From: James Edward Gray II <james@...>
Date: 2006-12-08T05:55:20+09:00
Subject: Re: [SUMMARY] Turtle Graphics (#104)

On Dec 7, 2006, at 10:56 AM, David Tran wrote:

>> Most of those should be obvious implementations.  The surprise, if  
>> any, comes
>> from the fact that pen_down() puts a point on the track.  This  
>> makes sense
>> though, if you think about it.  If you touch a pen to a piece of  
>> paper you have
>> made a mark, even though you have not yet drawn a line.  The  
>> Turtle should
>> function the same way.
>
> Well, using this way, it may create "invalid" segment.
>
> By definition:
> track   ::= [segment, segment, ...] # drawing data
> segment ::= [point, point, ...]     # points to be joined by line  
> segments
> point   ::= [x, y]                  # pair of floats
>
> I was thinking a "no-empty" segment must have at least 2 points.

Well a track with just one segment is legal so I assume a segment  
with just one point is fine too.  The code provided with the quiz  
handles individual points, though it seems Morton and I took  
different approaches as to how to handle them.

James Edward Gray II