\u201d\u7684\u7c7b\u578b\uff08array\u3001tuple\u3001variant\u3001\u6210\u529f\u201c\u5c0f\u5b57\u7b26\u4e32\u4f18\u5316\u201d\u7684 string\uff09\u65e0\u6548\u3002 \u6240\u4ee5\uff0c\u8ba9\u5f88\u591a\u201c\u79fb\u52a8\u8bed\u4e49\u201d\u5b5d\u5b50\u5931\u671b\u4e86\uff1a\u201c\u672c\u8eab\u5f88\u5927\u201d\u7684\u7c7b\uff0c\u79fb\u52a8\u548c\u62f7\u8d1d\u4e00\u6837\u6162\uff01 \u90a3\u4e48\u73b0\u5728\u6211\u4eec\u6709\u4e2a\u8d85\u5927\u7684\u7c7b\uff1a using BigType = array; // 4000 \u5b57\u8282\u5927\u5c0f\u7684\u5e73\u5766\u7c7b\u578b vector arr; void func(BigType x) { arr.push_back(std::move(x)); // \u62f7\u8d1d 4000 \u5b57\u8282\uff0c\u8d85\u6162\uff0cmove \u4e5f\u6ca1\u7528 } int main() { BigType x; func(std::move(x)); // \u62f7\u8d1d 4000 \u5b57\u8282\uff0c\u8d85\u6162\uff0cmove \u4e5f\u6ca1\u7528 } \u5982\u4f55\u52a0\u901f\u8fd9\u79cd\u672c\u8eab\u8d85\u5927\u7684\u53d8\u91cf\u8f6c\u79fb\uff1f\u4f7f\u7528 const \u5f15\u7528\uff1a void func(BigType const &x) \u4f3c\u4e4e\u53ef\u4ee5\u907f\u514d\u4f20\u53c2\u65f6\u7684\u62f7\u8d1d\uff0c\u4f46\u662f\u4f9d\u7136\u4e0d\u80fd\u907f\u514d push_back \u63a8\u5165 vector \u65f6\u6240\u4e0d\u5f97\u5df2\u7684\u62f7\u8d1d\u3002 \u5c0f\u6280\u5de7\uff1a\u6539\u7528 unique_ptr using BigType = array; // 4000 \u5b57\u8282\u5927\u5c0f\u7684\u5e73\u5766\u7c7b\u578b using BigTypePtr = unique_ptr; vector arr; void func(BigTypePtr x) { arr.push_back(std::move(x)); // \u53ea\u62f7\u8d1d 8 \u5b57\u8282\u7684\u6307\u9488\uff0c\u5176\u6307\u5411\u7684 4000 \u5b57\u8282\u4e0d\u7528\u6df1\u62f7\u8d1d\u4e86\uff0c\u76f4\u63a5\u79fb\u52a8\u6240\u6709\u6743\u7ed9 vector \u91cc\u7684 BigTypePtr \u667a\u80fd\u6307\u9488 // \u7531\u4e8e\u79fb\u8d70\u4e86\u6240\u6709\u6743\uff0cx \u6b64\u65f6\u5df2\u7ecf\u4e3a nullptr } int main() { BigTypePtr x = make_unique(); // \u6ce8\u610f\uff1a\u7528\u667a\u80fd\u6307\u9488\u7684\u8bdd\uff0c\u9700\u8981\u7528 make_unique \u624d\u80fd\u521b\u5efa\u5bf9\u8c61\u4e86 func(std::move(x)); // \u53ea\u62f7\u8d1d 8 \u5b57\u8282\u7684\u6307\u9488 // \u7531\u4e8e\u79fb\u8d70\u4e86\u6240\u6709\u6743\uff0cx \u6b64\u65f6\u5df2\u7ecf\u4e3a nullptr } \u4e0a\u9762\u6574\u4e2a\u7a0b\u5e8f\u4e2d\uff0c\u4e00\u5f00\u59cb\u901a\u8fc7 make_unique \u521b\u5efa\u7684\u8d85\u5927\u5bf9\u8c61\uff0c\u5168\u7a0b\u6ca1\u6709\u53d1\u751f\u4efb\u4f55\u79fb\u52a8\uff0c\u907f\u514d\u4e86\u65e0\u8c13\u7684\u6df1\u62f7\u8d1d\u3002 \u5bf9\u4e8e\u4e0d\u652f\u6301\u79fb\u52a8\u6784\u9020\u51fd\u6570\u7684\u7c7b\u578b\u6765\u8bf4\uff0c\u4e5f\u53ef\u4ee5\u7528\u8fd9\u4e2a\u65b9\u6cd5\uff0c\u5c31\u80fd\u5728\u51fd\u6570\u4e4b\u95f4\u7a7f\u68ad\u81ea\u5982\u4e86\u3002 // \u70ed\u77e5\u8bc6\uff1astd::mutex \u4e0d\u652f\u6301\u79fb\u52a8 void func(std::mutex lock); int