nested enum operator overloading

I have an enum nested in an object and I am unsuccessfully trying to increment it to the next value.

Here's the classes:

Code:

class Instruction
{
	public:
		Instruction(uint pc, uint op, int dest, int src1, int src2);
		~Instruction();
		enum Stages {IF = 0, ID, IS, EX, WB, RET};
		Stages stage() const;
		void incrementStage();
		bool operator==(const Instruction right);
		bool operator==( Instruction::Stages &rs );
		Stages operator++();
	private:
		Stages curr_stage;
};

And what I think is the closest to correct that I've done:

Code:

inline Instruction::Stages operator++(Instruction::Stages rs)
{
    return (Instruction::Stages)(rs + 1);
}

I am attempting to make prefix work but pre or post will be fine.

Here is the error I am getting: error: no match for ‘operator++’ in ‘++((Instruction*)this)->Instruction::curr_stage’|

User supplied operators can only be overloaded to work if one of its operands is a class/struct type. Enums (no matter how nested) are not a class/struct type.

Operator++ only acts on a class/struct of which it is a member.

Hmm...I see.

In that case, I could make curr_stage an int and set it equal to a stage and increment will work fine. But how would I then later compare curr_stage with IF, ID or one of the other stages?

I may be mistaken, but it appears to me that you can overload operators for enum types alright:

Code:

//as free functions
Instruction::Stages operator++(Instruction::Stages& n)
{
    n = Instruction::Stages(n + 1);
    return n;
}

Instruction::Stages operator++(Instruction::Stages& n, int)
{
    Instruction::Stages s = n;
    ++n;
    return s;
}

In that case, I could make curr_stage an int and set it equal to a stage and increment will work fine. But how would I then later compare curr_stage with IF, ID or one of the other stages?

Enum types are implicitly converted to integers. Those comparisons just work:

Code:

int i = Instructions::IF;
if (i == Instructions::IF) {}