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<a name="GAMMA-_002d_002d_002d-Gamma-function"></a>
<h3 class="section">9.118 <code>GAMMA</code> &mdash; Gamma function</h3>
<a name="index-GAMMA"></a>
<a name="index-DGAMMA"></a>
<a name="index-Gamma-function"></a>
<a name="index-Factorial-function"></a>

<dl compact="compact">
<dt><em>Description</em>:</dt>
<dd><p><code>GAMMA(X)</code> computes Gamma (<em>\Gamma</em>) of <var>X</var>. For positive,
integer values of <var>X</var> the Gamma function simplifies to the factorial
function <em>\Gamma(x)=(x-1)!</em>.
</p>

</dd>
<dt><em>Standard</em>:</dt>
<dd><p>Fortran 2008 and later
</p>
</dd>
<dt><em>Class</em>:</dt>
<dd><p>Elemental function
</p>
</dd>
<dt><em>Syntax</em>:</dt>
<dd><p><code>X = GAMMA(X)</code>
</p>
</dd>
<dt><em>Arguments</em>:</dt>
<dd><table>
<tr><td width="15%"><var>X</var></td><td width="70%">Shall be of type <code>REAL</code> and neither zero
nor a negative integer.</td></tr>
</table>

</dd>
<dt><em>Return value</em>:</dt>
<dd><p>The return value is of type <code>REAL</code> of the same kind as <var>X</var>.
</p>
</dd>
<dt><em>Example</em>:</dt>
<dd><div class="smallexample">
<pre class="smallexample">program test_gamma
  real :: x = 1.0
  x = gamma(x) ! returns 1.0
end program test_gamma
</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>GAMMA(X)</code></td><td width="20%"><code>REAL(4) X</code></td><td width="20%"><code>REAL(4)</code></td><td width="25%">GNU Extension</td></tr>
<tr><td width="20%"><code>DGAMMA(X)</code></td><td width="20%"><code>REAL(8) X</code></td><td width="20%"><code>REAL(8)</code></td><td width="25%">GNU Extension</td></tr>
</table>

</dd>
<dt><em>See also</em>:</dt>
<dd><p>Logarithm of the Gamma function: <a href="LOG_005fGAMMA.html#LOG_005fGAMMA">LOG_GAMMA</a>
</p>
</dd>
</dl>


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