Friday, June 03, 2005

Teaching about Loops

So I finally finished most of the artwork for the "if" section of my programming website for kids. It seems that the Java VM has improved a bit since I last used it. I'm finally getting consistent synchronization behaviour between when my applet running in a web broswer and my applet running stand-alone. And Swing now seems to support automatic text cut&paste with Windows applications (sigh, all of this could have been avoided if they used native widgets!).

And I'm now starting the section on loops. I've spent a few months thinking about this topic, but I'm still not sure about what the best approach is.

In traditional programming books about BASIC, the loop section would talk about FOR...NEXT loops:

FOR n=1 to 5
REM Stuff that happens 5 times

Unfortunately, the Javascript for loop is a little bit cryptic (especially since I haven't covered increment operators, the less-than operator, or the greater-than operator). Additionally, the convention for loops is that they start at 0. But, people are more comfortable with loops that start incrementing at 1 (like in BASIC). However, if I use 1-based loops throughout my examples, people might get confused when they later start working with normal code.

I suppose I could treat the syntax of the "for" loop as gobbledygook that should be treated as a black-box. This then reduces the number of concepts that need to be understood to work with loops.

Another alternative is that I could start with while loops. The advantage is that the word "while" actually means something, so it might be easier to understand. Unfortunately, there isn't all that much that one can do with a while loop without understanding the concept of sentry variables, which involves teaching 2 or 3 abstract concepts all at the same time.

I could teach the concept of the infinite loops first via "while(true)," but assuming that I don't teach boolean algebra beforehand (which I don't), then the whole command would need to be treated as a black-box, defeating the whole purpose of starting with the "while" loop in the first place. Then, I could follow that by teaching the concept of using "break" to break out of loops. This seems a little odd to me because no one else teaches loops in this way. Perhaps the "breaking out of loops" concept is simply too abstract a concept. But it does seem like a lot less work than discussing sentry variables and such.

Well, I don't know. For the past few months, I've been keen on the idea of starting with the while loop, but now I'm starting to come around to the idea of starting with infinite for loops. I'll have to ponder this some more.

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