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| 22 | <title>Operators/Punctuation (GNU C Language Manual)</title>
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| 23 |
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| 24 | <meta name="description" content="Operators/Punctuation (GNU C Language Manual)">
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| 29 | <link href="index.html" rel="start" title="Top">
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| 30 | <link href="Symbol-Index.html" rel="index" title="Symbol Index">
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| 31 | <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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| 32 | <link href="Lexical-Syntax.html" rel="up" title="Lexical Syntax">
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| 55 | </head>
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| 56 |
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| 57 | <body lang="en">
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| 58 | <span id="Operators_002fPunctuation"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Line-Continuation.html" accesskey="n" rel="next">Line Continuation</a>, Previous: <a href="Identifiers.html" accesskey="p" rel="prev">Identifiers</a>, Up: <a href="Lexical-Syntax.html" accesskey="u" rel="up">Lexical Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 61 | </div>
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| 62 | <hr>
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| 63 | <span id="Operators-and-Punctuation"></span><h3 class="section">5.6 Operators and Punctuation</h3>
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| 64 | <span id="index-operators"></span>
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| 65 | <span id="index-punctuation"></span>
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| 66 |
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| 67 | <p>Here we describe the lexical syntax of operators and punctuation in C.
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| 68 | The specific operators of C and their meanings are presented in
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| 69 | subsequent chapters.
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| 70 | </p>
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| 71 | <p>Most operators in C consist of one or two characters that can’t be
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| 72 | used in identifiers. The characters used for operators in C are
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| 73 | ‘<samp>!~^&|*/%+-=<>,.?:</samp>’.
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| 74 | </p>
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| 75 | <p>Some operators are a single character. For instance, ‘<samp>-</samp>’ is the
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| 76 | operator for negation (with one operand) and the operator for
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| 77 | subtraction (with two operands).
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| 78 | </p>
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| 79 | <p>Some operators are two characters. For example, ‘<samp>++</samp>’ is the
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| 80 | increment operator. Recognition of multicharacter operators works by
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| 81 | grouping together as many consecutive characters as can constitute one
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| 82 | operator.
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| 83 | </p>
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| 84 | <p>For instance, the character sequence ‘<samp>++</samp>’ is always interpreted
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| 85 | as the increment operator; therefore, if we want to write two
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| 86 | consecutive instances of the operator ‘<samp>+</samp>’, we must separate them
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| 87 | with a space so that they do not combine as one token. Applying the
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| 88 | same rule, <code>a+++++b</code> is always tokenized as <code>a++ ++ + b<!-- /@w --></code>, not as <code>a++ + ++b<!-- /@w --></code>, even though the latter could be part
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| 89 | of a valid C program and the former could not (since <code>a++</code>
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| 90 | is not an lvalue and thus can’t be the operand of <code>++</code>).
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| 91 | </p>
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| 92 | <p>A few C operators are keywords rather than special characters. They
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| 93 | include <code>sizeof</code> (see <a href="Type-Size.html">Type Size</a>) and <code>_Alignof</code>
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| 94 | (see <a href="Type-Alignment.html">Type Alignment</a>).
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| 95 | </p>
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| 96 | <p>The characters ‘<samp>;{}[]()</samp>’ are used for punctuation and grouping.
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| 97 | Semicolon (‘<samp>;</samp>’) ends a statement. Braces (‘<samp>{</samp>’ and
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| 98 | ‘<samp>}</samp>’) begin and end a block at the statement level
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| 99 | (see <a href="Blocks.html">Blocks</a>), and surround the initializer (see <a href="Initializers.html">Initializers</a>)
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| 100 | for a variable with multiple elements or components (such as arrays or
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| 101 | structures).
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| 102 | </p>
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| 103 | <p>Square brackets (‘<samp>[</samp>’ and ‘<samp>]</samp>’) do array indexing, as in
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| 104 | <code>array[5]</code>.
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| 105 | </p>
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| 106 | <p>Parentheses are used in expressions for explicit nesting of
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| 107 | expressions (see <a href="Basic-Arithmetic.html">Basic Arithmetic</a>), around the parameter
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| 108 | declarations in a function declaration or definition, and around the
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| 109 | arguments in a function call, as in <code>printf ("Foo %d\n", i)</code>
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| 110 | (see <a href="Function-Calls.html">Function Calls</a>). Several kinds of statements also use
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| 111 | parentheses as part of their syntax—for instance, <code>if</code>
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| 112 | statements, <code>for</code> statements, <code>while</code> statements, and
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| 113 | <code>switch</code> statements. See <a href="if-Statement.html">if Statement</a>, and following
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| 114 | sections.
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| 115 | </p>
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| 116 | <p>Parentheses are also required around the operand of the operator
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| 117 | keywords <code>sizeof</code> and <code>_Alignof</code> when the operand is a data
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| 118 | type rather than a value. See <a href="Type-Size.html">Type Size</a>.
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| 119 | </p>
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| 120 | <hr>
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| 121 | <div class="header">
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| 122 | <p>
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| 123 | Next: <a href="Line-Continuation.html" accesskey="n" rel="next">Line Continuation</a>, Previous: <a href="Identifiers.html" accesskey="p" rel="prev">Identifiers</a>, Up: <a href="Lexical-Syntax.html" accesskey="u" rel="up">Lexical Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 124 | </div>
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