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
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
|
<title>Idioms</title>
<head>
<script language="JavaScript">
</script>
</head>
<body bgcolor="#ffffcc">
<hr>
<center>
<h1>Idioms</h1>
</center>
<hr>
<p>
Here are some C idioms that may be usefull.
<p><hr align=center width="50%"><p>
Place <code>\0</code> at the location pointed to by <code>ptr</code>
then increment <code>ptr</code>
<p>
<center>
<table border=2 bgcolor=ivory>
<tr><td>
<pre>
*ptr++ = '\0';
</pre>
</td></tr>
</table>
</center>
<p><hr align=center width="50%"><p>
Increment <code>ptr</code> then
place <code>\0</code> at the location pointed to by <code>ptr</code>
<p>
<center>
<table border=2 bgcolor=ivory>
<tr><td>
<pre>
*++ptr = '\0';
</pre>
</td></tr>
</table>
</center>
<p><hr align=center width="50%"><p>
This program will print its self! I guess its not of any real
use, but I think its clever.
<p>
<center>
<table border=2 bgcolor=ivory>
<tr><td>
<pre>
main(a) {a="main(a) {a=%c%s%c;printf(a,34,a,34);}";printf(a,34,a,34);}
</pre>
</td></tr>
</table>
</center>
<p><hr align=center width="50%"><p>
This is something I saw out on the web. It swaps the value of two
variables without
using a third variable as a temporary store.
<p>
<center>
<table border=2 bgcolor=ivory>
<tr><td>
<pre>
one ^= two;
two ^= one;
one ^= two;
</pre>
</td></tr>
</table>
</center>
<a name=printf>
<p><hr align=center width="50%"><p>
Have you ever had a SEGV from <a href="../FUNCTIONS/printf.html">printf</a>
because you passed a NULL pointer to a %s flag???. This idiom will put
a stop to all that nonsence.
<p>
<center>
<table border=2 bgcolor=ivory>
<tr><td>
<pre>
printf("%s\n", Str ? Str : "Null");
</pre>
</td></tr>
</table>
</center>
<p><hr align=center width="50%"><p>
<p>
<img src="../../GRAPHICS/computer.gif" alt="o">
<a href=../EXAMPLES/swap.c>Program swapping the contents of two variables</a>.
<p>
<hr>
<h2>See Also:</h2>
<img src="../../GRAPHICS/whiteball.gif" alt="o">
<a href="got_ya.html">Common Coding Errors</a>.<p>
<p>
<hr>
<p>
<center>
<table border=2 width="80%" bgcolor="ivory">
<tr align=center>
<td width="25%">
<a href="../cref.html"> Top</a>
</td><td width="25%">
<a href="../master_index.html"> Master Index</a>
</td><td width="25%">
<a href="keywords.html"> Keywords</a>
</td><td width="25%">
<a href="../FUNCTIONS/funcref.htm"> Functions</a>
</td>
</tr>
</table>
</center>
<p>
<hr>
<address>Martin Leslie
</address><p>
</body>
</html>
|
