title: Ceiling / round / floor in prolog
body: <p>When I try to execute the following query with prolog swi  version 7.2.3,</p>
  
  <p><code>ceiling(1.5)</code> it says,</p>
  
  <pre><code> ERROR: toplevel: Undefined procedure: ceiling/1 (DWIM could not correct goal.)
  </code></pre>
  
  <p>How do I get the "ceiling" working for this case? </p>