Verifying and Executing

(case (command-action command)

((LIFT)

(when (verify-lift (command-object command))

(world-execute-command :LIFT)))

((DROP)

(when (verify-drop (command-object command))

(world-execute-command :DROP)))

((MOVE)

(let ((positions (verify-move (command-destination command))))

(when positions

(world-execute-command :MOVE (first positions)))))

(OTHERWISE (error "Unrecognized command ~a" (command-action command)))))

;;;****************************************************

(defun verify-lift (object)

(let* ((gripper-position (world-sense-gripper-position))

(gripper-contents (world-sense-gripper-contents))

(top-block (first (world-sense-position gripper-position))))

(cond

((not (null gripper-contents))

(format t "~%Execution error on LIFT: gripper not empty.~%")

NIL)

((null top-block)

(format t "~%Execution error on LIFT: no object to lift.~%")

NIL)

((not (objects-agree object top-block gripper-position))

(format t "~%Execution error on LIFT: invalid object description~%")

NIL)

(T T))))