c++运算符重载+实例

题目来源于：http://blog.csdn.net/sxhelijian/article/details/8723847

【项目2拓展2（思考）】这个思考题吊一下大家的胃口：设定义了两个分数类的对象，如CFraction c1, c2。如果定义了int i，我们能用cin>>i>>j;在键盘上输入i和j的值，是否期望用cin>>c1>>c2;输入分数呢？同理，用cout<<c1<<c2;进行输出，可以吗？进一步，用c1+c2得到新的一个分数，用c1/c2实现两个分数的除法，以及其他加、减、比较、求倒数等也是理所当然的。实际上，要自定义分数类，这些直观的基本运算应该要实现，这叫运算符的重载。本任务中用amplify()给出了“放大”运算的一种实现方案，更多内容值得期待地。

首先要说明：有的C++编译系统（如VC++6.0）没有完全实现C++标准，它所提供的后缀.h的头文件不支持把成员函数重载为友元函数，因此在VC++6.0，应把程序的头两行：

#include <iosteam>

using namespace std;

改为一行：#include <iosteam.h>   //C语言的风格

这是我自己编写的有关运算符重载的程序：

#include <iostream.h>

enum style_enum{zero, one, two, three };

class CFraction
{private:
	int nume;  // 分子
	int deno;  // 分母
 public:
	 CFraction(int nu=0,int de=1):nume(nu),deno(de){}   //构造函数，初始化用

	void simplify();				//化简（使分子分母没有公因子）

	//输入输出重载
	friend ostream& operator<<(ostream &out,const CFraction &cf);
    friend istream& operator>>(istream &in,CFraction &cf);
    
    //加减乘除，结果需要化简
	friend CFraction operator+(const CFraction &lcf,const CFraction &rcf);
	friend CFraction operator-(const CFraction &lcf,const CFraction &rcf);
	friend CFraction operator*(const CFraction &lcf,const CFraction &rcf);
	friend CFraction operator/(const CFraction &lcf,const CFraction &rcf);
    
	//关系运算符
	friend bool operator>(const CFraction &lcf,const CFraction &rcf);
	friend bool operator<(const CFraction &lcf,const CFraction &rcf);
	friend bool operator>=(const CFraction &lcf,const CFraction &rcf);
	friend bool operator<=(const CFraction &lcf,const CFraction &rcf);
	friend bool operator==(const CFraction &lcf,const CFraction &rcf);
	friend bool operator!=(const CFraction &lcf,const CFraction &rcf);


	//取+、-一目运算符
	CFraction operator+();
	CFraction operator-();
};



void CFraction::simplify()
{
	int v1 = nume;
	int v2 = deno;
	while(v2)
	{
		int temp = v2;
		v2 = v1 % v2;
		v1 = temp;
	}
	nume /= v1;
	deno /= v1;
	if(deno < 0)
	{
		deno = -deno;
		nume = -nume;
	}
}

//输出重载
ostream& operator<<(ostream &out,const CFraction &cf)
{
	out << cf.nume << '/' << cf.deno;
	return out;
}

