All pattern-matching has to be driven by *some* change to working memory. A few CEs (not, test, accumulate) can pass when they match no facts at all. Therefore, these CEs need a little help to know when to fire. If any of them appear first on the LHS of a rule, Jess inserts a pattern "(initial-fact)" before them, making them dependent on the "reset" function being called. It's always a good practice to use "reset" sometime before you call "run", but in this case it's a necessity: if "accumulate" is the first CE on the LHS of a rule, then you *must* call reset at some point before calling run, or the rule will never fire.
Other than that, yes, it should fire whenever the preceding patterns or its own embedded pattern match, returning 0 if the count is indeed 0. I think Roger Studner wrote: [Charset iso-8859-1 unsupported, filtering to ASCII...] > Are there situations or usages of (accumulate) that would actually prevent a > rule from firing? > > ?c <- (accumulate (bind ?count 0) ;; initializer > (bind ?count (+ ?count 1)) ;; action > ?count > (pattern to look for.. single fact, not even complex) > ) > > If there are *no matches* to this pattern, should it always fire and have ?c > bound to zero? > > Thanks, > Roger --------------------------------------------------------- Ernest Friedman-Hill Advanced Software Research Phone: (925) 294-2154 Sandia National Labs FAX: (925) 294-2234 PO Box 969, MS 9012 [EMAIL PROTECTED] Livermore, CA 94550 http://herzberg.ca.sandia.gov -------------------------------------------------------------------- To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]' in the BODY of a message to [EMAIL PROTECTED], NOT to the list (use your own address!) List problems? Notify [EMAIL PROTECTED] --------------------------------------------------------------------
