Re: LOGO-L> Total Turtle Trip

[Chuck Shavit <CShavit@MagicSquare.com>]

At 02:25 PM 10/27/97 -0500, George Mills wrote:
>Chuck Shavit wrote:
>>   * I do not think that the concept of  "turtle geometry" necessarily
>> precludes "real" circles.  It so happened that the original Logo's
>> implementation has FORWARD movements only along straight lines.  So this is
>> a limitation of Logo and not of the concept of turtle geometry.
>
>I agree with you, I consider a "true" ARC function as part Turtle
>Geometry.

If I understand you correctly, then I am not sure we are in a total
agreement -- although it's really semantics.  I do not consider ARC part of
turtle geometry.  To me, turtle geometry consists only of the basic
relative movement commands: forward/backward and right/left.  If you have
3D (and you do...), then you need two more rotation axes.  So drawing lines
and curves between absolute coords is not turtle geometry.  At least that's
my definition.  Your mileage may vary.

What I meant in my comment above is that Logo could have been extended so
that FORWARD would behave differently depending on whether the current mode
is to move in straight lines, in a circle of a given radius and direction,
etc.  Just like you can set the color and then draw a red line using
FORWARD, you could set the movement mode and draw a circle using the very
same FORWARD.

To illustrate: if the turtle movement mode is to move on a circle of radius
100, then FORWARD 100 would draw 1/(2*pi) of the circle's perimeter.

Chuck
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