//输入重载
istream& operator>>(istream &in,CFraction &cf)
{
	char ch;
	while(1)
	{
		in >> cf.nume >> ch >> cf.deno;
		if(cf.deno == 0)
			cerr << "分母为0请重新输入\n";
		else if(ch != '/')
			cerr << "格式错误（形如m/n）请重新输入\n";
		else break;
	}
	return in;
}
//加法重载
CFraction operator+(const CFraction &lcf,const CFraction &rcf)
{
	CFraction cf;
	cf.nume = lcf.nume*rcf.deno + lcf.deno*rcf.nume;
	cf.deno = lcf.deno*rcf.deno;
	cf.simplify();
	return cf;
}
//减法重载
CFraction operator-(const CFraction &lcf,const CFraction &rcf)
{
	CFraction cf;
	cf.nume = lcf.nume*rcf.deno - rcf.nume*lcf.deno;
	cf.deno = lcf.deno*rcf.deno;
	cf.simplify();
	return cf;
}
//乘法重载
CFraction operator*(const CFraction &lcf,const CFraction &rcf)
{
	CFraction cf;
	cf.nume = lcf.nume*rcf.nume;
	cf.deno = lcf.deno*rcf.deno;
	cf.simplify();
	return cf;
}
//除法重载
CFraction operator/(const CFraction &lcf,const CFraction &rcf)
{
	CFraction cf;
	cf.nume = lcf.nume*rcf.deno;
	cf.deno = lcf.deno*rcf.nume;
	cf.simplify();
	return cf;
}
//取正重载
CFraction CFraction::operator+()
{
	simplify();
	if(nume < 0)
		nume = -nume;
	return *this;
}
//取负重载
CFraction CFraction::operator-()
{
	simplify();
	nume = -nume;
	return *this;
}


//大于号重载
bool operator>(const CFraction &lcf,const CFraction &rcf)
{
	int l_nume = lcf.nume * rcf.deno;
	int r_nume = rcf.nume * lcf.deno;
	int common_deno = lcf.deno * rcf.deno;
	if((l_nume-r_nume) * common_deno > 0) return true;
	return false;
}

//小于号重载
bool operator<(const CFraction &lcf,const CFraction &rcf)
{
	return !(lcf > rcf);
}

//等于重载
bool operator==(const CFraction &lcf,const CFraction &rcf)
{
	return lcf.nume==rcf.nume && lcf.deno == rcf.deno;
}

//不等于重载
bool operator!=(const CFraction &lcf,const CFraction &rcf)
{
	return !(lcf==rcf);
}

//
bool operator>=(const CFraction &lcf,const CFraction &rcf)
{
	if(lcf < rcf) return false;
	return true;
}

//
bool operator<=(const CFraction &lcf,const CFraction &rcf)
{
	if(lcf > rcf) return false;
	return true;
}

int main()
{
	CFraction cf1;
	CFraction cf2;
	cin >> cf1 >> cf2;
	cout << "cf1: "<< cf1 << '\t' << "cf2: "<< cf2 << endl
		 << "cf1 + cf2 : " << cf1+cf2 << endl
		 << "cf1 - cf2 : " << cf1-cf2 << endl
		 << "cf1 * cf2 : " << cf1*cf2 << endl
		 << "cf1 / cf2 : " << cf1/cf2 << endl
		 << " +cf1 :     " << +cf1    << endl
		 << " -cf1 :     " << -cf1    << endl
		 << " +cf2 : 　　" << +cf2    << endl
		 << " -cf2 :     " << -cf2    << endl
		 << " cf1 > cf2? 1/YES 0/NO " << (cf1 > cf2) << endl
		 << " cf1 < cf2? 1/YES 0/NO " << (cf1 < cf2) << endl
		 << " cf1 == cf2? 1/YES 0/NO " << (cf1 == cf2) << endl
		 << " cf1 != cf2? 1/YES 0/NO " << (cf1 != cf2) << endl
		 << " cf1 >= cf2? 1/YES 0/NO " << (cf1 >= cf2) << endl
		 << " cf1 <= cf2? 1/YES 

   
	return 0;
}

贺老师的c++题目对我学习很有帮助，自己以前也学过，为了巩固一下自己所学，找了一些自己以前还不是很明白的题目来回顾c++方面的知识；话说要再把书拿起来（c++primer）看一遍是不太现实了，幸好有像贺老师这样愿意帮助他人学习的好老师，很感谢。而且他出题也是有讲究的。希望广大的朋友们也能从中受益。

参考资料：http://blog.csdn.net/sxhelijian/article/details/7467433

                    http://blog.csdn.net/zollty/article/details/6697174

                   http://blog.csdn.net/sxhelijian/article/details/8723847