Computing heading

Joshua 'Schwa' Gargus schwa at
Wed Jan 7 19:20:14 UTC 2004

On Sun, Jan 04, 2004 at 11:41:11PM +0100, Andreas Raab wrote:
> [Second reply in this thread - the first one was rejected by the list
> moderator with "No reason given". It included a project (117k) which
> illustrated the point below].
> > EToys doesn't have to use coordinates....  You can tell a morph to point
> > to another morph.
> >
> > Hmm, actually, you can't do that exactly.  But you can tell a morph to
> > *move toward* another morph.  So try moving it to right place, telling
> > it to move toward the other morph, and then moving it back to the right
> > place again.
> Here's another way of doing it: Just make up a morph which represents the
> angle (e.g., set its x/y to the difference of the guys being tracked) and
> use its "theta" to find out what the angle is.

Cool!  I think this will be a design pattern that will be common as we
develop visual programming tools for geometric domains.  It should
work with a wide range of possible GUIs.

<skipped the math lesson>

> And finally, you can put Angle into a playfield with "origin-at-center" and
> normalize the display using the "distance" property so you can actually see
> it moving. The project I had originally attached demonstrated this quite
> nicely.

That sounds cool; I hope to see it.

Perhaps we could address the problem of maximum attachment size (which
I also experienced recently) by hooking it into the reputation system
of Squeak People?  The default would be 100Kb, for list members who
have not registered on Sqeaple and for "Apprentices".  "Journeyers"
would have a higher limit, and "Masters" can send whatever the $#&*
they please.



> Cheers,
>   - Andreas

More information about the Squeak-dev mailing list