Re: LOGO-L> Total Turtle Trip

[George Mills <mills@softronix.com>]

Yes, I realized that soon after I posted the same fix.
Still, I consider it a gross error for 64bit floating point math.

What you see is still not floating point errors.
It's because the vertices are not on the circle
which is a nice property to have.

Thanks for correcting me though.

Yehuda Katz wrote:
> 
> George Mills wrote:
> >
> > Your correct, there is nothing in the universe that can create
> > a perfect physical representation of a circle. But you can choose
> > between different approximations to get different properties.
> >
> > The "equidistant from center" method has some nice properties the
> > "poly" method does not (assuming a finite number of points of course
> > on a finite precision machine).
> >
> > TO CIRCLE :RADIUS :POINTS
> > REPEAT :POINTS [FD (:RADIUS * 2) * PI/360 RT 1]
> > END
> >
> > TO DIFF
> > CIRCLE 100 90
> > SHOW POS
> > CS
> > ARC2 90 100
> > SHOW POS
> > END
> >
> > DIFF
> > [99.124796 100.870126] <<<< See how far off POLY is
> > [100 100] <<<< ARC2 basically uses the "equidistant model"
> 
> George,
> 
> You can minimize considerably the error in the above CIRCLE by saying:
> 
> ======================================================
> TO CIRCLE :RADIUS :POINTS
> REPEAT :POINTS [rt .5 FD (:RADIUS * 2) * PI/360 rt .5]
> END
> 
> TO DIFF
> cs
> CIRCLE 100 90
> SHOW POS
> CS
> ARC2 90 100
> SHOW POS
> END
> 
> DIFF
> [100.001269 100.001269]
> [100 100]
> ======================================================
> 
> [[Yehuda]]

-- 
===============================================================
George Mills
email: mills@softronix.com
http://www.softronix.com
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