[Haskell-beginners] How to include {-# LANGUAGE LambdaCase #-} at the ghci prompt

[Francesco Ariis]

Il 26 marzo 2021 alle 12:20 Galaxy Being ha scritto:
> I've got this code I've entered into the ghci by hand between :{ and :}
> 
> :{
> {-# LANGUAGE LambdaCase #-}
> data List a = Empty | Cons a (List a) deriving (Eq, Ord, Show)
> infixr 5 `Cons`
> 
> subst_c :: (a -> Bool)  -> (a, MyList a) -> MyList a
> subst_c pred = \ case
>                      (_, Empty)    -> Empty
>                      (n, Cons e t)
>                        | pred e    -> Cons n $ subst_c pred (n, t)
>                        | otherwise -> Cons e $ subst_c pred (n, t)
> :}
> 

    λ> :set -XLambdaCase