Week9: Partial Correctness & Term test 2

As expected, we discussed more on correctness this week. This time, the goal and the point of proving correctness are more clear to me after I studied the past term test 2, and there was a problem asking you to prove that a program terminates and the postconditions will be met (Though later I found out that it is a topic that we hadn't covered before this thursday). It makes sense that we should use some method and find some loop invariants to prove our program will meet the postcondition and terminate. It helps us to make sure that our program is correct and will terminate.

The part I didn't quite understand during the lecture is the process of deriving conditions from pictures. Because I was absent minded for a while, and when my mind came back, I couldn't figure out how the pictures were derived, namely I didn't know what the problem is! Then I asked my friend after lecture and reviewed the slides (I didn't find corresponding part in the textbook), I thin it's just another example of proving an iterative program, but expressing with some pictures to help understand.

We had out term test 2 this week. I had been worrying about writing Python code in the exam (because I didn't learn Python before), but it turned out that the test was easier than I had expected and didn't involve programming.

The lecture note for this week are as follows: