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| 22 | <title>Imaginary Constants (GNU C Language Manual)</title>
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| 58 | <span id="Imaginary-Constants"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Invalid-Numbers.html" accesskey="n" rel="next">Invalid Numbers</a>, Previous: <a href="Floating-Constants.html" accesskey="p" rel="prev">Floating Constants</a>, Up: <a href="Constants.html" accesskey="u" rel="up">Constants</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="Imaginary-Constants-1"></span><h3 class="section">12.4 Imaginary Constants</h3>
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| 64 | <span id="index-imaginary-constants"></span>
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| 65 | <span id="index-complex-constants"></span>
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| 66 | <span id="index-constants_002c-imaginary"></span>
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| 67 |
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| 68 | <p>A complex number consists of a real part plus an imaginary part.
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| 69 | (Either or both parts may be zero.) This section explains how to
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| 70 | write numeric constants with imaginary values. By adding these to
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| 71 | ordinary real-valued numeric constants, we can make constants with
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| 72 | complex values.
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| 73 | </p>
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| 74 | <p>The simple way to write an imaginary-number constant is to attach the
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| 75 | suffix ‘<samp>i</samp>’ or ‘<samp>I</samp>’, or ‘<samp>j</samp>’ or ‘<samp>J</samp>’, to an integer or
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| 76 | floating-point constant. For example, <code>2.5fi</code> has type
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| 77 | <code>_Complex float</code> and <code>3i</code> has type <code>_Complex int</code>.
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| 78 | The four alternative suffix letters are all equivalent.
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| 79 | </p>
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| 80 | <span id="index-_005fComplex_005fI"></span>
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| 81 | <p>The other way to write an imaginary constant is to multiply a real
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| 82 | constant by <code>_Complex_I</code>, which represents the imaginary number
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| 83 | i. Standard C doesn’t support suffixing with ‘<samp>i</samp>’ or ‘<samp>j</samp>’, so
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| 84 | this clunky way is needed.
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| 85 | </p>
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| 86 | <p>To write a complex constant with a nonzero real part and a nonzero
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| 87 | imaginary part, write the two separately and add them, like this:
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| 88 | </p>
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| 89 | <div class="example">
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| 90 | <pre class="example">4.0 + 3.0i
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| 91 | </pre></div>
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| 92 |
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| 93 | <p>That gives the value 4 + 3i, with type <code>_Complex double</code>.
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| 94 | </p>
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| 95 | <p>Such a sum can include multiple real constants, or none. Likewise, it
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| 96 | can include multiple imaginary constants, or none. For example:
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| 97 | </p>
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| 98 | <div class="example">
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| 99 | <pre class="example">_Complex double foo, bar, quux;
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| 100 |
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| 101 | foo = 2.0i + 4.0 + 3.0i; /* <span class="roman">Imaginary part is 5.0.</span> */
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| 102 | bar = 4.0 + 12.0; /* <span class="roman">Imaginary part is 0.0.</span> */
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| 103 | quux = 3.0i + 15.0i; /* <span class="roman">Real part is 0.0.</span> */
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| 104 | </pre></div>
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| 105 |
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| 106 | <p>See <a href="Complex-Data-Types.html">Complex Data Types</a>.
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| 107 | </p>
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