所谓重载，就是重新赋予新的含义，函数重载是对一个已有的函数赋予新的含义。
运算符重载的方法是定义一个重载运算符的函数，在需要执行被重载的运算符时，系统就自动调用该运算符。也就是说，运算符重载是通过定义函数实现的，运算符重载实质是是函数的重载。
实例1：复数加法
1 #include <iostream>
2
3 using namespace std;
4 class Complex//定义基类
5 {
6 public:
7 Complex();//构造器
8 Complex(double r,double i);//重载函数，输入参数不同，功能不同
9 Complex Complex_add(Complex &d);//加入一个方法，实现复数加法,Complex指其类型
10 void print();
11
12 private:
13 double real;
14 double imag;
15 };
16
17 Complex::Complex()//构造函数实现
18 {
19 real = 0;
20 imag = 0;
21 }
22 Complex::Complex(double r,double i)//重载函数实现
23 {
24 real = r;
25 imag = i;
26 }
27
28 Complex Complex::Complex_add(Complex &d)//Complex &d为定义基类对象d(被加数) complex_add为基类Complex方法
29 { //第二个Complex为继承基类的加数对象
30 Complex c;//定义基类对象c //第一个Complex为其类型
31
32 c.real = real + d.real;
33 c.imag = imag + d.imag;
34
35 return c;
36 }
37 void Complex::print()
38 {
39 cout << "(" << real << ", " << imag << "i)\n";
40 }
41
42 int main()
43 {
44 Complex c1(3,4),c2(5,-10),c3;//定义三个对象c1、c2、c3及其重载函数参数值
45 c3 = c1.Complex_add(c2);
46
47 cout << "c1 = ";
48 c1.print();
49 cout << "c2 = ";
50 c2.print();
51 cout << "c1 + c2 = ";
52 c3.print();
53
54 return 0;
55 }
实例2：复数加法2
1 #include <iostream>
2
3 using namespace std;
4 class Complex//定义基类
5 {
6 public:
7 Complex();//构造器
8 Complex(double r,double i);//重载函数，输入参数不同，功能不同
9 friend Complex operator+(Complex &c,Complex &d);//加入一个方法，实现复数加法,Complex指其类型
10 void print();
11
12 private:
13 double real;
14 double imag;
15 };
16
17 Complex::Complex()//构造函数实现
18 {
19 real = 0;
20 imag = 0;
21 }
22 Complex::Complex(double r,double i)//重载函数实现
23 {
24 real = r;
25 imag = i;
26 }
27 //注意：这里作为友元函数，不属于Complex,记得别写::
28 Complex operator+(Complex &c,Complex &d)//Complex &d为定义基类对象d(被加数) complex_add为基类Complex方法
29 {
30 return Complex(c.real + d.real,c.imag + d.imag);
31 }
32 void Complex::print()
33 {
34 cout << "(" << real << ", " << imag << "i)\n";
35 }
36
37 int main()
38 {
39 Complex c1(3,4),c2(5,-10),c3;//定义三个对象c1、c2、c3及其重载函数参数值
40 c3 = operator+(c1,c2);
41
42 cout << "c1 = ";
43 c1.print();
44 cout << "c2 = ";
45 c2.print();
46 cout << "c1 + c2 = ";
47 c3.print();
48
49 return 0;
50 }
作业：分数加减乘除的操作符重载
1 #include <iostream>
2 #include <string>
3 #include <math.h>
4
5 using namespace std;
6 class Rational//定义基类
7 {
8 public:
9 Rational(int num,int denom); //构造器 num = 分子，denom = 分母
10
11 Rational operator+(Rational rhs);// rhs == right hand side(右手边参数)
12 Rational operator-(Rational rhs);
13 Rational operator*(Rational rhs);
14 Rational operator/(Rational rhs);
15
16 void print();//打印
17
18 private:
19 void normalize();//负责对分数的简化处理
20
21 int numerator; //分子
22 int denominator; //分母
23 };
24
25 Rational::Rational(int num,int denom)//构造函数实现
26 {
27 numerator = num;
28 denominator = denom;
29
30 normalize();
31 }
32 //normalize()对分数进行简化操作包括：
33 //1.只允许分子为负数，如果分母为负数则把负数挪到分子部分，如1/-2==-1/2
34 //2.利用欧几里德算法(辗转求余原理)将分数进行简化:2/10 => 1/5
35
36 void Rational::normalize()
37 {
38 //确保分母为正
39 if( denominator < 0)
40 {
41 numerator = -numerator;
42 denominator = -denominator;
43 }
44 //欧几里德算法
45 int a = abs(numerator);
46 int b = abs(denominator);
47
48 //求出最大公约数
49 while(b>0)
50 {
51 int t = a % b;//取余
52 a = b;
53 b = t;
54 }
55
56 //分子、分母分别除以最大公约数得到最简化分数
57 numerator /= a;
58 denominator /= a;
59 }
60 //a c a*d c*b a*d + c*d
61 //- + - = --- + --- = ----------
62 //b d b*d b*d b*d
63 Rational Rational::operator+(Rational rhs)//分数的加运算
64 {
65 int a = numerator;
66 int b = denominator;
67 int c = rhs.numerator;
68 int d = rhs.denominator;
69
70 int e = a*b + c*d;
71 int f = b*d;
72
73 return Rational(e,f);
74 }
75 //a c a -c
76 //- - - = - + --
77 //b d b d
78 Rational Rational::operator-(Rational rhs)//分数的减运算
79 {
80 rhs.numerator = -rhs.numerator; //被减数分子取负数
81 return operator+(rhs);
82 }
83 //a c a*c
84 //- * - = ---
85 //b d b*d
86 Rational Rational::operator*(Rational rhs)//分数的乘运算
87 {
88 int a = numerator;
89 int b = denominator;
90 int c = rhs.numerator;
91 int d = rhs.denominator;
92
93 int e = a*c;
94 int f = b*d;
95
96 return Rational(e,f);
97 }
98 //a c a d
99 //- / - = - * -
100 //b d b c
101 Rational Rational::operator/(Rational rhs)//分数的除运算
102 {
103 //rhs的分子分母互换
104 int t = rhs.numerator;
105 rhs.numerator = rhs.denominator;
106 rhs.denominator = t;
107
108 return operator*(rhs);
109 }
110 void Rational::print() //打印最简分数
111 {
112 if(numerator % denominator == 0)
113 cout << numerator / denominator;
114 else
115 cout << numerator << "/" << denominator;
116 }
117
118 int main()
119 {
120 Rational f1(2,16);//定义f1对象，且传入(2,16)参数
121 Rational f2(7,8);
122
123 //测试有理数加法运算
124 Rational res = f1 + f2;//相当于res=f1.operator+(f2)
125 f1.print();
126 cout << " + ";
127 f2.print();
128 cout << " = ";
129 res.print();
130 cout << "\n";
131
132 //测试有理数减法运算
133 res = f1 - f2;
134 f1.print();
135 cout << " - ";
136 f2.print();
137 cout << " = ";
138 res.print();
139 cout << "\n";
140
141 //测试有理数乘法运算
142 res = f1 * f2;
143 f1.print();
144 cout << " * ";
145 f2.print();
146 cout << " = ";
147 res.print();
148 cout << "\n";
149
150 //测试有理数除法运算
151 res = f1 / f2;
152 f1.print();
153 cout << " / ";
154 f2.print();
155 cout << " = ";
156 res.print();
157 cout << "\n";
158
159 return 0;
160 }
