day-7 代码

对象的常量函数

class complex
{
public:
	complex(double r, double i = 0):re(r), im(i)
	{}
	complex() :re(1), im(0)
	{}
	complex& operator += (const complex&); //返回一个引用型 //引用传值类似指针，比值传递快
	double real() const { return re; } //返回一个double型
	double imag() const { return im; }
private:
	double re, im;

	friend complex& _doapl(complex*, const complex); 
};

int main()
{
	/*complex c1(2, 1);
	cout << c1.real() << "+i";
	cout << c1.imag();*/
	const complex c2(2, 5);
	cout << c2.real() << "+i";  //double real() { return re; },不能将“this”指针从“const complex”转换为“complex &”
	cout << c2.imag();


	cout << endl;
	return 0;
}

运算符重载 - 复数

class complex
{
public:
	complex(double r, double i = 0):re(r), im(i)
	{}
	complex() :re(1), im(0)
	{}
	double real() const { return re; }
	double imag() const { return im; }
	int func(const complex& param)
	{
		return param.im + param.re;
	}
	complex& operator += (const complex& r)
	{
		return _doapl(this, r);
	}
private:
	double re, im;
	friend complex& _doapl(complex* ths, const complex& r)
	{
		ths->re += r.re;
		ths->im += r.im;
		return *ths;
	}
};


int main()
{
	complex c1(2, 5);
	complex c2(6);
	c2 += c1;
	cout << c2.real() << " +i" << c2.imag() << endl;

	cout << endl;
	return 0;
}

相同class的各个objects互为友元

class complex
{
public:
	complex(double r, double i = 0):re(r), im(i)
	{}
	complex() :re(1), im(0)
	{}
	int func(const complex& param)  //不会报错
	{
		return param.im + param.re;
	}
private:
	double re, im;
};


int main()
{
	complex c1(2, 5);
	complex c2;
	cout << c2.func(c1) << endl;

	cout << endl;
	return 0;
}

+=符号重载

class complex
{
public:
	complex(double r, double i = 0):re(r), im(i)
	{}
	complex() :re(1), im(0)
	{}
	double real() const { return re; }
	double imag() const { return im; }
	int func(const complex& param)
	{
		return param.im + param.re;
	}
	complex& operator += (const complex& r)
	{
		return _doapl(this, r);
	}
private:
	double re, im;
	//返回值为complex不是void，为了防止c3 += c2 += c1不能执行
	friend complex& _doapl(complex* ths, const complex& r)
	{
		ths->re += r.re;
		ths->im += r.im;
		return *ths;
	}
};


int main()
{
	complex c1(2, 5);
	complex c2(6);
	c2 += c1;
	cout << c2.real() << " +i" << c2.imag() << endl;

	cout << endl;
	return 0;
}