studentinfo.cpp

#include "studentinfo.h"

bool compare( const StudentInfo& x, const StudentInfo& y )
{
    return x.name() < y.name();
}

StudentInfo::StudentInfo() : midterm(0), final(0) {}
StudentInfo::StudentInfo( double _midterm, double _final, std::vector<double> _homework ) {
    this->final = _final;
    this->midterm = _midterm;
    this->homework = _homework;
}

studentinfo.h

#ifndef STUDENTINFO_H
#define STUDENTINFO_H

#include <istream>
#include <string>
#include <vector>

class StudentInfo
{
public:

    StudentInfo();
    StudentInfo( double _midterm, double _final, std::vector<double>& _homework );

    double grade() const;
    std::istream& read(std::istream&);
    std::string name() const { return _name; }

private:
    std::string _name;
    double midterm, final;
    std::vector<double> homework;
};

bool compare( const StudentInfo& x, const StudentInfo& y );

#endif // STUDENTINFO_H

you can replace this constructor:

StudentInfo::StudentInfo( double _midterm, double _final, std::vector<double> _homework ) {
    this->final = _final;
    this->midterm = _midterm;
    this->homework = _homework;
}

by this (write this in the header file):

/* ... */
public:
StudentInfo( double _midterm, double _final, std::vector<double> _homework )
  : final(_final), midterm(_midterm), homework(_homework) {}