-- | Compares two Maybe AllocElement and chooses the best score.
bestAllocElement :: Maybe Node.AllocElement
                 -> Maybe Node.AllocElement
                 -> Maybe Node.AllocElement
bestAllocElement a Nothing = a
bestAllocElement :: Maybe Node.AllocElement
                 -> Maybe Node.AllocElement
                 -> Maybe Node.AllocElement
bestAllocElement a Nothing = a
bestAllocElement a Nothing = a