title: Prolog - how to clear the memory and start from scratch?
body: <p>I'm developing an algorithm in a .pl file, and examining it with queries on the command window.
  I use dynamic variables and retract/assert predicates. And when I modify the pl file and click on "reload modified files", I have extra facts that I don't want.</p>
  
  <p>for example, in the beginning I have 
  counter(0).</p>
  
  <p>and I do something, retract&amp;assert this counter, it becomes counter(7). Then, when I reload the modified pl file, I have both
  counter(0). and 
  counter(7).</p>
  
  <p>How can I prevent this and only have counter(0). in the beginning?</p>
  
  <p>Thanks in advance.</p>