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| 22 | <title>Write Assignments Separately (GNU C Language Manual)</title>
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| 24 | <meta name="description" content="Write Assignments Separately (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="Assignment-Expressions.html" rel="up" title="Assignment Expressions">
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| 33 | <link href="Execution-Control-Expressions.html" rel="next" title="Execution Control Expressions">
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| 57 | <body lang="en">
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| 58 | <span id="Write-Assignments-Separately"></span><div class="header">
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| 59 | <p>
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| 60 | Previous: <a href="Assignment-in-Subexpressions.html" accesskey="p" rel="prev">Assignment in Subexpressions</a>, Up: <a href="Assignment-Expressions.html" accesskey="u" rel="up">Assignment Expressions</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="Write-Assignments-in-Separate-Statements"></span><h3 class="section">7.7 Write Assignments in Separate Statements</h3>
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| 64 |
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| 65 | <p>It is often convenient to write an assignment inside an
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| 66 | <code>if</code>-condition, but that can reduce the readability of the
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| 67 | program. Here’s an example of what to avoid:
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| 68 | </p>
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| 69 | <div class="example">
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| 70 | <pre class="example">if (x = advance (x))
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| 71 | <span class="roman">…</span>
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| 72 | </pre></div>
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| 73 |
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| 74 | <p>The idea here is to advance <code>x</code> and test if the value is nonzero.
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| 75 | However, readers might miss the fact that it uses ‘<samp>=</samp>’ and not
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| 76 | ‘<samp>==</samp>’. In fact, writing ‘<samp>=</samp>’ where ‘<samp>==</samp>’ was intended
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| 77 | inside a condition is a common error, so GNU C can give warnings when
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| 78 | ‘<samp>=</samp>’ appears in a way that suggests it’s an error.
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| 79 | </p>
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| 80 | <p>It is much clearer to write the assignment as a separate statement, like this:
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| 81 | </p>
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| 82 | <div class="example">
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| 83 | <pre class="example">x = advance (x);
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| 84 | if (x != 0)
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| 85 | <span class="roman">…</span>
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| 86 | </pre></div>
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| 87 |
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| 88 | <p>This makes it unmistakably clear that <code>x</code> is assigned a new value.
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| 89 | </p>
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| 90 | <p>Another method is to use the comma operator (see <a href="Comma-Operator.html">Comma Operator</a>),
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| 91 | like this:
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| 92 | </p>
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| 93 | <div class="example">
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| 94 | <pre class="example">if (x = advance (x), x != 0)
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| 95 | <span class="roman">…</span>
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| 96 | </pre></div>
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| 97 |
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| 98 | <p>However, putting the assignment in a separate statement is usually clearer
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| 99 | unless the assignment is very short, because it reduces nesting.
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| 100 | </p>
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| 101 |
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| 102 |
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| 103 |
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| 104 | </body>
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| 105 | </html>
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