I want some Moore

How do you write your Flagged Enums?

A while ago i explained why do you need a [Flags] attribute on the Enum here.

We'll since then i was happy with my flags until i got to the point of having 16 flags.

So why is that a problem? Well it's not really but 2^16 is how much?

If you had to open the all mighty calculator you see my point. I stop counting powers of 2 after 4096 = 2^12.

I see no reason to remember those.

That's why I wanted to write my enums a bit simpler. Like saying this is 2 to the power of 1, 2, 3, 4 etc

Using Math.Pow won't work and it's not pretty. And C# doesn't have a Power operator.

So what to do?

Bit-shifting anyone? :)

I thought this didn't work in an enum but it does, so from now on i'm writing my enums like this:

[Flags]
enum bq
{ 
    a = 0,          // returns  0
    b = 2 >> 1,     // returns  1 = 2 to power of 0
    c = 2 << 0,     // returns  2 = 2 to power of 1
    d = 2 << 1,     // returns  4 = 2 to power of 2
    e = 2 << 2,     // returns  8 = 2 to power of 3
    f = 2 << 3,     // returns 16 = 2 to power of 4
    g = 2 << 4      // returns 32 = 2 to power of 5
    // etc, etc, etc
}

Quick bit-shifting lesson:

2 << n:  a left arithmetic shift by n is equivalent to multiplying by 2ⁿ

2 >> n:  a right arithmetic shift by n is equivalent to dividing by 2ⁿ

Of course you have to watch for overflow with this.

Happy enuming. :)

Print | posted on Monday, March 05, 2007 10:10 PM