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22:19:54 ' 2 <head>
' 3 <title>CL Unification: Class STANDARD-OBJECT-TEMPLATE</title>
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' 14 <strong><i>CL Unification: Class STANDARD-OBJECT-TEMPLATE</title></i></strong>
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' 33 <div class="content">
' 34 <div class="text" style="padding-top: 10px;">
' 35
' 36 <h1><i>Class</i> <strong>STANDARD-OBJECT-TEMPLATE</strong></h1>
' 37
' 38 <h2>Package:</h2>
' 39
' 40 <p><code>COMMON-LISP.EXTENSIONS.DATA-AND-CONTROL-FLOW.UNIFICATION</code></p>
' 41
' 42
' 43 <h2>Class Precedence List:</h2>
' 44
' 45 <p>
' 46 STANDARD-OBJECT-TEMPLATE, TYPE-TEMPLATE, TEMPLATE, STANDARD-OBJECT, T.
' 47 </p>
' 48
' 49 <h2>Known Subclasses:</h2>
' 50
' 51 <p>
' 52 None.
' 53 </p>
' 54
' 55
' 56 <h2>Slots:</h2>
' 57
' 58 <p>None.</p>
' 59
' 60
' 61 <h2>Description:</h2>
' 62
' 63 <p>The STANDARD-OBJECT-TEMPLATE class denotes those object that are used
' 64 to unify against any STANDARD-OBJECT.</p>
' 65
' 66
' 67 <h3>Template Syntax:</h3>
' 68
' 69 <p>
' 70 <pre>
' 71 #T(<i>&lt;<strong>CL</strong> class designator&gt;</i> <i>&lt;slot&nbsp;spec&gt;</i>*)
' 72
' 73 <i>&lt;slot&nbsp;spec&gt;</i> ::= <i>&lt;reader method&gt;</i> <i>&lt;object&gt;</i>
' 74 | (slot-value <i>&lt;slot name&gt;</i>) <i>&lt;object&gt;</i>
' 75 </pre>
' 76 </p>
' 77
' 78 <p>The STANDARD-OBJECT-TEMPLATE syntax denotes any
' 79 <strong>CL</strong> object that is an instance of a
' 80 STANDARD-OBJECT. The semantic of the template in a unification depends on which
' 81 <i>&lt;slot&nbsp;spec&gt;</i>'s appear. In the first case the meaning of
' 82 <i>&lt;slot&nbsp;spec&gt;</i> is such that the
' 83 <i>&lt;reader&nbsp;method&gt;</i> gets called against the instance
' 84 against which the STANDARD-OBJECT-TEMPLATE is being UNIFYed. In the
' 85 second case, SLOT-VALUE is called with the instance being UNIFYed
' 86 and <i>&lt;slot&nbsp;name&gt;</i>. The result value of the call to either
' 87 <i>&lt;reader&nbsp;method&gt;</i>, or SLOT-VALUE is UNIFYed against
' 88 <i>&lt;object&gt;</i>.</p>
' 89
' 90 <p><i>&lt;object&gt;</i> can be any <strong>CL</strong> object,
' 91 including a TEMPLATE (in which case the unification machinery
' 92 proceeds recursively.)</p>
' 93
' 94
' 95 <h2>Examples:</h2>
' 96
' 97 <p>
' 98 <pre>
' 99 cl-prompt> (defclass foo () ((a :initform 42 :accessor foo-a)))
' 100 #&lt;STANDARD-CLASS FOO XXXXX&gt;
' 101
' 102 cl-prompt> (defclass bar (foo) ())
' 103 #&lt;STANDARD-CLASS BAR XXXXX&gt;
' 104
' 105 cl-prompt> (defclass baz ()
' 106 ((a :reader the-a-in-a-baz)
' 107 (b :accessor bazb :initarg :b)))
' 108 #&lt;STANDARD-CLASS BAZ XXXXX&gt;
' 109
' 110 cl-prompt> (setf e (unify (make-instance 'foo) #T(<em>foo</em> <em>foo-a</em> 42)))
