docsrc/xlisp/xlisp-doc/reference/peek.htm


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86

<html><head><title>XLISP peek</title>

<link rel="stylesheet" type="text/css" href="reference.css">

</head>

<body>

<a href="../start.htm">Nyquist / XLISP 2.0</a>&nbsp; -&nbsp;
<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>peek</h1>

<hr>

<p><table cellpadding="0" cellspacing="0" style="margin-left:10px"><tbody>
<tr valign="top">
  <td><nobr>Type:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>function (subr)</nobr></td>
</tr>
<tr valign="top">
  <td><nobr>Source:</nobr></td>
  <td><nobr>&nbsp;&nbsp;-&nbsp;&nbsp;</nobr></td>
  <td width="100%"><nobr>xlsys.c</nobr></td>
</tr>
</tbody></table></p>

<h2>Syntax</h2>

<dl>
<dt>(peek <i>address</i>)</dt>
<dd><i>address</i> - an integer expression<br>
returns - the value at the specified address as an integer</dd>
</dl>

<h2>Description</h2>

<p>The 'peek' function returns the internal memory value at the 'address'.
The returned value is an integer.</p>

<h2>Examples</h2>

<pre class="example">
(setq var 0)                    <font color="#008844">; set up VAR with 0</font>
(address-of var)                <font color="#008844">; returns 123224</font>
(address-of 'var)               <font color="#008844">; returns 161922</font>
(peek (address-of var))         <font color="#008844">; returns 83951616</font>
(peek (1+ (address-of var)))    <font color="#008844">; returns 16777216</font>
(peek (+ 2 (address-of var)))   <font color="#008844">; returns 0  &lt;-- value of VAR</font>
(setq var 14)                   <font color="#008844">; change the value to 14</font>
(peek (+ 2 (address-of var)))   <font color="#008844">; returns 14</font>
(setq var 99)                   <font color="#008844">; change the value to 99</font>
(peek (+ 2 (address-of var)))   <font color="#008844">; returns 99</font>
</pre>

<p><b>Caution:</b> Be careful when modifying the internal state of XLISP. If
you have modified it, it would be a good idea to exit XLISP and re-enter
before doing any work you really want to retain.</p>

<p><b>Caution:</b> It is possible to 'peek' and
<a href="poke.htm">poke</a> not just XLISP's memory put other
parts of your computer's memory. Be very careful when doing this. Also, in
some computers, just looking at a memory location can cause things to
happen, I/O locations fall in this category.</p>

<p>See the
<a href="../manual/xlisp-man-031.htm#peek">peek</a>
function in the <nobr>XLISP 2.0</nobr> manual.</p>

<p><nobr>&nbsp;&nbsp;<a href="#top">Back to Top</nobr></a></p>

<hr>

<a href="../start.htm">Nyquist / XLISP 2.0</a>&nbsp; -&nbsp;
<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>

</body></html>