Advanced Red Gnus scoring syntax

[Lars Magne Ingebrigtsen <larsi@ifi.uio.no>]

It should be possible to score in a more advanced fashion.  For
instance, if "Lars" answers something "Geir" has written, you may want
to lower the score dramatically.  So we basically need locical
operators in the score files: `|', `&', `!', `1-', and so on.

((&
  ("from" "lars" s)
  (1- 
   ("from" "geir.*@ifi" r)))
 -1000)

Or how about lowering the score of all articles written by Lars or
containing the word "moron!" that is in reply to "Geir", unless the
Keywords header contains the word "important" or "Geir" was following
up "Per":

((&
  (|
   ("from" "lars")
   ("body" "moron!"))
  (1- ("from" "geir.*@ifi" r))
  (! ("head" "^Keywords: important"))
  (! (2- ("from" "per"))))
 -1000)

Is this syntax understandable?  Is it general enough?

This sort of scoring will be quite a bit slower than the current
scoring scheme.  It requires looping over all the articles and
applying these advanced score rules.  The `1-' and `2-' (etc)
directives requires reading all (or many) if the headers of read
articles to be able to find parents and stuff.

-- 
  "Yes.  The journey through the human heart 
     would have to wait until some other time."