alDistribution.html#cumulativeProbability(double)"><code>CDF</code></a>. If the derivative does not exist at <code>x</code>,
 then an appropriate replacement should be returned, e.g. <code>Double.POSITIVE_INFINITY</code>,
 <code>Double.NaN</code>, or the limit inferior or limit superior of the difference quotient. Note
 that due to the floating point precision and under/overflow issues, this method will for some
 distributions be more precise and faster than computing the logarithm of
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