[irtgraph.l] do not set cost when arc is not costed-arc

[knorth55]

When I try to solve graph with normal arc with depth-first-graph-search-solver, I got the following error.
this is because arc is assumed as costed-arc. which has :cost methods.
this PR check if arc has :cost or not, and set 0 cost when arc is not costed-arc.
this is useful for non-cost-using solvers such as depth-first-graph-solver and so on.

7.E1-irteusgl$ (setq path (send solver :solve *pddl-graph* :verbose t))
nil
8.E1-irteusgl$ Call Stack (max depth: 20):
  0: at (send arc :cost)
  1: at (+ (send from :cost) (send arc :cost))
  2: at (send prblm :path-cost self (car successor) (cdr successor))
  3: at (send #:inst2934 :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor)))
  4: at (let ((#:inst2934 (instantiate solver-node))) (send #:inst2934 :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) #:inst2934)
  5: at (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor)))
  6: at (cons (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret)
  7: at (setq ret (cons (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret))
  8: at (setf ret (cons (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret))
  9: at (push (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret)
  10: at (while #:dolist2932 (setq successor (pop #:dolist2932)) (push (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret))
  11: at (let ((successor nil) (#:dolist2932 successors)) nil (while #:dolist2932 (setq successor (pop #:dolist2932)) (push (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret)) nil)
  12: at (dolist (successor successors) (push (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret))
  13: at (let ((ret nil)) (dolist (successor successors) (push (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret)) ret)
  14: at (let ((successors (send* prblm :successors state args))) (let ((ret nil)) (dolist (successor successors) (push (instance solver-node :init (cdr successor) :parent self :action (car successor) :cost (send prblm :path-cost self (car successor) (cdr successor))) ret)) ret))
  15: at (send target-node :expand prblm :verbose verbose)
  16: at (send self :add-list-to-open-list (send target-node :expand prblm :verbose verbose))
  17: at (cond ((send prblm :goal-test (send target-node :state)) (return-from :solve (send target-node :path))) ((not (send self :find-node-in-close-list target-node)) (push (send target-node :state) close-list) (send self :add-list-to-open-list (send target-node :expand prblm :verbose verbose))))
  18: at (let ((target-node (send self :pop-from-open-list :debug verbose))) (cond ((send prblm :goal-test (send target-node :state)) (return-from :solve (send target-node :path))) ((not (send self :find-node-in-close-list target-node)) (push (send target-node :state) close-list) (send self :add-list-to-open-list (send target-node :expand prblm :verbose verbose)))))
  19: at (while (not (send self :null-open-list?)) (let ((target-node (send self :pop-from-open-list :debug verbose))) (cond ((send prblm :goal-test (send target-node :state)) (return-from :solve (send target-node :path))) ((not (send self :find-node-in-close-list target-node)) (push (send target-node :state) close-list) (send self :add-list-to-open-list (send target-node :expand prblm :verbose verbose))))))
/home/knorth55/install/jskeus/eus/Linux64/bin/irteusgl 0 error: cannot find method :cost in (send arc :cost)

[k-okada]

thanks for catch, Another solution might be

(defmethod graph
  ;; :path-cost returns cost from 'from-node' to 'to-node' by 'action'.                                          
  (:path-cost (from arc to)
    (if (or (not (derivedp from costed-arc))
            (not (derivedp to costed-arc)))
        1
      (+ (send from :cost) (send arc :cost))))

[knorth55]

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