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| 22 | <title>Pointer Declarations (GNU C Language Manual)</title>
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| 23 |
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| 24 | <meta name="description" content="Pointer Declarations (GNU C Language Manual)">
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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="Pointers.html" rel="up" title="Pointers">
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| 33 | <link href="Pointer-Type-Designators.html" rel="next" title="Pointer Type Designators">
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| 34 | <link href="Pointer-Types.html" rel="prev" title="Pointer Types">
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| 55 | </head>
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| 57 | <body lang="en">
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| 58 | <span id="Pointer-Declarations"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Pointer-Type-Designators.html" accesskey="n" rel="next">Pointer Type Designators</a>, Previous: <a href="Pointer-Types.html" accesskey="p" rel="prev">Pointer Types</a>, Up: <a href="Pointers.html" accesskey="u" rel="up">Pointers</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="Pointer_002dVariable-Declarations"></span><h3 class="section">14.3 Pointer-Variable Declarations</h3>
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| 64 |
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| 65 | <p>The way to declare that a variable <code>foo</code> points to type <var>t</var> is
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| 66 | </p>
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| 67 | <div class="example">
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| 68 | <pre class="example"><var>t</var> *foo;
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| 69 | </pre></div>
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| 70 |
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| 71 | <p>To remember this syntax, think “if you dereference <code>foo</code>, using
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| 72 | the ‘<samp>*</samp>’ operator, what you get is type <var>t</var>. Thus, <code>foo</code>
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| 73 | points to type <var>t</var>.”
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| 74 | </p>
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| 75 | <p>Thus, we can declare variables that hold pointers to these three
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| 76 | types, like this:
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| 77 | </p>
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| 78 | <div class="example">
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| 79 | <pre class="example">int *ptri; /* <span class="roman">Pointer to <code>int</code>.</span> */
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| 80 | double *ptrd; /* <span class="roman">Pointer to <code>double</code>.</span> */
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| 81 | double (*ptrda)[5]; /* <span class="roman">Pointer to <code>double[5]</code>.</span> */
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| 82 | </pre></div>
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| 83 |
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| 84 | <p>‘<samp>int *ptri;</samp>’ means, “if you dereference <code>ptri</code>, you get an
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| 85 | <code>int</code>.” ‘<samp>double (*ptrda)[5];</samp>’ means, “if you dereference
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| 86 | <code>ptrda</code>, then subscript it by an integer less than 5, you get a
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| 87 | <code>double</code>.” The parentheses express the point that you would
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| 88 | dereference it first, then subscript it.
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| 89 | </p>
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| 90 | <p>Contrast the last one with this:
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| 91 | </p>
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| 92 | <div class="example">
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| 93 | <pre class="example">double *aptrd[5]; /* <span class="roman">Array of five pointers to <code>double</code>.</span> */
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| 94 | </pre></div>
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| 95 |
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| 96 | <p>Because ‘<samp>*</samp>’ has higher syntactic precedence than subscripting,
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| 97 | you would subscript <code>aptrd</code> then dereference it. Therefore, it
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| 98 | declares an array of pointers, not a pointer.
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| 99 | </p>
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| 100 |
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| 101 |
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| 102 |
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| 103 | </body>
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| 104 | </html>
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