that take a user-suppiled lambda to generate the data needed to render our desired compile-time resource! These are e�ectively templated functions, but we will use the cleaner auto parameter syntax for

，就没必要去搞封装，只会让程序员 变得痛苦，同时还有一定性能损失：特别 是如果 getter/setter 函数分离了声明和定 义，实现在另一个文件时！ C++ 思想： RAII （ Resource Acquisition Is Initialization ） 资源获取视为初始化，反之，资源释放视为销毁 C++ 除了用于初始化的构造函数（ constructor ） 还包括了用于销毁的解构函数（ 更加明确用的哪一种类型转换（ cast ），从而避免一些像是 static_cast(ptr) 的错误 。 • 虽然作者也经常会忍不住在 zeno 中用 编译器默认生成的构造函数：无参数（小心 POD 陷阱！） • 除了我们自定义的构造函数外，编译器还会自动生成一些构造函数。 • 当一个类没有定义任何构造函数，且所有成员都有无参构造函数时，编译器会自动生成一 个无参构造函数 Pig() ，他会调用每个成员的无参构造函数。 这些类型被称为 POD （ plain-old-data ）。 • POD 的存在是出于兼容性和性能的考虑。 << 取决于内存的随机值 编译器默认生成的构造函数：无参数（ POD 陷阱解决方案） • 不过我们可以手动指定初始化 weight 为 0 。 • 通过 {} 语法指定的初始化值，会在编译器自 动生成的构造函数里执行。 编译器默认生成的构造函数：无参数（ POD 陷阱解决方案，续）

comfortable with C in embedded applications C++ Still viewed skeptically by many when considering resource constrained applicationsWhat are the advantages of C++? Obvious question: Why do this in C++? C++ v=I8UvQKvOSSw Fertig, Andreas (2020) “C++20: Aggregate, POD, trivial type, standard layout class, what is what.” https://andreasfertig.blog/2021/01/cpp20-aggregate-pod-trivial-type-standard-layout-class-what-is- what/

怎么样，是不是和 Go 语言很像？ 初始化列表 初始化是一个非常重要的语言特性，最常见的就是在对象进行初始化时进行使用。在传统 C++ 中， 不同的对象有着不同的初始化方法，例如普通数组、POD （Plain Old Data，即没有构造、析构和虚函 数的类或结构体）类型都可以使用 {} 进行初始化，也就是我们所说的初始化列表。而对于类对象的初始 化，要么需要通过拷贝构造、要么就需要使用 为解决这个问题，C++11 首先把初始化列表的概念绑定到类型上，称其为 std::initializer_list， 允许构造函数或其他函数像参数一样使用初始化列表，这就为类对象的初始化与普通数组和 POD 的初 始化方法提供了统一的桥梁，例如： #include #include #include class MagicFoo std::function>> resource_type; 以及服务端模板： template class ServerBase { public: resource_type resource; resource_type default_resource; void start() { // TODO }

which is the initialization of class objects provides a unified bridge between normal arrays and POD initialization methods, such as: #include #include #include space when the destructor (called when leaving the scope). That is, we often say that the RAII resource acquisition is the initialization technology. There are exceptions to everything, we always need is left in the last step, and B does not have any smart pointers to reference it, so this memory resource will also be released. std::weak_ptr has no implemented * and -> operators, therefore it cannot

point of declaration (POD), introduces entity 'i' int j = i; // POD, introduces entity 'j' // point of look-up (POL), names visible entity 'i' int k = l; // POD, introduces entity declared // (relative invisibility) int l; // point of declaration (POD), introduces entity 'l' int m = n; // POD, introduces entity 'm' // POL, names invisible entity 'n' invisibility) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 // translation unit 2 int n; // POD, introduces entity 'n' 1 2 3 STARTING SIMPLE global scope Lookup of entities at global scope

constructor, destructor, or copy assignment operator… This definition is essentially the same as a C++03 POD type. armv7-a System V x86 System V x86 Microsoft A Composite Type not larger than 4 bytes is returned 16 bytes x86 System V fundamental only x86-64 Microsoft 1,2,4,8 bytes, C++03 POD x86 Microsoft 1,2,4,8 bytes, C++03 POD Composite types are required to be “trivial” to get into registers!C.20: If you ___$ReturnUdt$[esp-4] mov DWORD PTR [eax], 60 mov DWORD PTR [eax+4], 0 ret 0 C H R 67 not a POD not a POD size > 4 not fundamentalCan we do something about it? ● std::chrono would have to give up encapsulation

14 Aside: POD Types  Standard-layout types are defined in C++11.  The 2003 Standard didn’t mention standard-layout types — it describes layout guarantees in terms of POD types.  POD stands for “Plain (There’s also a POF.)  A POD is a standard-layout class that also lacks:  private or protected non-static data members  user-declared constructors  base classes  In practice, POD classes are too restrictive

Implementation The C++ implementation will create expressive API calls through utilizing combination of : ▪POD structs -- structs with data members only ▪designated initializers -- initializing a struct with: { the road state -- There is only one. // the .= syntax is a designated initializer used to assign POD values auto result = processCarStateTransition({ .car = Car::FastSportsCar, .startingRoadState Why was there ambiguity? The RoadState type had 1. A default value when unspecified 2. Implicit POD construction could not differ between the three structs {.type = RoadType::Highway, .speed = Speed::FAST}

MFC 預設的印表機制 / 669 Scribble 列印機制的補強 / 685 印表機的頁和文件的頁 / 685 配置 GDI 繪圖工具 / 687 尺寸與方向：關於映像模式（座標系統） / 688 分頁 / 693 表頭（Header）與表尾（Footer）/ ----- #0008 #0009 #include // 每一个 Wi ndows 程序都需要包含此档 #0010 #include "resource.h" // 內含各个 resource IDs #0011 #include "generic.h" // 本程序之含入档 #0012 #0013 HINSTANCE _hInst; // Instance //--------------------------------------------------------------- #0004 #include "windows.h" #0005 #include "resource.h" #0006 #0007 jjhouricon ICON DISCARDABLE "jjhour.ico" #0008 #0009 GenericMenu MENU DISCARDABLE