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[Francisco Durán <duran AT lcc.uma.es>]

Hi Petr,

I'd keep the wheels as a lists of oids (references to these wheel objects). 

(omod CAR is 
      pr LIST{Oid} . ---- there is a predefined view Oid in Maude from TRIV 
to CONFIGURATION

      class Car | wheel : List{Oid} .

You can then make sure that these four references are actually to wheel 
object with a membership. 

Best regards,

Francisco


On 26/11/2012, at 21:13, Petr Vrchlavsky wrote:

> Hi, 
> 
> I am new to the Maude and I come across a problem. I am trying to model ORM 
> system with some data evolution features. I choose to use object-orientet 
> maude.
> I cannot find out how to model list of objects in an example below there is 
> a car which should have a collection of wheels. I would like to model this 
> by a list of wheels, something like an array list in Java.
> Can you pleas give me an example how to model a list of wheels inside CAR 
> modul? Thanx.
> 
> (omod WHEEL is
> 
>       pr QID .
>       
>       subsort Qid < Oid .
>       
>       sort WheelSize .
>       ops small big : -> WheelSize [ctor] .
>       class Wheel | type : WheelSize .
>       
>       sort Decoration .
>       ops nice bad : -> Decoration [ctor] .
>       class DecoratedWheel | decoration : Decoration .
>       
>       subclass DecoratedWheel < Wheel .
>       
> endom)
> 
> (omod CAR is
> 
>       pr WHEEL .
>       pr QID .
>       
>       subsort Qid < Oid .
>       subsort WheelSize < Msg .
>       
>       class Car | wheel : Oid .
> 
>       msg getWheel : Oid -> Msg .
> 
>       vars M N : Oid .
>       var W : Wheel .
>       var D : Decoration .
>       var S : WheelSize .
>       var W : Wheel .
>       var WS : WheelSize .
>       var D : Decoration .
>       
>       rl [getWheel] : getWheel(M) < M : Car | wheel : N > < N : Wheel | > 
> => < N : Wheel | > .  
> 
>       msg getWheelSize : Oid -> WheelSize .
>       
>       rl [getWheelSize] : getWheelSize(M) < M : Wheel | type : WS > => WS .
> 
> endom
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