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| 22 | <title>Array Example Variations (GNU C Language Manual)</title>
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| 23 |
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| 24 | <meta name="description" content="Array Example Variations (GNU C Language Manual)">
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| 31 | <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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| 32 | <link href="Beyond-Integers.html" rel="up" title="Beyond Integers">
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| 33 | <link href="Lexical-Syntax.html" rel="next" 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="Array-Example-Variations"></span><div class="header">
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| 59 | <p>
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| 60 | Previous: <a href="Array-Example-Call.html" accesskey="p" rel="prev">Array Example Call</a>, Up: <a href="Beyond-Integers.html" accesskey="u" rel="up">Beyond Integers</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="Variations-for-Array-Example"></span><h3 class="section">4.4 Variations for Array Example</h3>
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| 64 |
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| 65 | <p>The code to call <code>avg_of_double</code> has two declarations that
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| 66 | start with the same data type:
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| 67 | </p>
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| 68 | <div class="example">
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| 69 | <pre class="example"> /* <span class="roman">The array of values to average.</span> */
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| 70 | double nums_to_average[5];
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| 71 | /* <span class="roman">The average, once we compute it.</span> */
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| 72 | double average;
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| 73 | </pre></div>
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| 74 |
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| 75 | <p>In C, you can combine the two, like this:
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| 76 | </p>
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| 77 | <div class="example">
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| 78 | <pre class="example"> double nums_to_average[5], average;
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| 79 | </pre></div>
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| 80 |
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| 81 | <p>This declares <code>nums_to_average</code> so each of its elements is a
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| 82 | <code>double</code>, and <code>average</code> so that it simply is a
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| 83 | <code>double</code>.
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| 84 | </p>
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| 85 | <p>However, while you <em>can</em> combine them, that doesn’t mean you
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| 86 | <em>should</em>. If it is useful to write comments about the variables,
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| 87 | and usually it is, then it’s clearer to keep the declarations separate
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| 88 | so you can put a comment on each one.
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| 89 | </p>
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| 90 | <p>We set all of the elements of the array <code>nums_to_average</code> with
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| 91 | assignments, but it is more convenient to use an initializer in the
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| 92 | declaration:
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| 93 | </p>
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| 94 | <div class="example">
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| 95 | <pre class="example">{
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| 96 | /* <span class="roman">The array of values to average.</span> */
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| 97 | double nums_to_average[]
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| 98 | = { 58.7, 5.1, 7.7, 105.2, -3.14159 };
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| 99 |
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| 100 | /* <span class="roman">The average, once we compute it.</span> */
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| 101 | average = avg_of_double ((sizeof (nums_to_average)
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| 102 | / sizeof (nums_to_average[0])),
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| 103 | nums_to_average);
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| 104 |
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| 105 | /* <span class="roman">…now make use of <code>average</code>…</span> */
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| 106 | }
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| 107 | </pre></div>
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| 108 |
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| 109 | <p>The array initializer is a comma-separated list of values, delimited
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| 110 | by braces. See <a href="Initializers.html">Initializers</a>.
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| 111 | </p>
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| 112 | <p>Note that the declaration does not specify a size for
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| 113 | <code>nums_to_average</code>, so the size is determined from the
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| 114 | initializer. There are five values in the initializer, so
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| 115 | <code>nums_to_average</code> gets length 5. If we add another element to
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| 116 | the initializer, <code>nums_to_average</code> will have six elements.
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| 117 | </p>
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| 118 | <p>Because the code computes the number of elements from the size of
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| 119 | the array, using <code>sizeof</code>, the program will operate on all the
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| 120 | elements in the initializer, regardless of how many those are.
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| 121 | </p>
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| 122 | <hr>
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| 123 | <div class="header">
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| 124 | <p>
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| 125 | Previous: <a href="Array-Example-Call.html" accesskey="p" rel="prev">Array Example Call</a>, Up: <a href="Beyond-Integers.html" accesskey="u" rel="up">Beyond Integers</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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| 126 | </div>
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