Typedef in a header?

I am trying to do a problem that I can apply to both lists or vectors using an interator, and all I would have to do to change the problem is within a typedef declaration. However it does not work..I was wondering why two things I tried does not work. Can someone help explain this to me please?

This one just tells me no member is defined within the struct. I have no idea what that means though.

Code:

---

#ifndef GUARD_Student_info
#define GUARD_Student_info

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

typedef std::vector<double> homework;

struct Student_info{
        std::string name;
        double midterm, final;
        homework;
};


bool compare(const Student_info&, const Student_info&);
std::istream& read(std::istream&, Student_info&);
std::istream& read_hw(std::istream&, homework&);

#endif

---

This one just can't seem to find the type homework when I refer to it.

Code:

---

#ifndef GUARD_Student_info
#define GUARD_Student_info

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

struct Student_info{
        std::string name;
        double midterm, final;
        typedef 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&, homework&);

#endif

---

Code:

---

struct Student_info{
        std::string name;
        double midterm, final;
        homework;
};

---

homework is a type name. You can't just type a name like int; or double; by itself, because what would be the point? You need to give it a variable name like you did with the other members of your struct.