While learning about the Yoneda lemma, I came across the following encoding of the underlying natural isomorphism in Haskell: forward :: Functor f => (forall r . (a -> r) -> f r) -> f a...

This is valid syntax in GHC 9. What do the {..} mean (as distinct from (..) which GHC 8.10 requires here)? ign :: forall {f :: Type -> Type} {p}. Applicative f => p -> f () ign _ = pure ()...

I am a beginner in Haskell and I am taken aback by the undefined function's type signature. I expected something more simple, but I found this on Hackage: undefined :: forall (r :: RuntimeRep). f...

Since ghc-8.0 we have a very nice extension called TypeApplications. Which allows us instead of: λ> show (5 :: Int) "5" do so something like that: λ> :set -XTypeApplications λ> show @I...

I'm trying to understand the difference between using forall to quantify two type variables and using forall to quantify a single type variable of tuple kind. For example, given the following type...

I'm beginning to understand how the forall keyword is used in so-called "existential types" like this: data ShowBox = forall s. Show s => SB s This is only a subset, however, of how f...

Following this answer, I've implemented a generic lift function in my program: liftTupe :: (x -> c x) -> (a, b) -> (c a, c b) --This will error liftTuple :: (forall x. x -> c x) ->...

I want to insert in Different tables with only single FORALL Loop in oracle.but FORALL don't support it.any idea how can i do it?? create or replace PROCEDURE test IS TYPE avl_web_details IS TAB...

What is the purpose of the foralls in this code? class Monad m where (>>=) :: forall a b. m a -> (a -> m b) -> m b (>>) :: forall a b. m a -> m b -> m b -- Explicit f...

I am working on kernel development in AOSP, and the kernel repository that I work on is not a part of the operating system. It has an individual git repository. So when I try to push all AOSP sourc...

As shown below, in Haskell, it's possible to store in a list values with heterogeneous types with certain context bounds on them: data ShowBox = forall s. Show s => ShowBox s heteroList :: [Sh...

I'm struggling to understand the exists keyword in relation to Haskell type system. As far as I know, there is no such keyword in Haskell by default, but: There are extensions which add them, in ...

I am using C# 4.0 and Code Contracts and I have my own custom GameRoomCollection : IEnumerable<GameRoom>. I want to ensure, that no instances of GameRoomCollection will ever contain a null v...

I've been given a 2D matrix representing temperature points on the surface of a metal plate. The edges of the matrix (plate) are held constant at 20 degrees C and there is a constant heat source of...

Okay, I have yet another Code Contracts question. I have a contract on an interface method that looks like this (other methods omitted for clarity): [ContractClassFor(typeof(IUnboundTagGroup))] pu...