ostream& operator<< 中&的意义是什么
时间: 2024-03-30 21:33:40 浏览: 27
在 C++ 中,& 符号可以表示不同的含义。在这里,& 符号表示引用(reference)类型。引用是一个别名,它是指向另一个变量的地址的别名。因此,使用引用作为函数的参数或返回值,可以避免不必要的数据拷贝,提高程序的效率。
在 `ostream& operator<<` 中,& 的作用是将左值的地址传递给函数,这样可以避免对数据的拷贝,提高了输出流运算符的效率。同时,使用引用类型还可以通过修改引用的值来改变函数外部变量的值。
相关问题
ostream& operator<<是什么意思
Ostream is a C++ standard library class that represents an output stream. It provides a way to send data to an output device, such as the console or a file. The ostream class is defined in the iostream header file and is part of the standard C++ library. It is used to output data to the standard output stream, which is usually the console. It can also be used to output data to other types of output streams, such as files or network sockets. Some of the important member functions of the ostream class are the insertion operator (<<), the flush() function, and the put() function. The insertion operator is used to insert data into the output stream, whereas the flush() function is used to flush the output buffer and ensure that all data is written to the output device. The put() function is used to write a single character to the output stream.
ostream & operator<<(ostream& cout,Person& p)
这是一个重载输出流运算符的函数,它的作用是将一个 Person 类型的对象输出到标准输出流中。具体实现方式可以参考以下代码:
```c++
#include<iostream>
#include<string>
using namespace std;
class Person{
public:
Person(string name,int age):m_name(name),m_age(age){}
friend ostream & operator<<(ostream& cout,Person& p);
private:
string m_name;
int m_age;
};
ostream & operator<<(ostream& cout,Person& p){
cout<<"Name: "<<p.m_name<<", Age: "<<p.m_age<<endl;
return cout;
}
int main(){
Person p("Tom", 18);
cout << p; // 输出 "Name: Tom, Age: 18"
return 0;
}
```
在上述代码中,重载输出流运算符的函数 `operator<<` 被定义为 `Person` 类的友元函数,它可以直接访问 `Person` 类的私有成员变量 `m_name` 和 `m_age`,并将它们输出到标准输出流中。在主函数中,我们创建一个 `Person` 对象 `p`,然后通过 `cout << p` 的方式将其输出到标准输出流中。