上面的pddl有语法错误

非常抱歉，我在回答中犯了一个错误。以下是修正后的 PDDL 代码：

(define (problem crossing-river)
(:domain crossing)
(:objects farmer wolf sheep cabbage riverbank1 riverbank2)
(:init
    (at farmer riverbank1)    
    (at wolf riverbank1)
    (at sheep riverbank1)
    (at cabbage riverbank1)
    (at riverbank1 riverbank1)
    (at riverbank2 riverbank2)
)
(:goal
    (and
        (at farmer riverbank2)
        (at wolf riverbank2)
        (at sheep riverbank2)
        (at cabbage riverbank2)
    )
)
(:operators
    ; farmer crosses river alone
    (:operator cross-farmer-alone
        :precondition (at farmer ?from)
        :effect (and 
            (not (at farmer ?from))
            (at farmer ?to)
            (not (at ?any ?from))
            (at ?any ?to)
        )
    )
    ; farmer crosses river with wolf
    (:operator cross-farmer-wolf
        :precondition (and 
            (at farmer ?from)
            (at wolf ?from)
        )
        :effect (and 
            (not (at farmer ?from))
            (not (at wolf ?from))
            (at farmer ?to)
            (at wolf ?to)
            (not (at ?any ?from))
            (at ?any ?to)
        )
    )
    ; farmer crosses river with sheep
    (:operator cross-farmer-sheep
        :precondition (and 
            (at farmer ?from)
            (at sheep ?from)
        )
        :effect (and 
            (not (at farmer ?from))
            (not (at sheep ?from))
            (at farmer ?to)
            (at sheep ?to)
            (not (at ?any ?from))
            (at ?any ?to)
        )
    )
    ; farmer crosses river with cabbage
    (:operator cross-farmer-cabbage
        :precondition (and 
            (at farmer ?from)
            (at cabbage ?from)
        )
        :effect (and 
            (not (at farmer ?from))
            (not (at cabbage ?from))
            (at farmer ?to)
            (at cabbage ?to)
            (not (at ?any ?from))
            (at ?any ?to)
        )
    )
)
)

感谢您指出我的错误！