【C++ Primer Plus习题】12.3

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问题:

解答:
main.cpp

#include <iostream>
#include "stock20.h"
using namespace std;

const int STKS = 4;

int main()
{
	Stock stocks[STKS] =
	{
		Stock("NanoSmart",12,20.0),
		Stock("Boffo Objects",200,2.0),
		Stock("Monnlithic Obelisks",130,3.25),
		Stock("Fleep Enterpriser",60,6.5)
	};
	cout << "股票持有:" << endl;
	int st;
	for (st = 0; st < STKS; st++)
	{
		//stocks[st].show();
		cout << stocks[st] << endl;
	}
	const Stock* top = &stocks[0];
	for (st = 1; st < STKS; st++)
	{
		top = &top->topval(stocks[st]);
	}
	cout << "\n最有价值的持股:\n";
	//top->show();
	cout << *top << endl;

	return 0;
}

stock20.h

#pragma once
#include <iostream>
using namespace std;

class Stock
{
private:
	//string company;
	char* company;
	int shares;
	double share_val;
	double total_val;
	void set_tot() { total_val = shares * share_val; }
public:
	Stock();
	//Stock(const string& co, long n = 0, double pr = 0.0);
	Stock(const char* co, long n = 0, double pr = 0.0);

	Stock(const Stock& s);
	Stock& operator=(const Stock& s);
	~Stock();
	void buy(long num, double price);
	void sell(long num, double price);
	void update(double price);
	void show()const;
	const Stock& topval(const Stock& s)const;

	friend ostream& operator<<(ostream& os, const Stock& s);
};

stock20.cpp

#include "stock20.h"


Stock::Stock()
{
	company = NULL;
	shares = 0;
	share_val = 0.0;
	total_val = 0.0;
}

Stock::Stock(const Stock& s)
{
	int len = strlen(s.company);
	company = new char[len + 1];
	strcpy_s(company, len + 1, s.company);
	shares = s.shares;
	share_val = s.share_val;
	total_val = s.total_val;
}

Stock& Stock::operator=(const Stock& s)
{
	if (this == &s)return *this;
	if (company)delete[] company;
	int len = strlen(s.company);
	company = new char[len + 1];
	strcpy_s(company, len + 1, s.company);
	shares = s.shares;
	share_val = s.share_val;
	total_val = s.total_val;
	return *this;
}

//Stock::Stock(const string& co, long n, double pr)
//{
//	company = co;
//	if (n < 0)
//	{
//		cout << "股份不能为负;" << company << " 的股份设置为0" << endl;
//		shares = 0;
//	}
//	else
//	{
//		shares = n;
//	}
//	share_val = pr;
//	set_tot();
//}

Stock::Stock(const char* co, long n, double pr)
{
	company = new char[strlen(co) + 1];
	strcpy_s(company, strlen(co) + 1, co);
	if (n < 0)
	{
		cout << "股份不能为负;" << company << " 的股份设置为0" << endl;
		shares = 0;
	}
	else
	{
		shares = n;
	}
	share_val = pr;
	set_tot();
}
Stock::~Stock()
{
	if (company)
	{
		delete[] company;
	}
}
void Stock::buy(long num, double price)
{
	if (num < 0)
	{
		cout << "购买股份的数量不能为负." << endl;
		cout << "事物终止." << endl;
	}
	else
	{
		shares += num;
		share_val = price;
		set_tot();
	}
}
void Stock::sell(long num, double price)
{
	if (num < 0)
	{
		cout << "出售股份的数量不能为负." << endl;
		cout << "事物终止." << endl;
	}
	else if(num>shares)
	{
		cout << "您不能售卖股份超过您所拥有的." << endl;
		cout << "事物终止." << endl;
	}
	else
	{
		shares -= num;
		share_val = price;
		set_tot();
	}
}
void Stock::update(double price)
{
	share_val = price;
	set_tot();
}
void Stock::show()const
{
	ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);
	streamsize prec = cout.precision(3);
	
	cout << "Company: " << company << " Shares:" << shares << endl;
	cout << " Share Price: $" << share_val;
	cout.precision(2);
	cout << " Total Worth: $" << total_val << endl;

	cout.setf(orig, ios_base::floatfield);
	cout.precision(prec);
}

const Stock& Stock::topval(const Stock& s)const
{
	if (s.total_val > total_val)
	{
		return s;
	}
	else
	{
		return *this;
	}
}

ostream& operator<<(ostream& os, const Stock& s)
{
	ios_base::fmtflags orig = os.setf(ios_base::fixed, ios_base::floatfield);
	streamsize prec = os.precision(3);
	os << "Company: " << s.company << " Shares:" << s.shares << endl;
	os << " Share Price: $" << s.share_val;
	os.precision(2);
	os << " Total Worth: $" << s.total_val << endl;

	os.setf(orig, ios_base::floatfield);
	os.precision(prec);

	return os;
}