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<html><head><title>XLISP object</title>
<link rel="stylesheet" type="text/css" href="reference.css">
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="../examples/examples.htm">Examples</a> |
<a href="reference-index.htm">Reference</a>
<hr>
<h1>object</h1>
<hr>
<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
<td><nobr>Type:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>object</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xlobj.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt> object</dt>
</dl>
<h2>Description</h2>
<p>'object' is an object <a href="class.htm">class</a>. An object
is a composite structure that contains internal state information, methods
[which respond to messages], a pointer to the object's
<a href="class.htm">class</a> and a pointer to the object's
super-class. XLISP contains two built in objects: 'object' and
<a href="class.htm">class</a>. 'object' is the superclass for the
<a href="class.htm">class</a> object.</p>
<h2>Examples</h2>
<pre class="example">
(send object :show) <font color="#008844">; look at the object definition</font>
<font color="#008844">; example use of objects</font>
(setq my-class (send class :new '(state))) <font color="#008844">; new class MY-CLASS with STATE</font>
(send my-class :answer :isnew '() <font color="#008844">; set up initialization</font>
'((setq state nil) self))
(send my-class :answer :set-it '(value) <font color="#008844">; create :SET-IT message</font>
'((setq state value)))
(setq my-obj (send my-class :new)) <font color="#008844">; create MY-OBJ out of MY-CLASS</font>
(send my-obj :set-it 5) <font color="#008844">; STATE is set to 5</font>
</pre>
<p><b>Object definition:</b> The internal definition of the 'object' object
instance is:</p>
<pre class="example">
Object is #<Object: #23fd8>, Class is #<Object: #23fe2>
MESSAGES = ((:SHOW . #<Subr-: #23db2>)
(:CLASS . #<Subr-: #23dee>)
(:ISNEW . #<Subr-: #23e2a>))
IVARS = NIL
CVARS = NIL
CVALS = NIL
SUPERCLASS = NIL
IVARCNT = 0
IVARTOTAL = 0
#<Object: #23fd8>
</pre>
<p>The <a href="class.htm">class</a> of 'object' is
<a href="class.htm">class</a>. There is no superclass of 'object'.
Remember that the location information [like #23fd8] varies from system to
system, yours will probably look different.</p>
<p><b>Built-in methods:</b> The built in methods in XLISP include:</p>
<ul>
<li><nobr><a href="keyword-answer.htm">:answer</a> - add a method to an object</nobr></li>
<li><nobr><a href="keyword-class.htm">:class</a> - return the object's <a href="class.htm">class</a></nobr></li>
<li><nobr><a href="keyword-isnew.htm">:isnew</a> - run initialization code on object</nobr></li>
<li><nobr><a href="keyword-new.htm">:new</a> - create a new object [instance or <a href="class.htm">class</a>]</nobr></li>
<li><nobr><a href="keyword-show.htm">:show</a> - show the internal state of the object</nobr></li>
</ul>
<p><b>Message structure:</b> The normal XLISP convention for a 'message' is
to have a valid symbol preceeded by a colon like
<a href="keyword-isnew.htm">:isnew</a> or ':my-message'. However, it is
possible to define a 'message' that is a symbol without a colon, but this
makes the code less readable.</p>
<p>See the
<a href="../manual/xlisp-man-010.htm#object">object</a>
class in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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