ppLevelSymbol :: LevelSymbol -> Doc
ppLevelSymbol x
  | validLevelSymbol x = char x
  | otherwise          = error ("ppLevelSymbol: invalid character: " ++ [x])
ppLevelSymbol :: LevelSymbol -> Doc
ppLevelSymbol x
  | validLevelSymbol x = char x
  | otherwise          = error ("ppLevelSymbol: invalid character: " ++ [x])
ppLevelSymbol x
  | validLevelSymbol x = char x
  | otherwise          = error ("ppLevelSymbol: invalid character: " ++ [x])