Creating a composite type from two enum classes, ready for STL map

Question

I would like to create a composite type out of two enum classes.

enum class Color {RED, GREEN, BLUE};
enum class Shape {SQUARE, CIRCLE, TRIANGLE};

         


        

Answer 1

You only need to compare shape if color is the same for both.

Using a ternary you can make it look nice too:

friend bool operator< (const Object &lhs, const Object &rhs) {
     return lhs.color == rhs.color ? (lhs.shape < rhs.shape)
                                   : (lhs.color < rhs.color);
}