title: OCaml This is not a function; it cannot be applied
body: <p>I have a function <code>num_order rank -&gt; int</code> defined. </p>
  
  <p>the following function call will cause a error</p>
  
  <pre><code>let dom_rank r1 r = (num_order r1) &gt; (num_order r)
  dom_rank Seven Eight
  </code></pre>
  
  <blockquote>
    <p>Line 1: Error: This expression has type int</p>
  
  <pre><code>  This is not a function; it cannot be applied.
  </code></pre>
  </blockquote>
  
  <p>it seems to be the first line to be causing the problem... however when I remove the second line, the error is gone.</p>