[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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