The Interactive Geometry Software Cinderella
Forums-> Cinderella Support (E)-> Cindybugs (2): Non-existing points exist!
dirkd
|
Cindybugs (2): Non-existing points exist!
|
|
I'm not sure this qualifies as a genuine bug, but never the less, I think it's surely unwanted behaviour:
I define a point E as the intersectionpoint of two free segments. By moving the segments around I can make point E disappear and reappear at will.
Next I define two additional (free) points F and G, and the polygon (EFG). If the point E disappears, so does the polygon. So far so good, everything happens as expected.
Now let the point E show up and draw the same polygon with a Drawpoly instruction in the folder /Draw in the script editor. This second polygon is invisible (it lies 'behind' the first one), but when the point E disappears, the second polygon stays on screen.
Apparently the non-existent point E still exists. It doesn't show up anywhere on screen, or as a hidden element, but it still can be accessed in script. You can even find its coordinates bij executing E.xy in the /Shell folder.
I think the script-polygons should behave as much as possible as the interactively drawn polygons. Of course, there's an easy workaround: you can enclose the Drawpoly instruction in some kind of If() statement, so that the polygon only appears when the two segments really intersect. But apart from the added nuisance of programming the appropriate tests, this approach defeats a bit the purpose of working in a dynamic geometry environment.
|
|
|
|
|
