C++PrimerPlus第十一章类的使用 :练习6 关系运算符的重载

6.重新编写 Stonewt类(程序清单 11.16和程序清单11.17),重载全部6个关系运算符。运算符对 pounds成员进行比较，并返回一个bool值。
    编写一个程序，它声明一个包含6个Stonewt对象的数组，并在数组声明中初始化前3个对象。然后使用循环来读取用于设置剩余3个数
    组元素的值。接着报告最小的元素、最大的元素以及大于或等于11英石的元素的数量(最简单的方法是创建一个 Stonewt对象，
    并将其初始化为11英石，然后将其同其他对象进行比较)。

关系运算符，有6种关系，分别为小于、大于、 小于等于 、 大于等于 、 等于 、不等于

所以这里就重写这六种关系运算符，

头文件定义看一下

#ifndef STONEWT_H_
#define STONEWT_H_
class Stonewt
{
private:
	enum { Lbs_per_stn = 14 };	//pouns per stone 转换因子
	int stone;					//whole stone  英石 
	double pds_left;			//fractional pounds
	double pounds;				//entire weight in pounds 磅

public:
	Stonewt(double lbs);			//constructor for double pounds
	Stonewt(int stn, double lbs);	//constructor for stone,lbs
	Stonewt();						//default constructor 
	~Stonewt();
	void show_lbs()const;			//show weight in pounds format
	void show_stn()const;			//show weight in stone format
	bool operator<(Stonewt& t);
	bool operator<=(Stonewt& t);
	bool operator>(Stonewt& t);
	bool operator>=(Stonewt& t);
	bool operator=(Stonewt& t);
	bool operator!=(Stonewt& t);
};

#endif // !STONEWT_H_

实现的方法

//stonewt.cpp -- for pe11-6
#if 1



#include<iostream>
#include"stonewt.h"
using std::cout;

//construct Stonewt object from double value
Stonewt::Stonewt(double lbs)
{
	stone = int(lbs) / Lbs_per_stn;//integer division
	pds_left = int(lbs) % Lbs_per_stn + lbs - int(lbs);
	pounds = lbs;
}


//construct Stonewt object from stone,double values
Stonewt::Stonewt(int stn, double lbs)
{
	stone = stn;
	pds_left = lbs;
	pounds = stn * Lbs_per_stn + lbs;
}


//default construct Stonewt wt = 0
Stonewt::Stonewt()
{
	stone = pounds = pds_left = 0;
}

//destructor
Stonewt::~Stonewt()
{

}

//show weight in stones
void Stonewt::show_stn()const
{
	cout << stone << " stone, " << pds_left << " pounds\n";
}

//show weight in pounds
void Stonewt::show_lbs()const
{
	cout << pounds << " pounds\n";
}

//重载关系运算符

bool Stonewt::operator<(Stonewt& t)
{
	return this->pounds < t.pounds;
}
bool Stonewt::operator<=(Stonewt& t)
{
	return this->pounds <= t.pounds;
}
bool Stonewt::operator>(Stonewt& t)
{
	return this->pounds > t.pounds;
}
bool Stonewt::operator>=(Stonewt& t)
{
	return this->pounds >= t.pounds;
}
bool Stonewt::operator==(Stonewt& t)
{
	return this->pounds == t.pounds;
}
bool Stonewt::operator!=(Stonewt& t)
{
	return this->pounds != t.pounds;
}

#endif // 0

测试函数

#pragma region 第十一章练习6.cpp
程序清单
//xxx.cpp -- xxx
#if 1
#include <iostream>
#include"stonewt.h"
using namespace std;

int main()
{
	Stonewt stonewtArr[6] = { 1,2,3,0,0,0 };

	for (int i = 0; i < 3; i++)
	{
		stonewtArr[i + 3] = int(11 + i);
	}

	for (int i = 0; i < 6; i++)
	{
		stonewtArr[i].show_lbs();
	}

	Stonewt stTemp(11);
	Stonewt stMax(-9999);
	Stonewt stMin(9999);
	int cntNum = 0;
	stTemp.show_lbs();
	stMax.show_lbs();
	stMin.show_lbs();
	for (int i = 0; i < 6; i++)
	{
		if (stTemp >= stonewtArr[i])
		{
			cntNum++;
		}
		if (stonewtArr[i]>stMax)
		{
			stMax = stonewtArr[i];
		}
		if (stonewtArr[i]<stMin)
		{
			stMin = stonewtArr[i];
		}
	}
	cout << "最大值，最小值，和大于11石英(重载是的磅，所以这里暂时处理磅)的数量分别为";
	stMax.show_lbs();
	stMin.show_lbs();
	cout << cntNum << endl;
}
#endif
#pragma endregion