q; (real a, real z); -->
<p></p>
<p><code>real</code> <strong><code>gamma_q</code></strong><code>(real a, real z)</code><br>
Return the normalized upper incomplete gamma function of a and z
defined for positive a and nonnegative z. <span class="math display">\[ \mathrm{gamma\_q}(a,z) =
\begin{cases} \frac{1}{\Gamma(a)}\int_z^\infty t^{a-1}e^{-t}dt &amp;
\text{if } a &gt; 0, z \geq 0 \\[6pt] \textrm{error} &amp; \text{otherwise}
\end{cases} \]</span></p>
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