title: Find the index of element in list
body: <p>I need to get index of element in list in scheme. For example:</p>
  
  <blockquote>
    <blockquote>
      <p>(... 2 '(2 3 4 5))</p>
      
      <p>0</p>
      
      <p>(... 4 '(2 3 4 5))</p>
      
      <p>2</p>
    </blockquote>
  </blockquote>
  
  <p>Can someone help?</p>