You've just cracked the thought barrier that leads to formal methods. For each chunk of code, you create a list of assertions that impose constraints on what the code should do. Then you go through and make sure your code actually obeys those assertions. Formal methods take the idea a step farther by writing the assertions in mechanically-readable form, then running them through a postulate-matching engine to do the gruntwork of making sure everything checks. ... When you code to the assertions, you find yourself structuring programs so that no given operation can possibly fail. Ususally, you end up with a framework like so: ...

This is cool. Very cool. I admit that I didn't truly grasp your first paragraph at first read, and am still processing it. BUT, with the tutorial/example you gave, I saw the light! I will definitely try this! Thanks mstone - you have cracked my thought barrier, and I am looking forward to eliminating vast multi-level conditionals!!

..Jon

Update: Thanks again mstone for providing links to (what I'm sure will be) some great resources. And BTW I could not imagine pronouncing 'Z' anything but 'zed'... ; )