STL vector按多字段值排序

 #include <iostream>
 #include <vector>
 #include <string>
 #include <algorithm>
 using namespace std;  

 class Student
 {
 private:
     int id;            // 学号
     string name;        // 姓名
     float eyesight;        // 视力
     float height;        // 身高
     float chinese;        // 语文成绩
     float english;        // 英文成绩
     float math;        // 数学成绩
 public:
     Student(int id, string name, float eyesight, float height, float chinese, float english, float math)
     {
         this->id = id;
         this->name = name;
         this->eyesight = eyesight;
         this->height = height;
         this->chinese = chinese;
         this->english = english;
         this->math = math;
     }

     int get_id()
     {
         return id;
     }

     string get_name()
     {
         return name;
     }

     float get_eyesight()
     {
         return eyesight;
     }

     float get_height()
     {
         return height;
     }

     float get_chinese()
     {
         return chinese;
     }

     float get_english()
     {
         return english;
     }

     float get_math()
     {
         return math;
     }
 };

 // 比较大小的函数(谓词)
 bool comparer(Student& stu_a, Student& stu_b)
 {
     // 按eyesight升序 + height升序排列
     if(stu_a.get_eyesight() != stu_b.get_eyesight())
         return (stu_a.get_eyesight() < stu_b.get_eyesight());
     else
         return (stu_a.get_height() < stu_b.get_height());

     // 按eyesight降序° + height降序排列
     //if(stu_a.get_eyesight() != stu_b.get_eyesight())
     //    return (stu_a.get_eyesight() > stu_b.get_eyesight());
     //else
     //    return (stu_a.get_height() > stu_b.get_height());

     // 按eyesight升序 + height降序排列
     //if(stu_a.get_eyesight() != stu_b.get_eyesight())
     //    return (stu_a.get_eyesight() < stu_b.get_eyesight());
     //else
     //    return (stu_a.get_height() > stu_b.get_height());

     // 按eyesight降序 + height升序排列
     //if(stu_a.get_eyesight() != stu_b.get_eyesight())
     //    return (stu_a.get_eyesight() > stu_b.get_eyesight());
     //else
     //    return (stu_a.get_height() < stu_b.get_height());
 }

 int main(int argc, char** argv)
 {
     vector<Student> vec;
     vec.push_back(Student(, "Dudley", 1.1f, 170.2f, 90.5f, 89.5f, 93.0));
     vec.push_back(Student(, "Chris", 1.1f, 163.4f, 93.5f, 90.0f, 83.5f));
     vec.push_back(Student(, "Bob", 1.5f, 166.6f, 86.0f, 98.5f, 85.0f));
     vec.push_back(Student(, "Andrew", 1.5f, 173.2f, 98.5f, 100.0f, .f));

     // 调用STL中的sort函数，其中的第三个参数就是我们前面定义的，比较两个Student对象大小的函数
     sort(vec.begin(), vec.end(), comparer);

     vector<Student>::iterator iter;
     for(iter = vec.begin(); iter != vec.end(); ++iter)
     {
         cout << (*iter).get_eyesight() << "\t" << (*iter).get_height() << endl;
     }

     return ;
 }