main() { std::mutex lock; func(std::move(lock)); // \u9519\u8bef\uff1amutex(mutex &&) = delete } void func(std::unique_ptr lock); int main() { std::unique_ptr lock = std::make_unique(); func(std::move(lock)); // OK\uff1a\u8c03\u7528\u7684\u662f unique_ptr(unique_ptr &&)\uff0c\u4e0d\u5173 mutex \u4ec0\u4e48\u4e8b } \u66f4\u597d\u7684\u662f shared_ptr \uff0c\u8fde std::move \u90fd\u4e0d\u7528\u5199\uff0c\u66f4\u7701\u5fc3\u3002 void func(std::shared_ptr lock); int main() { std::shared_ptr lock = std::make_shared(); func(lock); // OK\uff1a\u8c03\u7528\u7684\u662f shared_ptr(shared_ptr const &)\uff0c\u4e0d\u5173 mutex \u4ec0\u4e48\u4e8b func(lock); // OK\uff1ashared_ptr \u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u662f\u6d45\u62f7\u8d1d\uff0c\u5373\u4f7f\u6d45\u62f7\u8d1d\u53d1\u751f\u591a\u6b21\uff0c\u6307\u5411\u7684\u5bf9\u8c61\u4e5f\u4e0d\u4f1a\u88ab\u62f7\u8d1d\u6216\u79fb\u52a8 }","title":"\u667a\u80fd\u6307\u9488\u9632\u6b62\u5927\u5bf9\u8c61\u79fb\u52a8"},{"location":"cpp_tricks/#optional","text":"\u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a\u7c7b\uff0c\u5177\u6709\u81ea\u5b9a\u4e49\u7684\u6784\u9020\u51fd\u6570\uff0c\u4e14\u6ca1\u6709\u9ed8\u8ba4\u6784\u9020\u51fd\u6570\uff1a struct SomeClass { int m_i; int m_j; SomeClass(int i, int j) : m_i(i), m_j(j) {} }; \u5f53\u6211\u4eec\u9700\u8981\u201c\u5ef6\u8fdf\u521d\u59cb\u5316\u201d\u65f6\u600e\u4e48\u529e\uff1f SomeClass c; if (test()) { c = SomeClass(1, 2); } else { c = SomeClass(2, 3); } do_something(c); \u53ef\u4ee5\u5229\u7528 optional \u9ed8\u8ba4\u521d\u59cb\u5316\u4e3a\u201c\u7a7a\u201d\u7684\u7279\u6027\uff0c\u5b9e\u73b0\u5ef6\u8fdf\u8d4b\u503c\uff1a std::optional c; if (test()) { c = SomeClass(1, 2); } else { c = SomeClass(2, 3); } do_something(c.value()); // \u5982\u679c\u62b5\u8fbe\u6b64\u5904\u524d\uff0cc \u6ca1\u6709\u521d\u59cb\u5316\uff0c\u5c31\u4f1a\u62a5\u9519\uff0c\u4ece\u800c\u628a\u7f16\u8bd1\u671f\u7684\u672a\u521d\u59cb\u5316\u8f6c\u6362\u4e3a\u8fd0\u884c\u65f6\u5f02\u5e38 \u5c31\u7c7b\u4f3c\u4e8e Python \u4e2d\u5148\u7ed9\u53d8\u91cf\u8d4b\u503c\u4e3a None\uff0c\u7136\u540e\u5728\u5faa\u73af\u6216 if \u91cc\u6761\u4ef6\u6027\u5730\u8d4b\u503c\u4e00\u6837\u3002 \u5982\u679c\u8981\u8fdb\u4e00\u6b65\u907f\u514d c = \u65f6\uff0c\u79fb\u52a8\u6784\u9020\u7684\u5f00\u9500\uff0c\u4e5f\u53ef\u4ee5\u7528 unique_ptr \u6216 shared_ptr \uff1a std::shared_ptr c; if (test()) { c = std::make_shared(1, 2); } else { c = std::make_shared(2, 3); } do_something(c); // \u5982\u679c\u62b5\u8fbe\u6b64\u5904\u524d\uff0cc \u6ca1\u6709\u521d\u59cb\u5316\uff0c\u90a3\u4e48\u4f20\u5165\u7684\u5c31\u662f\u4e00\u4e2a nullptr\uff0cdo_something \u5185\u90e8\u9700\u8981\u8d1f\u8d23\u68c0\u6d4b\u6307\u9488\u662f\u5426\u4e3a nullptr \u5982\u679c do_something \u53c2\u6570\u9700\u8981\u7684\u662f\u539f\u59cb\u6307\u9488\uff0c\u53ef\u4ee5\u7528 .get() \u83b7\u53d6\u51fa\u6765\uff1a do_something(c.get()); // .get() \u53ef\u4ee5\u628a\u667a\u80fd\u6307\u9488\u8f6c\u6362\u56de\u539f\u59cb\u6307\u9488\uff0c\u4f46\u8bf7\u6ce8\u610f\u539f\u59cb\u6307\u9488\u4e0d\u6301\u6709\u5f15\u7528\uff0c\u4e0d\u4f1a\u5ef6\u4f38\u6307\u5411\u5bf9\u8c61\u7684\u751f\u547d\u5468\u671f \u5b9e\u9645\u4e0a\uff0cJava\u3001Python \u4e2d\u7684\u4e00\u5207\u5bf9\u8c61\uff08\u9664 int\u3001str \u7b49\u201c\u94a6\u5b9a\u201d\u7684\u57fa\u7840\u7c7b\u578b\u5916\uff09\u90fd\u662f\u5f15\u7528\u8ba1\u6570\u7684\u667a\u80fd\u6307\u9488 shared_ptr \uff0c\u53ea\u4e0d\u8fc7\u56e0\u4e3a\u4e00\u5207\u7686\u6307\u9488\u4e86\uff0c\u6240\u4ee5\u770b\u8d77\u6765\u597d\u50cf\u6ca1\u6709\u6307\u9488\u4e86\u3002","title":"optional \u5b9e\u73b0\u5ef6\u8fdf\u521d\u59cb\u5316"},{"location":"cpp_tricks/#if-auto-while-auto","text":"\u9700\u8981\u5148\u5b9a\u4e49\u4e00\u4e2a\u53d8\u91cf\uff0c\u7136\u540e\u5224\u65ad\u67d0\u4e9b\u6761\u4ef6\u7684\u60c5\u51b5\uff0c\u975e\u5e38\u5e38\u89c1\uff1a extern std::optional some_func(); auto opt = some_func(); if (opt.has_value()) { std::cout << opt.value(); } C++17 \u5f15\u5165\u7684 if-auto \u8bed\u6cd5\uff0c\u53ef\u4ee5\u5c31\u5730\u4e66\u5199\u53d8\u91cf\u5b9a\u4e49\u548c\u5224\u65ad\u6761\u4ef6\uff1a extern std::optional some_func(); if (auto opt = some_func(); opt.has_value()) { std::cout << opt.value(); } \u5bf9\u4e8e\u652f\u6301 (bool)opt \u7684 optional \u7c7b\u578b\u6765\u8bf4\uff0c\u540e\u9762\u7684\u6761\u4ef6\u4e5f\u53ef\u4ee5\u7701\u7565\uff1a extern std::optional some_func(); if (auto opt = some_func()) { std::cout << opt.value(); } // \u7b49\u4ef7\u4e8e\uff1a auto opt = some_func(); if (opt) { std::cout << opt.value(); } \u7c7b\u4f3c\u7684\u8fd8\u6709 while-auto\uff1a extern std::optional some_func(); while (auto opt = some_func()) { std::cout << opt.value(); } // \u7b49\u4ef7\u4e8e\uff1a while (true) { auto opt = some_func(); if (!opt) break; std::cout << opt.value(); } if-auto \u6700\u5e38\u89c1\u7684\u914d\u5408\u83ab\u8fc7\u4e8e map.find\uff1a std::map table; int key = 42; if (auto it = table.find(key); it != table.end()) { std::cout << it->second << '\\n'; } else { std::cout << \"not found\\n\"; }","title":"if-auto \u4e0e while-auto"},{"location":"cpp_tricks/#bind-lambda","text":"\u4f17\u6240\u5468\u77e5\uff0c std::bind \u53ef\u4ee5\u4e3a\u51fd\u6570\u7ed1\u5b9a\u4e00\u90e8\u5206\u53c2\u6570\uff0c\u5f62\u6210\u4e00\u4e2a\u65b0\u7684\u51fd\u6570\uff08\u5bf9\u8c61\uff09\u3002 int func(int x, int y) { printf(\"func(%d, %d)\\n\", x, y); return x + y; } auto new_func = std::bind(func, 1, std::placeholders::_1); new_func(2); // \u8c03\u7528 