docsrc/xlisp/xlisp-doc/reference/cdddr.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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104

<html><head><title>XLISP cdaar ... cdddr</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>cdaar ... cdddr</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>xllist.c</nobr></td>
</tr>
</tbody></table></p>

<h2>Syntax</h2>

<p><div class="box">

<dl>
<dt>(<b>cdaar</b> <i>expr</i>)<br>
(<b>cdadr</b> <i>expr</i>)<br>
(<b>cddar</b> <i>expr</i>)<br>
(<b>cdddr</b> <i>expr</i>)</dt>
<dd><i>expr</i> - a list or list expression<br>
returns - the result of the last <a href="cdr.htm">cdr</a>
function</dd>
</dl>

</div></p>

<h2>Description</h2>

<p>The 'cdaar', 'cdadr', 'cddar' and 'cdddr' functions go through the list
expression and perform a sequence of <nobr><a href="car.htm">car</a> or
<a href="cdr.htm">cdr</a></nobr> operations. <nobr>The sequence</nobr> of
operations is performed from right to left. So 'cddar' does a
<a href="car.htm">car</a> on the expression, followed by a
<nobr> a<a href="cdr.htm">cdr</a></nobr>, followed by <nobr>another
<a href="cdr.htm">cdr</a></nobr>. <nobr>If at</nobr> any point the list
<nobr>is <a href="nil.htm">NIL</a></nobr>, then
<a href="nil.htm">NIL</a> is returned. <nobr>If at</nobr> any point a
<a href="car.htm">car</a> operation is performed on an atom [as
opposed to a list] an error is signalled:</p>

<pre class="example">
<font color="#AA0000">error: bad argument</font>
</pre>

<h2>Examples</h2>

<pre class="example">
(setq mylist '(((11A 11B) (12A 12B) (13A 13B))
               ((21A 21B) (22A 22B) (23A 23B))
               ((31A 31B) (32A 32B) (33A 33B))
               ((41A 41B) (42A 42B) (43A 43B))))

(cdaar mylist)  =&gt; (11B)
(cdadr mylist)  =&gt; ((22A 22B) (23A 23B))
(cddar mylist)  =&gt; ((13A 13B))
(cdddr mylist)  =&gt; (((41A 41B) (42A 42B) (43A 43B)))
</pre>

<p><b>Note:</b> The '<nobr>c...r</nobr>' functions are part of the
historical Lisp functions. You may find it easier to work with the modern
lisp functions like <a href="nth.htm">nth</a> and
<a href="nthcdr.htm">nthcdr</a>.</p>

<p>See also:</p>

<ul>
<li><nobr>Contents &rarr; <a href="../manual/contents.htm#list-functions">List Functions</a></nobr></li>
<li><nobr>Tutorials &rarr; Lisp Hints &rarr; <a href="../tutorials/lisp-hints.htm#list-accessors">List Accessors</a></nobr></li>
</ul>

<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>