title: How to pattern match an element in a list in prolog?
body: <p>In prolog how can you pattern match an element in a list?
  For example, if the list was like</p>
  
  <pre><code>[1/2,1/3,2/5,3/6]
  </code></pre>
  
  <p>then you can do something like</p>
  
  <pre><code>one([..,1/A,..]) :- A=2.
  one([..,1/A,..]) :- A=3.
  </code></pre>
  
  <p>Thanks.</p>