运算符重载类似于调用函数，对于用户定义的类，c++没有可以比较他们关系的运算符，所以就像定义函数那样来重载运算符。
#include <iostream>
using namespace std;
class Tricycle
{
public:
Tricycle();
// copy constructor and destructor use default
int getSpeed() const { return *speed; }
void setSpeed(int newSpeed) { *speed = newSpeed; }
//Tricycle operator=(const Tricycle&);
bool operator==(const Tricycle&); //congzai==
private:
int *speed;
};
Tricycle::Tricycle()
{
speed = new int;
*speed = 5;
}
bool Tricycle::operator==(const Tricycle& rhs)
{
if (this==&rhs)
{
return true;
}
if(this->getSpeed()>=rhs.getSpeed())
{
return true; //if getSpeed()>=rhs.getSpeed() return ture
}
return false;
}
/*Tricycle Tricycle::operator=(const Tricycle& rhs)
{
if (this == &rhs)
return *this;
delete speed;
speed = new int;
*speed = rhs.getSpeed();
return *this;
}*/
int main()
{
Tricycle wichita;
std::cout << "Wichita's speed: " << wichita.getSpeed()
<< "\n";
std::cout << "Setting Wichita's speed to 8 ...\n";
wichita.setSpeed(8);
Tricycle dallas;
std::cout << "Dallas' speed: " << dallas.getSpeed()
<< "\n";
std::cout << "Setting Dallass speed to 7 ...\n";
dallas.setSpeed(7);
cout<<"wichita.getSpeed= "<<wichita.getSpeed()<<endl;
cout<<"dallas.getSpeed= "<<dallas.getSpeed()<<endl;
if(wichita == dallas)
{
cout<<"Wichita speed>=Dallass speed\n"; //houmiande xiao fanhui ture
}
else
{
cout<<"Wichita speed < Dallas speed\n";
}
return 0;
}
其中，就像函数那样，此处是重载==运算符，但是并非是判断相等的，而是判断两个对象中的speed成员变量是否是运算符==左侧的>=右侧的，返回一个bool类型，通过调用运算符，打印他们之间的关系。
下面是重载=运算符的例子：
#include <iostream>
class Tricycle
{
public:
Tricycle();
// copy constructor and destructor use default
int getSpeed() const { return *speed; }
void setSpeed(int newSpeed) { *speed = newSpeed; }
Tricycle operator=(const Tricycle&);
private:
int *speed;
};
Tricycle::Tricycle()
{
speed = new int;
*speed = 5;
}
Tricycle Tricycle::operator=(const Tricycle& rhs)
{
if (this == &rhs)
return *this;
delete speed;
speed = new int;
*speed = rhs.getSpeed();
return *this;
}
int main()
{
Tricycle wichita;
std::cout << "Wichita's speed: " << wichita.getSpeed()
<< "\n";
std::cout << "Setting Wichita's speed to 6 ...\n";
wichita.setSpeed(6);
Tricycle dallas;
std::cout << "Dallas' speed: " << dallas.getSpeed()
<< "\n";
std::cout << "Copying Wichita to Dallas ...\n";
wichita = dallas;
std::cout << "Dallas' speed: " << dallas.getSpeed()
<< "\n";
return 0;
}