new_func(2) \u65f6\uff0c\u5b9e\u9645\u4e0a\u8c03\u7528\u7684\u662f func(1, 2) } \u8f93\u51fa\uff1a func(1, 2) \u5f53\u6211\u4eec\u7ed1\u5b9a\u51fa\u6765\u7684\u51fd\u6570\u5bf9\u8c61\u8fd8\u9700\u8981\u63a5\u53d7\u53c2\u6570\u65f6\uff0c\u5c31\u53d8\u5f97\u5c24\u4e3a\u590d\u6742\uff1a\u9700\u8981\u4f7f\u7528\u5360\u4f4d\u7b26\uff08placeholder\uff09\u3002 int func(int x, int y, int z, int &w); int w = rand(); auto bound = std::bind(func, std::placeholders::_2, 1, std::placeholders::_1, std::ref(w)); // int res = bound(5, 6); // \u7b49\u4ef7\u4e8e func(6, 1, 5, w); \u8fd9\u662f\u4e00\u4e2a\u7ed1\u5b9a\u5668\uff0c\u628a func \u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u548c\u7b2c\u56db\u4e2a\u53c2\u6570\u56fa\u5b9a\u4e0b\u6765\uff0c\u5f62\u6210\u4e00\u4e2a\u65b0\u7684\u51fd\u6570\u5bf9\u8c61\uff0c\u7136\u540e\u53ea\u9700\u8981\u4f20\u5165\u524d\u9762\u4e24\u4e2a\u53c2\u6570\u5c31\u53ef\u4ee5\u8c03\u7528\u539f\u6765\u7684\u51fd\u6570\u4e86\u3002 \u8fd9\u662f\u4e00\u4e2a\u975e\u5e38\u65e7\u7684\u6280\u672f\uff0cC++98 \u65f6\u4ee3\u5c31\u6709\u4e86\u3002\u4f46\u662f\uff0c\u73b0\u5728\u6709\u4e86 Lambda \u8868\u8fbe\u5f0f\uff0c\u53ef\u4ee5\u66f4\u7b80\u6d01\u5730\u5b9e\u73b0\uff1a int func(int x, int y, int z, int &w); int w = rand(); auto lambda = [&w](int x, int y) { return func(y, 1, x, w); }; int res = lambda(5, 6); Lambda \u8868\u8fbe\u5f0f\u6709\u8bb8\u591a\u4f18\u52bf\uff1a \u7b80\u6d01\uff1a\u4e0d\u9700\u8981\u5199\u4e00\u5927\u5806\u770b\u4e0d\u61c2\u7684 std::placeholders::_1 \uff0c\u76f4\u63a5\u5199\u53d8\u91cf\u540d\u5c31\u53ef\u4ee5\u4e86\u3002 \u7075\u6d3b\uff1a\u53ef\u4ee5\u5728 Lambda \u4e2d\u4f7f\u7528\u4efb\u610f\u591a\u7684\u53d8\u91cf\uff0c\u8c03\u6574\u987a\u5e8f\uff0c\u800c\u4e0d\u4ec5\u4ec5\u662f std::placeholders::_1 \u3002 \u6613\u61c2\uff1a\u5199\u8d77\u6765\u548c\u666e\u901a\u51fd\u6570\u8c03\u7528\u4e00\u6837\uff0c\u6240\u6709\u4eba\u90fd\u5bb9\u6613\u770b\u61c2\u3002 \u6355\u83b7\u5f15\u7528\uff1a std::bind \u4e0d\u652f\u6301\u6355\u83b7\u5f15\u7528\uff0c\u603b\u662f\u62f7\u8d1d\u53c2\u6570\uff0c\u5fc5\u987b\u914d\u5408 std::ref \u624d\u80fd\u6355\u83b7\u5230\u5f15\u7528\u3002\u800c Lambda \u53ef\u4ee5\u968f\u610f\u6355\u83b7\u4e0d\u540c\u7c7b\u578b\u7684\u53d8\u91cf\uff0c\u6309\u503c\uff08 [x] \uff09\u6216\u6309\u5f15\u7528\uff08 [&x] \uff09\uff0c\u8fd8\u53ef\u4ee5\u79fb\u52a8\u6355\u83b7\uff08 [x = move(x)] \uff09\uff0c\u751a\u81f3\u6355\u83b7 this\uff08 [this] \uff09\u3002 \u5939\u5e26\u79c1\u8d27\uff1a\u53ef\u4ee5\u5728 lambda \u4f53\u5185\u5f88\u65b9\u4fbf\u5730\u5939\u5e26\u5176\u4ed6\u989d\u5916\u8f6c\u6362\u64cd\u4f5c\uff0c\u6bd4\u5982\uff1a auto lambda = [&w](int x, int y) { return func(y + 8, 1, x * x, ++w) * 2; };","title":"bind \u662f\u5386\u53f2\u7cdf\u7c95\uff0c\u5e94\u8be5\u7531 Lambda \u8868\u8fbe\u5f0f\u53d6\u4ee3"},{"location":"cpp_tricks/#bind","text":"\u4e3a\u4ec0\u4e48 C++11 \u6709\u4e86 Lambda \u8868\u8fbe\u5f0f\uff0c\u8fd8\u8981\u63d0\u51fa std::bind \u5462\uff1f \u867d\u7136 bind \u548c lambda \u770b\u4f3c\u90fd\u662f\u5728 C++11 \u5f15\u5165\u7684\uff0c\u5b9e\u9645\u4e0a bind \u7684\u63d0\u51fa\u8fdc\u8fdc\u65e9\u4e8e lambda\u3002 \u6807\u51c6\u59d4\u5458\u4f1a\uff1a\u6211\u4eec\u4e0d\u751f\u4ea7\u5e93\uff0c\u6211\u4eec\u53ea\u662f boost \u7684\u642c\u8fd0\u5de5\u3002 \u5f53\u65f6\u8fd8\u662f C++98\uff0c\u7531\u4e8e\u6ca1\u6709 lambda\uff0c\u96be\u4ee5\u521b\u5efa\u51fd\u6570\u5bf9\u8c61\uff0c\u201c\u6355\u83b7\u53c2\u6570\u201d\u975e\u5e38\u56f0\u96be\u3002 \u4e3a\u4e86\u89e3\u51b3\u201c\u6355\u83b7\u96be\u201d\u95ee\u9898\uff0c\u5728\u7b2c\u4e09\u65b9\u5e93 boost \u4e2d\u63d0\u51fa\u4e86 boost::bind \uff0c\u7531\u4e8e\u5f53\u65f6\u53ea\u6709 C++98\uff0c\u5f88\u591a\u6709\u76ca\u4e8e\u51fd\u6570\u5f0f\u7f16\u7a0b\u7684\u7279\u6027\u90fd\u6ca1\u6709\uff0c\u6240\u4ee5\u5b9e\u73b0\u7684\u975e\u5e38\u4e11\u964b\u3002 \u4f8b\u5982\uff0c\u56e0\u4e3a C++98 \u6ca1\u6709\u53d8\u957f\u6a21\u677f\u53c2\u6570\uff0c\u65e0\u6cd5\u5b9e\u73b0 \u3002\u6240\u4ee5\u5b9e\u9645\u4e0a\u5f53\u65f6 boost \u6240\u6709\u652f\u6301\u591a\u53c2\u6570\u7684\u51fd\u6570\uff0c\u5b9e\u9645\u4e0a\u90fd\u662f\u901a\u8fc7\uff1a void some_func(); void some_func(int i1); void some_func(int i1, int i2); void some_func(int i1, int i2, int i3); void some_func(int i1, int i2, int i3, int i4); // ... \u8fd9\u6837\u66b4\u529b\u91cd\u8f7d\u51e0\u5341\u4e2a\u51fd\u6570\u6765\u5b9e\u73b0\u7684\uff0c\u800c\u4e14\u53c2\u6570\u6570\u91cf\u6709\u4e0a\u9650\u3002\u901a\u5e38\u4f1a\u5b9e\u73b0 0 \u5230 20 \u4e2a\u53c2\u6570\u7684\u91cd\u8f7d\uff0c\u66f4\u591a\u5c31\u4e0d\u652f\u6301\u4e86\u3002 \u4f8b\u5982\uff0c\u6211\u4eec\u77e5\u9053\u73b0\u5728 bind \u9700\u8981\u914d\u5408\u5404\u79cd std::placeholders::_1 \u4f7f\u7528\uff0c\u6709\u6ca1\u6709\u60f3\u8fc7\u8fd9\u5957\u4e11\u964b\u7684\u5360\u4f4d\u7b26\u662f\u4e3a\u4ec0\u4e48\uff1f\u4e3a\u4ec0\u4e48\u4e0d\u7528 std::placeholder<1> \uff0c\u8fd9\u6837\u4e0d\u662f\u66f4\u53ef\u6269\u5c55\u5417\uff1f \u6ca1\u9519\uff0c\u5f53\u65f6 boost::bind \u5c31\u662f\u7528\u66b4\u529b\u91cd\u8f7d\u51e0\u5341\u4e2a\u53c2\u6570\u6570\u91cf\u4e0d\u7b49\u7684\u51fd\u6570\uff0c\u6392\u5217\u7ec4\u5408\uff0c\u55ef\u662f\u6392\u51fa\u6765\u7684\uff0c\u6240\u4ee5\u6211\u4eec\u4f1a\u770b\u5230 boost::placeholders \u53ea\u6709\u6709\u9650\u4e2a\u6570\u7684\u5360\u4f4d\u7b26\u6570\u91cf\u3002 \u7cdf\u7cd5\u7684\u662f\uff0c\u6807\u51c6\u5e93\u7684 std::bind \u628a boost::bind \u539f\u5c01\u4e0d\u52a8\u642c\u4e86\u8fc7\u6765\uff0c\u751a\u81f3 