#ifndef GRADE_H
#define GRADE_H
#include <iostream> //for class ostream
#include <string>   //for class string
using namespace std;

class grade {
	int i;   //in range 0 to n-1 inclusive; 0 means F, 13 means A
	static const int n {14};  //the number of possible grades
	static const string a[n]; //names of the grades: "F", "F+", ..., "A+"
public:
	grade(): i {0} {}   //Constructor with no arguments.
	grade(const string& s);

	grade& operator+=(int inc);  //too big to be inline; see grade.C
	operator int() const {return i;}

	friend int operator-(const grade& g1, const grade& g2) {
		return g1.i - g2.i;
	}

	friend bool operator==(const grade& g1, const grade& g2) {
		return g1.i == g2.i;
	}

	friend bool operator<(const grade& g1, const grade& g2) {
		return g1.i < g2.i;
	}

	friend ostream& operator<<(ostream& ost, const grade& g) {
		return ost << grade::a[g.i];
	}

	friend istream& operator>>(istream& ist, grade& g);
};

inline grade& operator-=(grade& g, int i) {return g += -i;}

inline grade operator-(grade g, int i) {return g -= i;}
inline grade operator+(grade g, int i) {return g += i;}
inline grade operator+(int i, grade g) {return g += i;}

inline grade& operator++(grade& g) {return g += 1;} //prefix
inline grade& operator--(grade& g) {return g -= 1;} //prefix

inline const grade operator++(grade g, int) {       //postfix
	const grade old {g};
	++g;
	return old;
}

inline const grade operator--(grade g, int) {       //postfix
	const grade old {g};
	--g;
	return old;
}

inline bool operator<=(const grade& g1, const grade& g2) {
	return g1 == g2 || g1 < g2;
}

inline bool operator!=(const grade& g1, const grade& g2) {return !(g1 == g2);}
inline bool operator>=(const grade& g1, const grade& g2) {return !(g1 <  g2);}
inline bool operator> (const grade& g1, const grade& g2) {return !(g1 <= g2);}
#endif