_Y(y). \]</span> The reason to use CCDFs instead of CDFs in
floating-point arithmetic is that it is possible to represent numbers
very close to 0 (the closest you can get is roughly <span class="math inline">\(10^{-300}\)</span>), but
not numbers very close to 1 (the closest you can get is roughly <span class="math inline">\(1 - 10^{-15}\)</span>).</p>
<p>In Stan, there is a cumulative distribution function for each
probability function. For instance, <code>normal_cdf(y, mu, sigma)</code> is
defined by <spa