31课.完善的复数类

利用操作符重载的练习

注意事项：
1.赋值操作符（=）只能重载为成员函数
2.操作符重载不能改变原操作符的优先级（+， -， *， /）
3.操作符重载不能改变操作符的个数
4.操作符重载不应改变操作符的原有语义（3，4说明操作符重载只是对原有操作符功能的扩展，但是不能改变其本质的含义。比如：+只能是二目运算符的加法。不能是三目，也不能是减法）

练习：完善复数符+，-，*，/，==，！，=；
头文件：

#ifndef _COMPLEX_H_
#define _COMPLEX_H_

class Complex
{
	double a;
	double b;
public:
	Complex(double a = 0, double b = 0);
	double getA();
	double getB();
	double getModulus();
	
	Complex operator + (const Complex& c);
	Complex operator - (const Complex& c);
	Complex operator * (const Complex& c);
	Complex operator / (const Complex& c);
	
	bool operator == (const Complex& c);
	bool operator != (const Complex& c);
	
	Complex& operator = (const Complex& c);
};

#endif

.cpp文件

#include "Complex.h"
#include "math.h"

Complex::Complex(double a, double b)        
{
	this->a = a;
	this->b = b;
}

double Complex::getA()
{
	return a;
}

double Complex::getB()
{
	return b;
}

double Complex::getModulus()
{
	return sqrt(a * a + b * b);
}

Complex Complex::operator + (const Complex& c)
{
	double na = a + c.a;           //成员函数可以直接使用成员变量
	double nb = b + c.b;
	Complex ret(na, nb);
	
	return ret;
}

Complex Complex::operator - (const Complex& c)
{
	double na = a - c.a;
	double nb = b - c.b;
	Complex ret(na, nb);
	
	return ret;
}

Complex Complex::operator * (const Complex& c)
{
	double na = a * c.a - b * c.b;
	double nb = a * c.b + b * c.a;
	Complex ret(na, nb);
	
	return ret;
}

Complex Complex::operator / (const Complex& c)
{
	double cm = c.a * c.a + c.b * c.b;
	double na = (a * c.a + b * c.b) / cm;
	double nb = (b * c.a - a * c.b) / cm;
	Complex ret(na, nb);
	
	return ret;
}
	
bool Complex::operator == (const Complex& c)
{
	return (a == c.a) && (b == c.b);
}

bool Complex::operator != (const Complex& c)
{
	return !(*this == c);        //这里引用了上面的==
}
	
Complex& Complex::operator = (const Complex& c)
{
	if( this != &c )        //如果左右操作数不是同一个对象，再进行赋值
	{
		a = c.a;
		b = c.b;
	}
	
	return *this;            //赋值操作是可以是连续的返回（对象的引用），并且赋值操作返回值为做操作数（返回*this）。
}