title: Negative Exponents throwing NaN in Fortran
body: <p>Very basic Fortran question. The following function returns a NaN and I can't seem to figure out why:</p>
  
  <p><code>F_diameter = 1. - (2.71828**(-1.0*((-1. / 30.)**1.4)))</code></p>
  
  <p>I've fed 2.71... in rather than using <code>exp()</code> but they both fail the same way. I've noticed that I only get a NaN when the fractional part (-1 / 30) is negative. Positives evaluate ok.</p>
  
  <p>Thanks a lot</p>