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<h3 class="section">8.24 <code>BESSEL_J0</code> — Bessel function of the first kind of order 0</h3>
<p><a name="index-BESSEL_005fJ0-431"></a><a name="index-BESJ0-432"></a><a name="index-DBESJ0-433"></a><a name="index-Bessel-function_002c-first-kind-434"></a>
<dl>
<dt><em>Description</em>:<dd><code>BESSEL_J0(X)</code> computes the Bessel function of the first kind of
order 0 of <var>X</var>. This function is available under the name
<code>BESJ0</code> as a GNU extension.
<br><dt><em>Standard</em>:<dd>Fortran 2008 and later
<br><dt><em>Class</em>:<dd>Elemental function
<br><dt><em>Syntax</em>:<dd><code>RESULT = BESSEL_J0(X)</code>
<br><dt><em>Arguments</em>:<dd>
<p><table summary=""><tr align="left"><td valign="top" width="15%"><var>X</var> </td><td valign="top" width="70%">The type shall be <code>REAL</code>, and it shall be scalar.
<br></td></tr></table>
<br><dt><em>Return value</em>:<dd>The return value is of type <code>REAL</code> and lies in the
range - 0.4027... \leq Bessel (0,x) \leq 1. It has the same
kind as <var>X</var>.
<br><dt><em>Example</em>:<dd>
<pre class="smallexample"> program test_besj0
real(8) :: x = 0.0_8
x = bessel_j0(x)
end program test_besj0
</pre>
<br><dt><em>Specific names</em>:<dd>
<p><table summary=""><tr align="left"><td valign="top" width="20%">Name </td><td valign="top" width="20%">Argument </td><td valign="top" width="20%">Return type </td><td valign="top" width="25%">Standard
<br></td></tr><tr align="left"><td valign="top" width="20%"><code>DBESJ0(X)</code> </td><td valign="top" width="20%"><code>REAL(8) X</code> </td><td valign="top" width="20%"><code>REAL(8)</code> </td><td valign="top" width="25%">GNU extension
<br></td></tr></table>
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