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| 58 | <span id="Lvalues"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Modifying-Assignment.html" accesskey="n" rel="next">Modifying Assignment</a>, Previous: <a href="Simple-Assignment.html" accesskey="p" rel="prev">Simple Assignment</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="Lvalues-1"></span><h3 class="section">7.2 Lvalues</h3>
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| 64 | <span id="index-lvalues"></span>
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| 65 |
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| 66 | <p>An expression that identifies a memory space that holds a value is
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| 67 | called an <em>lvalue</em>, because it is a location that can hold a value.
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| 68 | </p>
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| 69 | <p>The standard kinds of lvalues are:
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| 70 | </p>
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| 71 | <ul>
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| 72 | <li> A variable.
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| 73 |
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| 74 | </li><li> A pointer-dereference expression (see <a href="Pointer-Dereference.html">Pointer Dereference</a>) using
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| 75 | unary ‘<samp>*</samp>’.
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| 76 |
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| 77 | </li><li> A structure field reference (see <a href="Structures.html">Structures</a>) using ‘<samp>.</samp>’, if
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| 78 | the structure value is an lvalue.
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| 79 |
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| 80 | </li><li> A structure field reference using ‘<samp>-></samp>’. This is always an lvalue
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| 81 | since ‘<samp>-></samp>’ implies pointer dereference.
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| 82 |
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| 83 | </li><li> A union alternative reference (see <a href="Unions.html">Unions</a>), on the same conditions
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| 84 | as for structure fields.
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| 85 |
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| 86 | </li><li> An array-element reference using ‘<samp>[<span class="roman">…</span>]</samp>’, if the array
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| 87 | is an lvalue.
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| 88 | </li></ul>
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| 89 |
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| 90 | <p>If an expression’s outermost operation is any other operator, that
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| 91 | expression is not an lvalue. Thus, the variable <code>x</code> is an
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| 92 | lvalue, but <code>x + 0</code> is not, even though these two expressions
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| 93 | compute the same value (assuming <code>x</code> is a number).
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| 94 | </p>
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| 95 | <p>An array can be an lvalue (the rules above determine whether it is
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| 96 | one), but using the array in an expression converts it automatically
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| 97 | to a pointer to the first element. The result of this conversion is
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| 98 | not an lvalue. Thus, if the variable <code>a</code> is an array, you can’t
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| 99 | use <code>a</code> by itself as the left operand of an assignment. But you
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| 100 | can assign to an element of <code>a</code>, such as <code>a[0]</code>. That is an
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| 101 | lvalue since <code>a</code> is an lvalue.
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| 102 | </p>
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