C++11：一些新的微小变化（新的数据类型、template表达式内的空格等）

本文介绍一些C++的两个新特性，它们虽然微小，但对你的编程十分重要
一、新的数据类型

C++11添加的新的数据类型如下：

char16_t、char32_t
long long、unsigned long long
std::nullptr_t（下面详细介绍）

二、Template表达式内的空格

C++11标准之前建议在“在两个template表达式的闭符之间放一个空格”的要求已经过时了
例如：

vector<list<int> >; //C++11之前

vector<list<int>>;  //C++11

三、nullptr
C++11允许你使用nullptr取代0或NULL，用来表示一个pointer（指针）指向所谓的no value nullptr会被自动转换为各种pointer类型，但是不会被转换为任何证书类型

演示案例

1 void f(int);
2 void f(void*);
3 f(0);       //调用f(int)
4 f(NULL);    //如果NULL被视为0，那么调用的是f(int)，可能与你的预期不符
5 f(nullptr); //调用f(void*)

四、std::nullptr_t
std::nullptr_t是一种基础数据类型，定义于<sctddef>中
std::nullptr_t定义的变量必须初始化
nullptr属于一种常量，它是属于std::nullptr_t数据类型的

演示案例

void f(int) {
    std::cout << "int" << std::endl;
}
void f(void*) {
    std::cout << "void*" << std::endl;
}
void f(std::nullptr_t) {
    std::cout << "std::nullptr_t" << std::endl;
} 
int main(){
    f(0);
    f(NULL);
    f(nullptr);     //必须初始化    
    std::nullptr_t t = nullptr;    
    f(t);     
    return 0;
}

除了每个容器有自己的迭代器之外，标准库在头文件iterator中还定义了额外几种迭代器

这些迭代器包括：
插入迭代器（insert iterator）：这些迭代器被绑定到一个容器上，可用来向容器插入元素
流迭代器（stream iterator）：这些迭代器被绑定到输入或输出流上，可用来遍历所有关联的IO流
反向迭代器（reverse iterator）：这些迭代器向后而不是向前移动。除了forward_list容器之外的标准库容器都有反向迭代器
移动迭代器（move iterator）：这些专门的迭代器不是拷贝其中的元素，而是移动它们

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C++11：一些新的微小变化（新的数据类型、template表达式内的空格等）

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