[Squeakland] Weird Heading numbers

Bert Freudenberg bert at freudenbergs.de
Sat May 26 01:54:40 PDT 2007


On May 26, 2007, at 0:19 , mstram wrote:

> While playing with the Etoys, I've noticed the "weird" heading  
> numbers.
>
> By that I mean when the object's heading passes 180 degrees,  
> instead of
> continuing on to 190 ... 270 .. 360, we get the negative numbers.
>
> Why was this convention adopted ?

I don't know the original motivation. I'm sure there was a lot of  
discussion about introducing negative numbers that early. But it's  
quite simple actually - rotate one direction 5 degrees and you get  
"5", rotate the other way and you get "-5". Relatively simple to grasp.

And, for example, it makes using objects as rotational controls  
simpler. Unrotated the heading is 0, rotate a bit clockwise it's  
positive, rotate a bit counter-clockwise it's negative. This can then  
directly to increment the heading of another, moving object.

> I think if kids ... and some us "older" kids are going to be using  
> headings
> it would be more educational and instructive to use "real" headings.

You can use headingTheta from the geometry category.

- Bert -




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