Say you had a class with 3 parameters within its constructor function created like so:
var class:ClassName = new ClassName(a, b, c);
Each parameter has a default value so how would you change the value of c and skip a and b?
You can’t really skip them because AS3 doesn’t have named arguments. You can pass in cardinal values for a and b so that you can later set them to the default values, but that wouldn’t be handled automatically.
