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<h1>Comments</h1>
<p>
DoNaLD uses <code>#</code> as the comment symbol.  Comment starts from <code>#</code> to the
end of the line.
</p>
<h2>Escape to EDEN</h2>
<p>
There are two ways of escaping from DoNaLD to EDEN.
</p>
<ol>
<li>A line beginning with <code>?</code> will be passed to EDEN directly.  Like
the DoNaLD comments, this is only for one line escape. The one line escape
is particularly useful for defining attributes.  For
example:
<pre>line cable
?A_cable is "linestyle=dotted";	/* this defines the attribute of cable */
cable = ...		# this is a DoNaLD definition
</pre>
<p>
Not only is this escape method convenient in this case, it also
gives the attribute definition a sense of close association with the
DoNaLD variable.
</p>
</li>
<li>Switching to EDEN and back is useful if several EDEN statements are
included in a DoNaLD script.
<pre>line cable
%eden
A_cable is "linestyle=dotted";	/* this defines the attribute of cable */
%donald
cable = ...		# this is a DoNaLD definition
</pre>
</li>
</ol>
<h2>Bugs</h2>
<ul><li>The maximum number of nested openshapes is 128.</li>
<li>
<em>atan2: DOMAIN error</em> It is a warning message only, does
not affect the operation of tkeden.  It occurs when the two end-points
of an arc are the same.</li>
<li>
Eden variables in DoNaLD (identifiers ended with !) do not need to be
declared and so the type checker may be confused with polymorphic operators such
as arithmetic operators.  In most cases, you can use trunc() or float() to force
the variable to int or real.</li></ul>

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