public override void Evaluate(Stack state, FormulaEngine engine) { var namedRef = (Reference)engine.ReferenceFactory.Named(_name); Formula target = engine.GetFormulaAt(namedRef); if (target != null) { var selfRef = (NamedReference)target.SelfReference; IOperand op = selfRef.ValueOperand; state.Push(op); } else { state.Push(new ErrorValueOperand(ErrorValueType.Name)); } }