Const vs. var at compile time?

1

I want to calculate the width of a MC and create a constant so that I can accurately figure out where to place it on the stage. So I create a new instance of the clip and assign the value of the width to a variable:

var Temp:MovieClip = new TempClip;
var TempWidth:Number = Temp.width;

which works fine, but if I initialize it as a constant:

var Temp:MovieClip = new TempClip;
const TEMP_WIDTH:Number = Temp.width;

I get a “null value” error. So I guess it’s something to do with when the compiler sets the values?