I have been working on a project about the well known problem fox-goose-beans-farmer. I am trying to implement it on a browser based compiler which is https://stripsfiddle.herokuapp.com/ . All of the functions except moveFoxAcross and moveFoxBack works. I couldn't see any flaws. Can someone point out my mistake or suggest any valid syntax source. Here is my domain code:

(define (domain domain-FGB)
(:requirements :strips :typing)
(:types fox goose beans farmer onLeftBank)

(:action moveGooseAcross
    :parameters (?g - goose ?l - onLeftBank ?f - farmer)
    :precondition (and (not (at ?g ?l)) (not (at ?f ?l)))
    :effect (and (at ?g ?l) (at ?f ?l))

    )

(:action moveFoxAcross
    :parameters (?fo - fox ?l - onLeftBank ?f - farmer ?b - beans ?g - goose)
    :precondition (and (not (at ?fo ?l)) (not (at ?f ?l))(or (and (not (at ?b ?l)) (at ?g ?l)) (and (at ?b ?l) (not (?g ?l)))))
    :effect (and (at ?fo ?l) (at ?f ?l))

    )

(:action moveBeansAcross 
    :parameters (?b - beans ?fo - fox ?l - onLeftBank ?f - farmer ?g - goose)
    :precondition (and (not (at ?b ?l)) (not (at ?f ?l))(or (and (not (at ?fo ?l)) (at ?g ?l)) (and (at ?fo ?l) (not (at ?g ?l)))))
    :effect (and (at ?b ?l) (at ?f ?l))

    )

(:action farmerAcrossRiver 
    :parameters (?f - farmer ?l - onLeftBank)
    :precondition (not (at ?f ?l))
    :effect (at ?f ?l)

    )

(:action moveGooseBack 
    :parameters (?g - goose ?l - onLeftBank ?f - farmer)
    :precondition (and (at ?g ?l)   (at ?f ?l))
    :effect (and (not (at ?g ?l)) (not (at ?f ?l))))

(:action moveFoxBack 
    :parameters (?fo - fox ?l - onLeftBank ?f - farmer ?b - beans ?g - goose)
    :precondition (and (at ?fo ?l) (at ?f ?l) (or (and (not (at ?b ?l)) (at ?g ?l)) (and (at ?b ?l) (not (?g ?l)))))
    :effect (and (not (at ?fo ?l)) (not (at ?f ?l))))

(:action moveBeansBack 
    :parameters (?b - beans ?fo - fox ?l - onLeftBank ?f - farmer ?g - goose)
    :precondition (and (at ?b ?l) (at ?f ?l)(or (and (not (at ?fo ?l)) (at ?g ?l)) (and (at ?fo ?l) (not (at ?g ?l)))))
    :effect (and (not (at ?b ?l)) (not (at ?f ?l))))

(:action farmerGoesBack 
    :parameters (?f - farmer ?l - onLeftBank)
    :precondition (at ?f ?l)
    :effect (not (at ?f ?l))
    ))

Here is my problem code:

(define (problem FGB)
(:domain domain-FGB)
(:objects 
    FOX - fox 
    GOOSE - goose 
    BEANS - beans 
    FARMER - farmer
    ONLEFTBANK - onLeftBank)

(:init 
    (and (not(at FOX ONLEFTBANK)) (not(at GOOSE ONLEFTBANK)) (not(at FARMER ONLEFTBANK)) (not(at BEANS ONLEFTBANK))))

(:goal (and (at FOX ONLEFTBANK) (at GOOSE ONLEFTBANK) (at FARMER ONLEFTBANK) (at BEANS ONLEFTBANK))))

Here is my question:

• only moveFoxAcross and moveFoxBack functions doesn't work and gives compilation error can you help me see why?.
• even though I compile without them, it gives me 0 solutions.
• is there any example that can help me solve this question ?

You can just select "Create your own" from the list at the domain section and copy/paste my code to try it yourself.

Thanks in advance

The problem is the missing "at" in the second and clause of the second or clause. The capital AT below.

:precondition (and 
               (not (at ?fo ?l)) 
               (not (at ?f ?l)) 
               (or (and 
                      (not (at ?b ?l)) 
                      (at ?g ?l)
                   ) 
                   (and 
                      (at ?b ?l) 
                      (not (AT ?g ?l))
                   )
                )
              )

But I could not find a solution with this correction. I keep on working and will inform if find any solution.