What is wrong with this code?

[STLreliant]

I am reading Accelerated C++ and I do not understand why this code:

#include<algorithm>
#include <iomanip>
#include<ios>
#include<iostream>
#include<stdexcept>
#include<string>
#include<vector>
#include"grade.h"
#include"student_info.h"
#include<conio.h>
using std::cin;               using std::setprecision;
using std::cout;              using std::sort;
using std::domain_error;      using std::streamsize;
using std::endl;              using std::string;
using std::max;               using std::vector;

int main (){



	vector<student_info> students;
	student_info record;
	string::size_type maxlen = 0; // length of the longest name

	// read and store all of the students data.
	// invariant: students contains all of the student records read so far
	//            maxlen contains the length of the longest name in students
	while (read (cin,record)){
		// find the longest name
		maxlen = max (maxlen, record.name.size ());
		students.push_back (record);
	}

	// alphabetize the student records
	sort (students.begin (), students.end () ,compare);

	// write the names and grades
	for (vector<student_info>::size_type i = 0;i != students.size (); ++i){
// write the name padded on the right to maxlen + 1 characters
		cout<<students [i].name
			<< string (maxlen = 1 - students [i].name.size(), ' ');


		// compute and write the grade
		try {
			double final_grade = grade (students [i]);
			streamsize prec = cout.precision ();;
			cout<< setprecision (3) << final_grade
				<< setprecision (prec);
} catch (domain_error e){
	cout<<e.what ();
		}
		cout<<endl;
	}


_getch (); // note I added this in myself
return 0;


}

with the header files:

#ifndef GUARD_grade_h
#define GUARD_grade_h

// grade.h

#include<vector>
#include"student_info.h"
double grade (double,double,double) ;
double grade (double , double, const std::vector<double>&) ;
double grade (const student_info) ;
#endif 

#ifndef GUARD_median_h
#define GUARD_median_h
// median.h - the final version
#include<vector>

double median (std::vector<double>);


#endif 

and

#ifndef GUARD_student_info
#define GUARD_student_info
// student_info.h header file

#include<iostream>
#include<vector>
#include<string>

struct student_info {


	std::string name;
	double midterm, final;
	std::vector<double> homework;

};

bool compare (const student_info&, const student_info&);
std::istream& read (std::istream, student_info&);
std::istream& read_hw (std::istream&, std::vector<double>&);

#endif 

is yielding this in the output dialog:

1>------ Build started: Project: Revised Grading Program, Configuration: Debug Win32 ------
1> source code.cpp
1>c:\program files\microsoft visual studio 10.0\vc\include\istream(860): error C2248: 'std::basic_ios<_Elem,_Traits>::basic_ios' : cannot access private member declared in class 'std::basic_ios<_Elem,_Traits>'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ios(176) : see declaration of 'std::basic_ios<_Elem,_Traits>::basic_ios'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> This diagnostic occurred in the compiler generated function 'std::basic_istream<_Elem,_Traits>::basic_istream(const std::basic_istream<_Elem,_Traits> &)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]

And also I do not really much understand the error itself. Thanks

[hamsterman]

I think this is because read() has an istream passed by value. It should be by reference. What the error says is that there is something wrong with basic_istream's copy constructor.
I can't explain why the error is so unclear and why copying a stream is not allowed though.

[STLreliant]

Thanks hamsterman, I am not sure how to fix it, does any body have any clue?

[Duthomhas]

Streams have never been copyable. The error exists because the copy constructor is private.

Your read() function should have the type:

std::istream& read (std::istream&, student_info&);

Hope this helps.

[STLreliant]

Should help, I will modify the code tomorrow. Thank You.

[STLreliant]

I changed std::istream& read (std::istream, student_info&); to std::istream& read (std::istream&, student_info&); And it yielded yet another error, It now has a problem with my bool compare and my double grade and yet again an istream error.




I apologise for having to ask again but what exactly should I do, should I move on or should I very hard to fix it (likely to no aveil).