title: Prolog - compare two numbers
body: <p>I have some atoms that stand for the numbers 1 to 4 for example.</p>
  
  <p>Like </p>
  
  <pre><code>number(one).
  number(two).
  number(three).
  number(four).
  </code></pre>
  
  <p>Now I have to write a predicate that checks if the first number is bigger then the second one. </p>
  
  <pre><code>istBiggerThen(X,Y) :-
      (  X &lt; Y
         -&gt; true
         ;  false
      ).
  </code></pre>
  
  <p>But now I can only ask sth like </p>
  
  <pre><code>isBiggerThan(3,4).
  </code></pre>
  
  <p>But I want to </p>
  
  <pre><code>isBiggerThan(three,four).
  </code></pre>
  
  <p>How can I do that? Please help me :) Thanks in advance. </p>