title: clips defrule doesn't work
body: <p>i have deftemplate for url that contains url itself and integer counter :</p>
  
  <pre><code>(deftemplate url_t
  (slot counter
  (type INTEGER)
  (default 0))
  (slot url
  (type STRING)
  (default "")))
  </code></pre>
  
  <p>and i am trying to define the rule to print url string if counter value >0</p>
  
  <pre><code>(defrule print-url
      (url_t (counter ?counter) (url ?url))
      (test (&gt; ?counter 0))
  =&gt;
  (printout t "url is " ?url crlf)
  )
  </code></pre>
  
  <p>But when i try to change the values of url_t:
  (assert url_t (counter 2) (url "hello hello"))
  The rule is not executed. Where's my error?</p>