// X-Macros used to keep an enumerated type aligned with
// To- and From- String functions.

#include <iostream>
#include <string>
#include <unordered_map>

// List the enumerated values
#define COLOURS \
	X(Red) \
	X(Orange) \
	X(Yellow) \
	X(Green) \
	X(Blue) \
	X(Indigo) \
	X(Violet)

enum Colour
{
#define X(x) x,
	COLOURS
#undef X
};

std::string ToString(Colour c)
{
	switch(c)
	{
#define X(x) case x: return #x;
		COLOURS
#undef X
	};
	throw std::runtime_error("Unknown colour");
}

Colour FromString(std::string const & s)
{
	static const std::unordered_map<std::string, Colour> lookup {
#define X(x) {#x, x},
		COLOURS
	};
	return lookup.at(s);
}

int main()
{
	Colour colour = FromString("Orange");
	std::cout << "My favourite colour is " << ToString(colour) << '\n';
	return 0;
}