Select a special element from a sequence.

Question

Hi,

I am trying to model a system in which an element can be inserted into any possible location in a container,and I am using an instance-based solution Modeling.

I would like to create a scenario that insert an element after the head element. I am using the following script to simulate the scenario, but it  does not work, and spec explorer crashes.The root reason seems to be "object for instance field selection neither reference nor compound nor native".

machine RandomInsertWithOneItem(DlinkAdapter container) : Main where ForExploration = true
{
    (let DLinkedListNode<string> newNode
    in
    ((. newNode!= container.GetHead() .):container.InsertAfter("c",newNode)))
} 

Here is the Debug Log:

FATAL ERROR: Executor failure:
Xrt Stacktrace:
   at DlinkTest.DlinkAdapter.GetHead
   at CordCode.constraint_5(DlinkTest.DlinkAdapter,DataStructures.DLinkedListNode<System.String>)

stacktrace: 
   在 Microsoft.SpecExplorer.VS.SpecExplorerPackage.RecoverFromFatalError(Exception exception)
   在 Microsoft.SpecExplorer.RecoverFromFatalErrorEventObserver.HandleEvent(ExplorerEvent e)
   在 Microsoft.SpecExplorer.EventManager.HandleEvent(ExplorerEvent e)

involved exception: Microsoft.Xrt.Execution.ExecutionFatalErrorException: Executor failure:
Xrt Stacktrace:
   at DlinkTest.DlinkAdapter.GetHead
   at CordCode.constraint_5(DlinkTest.DlinkAdapter,DataStructures.DLinkedListNode<System.String>)
 ---> Microsoft.Xrt.RecoverFromFatalErrorException: object for instance field selection neither reference nor compound nor native

I have two questions here.

1. how to get a reference to a single element from a container?

2. what is wrong with the the method "getHead"?

Thanks in advance.

Answer 1

Hi all,

Finally, I figured out why it does not work, and now it works.

After I read all the questions in this forum and the documents and trying again and again, it turns out I have used the wrong collection type.

Regards,