(define (domain trucks)
  (:requirements :strips) 
  (:predicates
    (package ?obj)
    (truck ?truck)
    (location ?loc)
    (in-city ?obj ?city)
    (city ?city)
    (at ?obj ?loc)
    (in ?obj ?obj)
  )

 
(:action load-truck
  :parameters (?obj ?truck ?loc)
  :precondition
   (and 
     (package ?obj) 
     (truck ?truck) 
     (location ?loc)
     (at ?truck ?loc) 
     (at ?obj ?loc))
  :effect
   (and (not (at ?obj ?loc)) (in ?obj ?truck)))

(:action unload-truck
  :parameters (?obj ?truck ?loc)
  :precondition
   (and 
     (package ?obj) 
     (truck ?truck) 
     (location ?loc)
     (at ?truck ?loc) 
     (in ?obj ?truck)
   )
  :effect
   (and (not (in ?obj ?truck)) (at ?obj ?loc)))

(:action drive-truck
  :parameters (?truck ?loc-from ?loc-to ?city)
  :precondition
   (and 
     (truck ?truck) 
     (location ?loc-from) 
     (location ?loc-to) 
     (city ?city)
     (at ?truck ?loc-from)
     (in-city ?loc-from ?city)
     (in-city ?loc-to ?city)
   )
  :effect
   (and (not (at ?truck ?loc-from)) (at ?truck ?loc-to)))
)