2020/3/4

网课+作业：5小时

cf：2小时

树哈希知识学习:1小时

英语单词：1小时

回顾c++第10章：1小时

#include"iostream"
#include"cstring"

class Stock
{
private:
    char company[30];
    int shares;
    double share_val;
    double total_val;
    void set_tot(){///类声明常将短小的成员函数作为内联函数
        total_val = shares * share_val;
    }
public:///定义于类声明中的函数都将自动成为内联函数
    Stock();
    Stock(const char *co,int n,double pr);///构造函数
    ~Stock();///析构函数
    void buy(int num,double price);
    void sell(int num,double price);
    void update(double price);
    void show();
    const Stock & topval(const Stock & s) const;
};

Stock :: Stock(const char * co,int n,double pr)
{
   // std::cout << "Constructor using "　;
    std::strncpy(company,co,29);
    company[29] = '';
    if(n < 0)
    {
        std :: cerr << "Number of shares can't be negative. "
        << company << " shares set to 0.
";
        shares = 0;
    }
    else
        shares = n;
    share_val = pr;
    set_tot();
}
Stock :: Stock()
{
    std :: cout <<" Default constructor called
";
    std :: strcpy(company,"no name");
    shares = 0;
    share_val = 0.0;
    total_val = 0.0;
}
Stock :: ~Stock()
{
    std :: cout << "Bye, " << company << "!
";
}
void Stock :: buy(int num,double price)
{
    if(num < 0)
    {
        std:: cerr<<"Number of shares purchased can't be negative. "
        << "Transaction is aborted.
";
    }
    else {
       shares += num;
       share_val = price;
       set_tot();
    }
}
void Stock::sell(int num,double price)
{
    using std::cerr;
    if(num < 0)
    {
        cerr << "Number of shares sold can't be negative."
        << "Transaction is aborted.
";
    } else if(num > shares)
    {
        cerr << "You can't sell more than you have! "
        << "Transaction is aborted.
";
    } else {
        shares -= num;
        share_val = price;
        set_tot();
    }
}

void Stock :: update(double price)
{
    share_val = price;
    set_tot();
}
void Stock::show()
{
    using std :: cout;
    using std :: endl;
    cout << "Company: " << company << " Shares: "
    << shares << endl <<" Share Price: $" << share_val
    << " Total Worth: $" << total_val << endl;
}
const Stock & Stock :: topval(const Stock & s)const
{
    if(s.total_val > total_val) return s;
    else return *this;
}
int main()
{
    using std :: cout;
    using std :: ios_base;
    cout.precision(2);
    cout.setf(ios_base :: fixed,ios_base :: floatfield);
    cout.setf(ios_base::showpoint);

    cout << "Using constructors to create new objects
";
    Stock stock1("NanoSmark",12,20.0);
    stock1.show();
    Stock stock2 = Stock("Boffo Objects",2,2.0);
    stock2.show();

    cout << "Assigning stock1 to stock2: 
";
    stock2 = stock1;
    cout << "Listing stock1 ans stock2: 
";
    stock1.show();
    stock2.show();
    cout << "Using a constructor to reset an object
";
    stock1 = Stock("Nofty Foods",10,50.0);///这里注意，因stock1是有值了的
    ///所以这里并不是stock1再次调用构造函数，而是有一个匿名对象赋值给
    ///stock1，赋值完成后，该匿名对象执行析构函数
    cout << "Revised stock1: 
";
    stock1.show();
    cout << "Done
";

    const Stock land = Stock("Kludgehorn Properties");
    //land.show();///注意这条语句会出错，因为无法保证，show函数，不对land进行更改
    ///除非在定义show()函数的时候定义为：void show() const;保证函数不会修改调用对象

    return 0;
}