+;; also in metatilites
+(defun graph-search-for-cl-graph (states goal-p successors combiner
+ &key (state= #'eql) old-states
+ (new-state-fn #'new-states))
+ "Find a state that satisfies goal-p. Start with states,
+ and search according to successors and combiner.
+ Don't try the same state twice."
+ (cond ((null states) nil)
+ ((funcall goal-p (first states)) (first states))
+ (t (graph-search-for-cl-graph
+ (funcall
+ combiner
+ (funcall new-state-fn states successors state= old-states)
+ (rest states))
+ goal-p successors combiner
+ :state= state=
+ :old-states (adjoin (first states) old-states
+ :test state=)
+ :new-state-fn new-state-fn))))
+