#include <stdexcept>   //for classes invalid_argument and range_error
#include "grade.h"
using namespace std;

const string grade::a[] {
	"F",   // 0
	"F+",  // 1
	"D-",  // 2
	"D",   // 3
	"D+",  // 4
	"C-",  // 5
	"C",   // 6
	"C+",  // 7
	"B-",  // 8
	"B",   // 9
	"B+",  //10
	"A-",  //11
	"A",   //12
	"A+"   //13
};

//Extra credit: instead of writing the for loop and the if statement in the
//constructor, can you figure out how to call the standard library function
//"find" instead?  Hint: you will have to #include <algorithm>.

grade::grade(const string& s)
{
	//Let the data member i be the index of the string s in the array a.
	for (i = 0; i < n; ++i) {
		if (s == a[i]) {
			return;   //All done. We found what we were looking for.
		}
	}

	//Hope we never arrive here.
	throw invalid_argument("Bad argument \"" + s + "\" for constructor"); 
}

grade& grade::operator+=(int inc) {
	const int sum {i + inc};
	if (sum < 0 || sum >= n) {
		throw range_error("grade out of range");
	}
	i = sum;
	return *this;
}

//operator<< has to call the array a by its full name grade::a, because
//operator<< is not a member function of class grade.  Note that the constructor
//did not have to call the array by its full name, because the constructor is a
//member function of class grade.
//operator<< is small enough to be inline, if you want to do that.

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