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<a name="LOG-_002d_002d_002d-Natural-logarithm-function"></a>
<h3 class="section">9.175 <code>LOG</code> &mdash; Natural logarithm function</h3>
<a name="index-LOG"></a>
<a name="index-ALOG"></a>
<a name="index-DLOG"></a>
<a name="index-CLOG"></a>
<a name="index-ZLOG"></a>
<a name="index-CDLOG"></a>
<a name="index-exponential-function_002c-inverse"></a>
<a name="index-logarithm-function"></a>
<a name="index-natural-logarithm-function"></a>

<dl compact="compact">
<dt><em>Description</em>:</dt>
<dd><p><code>LOG(X)</code> computes the natural logarithm of <var>X</var>, i.e. the
logarithm to the base <em>e</em>.
</p>
</dd>
<dt><em>Standard</em>:</dt>
<dd><p>Fortran 77 and later
</p>
</dd>
<dt><em>Class</em>:</dt>
<dd><p>Elemental function
</p>
</dd>
<dt><em>Syntax</em>:</dt>
<dd><p><code>RESULT = LOG(X)</code>
</p>
</dd>
<dt><em>Arguments</em>:</dt>
<dd><table>
<tr><td width="15%"><var>X</var></td><td width="70%">The type shall be <code>REAL</code> or
<code>COMPLEX</code>.</td></tr>
</table>

</dd>
<dt><em>Return value</em>:</dt>
<dd><p>The return value is of type <code>REAL</code> or <code>COMPLEX</code>.
The kind type parameter is the same as <var>X</var>.
If <var>X</var> is <code>COMPLEX</code>, the imaginary part <em>\omega</em> is in the range
<em>-\pi &lt; \omega \leq \pi</em>.
</p>
</dd>
<dt><em>Example</em>:</dt>
<dd><div class="smallexample">
<pre class="smallexample">program test_log
  real(8) :: x = 2.7182818284590451_8
  complex :: z = (1.0, 2.0)
  x = log(x)    ! will yield (approximately) 1
  z = log(z)
end program test_log
</pre></div>

</dd>
<dt><em>Specific names</em>:</dt>
<dd><table>
<tr><td width="20%">Name</td><td width="20%">Argument</td><td width="20%">Return type</td><td width="25%">Standard</td></tr>
<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>
<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>
<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>
<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>
<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>
</table>
</dd>
</dl>


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