Question

I get this exception when I run a transformation in GrGen.NET. I could narrow it down to this minimal example:

Rule set:

rule createNode : (Node) {
    modify {
        newNode:Node;
        return(newNode);
    }    
}

rule deleteAny {
    :Node;
    replace{}
}

Sequence set:

(myVariable) = createNode
deleteAny[*]

P.S.: GrGen.NET is a quite popular graph transformation library (check it out on http://grgen.net) based on the .NET-framework. It would be cool if someone could define a Tag for GrGen.NET, I don’t have enough reputation :-). Cheers!

Answer 1

Apparently, this bug comes from underneath from GrGen. The problem is the variable myVariable that contains the created node from the rule createNode.

When the node should be deleted using deleteAny, it’s deleted from the graph but still somehow trapped in this variable. A simple workaround is to assign an arbitrary value to this variable, e.g. myVariable = 0, before the nodes are getting deleted.

It’s a hack, but will do until this bug is fixed.