问题描述
据我所知，基本类型是标量，数组是聚合的，但用户定义的类型呢?我会根据什么标准将它们分为两类?
As far as I understand it fundamental types are Scalar and Arrays are aggregate but what about user defined types? By what criteria would I divide them into the two categories?
struct S { int i; int j };
class C { public: S s1_; S s2_ };
std::vector<int> V;
std::vector<int> *pV = &v;
推荐答案
简短版本: C++ 中的类型是:
Short version: Types in C++ are:
对象类型:标量、数组、类、联合
Object types: scalars, arrays, classes, unions
引用类型
函数类型
(成员类型)[见下文]
(Member types) [see below]
void
长版
对象类型
Object types
标量
算术(整数、浮点数)
arithmetic (integral, float)
指针:T * 用于任何类型 T
pointers: T * for any type T
枚举
成员指针
nullptr_t
数组:T[] 或 T[N] 用于任何完整的非引用类型 T
Arrays: T[] or T[N] for any complete, non-reference type T
类:class Foo 或 struct Bar
琐碎的课程
Trivial classes
聚合
POD 类
(等等等等)
联合:联合邮编
引用类型:T &、T && 用于任何对象或自由函数类型T
References types: T &, T && for any object or free-function type T
函数类型
自由函数:
R foo(Arg1, Arg2, ...)
成员函数:R T::foo(Arg1, Arg2, ...)
void
成员类型是这样工作的.成员类型的形式为 T::U，但您不能拥有成员类型的对象或变量.您只能拥有成员指针.成员指针具有类型 T::* U，如果 U 是(自由)对象类型，则它是指向成员对象的指针，并且指针-如果 U 是(自由)函数类型，则为成员函数.
Member types work like this. A member type is of the form T::U, but you can't have objects or variables of member type. You can only have member pointers. A member pointer has type T::* U, and it is a pointer-to-member-object if U is a (free) object type, and a pointer-to-member-function if U is a (free) function type.
所有类型都是完整的，除了 void、未定义大小的数组和声明但未定义的类和联合.除了 void 之外的所有不完整类型都可以完成.
All types are complete except void, unsized arrays and declared-but-not-defined classes and unions. All incomplete types except void can be completed.
所有类型都可以const/volatile限定.
All types can be const/volatile qualified.
The <type_traits> header provides trait classes to check for each of these type characteristics.
这篇关于什么是 C++ 中的标量对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！