You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
129 lines
5.0 KiB
HTML
129 lines
5.0 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!-- Copyright (C) 1987-2018 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. A copy of
|
|
the license is included in the
|
|
section entitled "GNU Free Documentation License".
|
|
|
|
This manual contains no Invariant Sections. The Front-Cover Texts are
|
|
(a) (see below), and the Back-Cover Texts are (b) (see below).
|
|
|
|
(a) The FSF's Front-Cover Text is:
|
|
|
|
A GNU Manual
|
|
|
|
(b) The FSF's Back-Cover Text is:
|
|
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
|
software. Copies published by the Free Software Foundation raise
|
|
funds for GNU development. -->
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<title>Elif (The C Preprocessor)</title>
|
|
|
|
<meta name="description" content="Elif (The C Preprocessor)">
|
|
<meta name="keywords" content="Elif (The C Preprocessor)">
|
|
<meta name="resource-type" content="document">
|
|
<meta name="distribution" content="global">
|
|
<meta name="Generator" content="makeinfo">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<link href="index.html#Top" rel="start" title="Top">
|
|
<link href="Index-of-Directives.html#Index-of-Directives" rel="index" title="Index of Directives">
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
|
<link href="Conditional-Syntax.html#Conditional-Syntax" rel="up" title="Conditional Syntax">
|
|
<link href="Deleted-Code.html#Deleted-Code" rel="next" title="Deleted Code">
|
|
<link href="Else.html#Else" rel="prev" title="Else">
|
|
<style type="text/css">
|
|
<!--
|
|
a.summary-letter {text-decoration: none}
|
|
blockquote.indentedblock {margin-right: 0em}
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
|
blockquote.smallquotation {font-size: smaller}
|
|
div.display {margin-left: 3.2em}
|
|
div.example {margin-left: 3.2em}
|
|
div.lisp {margin-left: 3.2em}
|
|
div.smalldisplay {margin-left: 3.2em}
|
|
div.smallexample {margin-left: 3.2em}
|
|
div.smalllisp {margin-left: 3.2em}
|
|
kbd {font-style: oblique}
|
|
pre.display {font-family: inherit}
|
|
pre.format {font-family: inherit}
|
|
pre.menu-comment {font-family: serif}
|
|
pre.menu-preformatted {font-family: serif}
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
|
pre.smallexample {font-size: smaller}
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
|
pre.smalllisp {font-size: smaller}
|
|
span.nolinebreak {white-space: nowrap}
|
|
span.roman {font-family: initial; font-weight: normal}
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
|
ul.no-bullet {list-style: none}
|
|
-->
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
<body lang="en">
|
|
<a name="Elif"></a>
|
|
<div class="header">
|
|
<p>
|
|
Previous: <a href="Else.html#Else" accesskey="p" rel="prev">Else</a>, Up: <a href="Conditional-Syntax.html#Conditional-Syntax" accesskey="u" rel="up">Conditional Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
<hr>
|
|
<a name="Elif-1"></a>
|
|
<h4 class="subsection">4.2.5 Elif</h4>
|
|
|
|
<a name="index-_0023elif"></a>
|
|
<p>One common case of nested conditionals is used to check for more than two
|
|
possible alternatives. For example, you might have
|
|
</p>
|
|
<div class="smallexample">
|
|
<pre class="smallexample">#if X == 1
|
|
…
|
|
#else /* X != 1 */
|
|
#if X == 2
|
|
…
|
|
#else /* X != 2 */
|
|
…
|
|
#endif /* X != 2 */
|
|
#endif /* X != 1 */
|
|
</pre></div>
|
|
|
|
<p>Another conditional directive, ‘<samp>#elif</samp>’, allows this to be
|
|
abbreviated as follows:
|
|
</p>
|
|
<div class="smallexample">
|
|
<pre class="smallexample">#if X == 1
|
|
…
|
|
#elif X == 2
|
|
…
|
|
#else /* X != 2 and X != 1*/
|
|
…
|
|
#endif /* X != 2 and X != 1*/
|
|
</pre></div>
|
|
|
|
<p>‘<samp>#elif</samp>’ stands for “else if”. Like ‘<samp>#else</samp>’, it goes in the
|
|
middle of a conditional group and subdivides it; it does not require a
|
|
matching ‘<samp>#endif</samp>’ of its own. Like ‘<samp>#if</samp>’, the ‘<samp>#elif</samp>’
|
|
directive includes an expression to be tested. The text following the
|
|
‘<samp>#elif</samp>’ is processed only if the original ‘<samp>#if</samp>’-condition
|
|
failed and the ‘<samp>#elif</samp>’ condition succeeds.
|
|
</p>
|
|
<p>More than one ‘<samp>#elif</samp>’ can go in the same conditional group. Then
|
|
the text after each ‘<samp>#elif</samp>’ is processed only if the ‘<samp>#elif</samp>’
|
|
condition succeeds after the original ‘<samp>#if</samp>’ and all previous
|
|
‘<samp>#elif</samp>’ directives within it have failed.
|
|
</p>
|
|
<p>‘<samp>#else</samp>’ is allowed after any number of ‘<samp>#elif</samp>’ directives, but
|
|
‘<samp>#elif</samp>’ may not follow ‘<samp>#else</samp>’.
|
|
</p>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|