I'm almost sure that there's no way for a turtle to know anything

about the background. That's an unfortunate limitation!

As for putting a limit on a turtle's travel, you need to write an

appropriate conditional. For example, if you want your turtle to stay

within a 200x200 square centered around the origin and stop if it gets

out, do something roughly like:

while(math.abs(t.xcor()) < 100 and math.abs(t.ycor()) < 100):

move turtle

Of course, you could instead use if statements and simulate bouncing

(if my turtle's x coordinate is beyond my bounding box, subtract from

its x coordinate).

Best,

Hélène.

Computer Science Teacher

Garfield High School

http://garfieldcs.comOn Sun, Jan 24, 2010 at 7:29 AM, Brian Blais <

[hidden email]> wrote:

> Hello,

> I am trying to think of things to do with the turtle module with my

> students, and I have some ideas where I am not sure whether the turtle

> module can do it.

> 1) is there a way to determine the current screen pixel color? I am

> thinking about having the turtle go forward until it reaches an object, say

> a red circle. I can probably do this by making circle objects (drawn with

> turtles themselves) which know their own position, and check against this

> info. But I thought it might be useful also for the turtle to know.

> 2) is there a way to put a limit on the extent the turtle can travel? it

> seems I can keep moving off of the screen. Is there a way to make it so

> that a forward(50) command, at the edge, either raises an exception (at the

> wall) or simply doesn't move the turtle because of the limit?

>

> thanks!

>

> bb

>

> --

> Brian Blais

>

[hidden email]
>

http://web.bryant.edu/~bblais>

http://bblais.blogspot.com/>

>

>

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