title: XPATH : replace every ohter whitespace
body: <p>I'd like to replace every other (odd?) space with <code>x</code>. The result should be:</p>
  
  <blockquote>
    <p>axb axb axb axb axb</p>
  </blockquote>
  
  <p>I tried something like:</p>
  
  <pre><code>replace ("a b a b a b a b" , " " , "x")[position() mod 2 = 0]
  </code></pre>
  
  <p>-- but with no result.</p>