[plt-scheme] scaling and rotating images using image.ss

> Another question about the world/universe approach: how do you guys think
> about randomness?  I've found that adding a bit of randomness can make games
> considerably more compelling.  But it's not clear how to include randomness
> in a reasonably simple way that doesn't compromise on the purely-functional
> nature of the callbacks...

There are two ways to think about this.  What is the most important
thing: pure functionality or testability?

We have a good story on testability in the presence of randomness
(essentially, the tester indicates what the randomness is supposed to
do).  The same approach scales to other "input effects".  That avoids
cluttering the code with callbacks and inversion of control.

For instance, some of the demo programs in Moby do use random without
sweating it.

Shriram