never executed always true always false

    1 module HelVM.HelMA.Automaton.WrapTokenList where
    2 
    3 import qualified Text.Read
    4 import qualified Text.Show
    5 
    6 newtype WrapTokenList a = WrapTokenList { unWrapTokenList :: a }
    7   deriving stock (Eq)
    8 
    9 ----
   10 
   11 instance Show a => Show (WrapTokenList [a]) where
   12   show (WrapTokenList tokens) = show =<< tokens
   13 
   14 instance Read a => Read (WrapTokenList [a]) where
   15   readsPrec _ source = [( WrapTokenList $ maybeToList . readMaybe . one =<< source , "")]