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
|
<html>
<head>
<title>BOOST_PP_LIST_FIRST</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
</head>
<body>
<div style="margin-left: 0px;">
The <b>BOOST_PP_LIST_FIRST</b> macro expands to the head of a <i>list</i>.
</div>
<h4>Usage</h4>
<div class="code">
<b>BOOST_PP_LIST_FIRST</b>(<i>list</i>)
</div>
<h4>Arguments</h4>
<dl>
<dt>list</dt>
<dd>
A non-nil <i>list</i>.
</dd>
</dl>
<h4>Requirements</h4>
<div>
<b>Header:</b> <a href="../headers/list/adt.html"><boost/preprocessor/list/adt.hpp></a>
</div>
<h4>Sample Code</h4>
<div><pre>
#include <<a href="../headers/list/adt.html">boost/preprocessor/list/adt.hpp</a>>
#define OLD \
<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
a, \
<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
b, \
<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
c, \
<a href="list_nil.html">BOOST_PP_LIST_NIL</a> \
) \
) \
) \
/**/
#define NEW (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
<a href="list_first.html">BOOST_PP_LIST_FIRST</a>(OLD) == <a href="list_first.html">BOOST_PP_LIST_FIRST</a>(NEW)
// expands to a == a
<a href="list_rest.html">BOOST_PP_LIST_REST</a>(OLD) == <a href="list_rest.html">BOOST_PP_LIST_REST</a>(NEW)
// expands to (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)) == (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))
</pre></div>
</body>
</html>
|
