;;; for rule filter construction test - see comments
;;; in rules.lsp wrt build-lrfsm, repeated below

;;; suppose A can feed B, B can feed C, C can feed D, A can feed C
;;; and D can feed B (so there's a cycle)

;;; rule-feeders of A - nil
;;;                 B - (A D)
;;;                 C - (B A)
;;;                 D - (C) 

;;; desired result
;;;
#|
   --- A     B     C     D
   A   nil   nil   nil   nil
   B   t     t     t     t
   C   t     t     t     t
   D   t     t     t     t
|#

rule-a :=
[ ORTH #1,
  CATEG cat5,
  ARGS < [ ORTH #1, CATEG cat4 ] > ].

rule-b :=
[ ORTH #1,
  CATEG cat6,
  ARGS < [ ORTH #1, CATEG cat5 ] > ].

rule-c :=
[ ORTH #1,
  CATEG cat7,
  ARGS < [ ORTH #1, CATEG cat5or6 ] > ].

rule-d :=
[ ORTH #1,
  CATEG cat5,
  ARGS < [ ORTH #1, CATEG cat7 ] > ].