forall

SHOP2 一个人工智能里面关于任务分解和任务规划的系统。JSHOP2是其java版本。

; This extremely simple example shows how to use forall constructs both in
; logical expressions and operator delete/add lists. Note the similar syntax
; and the different semantics of these two very different usages of the forall
; keyword.

(defdomain forallexample (
  ; To load a package ?z in a truck ?t
  (:operator (!load ?z ?t) () () ((in ?z ?t)))

  ; To move a truck ?t from city ?x to city ?y
  (:operator (!drive ?t ?x ?y)
    ()
    ; The packages in the car move with it from city ?x to city ?y too, hence
    ; the following add and delete list using forall keyword.
    ((truck-at ?t ?x) (forall (?z) ((package ?z) (in ?z ?t)) ((at ?z ?x))))
    ((truck-at ?t ?y) (forall (?z) ((package ?z) (in ?z ?t)) ((at ?z ?y))))
  )

  ; The top-layer method to move packages from city ?x to city ?y.
  (:method (move-packages ?x ?y)
    ((truck ?t) (truck-at ?t ?x))
    ((load-packages ?x ?t) (!drive ?t ?x ?y)))

  ; To verify if all the packages are loaded, and if not load them. Note that
  ; this method can be implemented much easier and more efficiently without
  ; using the forall keyword. The use of forall here is just to show how it is
  ; used and does not necessarily reflect the best way to implement this
  ; or similar methods.
  (:method (load-packages ?x ?t)
    ; Are all the packages loaded?
    (forall (?z) ((package ?z) (at ?z ?x)) (in ?z ?t))
    nil

    ; If not, choose a package, load it, and recursively call the same method.
    ((package ?z) (at ?z ?x) (not (in ?z ?t)))
    ((!load ?z ?t) (load-packages ?x ?t)))
  )
)