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| <a name="LOG-_002d_002d_002d-Natural-logarithm-function"></a> |
| <h3 class="section">8.153 <code>LOG</code> — 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 \leq \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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