151 lines
5.9 KiB
HTML
151 lines
5.9 KiB
HTML
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<head>
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<title>The GNU Fortran Compiler: LOG</title>
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Intrinsic-Procedures.html#Intrinsic-Procedures" rel="up" title="Intrinsic Procedures">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="LOG"></a>
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<div class="header">
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<p>
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Next: <a href="LOG10.html#LOG10" accesskey="n" rel="next">LOG10</a>, Previous: <a href="LOC.html#LOC" accesskey="p" rel="prev">LOC</a>, Up: <a href="Intrinsic-Procedures.html#Intrinsic-Procedures" accesskey="u" rel="up">Intrinsic Procedures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="LOG-_002d_002d_002d-Natural-logarithm-function"></a>
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<h3 class="section">9.168 <code>LOG</code> — Natural logarithm function</h3>
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<a name="index-LOG"></a>
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<a name="index-ALOG"></a>
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<a name="index-DLOG"></a>
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<a name="index-CLOG"></a>
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<a name="index-ZLOG"></a>
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<a name="index-CDLOG"></a>
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<a name="index-exponential-function_002c-inverse"></a>
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<a name="index-logarithm-function"></a>
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<a name="index-natural-logarithm-function"></a>
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<dl compact="compact">
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<dt><em>Description</em>:</dt>
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<dd><p><code>LOG(X)</code> computes the natural logarithm of <var>X</var>, i.e. the
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logarithm to the base <em>e</em>.
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</p>
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</dd>
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<dt><em>Standard</em>:</dt>
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<dd><p>Fortran 77 and later
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</p>
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</dd>
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<dt><em>Class</em>:</dt>
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<dd><p>Elemental function
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</p>
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</dd>
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<dt><em>Syntax</em>:</dt>
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<dd><p><code>RESULT = LOG(X)</code>
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</p>
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</dd>
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<dt><em>Arguments</em>:</dt>
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<dd><table>
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<tr><td width="15%"><var>X</var></td><td width="70%">The type shall be <code>REAL</code> or
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<code>COMPLEX</code>.</td></tr>
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</table>
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</dd>
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<dt><em>Return value</em>:</dt>
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<dd><p>The return value is of type <code>REAL</code> or <code>COMPLEX</code>.
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The kind type parameter is the same as <var>X</var>.
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If <var>X</var> is <code>COMPLEX</code>, the imaginary part <em>\omega</em> is in the range
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<em>-\pi < \omega \leq \pi</em>.
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</p>
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</dd>
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<dt><em>Example</em>:</dt>
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<dd><div class="smallexample">
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<pre class="smallexample">program test_log
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real(8) :: x = 2.7182818284590451_8
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complex :: z = (1.0, 2.0)
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x = log(x) ! will yield (approximately) 1
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z = log(z)
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end program test_log
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</pre></div>
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</dd>
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<dt><em>Specific names</em>:</dt>
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<dd><table>
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<tr><td width="20%">Name</td><td width="20%">Argument</td><td width="20%">Return type</td><td width="25%">Standard</td></tr>
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<tr><td width="20%"><code>ALOG(X)</code></td><td width="20%"><code>REAL(4) X</code></td><td width="20%"><code>REAL(4)</code></td><td width="25%">f95, gnu</td></tr>
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<tr><td width="20%"><code>DLOG(X)</code></td><td width="20%"><code>REAL(8) X</code></td><td width="20%"><code>REAL(8)</code></td><td width="25%">f95, gnu</td></tr>
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<tr><td width="20%"><code>CLOG(X)</code></td><td width="20%"><code>COMPLEX(4) X</code></td><td width="20%"><code>COMPLEX(4)</code></td><td width="25%">f95, gnu</td></tr>
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<tr><td width="20%"><code>ZLOG(X)</code></td><td width="20%"><code>COMPLEX(8) X</code></td><td width="20%"><code>COMPLEX(8)</code></td><td width="25%">f95, gnu</td></tr>
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<tr><td width="20%"><code>CDLOG(X)</code></td><td width="20%"><code>COMPLEX(8) X</code></td><td width="20%"><code>COMPLEX(8)</code></td><td width="25%">f95, gnu</td></tr>
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</table>
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</dd>
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</dl>
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