placeholders \u7684\u66b4\u529b\u7ec4\u5408\u4e5f\u6ca1\u6709\u53d8\uff0c\u9020\u6210\u4e86 std::bind \u5982\u4eca\u4e11\u964b\u7684\u63a5\u53e3\u3002 \u4eba\u5bb6 boost::bind \u662f\u56e0\u4e3a\u4e0d\u80fd\u4fee\u6539\u8bed\u8a00\u8bed\u6cd5\uff0c\u624d\u53ea\u80fd\u90a3\u6837\u618b\u5c48\u7684\u554a\uff1f\u53ef\u73b0\u5728\u4f60\u7801\u662f\u6807\u51c6\u59d4\u5458\u4f1a\u554a\uff0c\u4f60\u53ef\u4ee5\u4fee\u6539\u8bed\u8a00\u8bed\u6cd5\u554a\uff1f \u7136\u800c\uff0cC++ \u6807\u51c6\u7684\u66f4\u65b0\u662f\u4ee5\u201c\u63d0\u6848\u201d\u7684\u65b9\u5f0f\uff0c\u9010\u6b65\u201c\u589e\u91cf\u201d\u66f4\u65b0\u8fdb\u5165\u8bed\u8a00\u6807\u51c6\u7684\u3002\u5373\u4f7f\u662f\u5728 C++98 \u5230 C++11 \u8fd9\u6bb5\u65f6\u95f4\u5185\uff0c\u5185\u90e8\u4e5f\u662f\u6709\u4e00\u4e2a\u5f88\u957f\u7684\u6d88\u5316\u6d41\u7a0b\u7684\uff0c\u4e5f\u5c31\u662f\u8bf4\u6709\u5f88\u591a\u5b50\u7248\u672c\uff0c\u53ea\u662f\u5bf9\u5916\u770b\u8d77\u6765\u597d\u50cf\u53ea\u6709\u4e00\u4e2a C++11\u3002 \u6bd4\u65b9\u8bf4\uff0c\u6211 2001 \u5e74\u63d0\u51fa std::bind \u63d0\u6848\uff0c2005 \u5e74\u88ab\u6279\u51c6\u8fdb\u5165\u672a\u6765\u5c06\u8981\u53d1\u5e03\u7684 C++11 \u6807\u51c6\u3002\u7136\u540e\u53c8\u4e00\u4e2a\u4eba\u5728 2006 \u5e74\u63d0\u51fa\u5176\u5b9e\u4e0d\u9700\u8981 bind\uff0c\u5b8c\u5168\u53ef\u4ee5\u7528\u66f4\u597d\u7684 lambda \u8bed\u6cd5\u6765\u4ee3\u66ff bind\uff0c\u7136\u540e\u7b49\u5230\u4e86 2008 \u5e74\u624d\u6279\u51c6\u8fdb\u5165\u5373\u5c06\u53d1\u5e03\u7684 C++11 \u6807\u51c6\u3002\u4f46\u662f\u5df2\u7ecf\u8fdb\u5165\u6807\u51c6\u7684\u4e1c\u897f\u5c31\u4e0d\u4f1a\u518d\u9000\u51fa\u4e86\uff0c\u54ea\u6015\u8fd8\u6ca1\u6709\u53d1\u5e03\u3002\u5c31\u8fd9\u6837 bind \u548c lambda \u540c\u65f6\u8fdb\u5165\u4e86\u6807\u51c6\u3002 \u6240\u4ee5\u95f9\u4e86\u534a\u5929\uff0clambda \u5b9e\u9645\u4e0a\u662f bind \u7684\u4e0a\u4f4d\u66ff\u4ee3\uff0c\u6709\u4e86 lambda \u6839\u672c\u4e0d\u9700\u8981 bind \u7684\u3002\u53ea\u4e0d\u8fc7\u662f\u7531\u4e8e C++ \u59d4\u5458\u4f1a\u524d\u540e\u626f\u76ae\u7684\u201c\u5236\u5ea6\u4f18\u52bf\u201d\uff0c\u5bfc\u81f4 bind \u548c\u4ed6\u7684\u4e0a\u4f4d\u66ff\u4ee3 lambda \u540c\u65f6\u8fdb\u5165\u4e86 C++11 \u6807\u51c6\u4e00\u8d77\u53d1\u5e03\u3002 \u8fd9\u4e0b\u770b\u61c2\u4e86\u3002 \u5f88\u591a\u540c\u5b66\u5c31\u4e0d\u7406\u89e3\uff0c\u5c0f\u5f6d\u8001\u5e08\u8bf4\u201clambda \u662f bind \u7684\u4e0a\u4f4d\u66ff\u4ee3\u201d\uff0c\u4ed6\u5c31\u8d28\u7591\u201c\u53ef\u4ed6\u4eec\u4e0d\u90fd\u662f C++11 \u63d0\u51fa\u7684\u5417\uff1f\u201d \u6709\u6ca1\u6709\u4e00\u79cd\u53ef\u80fd\uff0cC++11 \u548c C++98 \u4e4b\u95f4\u4e3a\u4ec0\u4e48\u5e74\u4ee3\u5dee\u4e86\u90a3\u4e48\u4e45\u8fdc\uff0c\u5c31\u662f\u56e0\u4e3a\u4e00\u4e2a\u6807\u51c6\u4e00\u62d6\u518d\u62d6\uff0c\u5185\u90e8\u5b9e\u9645\u4e0a\u5df2\u7ecf\u8fed\u4ee3\u4e86\u597d\u51e0\u4e2a\u5c0f\u7248\u672c\u4e86\uff0c\u624d\u53d1\u5e03\u51fa\u6765\u3002 \u518d\u4e3e\u4e2a\u4f8b\u5b50\uff0cCTAD \u548c optional \u90fd\u662f C++17 \u5f15\u5165\u7684\uff0c\u4e3a\u4ec0\u4e48\u8fd8\u8981 make_optional \u8fd9\u4e2a\u5e2e\u624b\u51fd\u6570\uff1f\u4e0d\u662f\u8bf4 CTAD \u662f make_xxx \u7684\u4e0a\u4f4d\u66ff\u4ee3\u5417\uff1f\u53ef\u89c1\uff0cC++ \u6807\u51c6\u4e2d\u8fd9\u79cd\u201c\u540c\u4e00\u4e2a\u7248\u672c\u5185\u201d\u81ea\u5df1\u6253\u81ea\u5df1\u8033\u5149\u7684\u73b0\u8c61\u6bd4\u6bd4\u7686\u662f\u3002 \u6240\u4ee5\uff0c\u73b0\u5728\u8fd8\u575a\u6301\u7528 bind \u7684\uff0c\u90fd\u662f\u4e9b 2005 \u5e74\u524d\u540e\u5728\u8c61\u7259\u5854\u63a5\u53d7 C++ \u6559\u80b2\uff0c\u4f46\u53c8\u4e0d\u80af\u201c\u7ec8\u8eab\u5b66\u4e60\u201d\u7684\u52b3\u4fdd\u3002\u8fd9\u6279\u52b3\u4fdd\u53c8\u53bb\u201c\u4e0a\u5cb8\u201d\u5f53\u201c\u6559\u5e08\u201d\uff0c\u7ee7\u7eed\u590d\u5236 2005 \u5e74\u7684\u9519\u8bef\u6bd2\u5bb3\u9752\u5c11\u5e74\uff0c\u5b9e\u73b0\u4e86\u52b3\u4fdd\u7684\u518d\u751f\u4ea7\u3002","title":"bind \u7684\u5386\u53f2"},{"location":"cpp_tricks/#thread","text":"\u7cdf\u7cd5\u7684\u662f\uff0cbind \u7684\u8fd9\u79cd\u837c\u6bd2\uff0c\u751a\u81f3\u5f71\u54cd\u5230\u4e86\u7ebf\u7a0b\u5e93\uff1a std::thread \u7684\u6784\u9020\u51fd\u6570\u5c31\u662f\u57fa\u4e8e std::bind \u7684\uff01 \u8fd9\u5bfc\u81f4\u4e86 std::thread \u548c std::bind \u4e00\u6837\uff0c\u65e0\u6cd5\u6355\u83b7\u5f15\u7528\u3002 void thread_func(int &x) { x = 42; } int x = 0; std::thread t(thread_func, x); t.join(); printf(\"%d\\n\", x); // 0 \u4e3a\u4e86\u907f\u514d\u8e29\u5230 bind \u7684\u5751\uff0c\u6211\u5efa\u8bae\u6240\u6709\u540c\u5b66\uff0c\u6784\u9020 std::thread \u65f6\uff0c\u7edf\u4e00\u53ea\u6307\u5b9a\u201c\u5355\u4e2a\u53c2\u6570\u201d\uff0c\u4e5f\u5c31\u662f\u51fd\u6570\u672c\u8eab\u3002\u5982\u679c\u9700\u8981\u6355\u83b7\u53c2\u6570\uff0c\u8bf7\u4f7f\u7528 lambda\u3002\u56e0\u4e3a lambda \u4e2d\uff0c\u6355\u83b7\u4e86\u54ea\u4e9b\u53d8\u91cf\uff0c\u53c2\u6570\u7684\u987a\u5e8f\u662f\u4ec0\u4e48\uff0c\u54ea\u4e9b\u6355\u83b7\u662f\u5f15\u7528\uff0c\u54ea\u4e9b\u6355\u83b7\u662f\u62f7\u8d1d\uff0c\u975e\u5e38\u6e05\u6670\u3002 void thread_func(int &x) { x = 42; } int x = 0; std::thread t([&x] { // [&x] \u8868\u793a\u6309\u5f15\u7528\u6355\u83b7 x\uff1b\u5982\u679c\u5199\u4f5c [x]\uff0c\u90a3\u5c31\u662f\u62f7\u8d1d\u6355\u83b7 thread_func(x); }); t.join(); printf(\"%d\\n\", x); // 42","title":"thread \u819d\u76d6\u4e2d\u7bad"},{"location":"cpp_tricks/#_13","text":"bind \u5199\u6cd5\uff1a std::mt19937 gen(seed); std::uniform_real_distribution uni(0, 1); auto frand = std::bind(uni, std::ref(gen)); double