' 111 #&lt;ENVIRONMENT xxx&gt;
' 112
' 113 cl-prompt> (setf e (unify (make-instance 'bar) #T(<em>foo</em> <em>foo-a</em> 42)))
' 114 #&lt;ENVIRONMENT xxx&gt;
' 115
' 116 cl-prompt> (find-variable-value '?x e)
' 117 42
' 118 T
' 119
' 120 cl-prompt> (setf e (unify (make-instance 'bar) #T(<em>foo</em> <em>foo-a</em> 42)))
' 121 #&lt;ENVIRONMENT xxx&gt;
' 122
' 123 cl-prompt> (find-variable-value '?x e)
' 124 42
' 125 T
' 126
' 127 cl-prompt> (setf e (unify (make-instance 'baz) #T(<em>baz</em> <em>the-a-in-baz</em> 42)))
' 128 #&lt;ENVIRONMENT xxx&gt;
' 129
' 130 cl-prompt> (find-variable-value '?x e)
' 131 42
' 132 T
' 133
' 134 cl-prompt> (setf e (unify (make-instance 'baz) #T(<em>baz</em> <em>(slot-value b)</em> 42)))
' 135 #&lt;ENVIRONMENT xxx&gt;
' 136
' 137 cl-prompt> (find-variable-value '?x e)
' 138 42
' 139 T
' 140
' 141 cl-prompt> (setf e (unify (make-instance 'baz :b '?e) #T(<em>baz</em> <em>bazb</em> 42)))
' 142 #&lt;ENVIRONMENT xxx&gt;
' 143
' 144 cl-prompt> (find-variable-value '?x e)
' 145 42
' 146 T
' 147
' 148 cl-prompt> (setf e (unify (make-instance 'bar) #T(<em>baz</em> <em>foo-a</em> 42)))
' 149 --> Error: UNIFICATION-FAILURE
' 150 </pre>
' 151 </p>
' 152
' 153
' 154 <h2>Affected By:</h2>
' 155
' 156 <p>None.</p>
' 157
' 158
' 159 <h2>Exceptional Situations:</h2>
' 160
' 161 <p>Unifying a STANDARD-OBJECT-TEMPLATE against a non-STANDARD-OBJECT object results in
' 162 an UNIFICATION-FAILURE error being signaled.</p>
' 163
' 164 <p>Unifying a STANDARD-OBJECT-TEMPLATE denoting an instance of class
' 165 C1 against an instance of class C2, results in
' 166 an UNIFICATION-FAILURE error being signaled, when C1 is not in the
' 167 class precedence list of C2.</p>
' 168
' 169
' 170 <h2>See Also:</h2>
' 171
' 172 <p>UNIFY</p>
' 173
' 174
' 175 <h2>Notes:</h2>
' 176
' 177 <p>None.</p>
' 178
' 179
' 180 </td>
' 181
' 182 <!-- <td height="100%">&nbsp;</td> -->
' 183 </tr>
' 184
' 185 <tr height="100%">
' 186 <td height="100%">&nbsp;</td>
' 187 <td valign="top" width="80%" height="100%">
' 188
' 189 <div class="content">
' 190 <div class="text" style="padding-top: 10px;">
' 191
' 192 <h1>News</h1>
' 193
' 194 <p>News in chronological order, most recent on top.
' 195 </p>
' 196
' 197 <ul>
' 198 <li><strong>2004-10-30</strong><br>
' 199 Completed description.
' 200 </li>
' 201
' 202 </ul>
' 203
' 204 </div>
' 205 </div>
' 206
' 207 </td>
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' 210 </tr>
' 211
' 212
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' 214
' 215 <tr>
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' 217 <div class="copyright">
' 218 &copy; 2003-2004, Marco Antoniotti, all rights reserved.
' 219 </div>
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' 226
' 227 <!-- end of file -- expression-template-class.html -->