draggable_equal: (d1, d2) ->
return d1.data("no") == d2.data("no")
+ draggable_accept: ($draggable, $droppable) ->
+ dropped = $droppable.closest("ul, ol").find(".draggable")
+ return (super $draggable, $droppable) && dropped.length == 0
check_question: (question) ->
# subjects placed in predicates