x = frand(); double y = frand(); \u6539\u7528 lambda\uff1a std::mt19937 gen(seed); std::uniform_real_distribution uni(0, 1); auto frand = [uni, &gen] { return uni(gen); }; double x = frand(); double y = frand();","title":"\u4e3e\u4e2a\u7ed1\u5b9a\u968f\u673a\u6570\u751f\u6210\u5668\u4f8b\u5b50"},{"location":"cpp_tricks/#forward-fwd","text":"\u4f17\u6240\u5468\u77e5\uff0c\u5f53\u4f60\u5728\u8f6c\u53d1\u4e00\u4e2a\u201c\u4e07\u80fd\u5f15\u7528\u201d\u53c2\u6570\u65f6\uff1a template void some_func(Arg &&arg) { other_func(arg); } \u5982\u679c\u6b64\u5904 arg \u4f20\u5165\u7684\u662f\u53f3\u503c\u5f15\u7528\uff0c\u90a3\u4e48\u4f20\u5165 other_func \u5c31\u4f1a\u53d8\u56de\u5de6\u503c\u5f15\u7528\u4e86\uff0c\u4e0d\u7b26\u5408\u5b8c\u7f8e\u8f6c\u53d1\u7684\u8981\u6c42\u3002 \u56e0\u6b64\u5f15\u5165\u4e86 forward \uff0c\u4ed6\u4f1a\u68c0\u6d4b arg \u662f\u5426\u4e3a\u201c\u53f3\u503c\u201d\uff1a\u5982\u679c\u662f\uff0c\u5219 forward \u7b49\u4ef7\u4e8e move \uff1b\u5982\u679c\u4e0d\u662f\uff0c\u5219 forward \u4ec0\u4e48\u90fd\u4e0d\u505a\uff08\u9ed8\u8ba4\u5c31\u662f\u5de6\u503c\u5f15\u7528\uff09\u3002 \u8fd9\u5f04\u5f97 forward \u7684\u5916\u89c2\u975e\u5e38\u5177\u6709\u8ff7\u60d1\u6027\uff0c\u53c8\u662f\u5c16\u62ec\u53f7\u53c8\u662f\u5706\u62ec\u53f7\u7684\u3002 template void some_func(Arg &&arg) { other_func(std::forward(arg)); } \u5b9e\u9645\u4e0a\uff0cforward \u7684\u7528\u6cd5\u975e\u5e38\u5355\u4e00\uff1a\u6c38\u8fdc\u662f forward(t) \u7684\u5f62\u5f0f\uff0c\u5176\u4e2d T \u662f t \u53d8\u91cf\u7684\u7c7b\u578b\u3002 \u53c8\u662f\u52b3\u4fdd\u7684\u9b45\u529b\uff0c\u5229\u7528\u540c\u6837\u662f C++11 \u7684 decltype \u5c31\u80fd\u83b7\u5f97 t \u5b9a\u4e49\u65f6\u7684 T \u3002 void some_func(auto &&arg) { other_func(std::forward(arg)); } \u6240\u4ee5 std::forward(arg) \u5b9e\u9645\u624d\u662f forward \u7684\u6b63\u786e\u7528\u6cd5\uff0c\u53ea\u4e0d\u8fc7\u56e0\u4e3a\u5927\u591a\u6570\u65f6\u5019\u4f60\u662f\u6a21\u677f\u53c2\u6570 Arg && \uff0c\u6709\u7684\u4eba\u5077\u61d2\uff0c\u5c31\u628a decltype(arg) \u66ff\u6362\u6210\u5df2\u7ecf\u5339\u914d\u597d\u7684\u6a21\u677f\u53c2\u6570 Arg \u4e86\uff0c\u5b9e\u9645\u4e0a\u662f\u7b49\u4ef7\u7684\u3002 \u8fd9\u91cc\u9700\u8981\u590d\u8bfb arg \u592a\u7eb1\u5e01\u4e86\u3002\u5b9e\u9645\u4e0a\uff0c\u6211\u4eec\u53ef\u4ee5\u5b9a\u4e49\u4e00\u4e2a\u5b8f\uff1a #define FWD(arg) std::forward(arg) \u8fd9\u6837\u5c31\u53ef\u4ee5\u7b80\u5316\u4e3a\uff1a void some_func(auto &&arg) { other_func(FWD(arg)); } \u5c11\u4e86\u70e6\u4eba\u7684\u5c16\u62ec\u53f7\uff0c\u770b\u8d77\u6765\u5bb9\u6613\u61c2\u591a\u4e86\u3002 \u4f46\u662f\uff0c\u6211\u4eec\u540c\u5b66\u6709\u4e00\u4e2a\u95ee\u9898\uff0c\u4e3a\u4ec0\u4e48 std::forward \u8981\u5199\u6210 std::forward