rolling Precision, Error Handling etc">policy
        documentation for more details</a>.
      </p>
<p>
        There are effectively two versions of this function internally: a fully generic
        version that is slow, but reasonably accurate, and a much more efficient
        approximation that is used where the number of digits in the significand
        of T correspond to a certain <a class="link" href="../lanczos.html" title="The Lanczos Approximation">Lanczos
        approximation</a>. In practice 