import Data.Semigroup hiding (diff)
import Data.Set (Set)
import qualified Data.Set as Set

newtype DeckList = DeckList {runDeckList :: Set (Arg Text Card)}
    deriving (Show, Eq, Ord)

    let deckSort = sortBy (compare `on` name)
        in go mempty (deckSort left) (deckSort right)

    let deckSort = map (\(Arg _ x) -> x) . Set.toDescList . runDeckList
     in go mempty (deckSort left) (deckSort right)

    go :: DeckDiff -> DeckList -> DeckList -> DeckDiff

    go :: DeckDiff -> [Card] -> [Card] -> DeckDiff

        containers >= 0.6.7 && < 0.7,