1 <html> 2 <head> 3 <title>CL Unification: Class NIL-TEMPLATE</title> 4 <link rel="stylesheet" href="main.css"> 5 </head> 6 7 <body marginheight="0" marginwidth="0" leftmargin="0" topmargin="0" bgcolor="#ffffff"> 8 9 <table border="0" cellpadding="0" cellspacing="0" width="100%" height="100%" vspace="0" hspace="0"> 10 <tr> 11 <td colspan="3"> 12 <div class="header" 13 style="font-family:=Verdana,Arial,Helvetica; font-size: 18px; color: #41286f;"> 14 <strong><i>CL Unification: Class NIL-TEMPLATE</title></i></strong> 15 <div class="navigation"> 16 <a href="index.html" class="navigation-link">Home</a> 17 | <a href="unification-package.html" class="navigation-link">Previous</a> 18 | <a href="index.html" class="navigation-link">Next</a> 19 | <a href="downloads.html" class="navigation-link">Downloads</a> 20 | <a href="links.html" class="navigation-link">Links</a> 21 </div> 22 </div> 23 <div class="black-line"><img src="images/shim.gif" height="1" width="1"></div> 24 <div class="middle-bar"><img src="images/shim.gif" height="5" width="1"></div> 25 <div class="black-line"><img src="images/shim.gif" height="1" width="1"></div> 26 </td> 27 </tr> 28 29 <tr height="100%"> 30 <td height="100%"> </td> 31 <td valign="top" width="80%" height="100%"> 32 33 <div class="content"> 34 <div class="text" style="padding-top: 10px;"> 35 36 <h1><i>Class</i> <strong>NIL-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 NIL-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 NIL-TEMPLATE class denotes those object that are used 64 to unify against NIL.</p> 65 66 <h3>Template Syntax:</h3> 67 68 <p> 69 <pre> 70 #Tnil 71 </pre> 72 </p> 73 74 <p> 75 <pre> 76 #T() 77 </pre> 78 </p> 79 80 81 <p>The NIL-TEMPLATE syntax denotes NIL. 82 NIL-TEMPLATE can only unified against NIL.</p> 83 84 <p>The NIL-TEMPLATE is used for symmetry reasons, given that the 85 template hierarchy (almost) mirrors the regular <strong>CL</strong> 86 type hierarchy.</p> 87 88 89 <h2>Examples:</h2> 90 91 <p> 92 <pre> 93 cl-prompt> (setf e (unify nil #Tnil)) 94 #<ENVIRONMENT xxx> 95 96 cl-prompt> (setq e (unify 42 #T())) 97 --> Error: UNIFICATION-FAILURE 98 </pre> 99 </p> 100 101 102 <h2>Affected By:</h2> 103 104 <p>None.</p> 105 106 107 <h2>Exceptional Situations:</h2> 108 109 <p>Unifying an NIL-TEMPLATE against a non-NIL object results in 110 an UNIFICATION-FAILURE error being signaled.</p> 111 112 113 <h2>See Also:</h2> 114 115 <p>UNIFY</p> 116 117 118 <h2>Notes:</h2> 119 120 <p>None.</p> 121 122 </td> 123 124 <!-- <td height="100%"> </td> --> 125 </tr> 126 127 <tr height="100%"> 128 <td height="100%"> </td> 129 <td valign="top" width="80%" height="100%"> 130 131 <div class="content"> 132 <div class="text" style="padding-top: 10px;"> 133 134 <h1>News</h1> 135 136 <p>News in chronological order, most recent on top. 137 </p> 138 139 <ul> 140 <li><strong>2004-10-30</strong><br> 141 Completed description. 142 </li> 143 144 </ul> 145 146 </div> 147 </div> 148 149 </td> 150 151 <td height="100%"> </td> 152 </tr> 153 154 155 156 157 <tr> 158 <td colspan="3" valign="bottom" align="right"> 159 <div class="copyright"> 160 © 2003-2004, Marco Antoniotti, all rights reserved. 161 </div> 162 </td> 163 </tr> 164 165 </table> 166 </body> 167 </html> 168 169 <!-- end of file -- expression-template-class.html -->