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.