#ifndef COFFEE_H
#define COFFEE_H

#include <iosfwd>   //forward declaration of ostream (lighter than <iostream>)

class coffee {
	int mg;  //caffeine remaining, in milligrams (>= 0)

public:
	coffee(int init_mg);
	coffee();                    //default constructor

	coffee& operator+=(int n);   //add caffeine
	coffee& operator-=(int n);   //subtract caffeine

	coffee& operator++();        //prefix ++  (add 1 mg)
	const coffee operator++(int);//postfix ++ (return old value, then add 1)

	coffee& operator--();        //prefix --
	const coffee operator--(int);//postfix --

	friend std::ostream& operator<<(std::ostream& os, const coffee& c);

	//Friends that use two objects of the same class often become friends.
	friend int operator-(const coffee& a, const coffee& b);   //difference in mg

	friend bool operator==(const coffee& a, const coffee& b);
	friend bool operator<(const coffee& a, const coffee& b);

	//Define the rest in terms of == and < (no need to touch private data).
};

inline bool operator!=(const coffee& a, const coffee& b) { return !(a == b); }
inline bool operator>(const coffee& a, const coffee& b)  { return  (b < a); }
inline bool operator<=(const coffee& a, const coffee& b) { return !(b < a); }
inline bool operator>=(const coffee& a, const coffee& b) { return !(a < b); }

//Two flavors of operator+ (implemented using operator+=)
inline const coffee operator+(coffee c, int n) { c += n; return c; }   //coffee + int
inline const coffee operator+(int n, coffee c) { c += n; return c; }   //int + coffee

inline const coffee operator-(coffee c, int n) { c -= n; return c; }   //coffee - int

#endif