-{- Why so complicated? -=chak
-plusParent :: Parent -> Parent -> Parent
-plusParent NoParent rel =
- ASSERT2( case rel of { NoParent -> True; other -> False },
- ptext (sLit "plusParent[NoParent]: ") <+> ppr rel )
- NoParent
-plusParent (ParentIs n) rel =
- ASSERT2( case rel of { ParentIs m -> n==m; other -> False },
- ptext (sLit "plusParent[ParentIs]:") <+> ppr n <> comma <+> ppr rel )
- ParentIs n
- -}
-