Question

I have the following enums defined in my code:

[Flags]
public enum Symbol
{
    A,
    B,
}

public enum Production
{
    AA = Symbol.A | Symbol.A,
    AB = Symbol.A | Symbol.B,
    BA = Symbol.B | Symbol.A, // <- this will obviously not work
}

I was planning to make use of enums as they eventually would prevent unwanted Symbols to be used for Productions. The problem is that the following code does not produce the output that I’m after:

Productions product1 = (Productions) (Symbol.A | Symbol.A); // Production.AA
Productions product2 = (Productions) (Symbol.A | Symbol.B); // Production.AB
Productions product3 = (Productions) (Symbol.B | Symbol.A); // Production.AB (and not Production.BA as I would like)

I completely understand why this is happening, but was wondering if there is a combination of bitwise operators that I could use to make it work as I originally intended?

Or maybe in general I’m trying to use enums in a incorrect way, therefore should switch to chars or even custom structs?

Answer 1

Well, because you need to take care of the order of A and B than you should use some operation that is not commutative. I would better suggest the approach where each position should have the assigned weight and you can have simple addition of symbols with weights. Since Enums are ints you can assign to each position a weight of 10^i where i is the zero-based index of the position looking from right to left. Even then you can have calculations for even more Symbols. This is like with classic Arabic numbers but with your symbols instead of regular digits. The code can be like this:

    [Flags]
    public enum Symbol
    {
        A,
        B,
    }

    public enum Production
    {
        AA = Symbol.A *10 + Symbol.A, //0
        AB = Symbol.A *10 + Symbol.B, //1
        BA = Symbol.B *10 + Symbol.A, //10
    }