On 4/9/06, Jack Unrue jdunrue@gmail.com wrote:
Well, I've gotten through my first round of experimenting with Cells, and I have to say I like it a lot. If you want to see some code, take a look at:
http://common-lisp.net/websvn/filedetails.php?repname=graphic-forms&path...
which is the data model for a simple game where you click on blocks to score points (and where the remaining blocks fall down to fill in the hole(s)). The game gets progressively harder as you pass from one level to the next. The UI displays the current level, current score, and points needed for the next level. Screenshot here:
http://sourceforge.net/project/screenshots.php?group_id=163034&ssid=3154...
If you look at the model, there is a shape-data slot that really ought to be ephemeral based on how the score slot's formula depends on it (the 'shape' score should only be added to the overall score tally once, no matter how many times the UI asks for the score). But I was seeing some intermittent behavior where it seemed like the shape-data value had already been propagated (and thus cleared) by the time that my UI code asked for the score. So I took the :ephemeral attribute off until I get some more time to figure that out. I'm sure this is a bug in my understanding, not in Cells.
It would be good to document some typical strategies for dealing with self-referential slots (circularity) but in thinking about how I would describe what I did, I can see how it would be hard to explain to someone else :-)
it is pretty clear to me as an old Cells hand. I am toast right now, but I'll send some comments tomorrow. One Q: where does game-shape-data get called, in some imperative logic responding to events, that detects that a shape has been placed?
ken