title: How can i define different in Prolog?
body: <p>How can i define that two variables are not equal in Prolog? For example :</p>
  
  <pre><code>z is X and Y parent
  
  X is male and Y is female
  </code></pre>
  
  <p>Now i want find sisters or brothers. But Prolog result is:</p>
  
  <pre><code>Y sister Y when parent have one child and not have X
  </code></pre>
  
  <p>Now i want define: </p>
  
  <pre><code>different(X,y).
  </code></pre>
  
  <p>I think old or other version of Visual Prolog have "different" in library but i dont find this in new Visual Prolog. What can i do?</p>