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<html><head><title>XLISP intern</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>intern</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>function (subr)</nobr></td>
</tr>
<tr valign="top">
<td><nobr>Source:</nobr></td>
<td><nobr> - </nobr></td>
<td width="100%"><nobr>xlbfun.c</nobr></td>
</tr>
</tbody></table></p>
<h2>Syntax</h2>
<dl>
<dt>(intern <i>name-str</i>)</dt>
<dd><i>name-str</i> - a string expression<br>
returns - the new symbol</dd>
</dl>
<h2>Description</h2>
<p>The 'intern' function takes a string name 'name-str' and creates a new
interned symbol. What this means is that the symbol 'name-str' will be
placed into the symbol hash table
<a href="global-obarray.htm">*obarray*</a>. It's value will be unbound. It's
property list will be <a href="nil.htm">NIL</a> [empty]. If the
symbol already exists, no error or action is taken and the old values and
property lists remain intact. The 'intern' function returns the symbol as
its result.</p>
<h2>Examples</h2>
<pre class="example">
(defun lookin (sym) <font color="#008844">; create a function to</font>
(aref *obarray* <font color="#008844">; look inside *OBARRAY* and</font>
(hash sym (length *obarray*)))) <font color="#008844">; look for a specific symbol</font>
<font color="#008844">; returns a list</font>
(lookin "FINGERS") <font color="#008844">; see if "FINGERS" is a symbol</font>
<font color="#008844">; returns (:START1) - it isn't</font>
(intern "FINGERS") <font color="#008844">; intern "FINGERS" as a symbol</font>
<font color="#008844">; returns FINGERS</font>
(lookin "FINGERS") <font color="#008844">; returns (FINGERS :START1)</font>
(print fingers) <font color="#008844">; error: unbound variable</font>
<font color="#008844">; it exists, but has no value</font>
(lookin "TOES") <font color="#008844">; returns NIL - doesn't exist</font>
toes <font color="#008844">; error: unbound variable</font>
(lookin "TOES") <font color="#008844">; returns (TOES)</font>
<font color="#008844">; the act of looking for a</font>
<font color="#008844">; value or using a symbol</font>
<font color="#008844">; causes it to be INTERNed</font>
(lookin "KNEECAPS") <font color="#008844">; returns (MAX MAPLIST)</font>
<font color="#008844">; KNEECAPS doesn't exist</font>
(setq kneecaps 'a-bone) <font color="#008844">; create symbol with a value</font>
(lookin "KNEECAPS") <font color="#008844">; returns (KNEECAPS MAX MAPLIST)</font>
</pre>
<p><b>Note:</b> When you 'intern' a string symbol like "fingers"
in lower case letters, this gets placed in the
<a href="global-obarray.htm">*obarray*</a> symbol table as a lower case
symbol. Note that this is different from doing an 'intern' on a string
symbol "FINGERS" in upper case letters which will get placed in
the <a href="global-obarray.htm">*obarray*</a> as a upper case symbol.
"fingers" and "FINGERS" then are two different symbols
in <a href="global-obarray.htm">*obarray*</a>. Remember also that normal
symbols created by XLISP are automatically converted to upper case names.
So, an intern of the lower case symbol name 'fingers and the upper case
symbol name 'FINGERS will result in the effect that both symbol names get
interned as the same upper-case symbol FINGERS.</p>
<p><b>Common Lisp:</b> Common LISP allows an optional package
specification, which XLISP does not support.</p>
<p>See the
<a href="../manual/xlisp-man-013.htm#intern">intern</a>
function in the <nobr>XLISP 2.0</nobr> manual.</p>
<p><nobr> <a href="#top">Back to Top</nobr></a></p>
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