【C++】运算符的重载

一.重载运算符加减乘除“+”“-“*”“/”

函数类型 operator 运算符名称(形参表)
	{对运算符的重载处理}
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例题1：复数类进行加减乘除

复数运算相关公式

1.加法运算
(a+bi)+(c+di)=(a+c)+(b+d)i

2.减法运算
(a+bi)-(c+di)=(a-c)+(b-d)i

3.乘法运算
(a+bi)(c+di)=(ac-bd)+(bc+ad)i

4.除法运算
(a+bi)/(c+di)=(ac + bd)/(c^2 + d ^2) +((bc - ad)/(c ^2 + d ^2)) i

#include
using namespace std;
class Complex {
public:
	Complex(double a, double b) :real(a), imag(b) {}
	void display();
	double get_real();
	double get_imag();
	Complex operator+(Complex&);
	Complex operator-(Complex&);
	Complex operator*(Complex&);
	Complex operator/(Complex&);
private:
	double real;
	double imag;
};
Complex Complex::operator+(Complex& c) {
	return Complex(this->get_real() + c.get_real(), this->get_imag() + c.get_imag());
}
Complex Complex::operator-(Complex& c)
{
	return Complex(this->get_real() - c.get_real(), this->get_imag() - c.get_imag());
}
Complex Complex::operator*(Complex& c)
{
	return Complex(this->get_real() * c.get_real()- this->get_imag() * c.get_imag(), this->get_imag() * c.get_real()+this->get_real() * c.get_imag());
}
Complex Complex::operator/(Complex& c)
{
	return Complex((real * c.get_real() + imag * c.get_imag())/(pow(c.get_real(),2)+(pow(c.get_imag(), 2))),
		(imag * c.get_real() - real * c.get_imag()) / (pow(c.get_real(), 2) +(pow(c.get_imag(), 2))));
}
void Complex::display() {
	cout << "(" << real << "," << imag << "i)" << endl;
}
double Complex::get_real() {
	return real;
}
double Complex::get_imag() {
	return imag;
}
int main() {
	Complex c1(3, 4);
	Complex c2(5, -10);
	Complex c3 = c1 + c2;
	c3.display();//(8,-6i)
	c3 = c1 - c2;
	c3.display();//(-2,14i)
	c3 = c1 * c2;
	c3.display();//(55,-10i)
	c3 = c1 / c2;
	c3.display();//(-0.2,0.4i)
	return 0;
}
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例题2：求两个复数之和（c1+c2）、整数和复数之和（c+i或者i+c）

#include
using namespace std;
class Complex {
public:
	Complex(double a, double b) :real(a), imag(b) {}
	void display();
	double get_real();
	double get_imag();
	Complex operator+(int &i);
	Complex operator+(Complex &c);
	friend Complex operator+(int &,Complex&);
private:
	double real;
	double imag;
};
double Complex::get_real() {
	return real;
}
double Complex::get_imag() {
	return imag;
}
Complex Complex::operator+(int& i) {
	return Complex(real + i, imag);
}
Complex Complex::operator+(Complex &c) {
	return Complex(real + c.get_real(), imag+c.get_imag());
}
void Complex::display() {
	cout << "(" << real << "," << imag << "i)" << endl;
}
Complex operator+(int& i, Complex& c)
{
	return Complex(c.get_real() + i, c.get_imag());
}
int main() {
	Complex c1(3, 4);
	Complex c2(5, -10);
	int i = 5;
	Complex c3 = c1 + c2;
	c3.display();//(8,-6i)
	c3 = c1 + i;
	c3.display();//(8,4i)
	c3 = i + c1;
	c3.display();//(8,4i)
	return 0;
}


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二.重载流插入运算符“<<”和流提取运算符“>>”

只能作为友元函数，不能将它们定义为成员函数
【个人理解：统一写成非成员函数可能是怕原来的流运算符会调用类库里的 ，无法重载自己定义的】

例题：输入两个矩阵，输出两个矩阵的和

istream& operator>>(istream &,自定义类 &);
ostream& operator<<(ostream &,自定义类 &);
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#include
using namespace std;
class Matrix {
public:
	Matrix();
	friend ostream& operator<<(ostream& out,Matrix &m);
	friend istream& operator>>(istream& input, Matrix& m);
	friend Matrix operator+(Matrix& a, Matrix& b);
private:
	int a[2][3];
};

//重载运算符“++”————矩阵的相加
Matrix operator+(Matrix& x, Matrix& z) {
	Matrix t;
	for (int i = 0;i < 2;i++) {
		for (int j = 0;j < 3;j++) {
			t.a[i][j] = x.a[i][j] + z.a[i][j];
		}
	}
	return t;
}
//重载运算符“<<”————矩阵的输入
ostream& operator<<(ostream& out, Matrix& m) {
	for (int i = 0;i < 2;i++) {
		for (int j = 0;j < 3;j++) {
			out << m.a[i][j] << " ";
		}
		out << endl;
	}
	return out;
}
//重载运算符“<<”————矩阵的输出
istream& operator>>(istream& in, Matrix& m) {
	for (int i = 0;i < 2;i++) {
		for (int j = 0;j < 3;j++) {
			in >> m.a[i][j];
		}
	}
	return in;
}
//构造函数
Matrix::Matrix() {
	for (int i = 0;i < 2;i++) {
		for (int j = 0;j < 3;j++) {
			a[i][j] = 0;
		}
	}
}


int main() {
	Matrix m1, m2, m3;
	cin >> m1 >> m2;
	m3 = m1 + m2;
	cout << m3 << endl;
	return 0;
}
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三.重载类型转换符

将一个类的对象转换成另一类型的数据。

• 函数名前不能指定函数类型，函数没有参数。
• 类型转换函数只能作为成员函数，因为转换的主体是本类的对象，不能作为友元函数或普通函数。

operator 类型名
	{实现转换的语句}
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例题：处理一个复数和一个double数相加的运算

#include
using namespace std;
class Complex {
public:
	Complex() {
		real = 0;
		imag = 0;
	}
	Complex(double r) {
		real = r;
		imag = 0;
	}
	Complex(double a, double b) :real(a), imag(b) {}
	void display();
	double get_real();
	double get_imag();
	operator double() { return real; }//重载类型转换符
private:
	double real;
	double imag;
};
void Complex::display() {
	cout << "(" << real << "," << imag << ")" << endl;
}
int main() {
	Complex c1(3, 4), c2;
	double d;
	d = 2.5 + c1;
	cout << d << endl;
	c2 = Complex(d);
	c2.display();
	return 0;
}
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