title: Check if List C is the difference of List A and List B
body: <p>I am trying to write a Prolog program which returns true if list C is list A without List B ( so using set operators: C = A \ B )</p>
  <pre><code>difference(A,B,C) :-
  
  ?- difference([1,2,3,5],[1,2,3], [5]).
  true
  ?- difference([1,2,3,5,5],[1,2,3], [5]).
  false
  ?- difference([4,7,6],[4,6], [7]).
  true
  </code></pre>
  <p>Although this problem looks simple (might not be) I just can not figure it out.</p>
  <p>Cheers!</p>