yidabu 2007-4-26 15:47
13 D语言 结构 联合Structs & Unions
13 D语言 结构 联合Structs & Unions知识若不分享 实在没有意义 http://www.d-programming-language-china.org 20070423点击下面网址查看原文:http://www.d-programming-language-china.org by: uFramer D语言论坛 http://www.d-programming-language-china.org from: http://www.digitalmars.com/d/struct.html version: 基于D 1.013 (Apr 19, 2007) Whereas classes are reference types, structs are value types. Any C struct can be exactly represented as a D struct. In C++ parlance, a D struct is a POD (Plain Old Data) type, with a trivial constructors and destructors. Structs and unions are meant as simple aggregations of data, or as a way to paint a data structure over hardware or an external type. External types can be defined by the operating system API, or by a file format. Object oriented features are provided with the class data type. A struct is defined to not have an identity; that is, the implementation is free to make bit copies of the struct as convenient. Struct, Class Comparison Table Feature struct class C struct C++ struct C++ class Struct, Class Comparison Table Feature struct class C struct C++ struct C++ class value type X X X X reference type X data members X X X X X hidden members X X X static members X X X X default member initializers X X bit fields X X X non-virtual member functions X X X X virtual member functions X X X constructors X X X destructors X X X RAII X X X operator overloading X X X X inheritance X X X invariants X X unit tests X X synchronizable X parameterizable X X X X alignment control X X member protection X X X X default public X X X X tag name space X X X anonymous X X X X 结构的声明： QUOTE: AggregateDeclaration: Tag { DeclDefs } Tag Identifier StructBody Tag Identifier ; Tag: struct union StructBody: { } { StructBodyDeclarations } StructBodyDeclarations: StructBodyDeclaration StructBodyDeclaration StructBodyDeclarations StructBodyDeclaration: Declaration StaticConstructor StaticDestructor Invariant UnitTest StructAllocator StructDeallocator StructAllocator: ClassAllocator StructDeallocator: ClassDeallocator 它们同在 C 中的结构基本一样，除了以下一些例外： 没有位域 可以显式指定对齐 没有单独的标记名字空间 —— 标记名并入当前的作用域 如下面这样的声明： [Copy to clipboard] [ - ]CODE: struct ABC x; 不允许这样使用：( 本文出处: http://www.d-programming-language-china.org ) [Copy to clipboard] [ - ]CODE: ABC x; 匿名结构/联合可以作为其他结构/联合的成员存在 可以为成员提供默认初始值 可以拥有成员函数和静态成员Static Initialization of Structs结构的静态初始化 如果不提供初始值，静态结构成员会被默认地初始化为成员类型的初始值。如果提供了静态初始值，成员会按照这样的语法初始化：成员名，冒号，表达式。成员可以按照任意顺序初始化。没有出现在初始化列表中的成员会被默认值初始化。( 本文出处: http://www.d-programming-language-china.org ) [Copy to clipboard] [ - ]CODE: struct X { int a; int b; int c; int d = 7;} static X x = { a:1, b:2}; // c 被设置为 0, d 为 7 static X z = { c:4, b:5, a:2 , d:5}; // z.a = 2, z.b = 5, z.c = 4, z.d = 5 C 风格的初始化，依赖于结构声明中的成员的顺序，也是被支持的： [Copy to clipboard] [ - ]CODE: static X q = { 1, 2 }; // q.a = 1, q.b = 2, q.c = 0, q.d = 7 Static Initialization of Unions联合的静态初始化 联合需要显式地初始化。 [Copy to clipboard] [ - ]CODE: union U { int a; double b; } static U u = { b : 5.0 }; // u.b = 5.0 如果联合的其他成员占用的存储空间更大，剩下的部分被初始化为零。( 本文出处: http://www.d-programming-language-china.org )Dynamic Initialization of Structs结构的动态初始化 结构可以被同类型值动态初始化： [Copy to clipboard] [ - ]CODE: struct S { int a; } S t; // default initialized t.a = 3; S s = t; // s.a is set to 3 If opCall is overridden for the struct, and the struct is initialized with a value that is of a different type, then the opCall operator is called: [Copy to clipboard] [ - ]CODE: struct S { int a; static S opCall(int v) { S s; s.a = v; return s; } static S opCall(S v) { S s; s.a = v.a + 1; return s; } } S s = 3; // sets s.a to 3 S t = s; // sets t.a to 3, S.opCall(s) is not called Struct Properties结构属性 .sizeof 以字节为单位的结构大小 .alignof 要对齐到的边界值 .tupleof Gets type tuple of fieldsStruct Field Properties结构域属性 .offsetof 从结构开始的字节偏移量 of struct( lastupdate:20070426 最新文章请访问http://www.d-programming-language-china.org )关于一大步成功社区:yidabu提倡在交流中学习，在分享中提高收集感兴趣的知识，写下心得，通过网络与别人一起分享理解一点就实践一步，收获什么就分享什么，成功就是这样一点点一步步累积起来的网络只是一个工具，只有自己身心提高才是实实在在的。d-programming-language-china.org为大家提供一个学习交流各种知识的平台