setpc-at?

[markf@marlboro.edu (Mark Francillon)]

Please excuse newbie ignorance.

I'm trying to propagate colors from a patch to adjacent patches
using setpc-at, am getting unexpected results, and plead for help.

Here's a simple way to see the problem:
  1. Start from scratch
  2. Set the color of the patch in the middle of the screen to yellow
  3. Under a forever button, run the following code:
    to run-it
      if pc = yellow
        [setpc black setpc-at 1 1 yellow]
    end

...and everything works perfectly (we get a single yellow cell
marching to the 'northeast'). However, substitute the offsets
'-1 -1' and what I get is a cell on the edge of the screen turning
yellow, and no motion thereafter.

Offsets that seem to work: -1 0; -1 1; 0, 1; 1 1. The others seem not
to. What am I missing?

Thanks,  Mark


Mark Francillon
Marlboro College
markf@marlboro.edu