’15 -’16 General Discussion for Lesson 5.11

CS Principles Unit and Lesson Discussion
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1

Use this thread to discuss your questions and comments about how to run the lesson.

2

I had to spend a bit of extra time discussing and working with the how and why a WHILE loop is not an “UNTIL” loop – the distinction between the two and the use of the NOT was a bit confusing.

3

I can imagine that I will need to spend a couple of days on this lesson. How dd people explain the difference between why using an “or” statement resulted in an infinite loop versus the use of “and”?

4

I’ll only chime in that logic can be a tricky thing - and that’s really the big point - because it doesn’t always map to the way we say things in English. Whether you use a while loop or a repeat until, there are scenarios that are confusing to construct for both. Humans in general (myself included) have a hard time with NOT when combined with other logic. I find it useful to read NOT out loud as: “it is not the case”.

Then recognize that for OR, it means if any one of these conditions is true, and and AND means if "every one* of these conditions is true. So for a convoluted example:

while ( !(flips > 200) && heads < 20)

You could say…

  • there is an AND here so EVERY ONE of these conditions must be true in order for the loop to run one more time.
  • Condition 1: “it is not the case that flips is greater than 200”
  • Condition 2: “heads is less than 20”

From there you could work up to realizing that this is saying: continue to loop as long as I haven’t flipped 200 times or gotten 20 heads"

Hope this helps.

-Baker