C++Primer Plus 第十四章代码重用：编程练习,第一题

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C++Primer Plus 第十四章代码重用：编程练习,第一题

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14.7 编程练习

题.

Wine 类有一个 sting类对象成员(参见第4章)和一个Pair 对象(参见本章);其中前者用于存储葡萄酒的名称，而后者有2个valamray<inp对象(参见本章)，这两个valanay对象分别保存了葡萄酒的酿造年份和该年生产的瓶数。例如，Pair的第1个valarray对象可能为1988、1992和1996年，第2个valarray对象可能为 24、48和144瓶。Wine 最好有1个imnt 成员用于存储年数。另外，一些typedef可能有助于简化编程工作:

typedef std::valarray<int> ArrayInt;
typedef Pair<ArrayInt,ArrayInt> PairArray;

这样，PairAmray 表示的是类型 Pair<std::valarray,std:valarray>。使用包含来实现 Wine 类，并用一个简单的程序对其进行测试。Wine 类应该有一个默认构造函数以及如下构造函数:

//initialize label to l,number of years to y,
//vintage years to yrl],bottles to bot[]
wine(const char*l,int y,const int yr[],const int bot[]);
//initialize label to l,number of years to y.
//create array objects of length y
Wine(const char*l int y);

Wimne 类应该有一个 GetBotles()方法，它根据 Wine 对象能够存储儿种年份(y)，提示用户输入年份和瓶数。方法 Label()返回一个指向葡萄酒名称的引用。sum()方法返回 Pair 对象中第二个 valamay对象中的瓶数总和。测试程序应提示用户输入葡萄酒名称、元素个数以及每个元素存储的年份和瓶数等信息。程序将使用这些数据来构造一个 Wine 对象，然后显示对象中保存的信息。
下面是一个简单的测试程序:

// pe14-1.cpp--using Wine class with containment
#include <iostream>
#include "winec.h"
int main (void )
{using std::cin;using std::cout;using std::endl;cout <<"Enter name of wine:";char lab[50];cin.getline(lab，50);cout <<"Enter numberofyears:";int yrs;cin >>yrs;Wine holding(lab,yrs);//store label,years,give arrays yrs elementsholding.GetBottles();//solicit input for year,bottle countholding.show();//display object contentsconst int YRs =3;int y[YRs]={1993，1995，1998};int b[YRs]={48，60，72};
//create new object,initialize using data in arrays y and b
Wine more("Gushing Grape Red",YRS,y，b);
more.Show();
cout << "Total bottles for "<< more.Label()//use Label()method<<":"<< more.sum()<< endl;//use sum()method
cout << "Bye\n";return 0;
}

答

仅供参考

头文件定义

#pragma once#include <iostream>
#include <valarray>namespace n_wine
{using std::string;using std::pair;using std::valarray;class Wine{private:typedef valarray<unsigned> UnsignedArray;public:Wine (const string& name, unsigned years_total, unsigned vintage_years[], unsigned bottles_total[]);Wine (const string& name, unsigned years_total);const string& getLabel (void) const;void getBottles (void);void show (void) const;unsigned sum (void) const;private:const string	name_;const unsigned	years_total_;	// 年份数量pair<UnsignedArray, UnsignedArray>	vintage_year_and_bottles_total_;	// 酿造年份与对应瓶数};
}

方法的实现

#include "Wine.h"namespace n_wine
{using std::cin;using std::cout;using std::endl;using std::cerr;// ====================================// 公有成员函数// ====================================Wine::Wine (const string& name, unsigned years_total, unsigned vintage_years[], unsigned bottles_total[]):	name_(name),years_total_(years_total), vintage_year_and_bottles_total_(UnsignedArray(vintage_years, years_total), UnsignedArray(bottles_total, years_total)){;}Wine::Wine (const string& name, unsigned years_total):	name_(name),years_total_(years_total), vintage_year_and_bottles_total_(UnsignedArray(years_total), UnsignedArray(years_total)){;}const string&Wine::getLabel (void) const{return (name_);}voidWine::getBottles (void){cout << "Enter "<< name_ << " data for " << years_total_ << " year(s) ---- \n";for (unsigned i = 0; i < years_total_; ++i) {unsigned	vintage_year;cout << "Enter year: ";cin >> vintage_year;if (!cin) {cerr << "ERREOR! " << __FILE__ << ", " << __LINE__ << endl;exit(EXIT_FAILURE);}vintage_year_and_bottles_total_.first[i] = vintage_year;unsigned	bottles_total;cout << "Enter bottles for that year: ";cin >> bottles_total;if (!cin) {cerr << "ERREOR! " << __FILE__ << ", " << __LINE__ << endl;exit(EXIT_FAILURE);}vintage_year_and_bottles_total_.second[i] = bottles_total;}}voidWine::show (void) const{cout << "Wine: " << name_ << '\n';cout << '\t' << "Year" << '\t' << "Bottles" << '\n';for (unsigned i = 0; i < years_total_; ++i) {cout << '\t' << vintage_year_and_bottles_total_.first[i] << '\t' << vintage_year_and_bottles_total_.second[i] << endl;}}unsignedWine::sum (void) const{return (vintage_year_and_bottles_total_.second.sum());}
}