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| 22 | <title>Assigning Function Pointers (GNU C Language Manual)</title>
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| 31 | <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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| 32 | <link href="Function-Pointers.html" rel="up" title="Function Pointers">
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| 58 | <span id="Assigning-Function-Pointers"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Calling-Function-Pointers.html" accesskey="n" rel="next">Calling Function Pointers</a>, Previous: <a href="Declaring-Function-Pointers.html" accesskey="p" rel="prev">Declaring Function Pointers</a>, Up: <a href="Function-Pointers.html" accesskey="u" rel="up">Function 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="Assigning-Function-Pointers-1"></span><h4 class="subsection">22.5.2 Assigning Function Pointers</h4>
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| 64 | <span id="index-assigning-function-pointers"></span>
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| 65 | <span id="index-function-pointers_002c-assigning"></span>
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| 66 |
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| 67 | <p>Assuming we have declared the variable <code>binary_op</code> as in the
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| 68 | previous section, giving it a value requires a suitable function to
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| 69 | use. So let’s define a function suitable for the variable to point
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| 70 | to. Here’s one:
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| 71 | </p>
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| 72 | <div class="example">
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| 73 | <pre class="example">double
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| 74 | double_add (double a, double b)
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| 75 | {
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| 76 | return a+b;
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| 77 | }
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| 78 | </pre></div>
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| 79 |
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| 80 | <p>Now we can give it a value:
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| 81 | </p>
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| 82 | <div class="example">
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| 83 | <pre class="example">binary_op = double_add;
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| 84 | </pre></div>
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| 85 |
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| 86 | <p>The target type of the function pointer must be upward compatible with
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| 87 | the type of the function (see <a href="Compatible-Types.html">Compatible Types</a>).
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| 88 | </p>
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| 89 | <p>There is no need for ‘<samp>&</samp>’ in front of <code>double_add</code>.
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| 90 | Using a function name such as <code>double_add</code> as an expression
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| 91 | automatically converts it to the function’s address, with the
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| 92 | appropriate function pointer type. However, it is ok to use
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| 93 | ‘<samp>&</samp>’ if you feel that is clearer:
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| 94 | </p>
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| 95 | <div class="example">
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| 96 | <pre class="example">binary_op = &double_add;
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| 97 | </pre></div>
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| 98 |
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| 99 |
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| 100 |
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| 101 |
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