anchor.diff:          verticesToRecalc
   
       let processVertex v = 
  -        let temp = nodes
  -
           makeReductions v
   
           let newGssVs = new ResizeArray<_>(2)
  
positive.code:                             for (prod, pos) in arr do
                                  currentGraphV.AddReduction(new Reduction(newVertex, prod, pos, Some edge))
                  edge.Ast
              | x -> (newVertex.Edge x).Ast //!!!!!!
          if ast >= 0 
          then addChildren nodes.[ast] path prod
          else 
  
negative.code:             this = null && other = null || compare this.Head other.Head && this.Tail.IsEqual(other.Tail)
  
      member this.IsEqual (nodes : Nodes) = 
          nodes.Length = this.Length 
          && let h = ref this in nodes.isForAll(fun x -> let res = compare x h.Value.Head
                                                         h := h.Value.Tail
  