object states

[Henning Pohl]

Imagine you want an image to keep the width of 512:

void func(Image img) {
     assert(img.width == 512);

     img.doSomething();
     assert(img.width == 512);

     while (img.somethingElse()) {
         assert(img.width == 512)

         someFunc(img);
         assert(img.width == 512);
     }
}

In theory, every call to a function can change the width of the 
image. What do you think about this: 
https://dl.dropbox.com/u/34762907/temp/prop1.html

I do know it can be implemented in D4 only.