目录

以一个股票为例

如何使用类？注意看usestock00.cpp代码

usestock00.cpp

stock00.h

stock00.cpp

C++如何设定数字输出格式？看stock00.cpp这个show_pre（）函数

函数解读

程序运行结果

以一个股票为例

• stock00.cpp 是stock00.h类函数实现
• usestock00.cpp就是主函数

如何使用类？注意看usestock00.cpp代码

usestock00.cpp

      //uesstock00.cpp -- 客户端程序
      //记得和stock00.cpp stock00.h编译
      #include<iostream>
      #include"stock00.h"
      int main()
      {
      	Stock one;
      	one.acquire("BWM", 12, 25.12);
      	one.show();
      	one.show_pre();
      	one.buy(15, 18.125);
      	one.show();
      	one.show_pre();
      	one.sell(400, 20.00);
      	one.show();
      	one.show_pre();
      	one.buy(300000, 40.125);
      	one.show();
      	one.show_pre();
      	one.sell(300000, 0.125);
      	one.show();
      	one.show_pre();
      }
  
 

stock00.h

      // stock00.h -- Stock class interface
      // 版本 00 类的声明
      #ifndef STOCK00_H_
      #define STOCK00_H_
      #include<string>
      class Stock
      {
      public:
     	void acquire(const std::string & co, long n, double pr);
     	void buy(long num, double price);
     	void sell(long num, double price);
     	void update(double price);
     	void show();
     	void show_pre();
      private:
     	std::string company;
     	long shares;  //股票数量
     	double share_val;  // 每股的价格
     	double total_val;   //股票的总价格
     	void set_tot()
      	{
      		total_val = shares*share_val;
      	}
      };
      #endif
  
 

stock00.cpp

      // stock00.cpp -- 对类stock00.h进行函数描述
      // 版本还是00
      #include<iostream>
      #include"stock00.h"
      void Stock::acquire(const std::string & co, long n, double pr)
      {
      	company = co;
     	if (n < 0)
      	{
     		std::cout << "股票数量不能设置为0; "
      			<< company << " shares set to 0. \n";
      		shares = 0;
      	}
     	else
      	{
      		shares = n;
      	}
      	share_val = pr;
      	set_tot();
      }
      void Stock::buy(long num, double price)
      {
     	if (num < 0)
      	{
     		std::cout << "股票购买数量不能是负数。" << "交易被终止了！！\n";
      	}
     	else
      	{
      		shares += num;
      		share_val = price;
      		set_tot();
      	}
      }
      void Stock::sell(long num, double price)
      {
     	using std::cout;
     	if (num < 0)
      	{
     		cout << "股票不能卖负数，你脑筋有问题？" << "中断交易了";
      	}
     	else if (num>shares)
      	{
     		cout << "你自己有几个股票不清楚吗？你能卖比自己持有还多的股票吗？！" << "交易终止！！！";
      	}
     	else
      	{
      		shares -= num;
      		share_val = price;
      		set_tot();
      	}
      }
      void Stock::update(double price)
      {
      	share_val = price;
      	set_tot();
      }
      void Stock::show()
      {
     	std::cout << "Company: " << company
      		<< " Shares: " << shares << "\n"
      		<< " Share Price: $ " << share_val
      		<< "Total Worth: $" << total_val << "\n";
      }
      // 设置输出的数字格式
      void Stock::show_pre()
      {
     	using std::cout;
     	using std::ios_base;
     	//设置格式为#.###
      	ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);
     	std::streamsize prec = cout.precision(3);
     	cout << "Company: " << company
      		<< " Shares: " << shares << '\n';
     	cout << " Share Price: $ " << share_val;
     	//设置格式为#.##
     	cout.precision(2);
     	cout << " Total Worth: $" << total_val << '\n';
     	//重新恢复原来的格式
     	cout.setf(orig, ios_base::floatfield);
     	cout.precision(prec);
      }
  
 

C++如何设定数字输出格式？看stock00.cpp这个show_pre（）函数

      // 设置输出的数字格式
      void Stock::show_pre()
      {
     	using std::cout;
     	using std::ios_base;
     	//设置格式为#.###
      	ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);
     	std::streamsize prec = cout.precision(3);
     	cout << "Company: " << company
      		<< " Shares: " << shares << '\n';
     	cout << " Share Price: $ " << share_val;
     	//设置格式为#.##
     	cout.precision(2);
     	cout << " Total Worth: $" << total_val << '\n';
     	//重新恢复原来的格式
     	cout.setf(orig, ios_base::floatfield);
     	cout.precision(prec);
      }
  
 

函数解读

使用ios_base设定了小数点后三位显示

然后又设定小数点后2位显示

然后最后恢复默认设置

程序运行结果

文章来源: kings.blog.csdn.net，作者：人工智能博士，版权归原作者所有，如需转载，请联系作者。

原文链接：kings.blog.csdn.net/article/details/98063650