class Foo a where
  fromFoo :: Maybe a -> Int

data Bar = Bar
instance Foo Bar where
  fromFoo (Just Bar) = 1
  fromFoo _ = 0

parseBar :: String -> Maybe Bar
parseBar "Bar" = Just Bar
parseBar _ = Nothing

data Baz = Baz
instance Foo Baz where
  fromFoo (Just Baz) = 2
  fromFoo _ = 0

parseBaz :: String -> Maybe Baz
parseBaz "Baz" = Just Baz
parseBaz _ = Nothing


myFunction :: Bool -> String -> Int
myFunction selector toParse = fromFoo $
  if selector
  then parseBar toParse
  else parseBaz toParse