包含对象的成员类

将学生简化成姓名和一组考试分数后，可以使用一个包含两个成员的类来表示它：一个成员用于表示姓名，另一个成员用于表示分数。对于姓名，可以使用字符数组束表示，但这将限制姓名的长度。当然，也可以使用char指针和动态内存分配，然而正如第12章指出的，这将要求提供大量的支持代码。-种更
好的方法是，使用一个由他人开发好的类的对象来表示。例如，可以使用一个String类(参见第12章)或
标准C++的string 类的对象来表示姓名。较简单的选择是使用string 类，因为C++库提供了这个类的所有

#ifndef STUDENTC_H_
#define STUDENTC_H_

#include 
#include 
#include 
class Student
{
private:
	typedef std::valarray ArrayDb;
	std::string name;
	ArrayDb scores;
	//私有方法，将scores输出
	std::ostream & arr_out(std::ostream & os) const;

public:
	Student() : name("Null Student"), scores() {}
	explicit Student(const std::string & s)
		: name(s), scores() {}
	explicit Student(int n) : name("Nully"), scores(n) {}
	Student(const std::string & s, int n)
		: name(s), scores(n) {}
	Student(const std::string & s, const ArrayDb & a)
		: name(s), scores(a) {}
	Student(const char * str, const double * pd, int n)
		: name(str), scores(pd, n) {}
	~Student() {}
	double Average() const;
	const std::string & Name() const;
	double & operator[](int i);
	double operator[](int i) const;

	//友元
	//input
	friend std::istream & operator>>(std::istream & is, Student & stu);
	friend std::istream & getline(std::istream & is, Student & stu);
	//output
	friend std::ostream & operator<<(std::ostream & os, const Student & stu);
};
#endif // !STUDENTC_H_

#include "studentc.h"
using std::ostream;
using std::endl;
using std::istream;
using std::string;

//private
ostream & Student::arr_out(std::ostream & os) const
{
	int i;
	int lim = scores.size();
	if (lim > 0)
	{
		for (i = 0; i < lim; i++)
		{
			os << scores[i] << " ";
			if (i % 5 == 4)
				os << endl;
		}
		if (i % 5 != 0)
			os << endl;
	}
	else
		os << " empty array ";
	return os;
}

//public
double Student::Average() const
{
	if (scores.size() > 0)
		return scores.sum();
	else
		return 0;
}

const std::string & Student::Name() const
{
	return name;
}

double & Student::operator[](int i)
{
	return scores[i];
}

double Student::operator[](int i) const
{
	return scores[i];
}

//friends
istream & operator>>(istream & is, Student & stu)
{
	is >> stu.name;
	return is;
}

istream & getline(istream & is, Student & stu)
{
	getline(is, stu.name);
	return is;
}

ostream & operator<<(ostream & os, const Student & stu)
{
	os << "Scores for " << stu.name << ":n";
	stu.arr_out(os);
	return os;
}

#include 
#include "studentc.h"
using std::cin;
using std::cout;
using std::endl;

void set(Student & sa, int n);
const int pupils = 3;
const int quizzes = 5;

int main()
{
	Student ada[pupils] = { Student(quizzes), Student(quizzes), Student(quizzes) };
	int i;
	for (i = 0; i < pupils; ++i)
		set(ada[i], quizzes);
	cout << "nStudent List:n";
	for (i = 0; i < pupils; ++i)
		cout << ada[i].Name() << endl;
	cout << "nResults:";
	for (i = 0; i < pupils; ++i)
	{
		cout << endl << ada[i];
		cout << "average: " << ada[i].Average() << endl;
	}
	cout << "Done.n";
	return 0;
}

void set(Student & sa, int n)
{
	cout << "Please enter the student's name: ";
	getline(cin, sa);
	cout << "Please enter " << n << " quiz scores:n";
	for (int i = 0; i < n; i++)
		cin >> sa[i];
	while (cin.get() != 'n')
		continue;
}