// This file is one of a series that demonstrates how to write & use
// a comparison functor for an STL container.
//
// This version does a multi-level sort on an array of structures.

#include <iostream>
#include <set>
#include <algorithm>
#include <string>
#include <iterator>
#include <iomanip>

using namespace std;

struct student {
    int id;
    string name;
    float gpa;
};

struct compare {
    // Primary sort: descending order by gpa
    // Secondary sort: ascending by student id
    bool operator()(const student &a, const student &b) const {
	if (a.gpa != b.gpa)
		return a.gpa > b.gpa;
	return a.id < b.id;
    }
};

int main() {
    student roster[] = {
    	{81234567, "Jack Applin",      3.999999},
    	{84444444, "Joe Kolledge",     2.2},
    	{83333333, "Homecoming Queen", 2.2},
    	{80000000, "Darrell Whitley",  1.0},
    };
    typedef set<student,compare> con;
    con s(roster, roster+4);
    for (con::iterator i=s.begin(); i!=s.end(); i++)
    	cout << i->id << ' '
	     << left << setw(18) << i->name
	     << fixed << setprecision(2) << i->gpa << '\n';
}