has-a关系——包含对象成员的类

#ifndef _STUDENT_H_
#define _STUDENT_H_

#include <iostream>
#include <string>
#include <valarray>

class Student
{
private:
typedef std::valarray<double> ArrayDb;
std::string name;   //contained object
ArrayDb scores;     //contained object

//private method for scores output
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(void) const;
const std::string & Name(void) const;

double & operator[](int i);
const double & operator[](int i) const;

//friends
//inout
friend std::istream & operator>>(std::istream & is, Student & stu); //1 word
friend std::istream & getline(std::istream & is, Student & stu);    //1 line
//output
friend std::ostream & operator<<(std::ostream & os, const Student & stu);
};

#endif

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

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

return 0;
}
}

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

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

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

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

//friend methods
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 <iostream>
#include "student.h"
using std::cin;
using std::cout;
using std::endl;

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;
}
}

const int pupils = 3;
const int quizzes = 5;

int main(void)
{
Student ada[pupils] = {Student(quizzes), Student(quizzes), Student(quizzes)};

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

return 0;
}