1<html lang="en"> 2<head> 3<title>Conditionals - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="C-Extensions.html#C-Extensions" title="C Extensions"> 9<link rel="prev" href="Typeof.html#Typeof" title="Typeof"> 10<link rel="next" href="Long-Long.html#Long-Long" title="Long Long"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 141998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 152010 Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation; with the 20Invariant Sections being ``Funding Free Software'', the Front-Cover 21Texts being (a) (see below), and with the Back-Cover Texts being (b) 22(see below). A copy of the license is included in the section entitled 23``GNU Free Documentation License''. 24 25(a) The FSF's Front-Cover Text is: 26 27 A GNU Manual 28 29(b) The FSF's Back-Cover Text is: 30 31 You have freedom to copy and modify this GNU Manual, like GNU 32 software. Copies published by the Free Software Foundation raise 33 funds for GNU development.--> 34<meta http-equiv="Content-Style-Type" content="text/css"> 35<style type="text/css"><!-- 36 pre.display { font-family:inherit } 37 pre.format { font-family:inherit } 38 pre.smalldisplay { font-family:inherit; font-size:smaller } 39 pre.smallformat { font-family:inherit; font-size:smaller } 40 pre.smallexample { font-size:smaller } 41 pre.smalllisp { font-size:smaller } 42 span.sc { font-variant:small-caps } 43 span.roman { font-family:serif; font-weight:normal; } 44 span.sansserif { font-family:sans-serif; font-weight:normal; } 45--></style> 46<link rel="stylesheet" type="text/css" href="../cs.css"> 47</head> 48<body> 49<div class="node"> 50<a name="Conditionals"></a> 51<p> 52Next: <a rel="next" accesskey="n" href="Long-Long.html#Long-Long">Long Long</a>, 53Previous: <a rel="previous" accesskey="p" href="Typeof.html#Typeof">Typeof</a>, 54Up: <a rel="up" accesskey="u" href="C-Extensions.html#C-Extensions">C Extensions</a> 55<hr> 56</div> 57 58<h3 class="section">6.7 Conditionals with Omitted Operands</h3> 59 60<p><a name="index-conditional-expressions_002c-extensions-2268"></a><a name="index-omitted-middle_002doperands-2269"></a><a name="index-middle_002doperands_002c-omitted-2270"></a><a name="index-extensions_002c-_0040code_007b_003f_003a_007d-2271"></a><a name="index-g_t_0040code_007b_003f_003a_007d-extensions-2272"></a> 61The middle operand in a conditional expression may be omitted. Then 62if the first operand is nonzero, its value is the value of the conditional 63expression. 64 65 <p>Therefore, the expression 66 67<pre class="smallexample"> x ? : y 68</pre> 69 <p class="noindent">has the value of <code>x</code> if that is nonzero; otherwise, the value of 70<code>y</code>. 71 72 <p>This example is perfectly equivalent to 73 74<pre class="smallexample"> x ? x : y 75</pre> 76 <p><a name="index-side-effect-in-_0040code_007b_003f_003a_007d-2273"></a><a name="index-g_t_0040code_007b_003f_003a_007d-side-effect-2274"></a>In this simple case, the ability to omit the middle operand is not 77especially useful. When it becomes useful is when the first operand does, 78or may (if it is a macro argument), contain a side effect. Then repeating 79the operand in the middle would perform the side effect twice. Omitting 80the middle operand uses the value already computed without the undesirable 81effects of recomputing it. 82 83 </body></html> 84 85