Re: LOGO-L> Total Turtle Trip

[Jim Muller <jmul@cyberramp.net>]

At 09:46 PM 10/27/97 -0500, Chuck Shavit wrote:
>
>
>Hi Jim,
>
>At 06:23 PM 10/27/97 -0600, you wrote:
>>Chuck ==>
>>
>>Here's a procedure that does just what you stated above. Other than some
>>added steps, how does this differ from the polygon procedure? It's still FD
>>1, RT 1 repeated for as many times as required to draw a line equidistant
>>from a center.
>>
>>TO CIRCLE :SIDE
>>HOME CS PU
>>REPEAT 360 [FD :SIDE POINT BK :SIDE RT 1]
>>END
>
>The obvious difference between the above CIRCLE and a "classic"
>polygon-based procedure (call it MCIRCLE) is that CIRCLE draws a circle
>around the turtle position, while MCIRCLE draw a circle which is tangent to
>the direction of the turtle.  BTW, I would remove HOME CS from the
>function, to make it more general.

HOME CS is simple housekeeping to start from a clean slate.

>
>But other than the above, CIRCLE differs from MCIRCLE in two very
>fundamental ways.
>
>A mathematical circle is defined by two parameters: its center, and its
>radius.  If you have a specific circle in mind (=defined by a specific
>center+radius), you can use CIRCLE to draw it for you.  But you cannot use
>MCIRCLE because you never know what center and radius you'll get.  That's
>why I call it MCIRCLE -- Mystery Circle.  Note that the mystery is even
>bigger if the caller doesn't know how MCIRCLE is implemented, e.g., with
>180 iterations of RIGHT 2, vs. 360 iterations of RIGHT 1.  
>
>The other difference is more subtle, yet important.  MCIRCLE is implemented
>with three variables: the FORWARD amount, the RIGHT amount, and the
>iteration count.  The three are interrelated in a somewhat complex way.
>For example, you have to make sure that 360 modulo the RIGHT amount is
>zero.  In CIRCLE, the only number that matters is the radius (what you call
>SIDE).  The RIGHT amount can be any non-zero number.  It can even be a
>random number, with a different value in each iteration.  And the RIGHT can
>be replaced with LEFT.  Likewise the iteration count can be any number, and
>the bigger it gets, the "more" circle you get. 

You've lost me here.  The result I got was definitely not circular. WHen I
try to change the relationship of...

REPEAT 360 [... FD 1 ... RT 1]

the result isn't a circle. POINT is, in effect, the same as FD 1.

TO POINT
PD RT 90 FD 1 
BK 1 LT 90 PU
END

I'm asking out of ignorance...not as a challenge. I don't understand what
you're saying. 


>
>This last issue is related, I think, to what Mike Doyle was saying.  The
>relation between MCIRCLE and a mathematical circle is somewhat fuzzy.
>Mike's mistake, if I understand him correctly, is that he thought that
>MCIRCLE is the only Logo-ish way to draw circles.  But maybe I missed
>something in what Mike was saying.
>
>Chuck Shavit
>
>
>
>+>+>+>+>+>+>+>+>+>+>+>+>+>+>+>
Jim Muller
jmul@cyberramp.net
The Great Logo Adventure at
http://www.cyberramp.net/~jmul
>+>+>+>+>+>+>+>+>+>+>+>+>+>+>+>
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