| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- Copyright (C) 1988-2015 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 the |
| Invariant Sections being "Funding Free Software", the Front-Cover |
| Texts being (a) (see below), and with the Back-Cover Texts being (b) |
| (see below). A copy of the license is included in the section entitled |
| "GNU Free Documentation License". |
| |
| (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 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>Using the GNU Compiler Collection (GCC): Conditionals</title> |
| |
| <meta name="description" content="Using the GNU Compiler Collection (GCC): Conditionals"> |
| <meta name="keywords" content="Using the GNU Compiler Collection (GCC): Conditionals"> |
| <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="Option-Index.html#Option-Index" rel="index" title="Option Index"> |
| <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> |
| <link href="C-Extensions.html#C-Extensions" rel="up" title="C Extensions"> |
| <link href="_005f_005fint128.html#g_t_005f_005fint128" rel="next" title="__int128"> |
| <link href="Typeof.html#Typeof" rel="prev" title="Typeof"> |
| <style type="text/css"> |
| <!-- |
| a.summary-letter {text-decoration: none} |
| blockquote.smallquotation {font-size: smaller} |
| div.display {margin-left: 3.2em} |
| div.example {margin-left: 3.2em} |
| div.indentedblock {margin-left: 3.2em} |
| div.lisp {margin-left: 3.2em} |
| div.smalldisplay {margin-left: 3.2em} |
| div.smallexample {margin-left: 3.2em} |
| div.smallindentedblock {margin-left: 3.2em; font-size: smaller} |
| 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.nocodebreak {white-space:nowrap} |
| span.nolinebreak {white-space:nowrap} |
| span.roman {font-family:serif; font-weight:normal} |
| span.sansserif {font-family:sans-serif; font-weight:normal} |
| ul.no-bullet {list-style: none} |
| --> |
| </style> |
| |
| |
| </head> |
| |
| <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> |
| <a name="Conditionals"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="_005f_005fint128.html#g_t_005f_005fint128" accesskey="n" rel="next">__int128</a>, Previous: <a href="Typeof.html#Typeof" accesskey="p" rel="prev">Typeof</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| <hr> |
| <a name="Conditionals-with-Omitted-Operands"></a> |
| <h3 class="section">6.7 Conditionals with Omitted Operands</h3> |
| <a name="index-conditional-expressions_002c-extensions"></a> |
| <a name="index-omitted-middle_002doperands"></a> |
| <a name="index-middle_002doperands_002c-omitted"></a> |
| <a name="index-extensions_002c-_003f_003a"></a> |
| <a name="index-_003f_003a-extensions"></a> |
| |
| <p>The middle operand in a conditional expression may be omitted. Then |
| if the first operand is nonzero, its value is the value of the conditional |
| expression. |
| </p> |
| <p>Therefore, the expression |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">x ? : y |
| </pre></div> |
| |
| <p>has the value of <code>x</code> if that is nonzero; otherwise, the value of |
| <code>y</code>. |
| </p> |
| <p>This example is perfectly equivalent to |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">x ? x : y |
| </pre></div> |
| |
| <a name="index-side-effect-in-_003f_003a"></a> |
| <a name="index-_003f_003a-side-effect"></a> |
| <p>In this simple case, the ability to omit the middle operand is not |
| especially useful. When it becomes useful is when the first operand does, |
| or may (if it is a macro argument), contain a side effect. Then repeating |
| the operand in the middle would perform the side effect twice. Omitting |
| the middle operand uses the value already computed without the undesirable |
| effects of recomputing it. |
| </p> |
| |
| |
| |
| </body> |
| </html> |
