-- Indicates the legal transitions on bracket( [| |] ).
bracketOK :: ThStage -> Maybe ThLevel
bracketOK (Brack _ _ _) = Nothing -- Bracket illegal inside a bracket
-bracketOK stage = (Just (thLevel stage + 1))
+bracketOK stage = Just (thLevel stage + 1)
-- Indicates the legal transitions on splice($).
spliceOK :: ThStage -> Maybe ThLevel