title: Numerical Recipies Spline
body: <p>I am trying to implement the numerical receipes function spline and splint as described here:</p>
  
  <p><a href="http://www.arcetri.astro.it/irlab/library/recipes/bookcpdf/c3-3.pdf" rel="nofollow">http://www.arcetri.astro.it/irlab/library/recipes/bookcpdf/c3-3.pdf</a> -- Section 3.3</p>
  
  <p>The code is still pretty confusing to me.  Can someone explain what this number means?</p>
  
  <p>if (yp1 > <strong>0.99e30</strong>) -- What is this number?</p>
  
  <p>Or if anyone could give some links to explain this more, I would be grateful.</p>
  
  <p>Thanks.</p>