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
|
<!DOCTYPE html>
<html>
<!-- Created by GNU Texinfo 7.0.3, https://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<!-- This manual documents GNU troff version 1.23.0.
Copyright � 1994-2023 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
copy of the license is included in the section entitled "GNU Free
Documentation License". -->
<title>if-then (The GNU Troff Manual)</title>
<meta name="description" content="if-then (The GNU Troff Manual)">
<meta name="keywords" content="if-then (The GNU Troff Manual)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta name="viewport" content="width=device-width,initial-scale=1">
<link href="index.html" rel="start" title="Top">
<link href="Request-Index.html" rel="index" title="Request Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Conditionals-and-Loops.html" rel="up" title="Conditionals and Loops">
<link href="if_002delse.html" rel="next" title="if-else">
<link href="Operators-in-Conditionals.html" rel="prev" title="Operators in Conditionals">
<style type="text/css">
<!--
a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em}
div.example {margin-left: 3.2em}
span:hover a.copiable-link {visibility: visible}
strong.def-name {font-family: monospace; font-weight: bold; font-size: larger}
-->
</style>
</head>
<body lang="en">
<div class="subsection-level-extent" id="if_002dthen">
<div class="nav-panel">
<p>
Next: <a href="if_002delse.html" accesskey="n" rel="next">if-else</a>, Previous: <a href="Operators-in-Conditionals.html" accesskey="p" rel="prev">Operators in Conditionals</a>, Up: <a href="Conditionals-and-Loops.html" accesskey="u" rel="up">Conditionals and Loops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<h4 class="subsection" id="if_002dthen-1">5.23.2 if-then</h4>
<a class="index-entry-id" id="index-if_002dthen"></a>
<dl class="first-deffn">
<dt class="deffn" id="index-_002eif"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.if</code></strong> <var class="def-var-arguments">cond-expr anything</var><a class="copiable-link" href='#index-_002eif'> ¶</a></span></dt>
<dd><a class="index-entry-id" id="index-if"></a>
<p>Evaluate the conditional expression <var class="var">cond-expr</var>, and if it evaluates
true (or to a positive value), interpret the remainder of the line
<var class="var">anything</var> as if it were an input line. Recall from <a class="ref" href="Invoking-Requests.html">Invoking Requests</a> that any quantity of spaces between arguments to requests
serves only to separate them; leading spaces in <var class="var">anything</var> are thus
not seen. <var class="var">anything</var> effectively <em class="emph">cannot</em> be omitted; if
<var class="var">cond-expr</var> is true and <var class="var">anything</var> is empty, the newline at the
end of the control line is interpreted as a blank input line (and
therefore a blank text line).
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">super\c
tanker
.nr force-word-break 1
super\c
.if ((\n[force-word-break] = 1) & \n[.int])
tanker
⇒ supertanker super tanker
</pre></div></div>
</dd></dl>
<dl class="first-deffn">
<dt class="deffn" id="index-_002enop"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.nop</code></strong> <var class="def-var-arguments">anything</var><a class="copiable-link" href='#index-_002enop'> ¶</a></span></dt>
<dd><a class="index-entry-id" id="index-nop"></a>
<p>Interpret <var class="var">anything</var> as if it were an input line. This is similar
to ‘<samp class="samp">.if 1</samp>’. <code class="code">nop</code> is not really “no operation”; its
argument <em class="emph">is</em> processed—unconditionally. It can be used to cause
text lines to share indentation with surrounding control lines.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">.als real-MAC MAC
.de wrapped-MAC
. tm MAC: called with arguments \\$@
. nop \\*[real-MAC]\\
..
.als MAC wrapped-MAC
\# Later...
.als MAC real-MAC
</pre></div></div>
<p>In the above, we’ve used aliasing, <code class="code">nop</code>, and the interpolation of
a macro as a string to interpose a wrapper around the macro ‘<samp class="samp">MAC</samp>’
(perhaps to debug it).
</p></dd></dl>
</div>
<hr>
<div class="nav-panel">
<p>
Next: <a href="if_002delse.html">if-else</a>, Previous: <a href="Operators-in-Conditionals.html">Operators in Conditionals</a>, Up: <a href="Conditionals-and-Loops.html">Conditionals and Loops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
