1.二元运算符
二元运算符指的是一个运算符有左操作数和右操作数两个对象，比如常见的+、-、*、/等等
1）算术运算符：+、-、*、/、%
2）关系运算符：<=、>=、<、>、!=、==
3）位运算符：^、&、|
4）逻辑运算符：&&、||
以>=为例：
#include <iostream>
using namespace std;
class Cperson
{
public:
int _age;
Cperson(int age):_age(age)
{
}
};
int operator >= (Cperson ob1, Cperson ob2)
{
if (ob1._age >= ob2._age)
return 1;
else
return 0;
}
int main()
{
Cperson per1(14);
Cperson per2(6);
cout << (per1 >= per2) << endl;
system("pause");
return 0;
}
2.一元运算符
1）+、-、&、*（正、负、取地址、内存操作符）
2）~、！
以&为例：
#include <iostream>
using namespace std;
class Cperson
{
public:
int _age;
Cperson(int age):_age(age)
{
}
int* operator & ()
{
return &this->_age;
}
};
int main()
{
Cperson per1(14);
int *p = &per1;
cout << p << endl;
system("pause");
return 0;
}
3.输入输入
<<、>>
3.1输出<<
格式：
ostream &operator << (ostream &os, const class &classname) {return os}
1）参数1是ostream引用，参数2是对象的常引用
2）返回值保证连续输出
3）必须在类外
4）类友元。因为一般成员数据都是私有的，外部定义的运算符无法访问私有成员，这时就需要将运算符重载在类中声明为友元函数
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson(int age):_age(age)
{
}
private:
int _age;
friend ostream &operator << (ostream &os, const Cperson &ob);
};
ostream &operator << (ostream &os, const Cperson &ob)
{
os << ob._age;
return os;
}
int main()
{
Cperson per1(14);
Cperson per2(18);
cout << per1 << " " << per2 << endl;
system("pause");
return 0;
}
执行结果：
3.2输入>>
格式：
istream &operator >> (istream & is, class &classname) {return is}
输入的时候需要检测是否失败
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson():_age(0),_weight(0)
{
}
void show()
{
cout << "age = " << _age << endl;
cout << "weight = " << _weight << endl;
}
private:
int _age;
double _weight;
friend istream &operator >> (istream &io, Cperson &ob);
};
istream &operator >> (istream &is, Cperson &ob)
{
is >> ob._age >> ob._weight;
if (is.fail())
{
cout << "Input Error" << endl;
abort(); //输入错误就以非正常方式结束程序
}
return is;
}
int main()
{
Cperson per1;
cin >> per1;
per1.show();
system("pause");
return 0;
}
执行结果：
4.赋值运算符
1）=，必须类内
2）复合赋值运算符：+=、-=、*=、/=、%=、<<=、>>=、^=、&=、|=，建议类内，内外也行
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson():_age(0),_weight(0)
{
}
void operator = (int age)
{
this->_age = age;
}
void operator = (double weight)
{
this->_weight = weight;
}
void show()
{
cout << "age = " << _age << endl;
cout << "weight = " << _weight << endl;
}
private:
int _age;
double _weight;
};
int main()
{
Cperson per1;
per1 = 23;
per1 = 68.12;
per1.show();
system("pause");
return 0;
}
执行结果：
5.下标运算符——[ ]
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson():_a(0),_b(0),_c(0),_d(0)
{
}
int &operator [] (int num)
{
switch (num)
{
case(0):
return _a;
case(1):
return _b;
case(2):
return _c;
case(3):
return _d;
default:
cout << "Error" << endl;
abort();
}
}
public:
int _a;
int _b;
int _c;
int _d;
};
int main()
{
Cperson per1;
for (int i = 0; i < 4; i++)
{
per1[i] = i * 2;
cout << per1[i] << endl;
}
system("pause");
return 0;
}
执行结果：
注意：这是对于类内只有一种数据类型的情况，如果类内又有int型又有double型等等，就要通过返回指针来运算了
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson():_a(0),_b(0),_c(0),_d(0)
{
}
void *operator [] (int num)
{
switch (num)
{
case(0):
return &_a;
case(1):
return &_b;
case(2):
return &_c;
case(3):
return &_d;
default:
cout << "Error" << endl;
abort();
}
}
public:
int _a;
char _b;
float _c;
double _d;
};
int main()
{
Cperson per1;
*(int *)per1[0] = 5;
*(char *)per1[1] = 'A';
*(float *)per1[2] = 3.14f;
*(double *)per1[3] = 8.12;
cout << *(int *)per1[0] << endl;
cout << *(char *)per1[1] << endl;
cout << *(float *)per1[2] << endl;
cout << *(double *)per1[3] << endl;
system("pause");
return 0;
}
执行结果：
6.递增递减运算符
1）可以写在类内也可以写在类外
2）左++和左--，函数只用传递一个参数，那就是一个对象；但是右++和右--需传递两个参数，一个是对象，另一个是int n，这个参数可以理解为一个标记，用来区分左++和左--
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson(int a):_a(a)
{
}
int operator ++ ()
{
return ++_a;
}
int operator ++ (int n)
{
n = _a;
++_a;
return n;
}
public:
int _a;
};
int main()
{
Cperson per1(15);
cout << ++per1 << endl;
cout << per1++ << endl;
system("pause");
return 0;
}
执行结果：
7.重载类型转换
1）运算符重载没有显式的返回类型，但是要写返回值
2）没有参数
3）必须定义成类成员函数
4）不应该改变对象的内容，所以应该是const函数
5）避免过度使用，一般情况下可以用对象.成员来访问成员
#include <iostream>
using namespace std;
class Cperson
{
public:
Cperson(int a,double b):_a(a),_b(b)
{
}
operator int()
{
return _a;
}
operator double()
{
return _b;
}
public:
int _a;
double _b;
};
int main()
{
Cperson per1(2,3.14);
cout << (int)per1 << endl;
cout << (double)per1 << endl;
system("pause");
return 0;
}
执行结果：
