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(4, "Dudley", 1.1f, 170.2f, 90.5f, 89.5f, 93.0));
    vec.push_back(Student(3, "Chris", 1.1f, 163.4f, 93.5f, 90.0f, 83.5f));
    vec.push_back(Student(2, "Bob", 1.5f, 166.6f, 86.0f, 98.5f, 85.0f));
    vec.push_back(Student(1, "Andrew", 1.5f, 173.2f, 98.5f, 100.0f, 100.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() << "	" << (*iter).get_height() << endl;
    }

    return 0;
}