I have the following class that I can't compile in g++. It comes from the book C++ Primer Plus
Code:
#ifndef STUDENT_H_
#define STUDENT_H_
#include <iostream>
#include <valarray>
#include <string>
class Student: private std::string, private std::valarray<double>
{
private:
typedef std::valarray<double> ArrayDb;
std::ostream & arr_out(std::ostream & os) const;
public:
Student()
: std::string("Null Student"),ArrayDb() {};
Student( const std::string & s)
: std::string(s), ArrayDb() {};
Student( int n)
: std::string(), ArrayDb(n) {};
Student(const std::string & s, int n)
: std::string(s), ArrayDb(n) {};
Student ( const std:: string & s, const ArrayDb & a)
: std::string(s), ArrayDb(a) {};
Student( const std:: string & s, const double * pd, int n)
: std::string(s), ArrayDb(pd,n) {};
~Student() {};
double average() const;
double & operator[](int i);
double operator[](int i) const;
const std::string & Name() const;
// Friends
friend std::istream & operator>>(std::istream & is, const Student & stu);
friend std::istream & getline(std::istream & is, const Student & stu);
friend std::ostream & operator<<(std::ostream & os, const Student & stu);
};
#endif
Code:
#include "student.h"
using std::ostream;
using std::endl;
using std::istream;
using std::string;
// public mehods
double Student::average() const
{
if ( ArrayDb::size() > 0)
return ArrayDb::sum() / ArrayDb::size();
else
return 0;
}
const string & Student::Name() const
{
return ( const string & ) * this;
}
double & Student::operator[](int i)
{
return ArrayDb::operator[](i);
}
// private method
ostream & Student::arr_out(ostream & os) const
{
int i;
int lim = ArrayDb::size();
if( lim > 0 )
{
for (i = 0; i < lim ; i++)
{
os << ArrayDb::operator[](i) << " ";
if( i % 5 == 4)
os << endl;
}
if( i % 5 != 0)
os << endl;
}
else
os << "empty array";
return os;
}
// friends
istream & operator>>(istream & is, const Student & stu)
{
is >> (string &) stu;
return is;
}
istream & getline(istream & is, const Student & stu)
{
getline(is, (string &) stu);
return is;
}
ostream & operator<<(ostream & os, const Student stu)
{
os << "Scores for " << (const string &) stu << ":\n";
stu.arr_out(os);
return os;
}
Code:
#include <iostream>
#include "student.h"
using std::cin;
using std::cout;
using std::endl;
void set(Student & sa , int n);
const int pupils = 3;
const int quizzes = 3;
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 << "Enter Student name: ";
getline(cin, sa);
cout << "Enter " << n << "quiz scores: \n";
for ( int i = 0; i < n ; i++)
cin >> sa[i];
while ( cin.get() != '\n')
continue;
}
When I tried to compile, i get
Code:
student.cpp: In function ‘std::ostream& operator<<(std::ostream&, Student)’:
student.cpp:27: error: ‘std::ostream& Student::arr_out(std::ostream&) const’ is private
student.cpp:64: error: within this context
the "student.cpp:64" is the line:
Code:
ostream & operator<<(ostream & os, const Student stu)
{
os << "Scores for " << (const string &) stu << ":\n";
stu.arr_out(os);
return os;
}
Why didn't it compile? Should i make the method public instead?