search.lisp

(defun tree-search (states goal-p successors combiner)
  "Find a state that satisfies goal-p.  Start with states,
  and search according to successors and combiner."
  (dbg :search "~&;; Search: ~a" states)
  (cond ((null states) fail)
        ((funcall goal-p (first states)) (first states))
        (t (tree-search
             (funcall combiner
                      (funcall successors (first states))
                      (rest states))
             goal-p successors combiner))))