{- | This predicate is true for nodes which are instantiations of a
specification with the given name -}
dgnPredParameterized :: String -> LNode DGNodeLab -> Maybe (LNode DGNodeLab)
dgnPredParameterized n nd@(_, DGNodeLab
                               { nodeInfo = DGNode { node_origin = DGInst sid }
                               })
    | show sid == n = Just nd
    | otherwise = Nothing
dgnPredParameterized :: String -> LNode DGNodeLab -> Maybe (LNode DGNodeLab)
dgnPredParameterized n nd@(_, DGNodeLab
                               { nodeInfo = DGNode { node_origin = DGInst sid }
                               })
    | show sid == n = Just nd
    | otherwise = Nothing
dgnPredParameterized n nd@(_, DGNodeLab
                               { nodeInfo = DGNode { node_origin = DGInst sid }
                               })
    | show sid == n = Just nd
    | otherwise = Nothing