How do I use classes to store and print out student objects

[zhfjE3v7]

Hi, I'm relatively new to C++ and I am trying to dynamically store student objects using classes, but I am getting strange errors when I try to compile it. Here is what I have so far.

student.cpp

#include "Name.h"
#include "Student.h"
#include<iostream>
#include<string>
#include<set>
using namespace std;

int main()
{
	Student s1();
	set<Student *> s;
	while(cin>>s1)
	{
		s.insert(new Student(s1));
	}
	s1.display(cout);
}

Name.h - handles the name of the student

#ifndef NAME_H
#define NAME_H
#include <string>
#include <iostream>
class Name{
    public:
        explicit Name(const std::string& first = "",const std:: string& last = ""):first_(first),last_(last){}
        friend std::ostream& operator<<(std::ostream&, const Name&);
        friend std::istream& operator>>(std::istream&, Name&);
	private:
        std::string first_;
        std::string last_;
};

inline std::ostream& operator<<(std::ostream& os, const Name& n){
    return os << n.first_<< " " << n.last_;
}
inline std::istream& operator>>(std::istream& is, Name& n){
    std::string first,last;
    if(is >> first >> last ){
        n.first_ = first;
        n.last_ = last;
    }
    else
        is.setstate(std::ios_base::failbit);
    return is;
}
#endif 

Student.h - stores a student along with their grades for all their classes

#ifndef STUDENT_H
#define STUDENT_H
#include<string>
#include<iostream>
#include<map>
#include "Name.h"
typedef std::map<std::string, int> GradeMap;

class Student {
public:
	Student(const std::string id="", const Name& name = Name(), GradeMap grades = GradeMap());
	Student(const Student& s):id_(s.id_), name_(s.name_){}
	virtual ~Student(){}
	friend std::istream& operator>>(std::istream& is, Student& s);
	
	virtual void display(std::ostream& os) const{
		os << "ID: " << id_ << "Name: " << name_ << std::endl;
		
		for(std::map<std::string, int>::const_iterator it = grades_.begin(); it != grades_.end(); ++it)
			os<<it->first<<' '<<it->second;
	}
	
private:
	std::string id_;
	Name name_;
	GradeMap grades_;

};

inline std::istream& operator>>(std::istream& is, Student& s)
{
	std::string id;
	std::string key;
	int grade;
	int count = 0;
	Name name;
	
	if(is>>id>>name>>count){
		s.id_ = id;
		s.name_ = name;
	}
	
	for(int i = 0; i < count; i++)
	{
		if(is>>key>>grade)
		{
			s.grades_[key] = grade;
		}
	}
}
#endif 

Here is the text file I am testing my program with using I/O redirection. The first row is the id of the student followed by their name and the number of courses they have taken.

111111111
john doe
3
comp2510 25
phys2525 60
chem3512 45
222222222
jane smith
2
bio1510 90
eng2514 85

Here is the error that I am getting.

student.cpp: In function 'int main()':
student.cpp:12:13: error: ambiguous overload for 'operator>>' in 'std::cin >> s1
'
/usr/lib/gcc/i686-pc-cygwin/4.5.3/include/c++/istream:120:7: note: candidates ar
e: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_Char
T, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)
(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char, _Tr
aits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_ty
pe = std::basic_istream<char>] <near match>
/usr/lib/gcc/i686-pc-cygwin/4.5.3/include/c++/istream:124:7: note:
   std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_Char
T, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std
::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char, _Traits = s
td::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std
::basic_istream<char>, std::basic_istream<_CharT, _Traits>::__ios_type = std::ba
sic_ios<char>] <near match>
/usr/lib/gcc/i686-pc-cygwin/4.5.3/include/c++/istream:131:7: note:
   std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_Char
T, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char,
 _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istrea
m_type = std::basic_istream<char>] <near match>
student.cpp:14:26: error: no matching function for call to 'Student::Student(Stu
dent (&)())'
Student.h:12:2: note: candidates are: Student::Student(const Student&)
Student.h:11:2: note:                 Student::Student(std::string, const Name&,
 GradeMap)
student.cpp:16:5: error: request for member 'display' in 's1', which is of non-c
lass type 'Student()'

any help would be appreciated.

[zhfjE3v7]

bump

[long double main]

Could you post the first 20 or so lines of student.cpp?
That's where the errors seem to be coming from...

[zhfjE3v7]

What i posted here is all i have....

[zhfjE3v7]

bump

[zb0S216C]

1) In Name.h, the use of explicit will be ignored by the compiler. Consider reading up on that.
2) In Student.h, Student::display doesn't need to be virtual.
3) In Student.h, instead of overloading the operator as a friend, why not overload it internally?

Can you post the contents of Student.cpp? It seems some of the errors are originating from there.

_Wazzak

[zhfjE3v7]

Oh sorry I mistyped my first post its suppose to be student.cpp

also is there a difference if i overload operator internally? Because i thought it would be less clutter in the class.

[zb0S216C]

In Student.cpp, on line 10, s1 is not an object declaration but a function prototype. It returns a Student object, and takes no arguments. Remove the parentheses. C++ allows function prototypes within local scopes, which is why you never get an error from such a declaration.

Still in Student.cpp, there's a memory leak - multiple, actually. Every call to new/new[] must have a corresponding call to delete/delete[]. As I've stated in another thread, C++ doesn't have a garbage collection system, so the programmer is in charge of how the memory is used and when it's released.

ogglock wrote:

also is there a difference if i overload operator internally?

An internally overloaded operator has precedence over externally overloaded operators (assuming that the operators operate on the object in question). Personally, I prefer to overload an operator internally - it's more explicit.

_Wazzak

[zhfjE3v7]

Thanks for responding so fast. I tried out what you said, but it still can't compile

here is the student.cpp

#include "Name.h"
#include "Student.h"
#include<iostream>
#include<string>
#include<set>
using namespace std;

int main()
{
	Student s1;
	set<Student *> s;
	while(cin>>s1)
	{
		s.insert(new Student(s1));
	}
	s1.display(cout);
	
	for(set<Student *>::iterator it = s.begin(); it != s.end();++it)
		s.clear();
}

and the error I'm getting is

/cygdrive/c/Users/Michael/AppData/Local/Temp/cc7cD3Z4.o:student.cpp:(.text+0xf7)
: undefined reference to `Student::Student(std::basic_string<char, std::char_tra
its<char>, std::allocator<char> >, Name const&, std::map<std::basic_string<char,
 std::char_traits<char>, std::allocator<char> >, int, std::less<std::basic_strin
g<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pa
ir<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const,
 int> > >)'
collect2: ld returned 1 exit status 

I'm starting to think that the problem is in my student.h file because of the map that I am implementing there.

[zb0S216C]

Where's the definition for:
Student(const std::string id="", const Name& name = Name(), GradeMap grades = GradeMap())? I can't see it.

_Wazzak

[zhfjE3v7]

you mean something like

Student(const std::string id="", const Name& name = Name(),const GradeMap & grades = GradeMap()):id_(id),name_(name),grades_(grades){}

?

but does that mean I don't need the

Student(const Student& s):id_(s.id_), name_(s.name_){}

constructor anymore?

EDIT:

okay ignore what I said above I managed to find the root cause of my problem. It is the line

while(cin>>s1)
{
      //do whatever
}

which is weird because it works fine if i do

cin>>s1;