#12772: (type f1 ~> f2 = forall a. f1 a -> f2 a) to core libraries -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Build System | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by Iceland_jack: @@ -9,1 +9,1 @@ - that maybe it's not worth it) + that maybe it's not worth it, ‘Fairbairn threshold’ something something) New description: Is this something that belongs to core libraries (it has other names in the wild, `:~>`, `Natural`..) {{{#!hs type f1 ~> f2 = forall a. f1 a -> f2 a }}} I use it all the time and end up redefining it (it is such a short type that maybe it's not worth it, ‘Fairbairn threshold’ something something) {{{#!hs unLift :: Applicative f => Lift f a -> f a mapLift :: (f a -> g a) -> Lift f a -> Lift g a mapFreeT :: (Functor f, Functor m) => (forall a. m a -> m' a) -> FreeT f m a -> FreeT f m' a vmap :: (a -> a') -> Vec a n -> Vec a' n liftIO :: MonadIO m => IO a -> m a hoist :: Monad m => (forall a. m a -> n a) -> t m b -> t n b trans :: (Monad m, Monad m') => (forall a. m a -> m' a) -> Bundle m v a -> Bundle m' v a process :: Monad m => (forall a. k a -> i -> a) -> MachineT m k o -> ProcessT m i o runAlt :: Alternative g => (forall x. f x -> g x) -> Alt f a -> g a hoistAlt :: (forall a. f a -> g a) -> Alt f b -> Alt g b fromCurried :: Functor f => (forall a. k a -> Curried f h a) -> Day f k b -> h b hoistScope :: Functor f => (forall x. f x -> g x) -> Scope b f a -> Scope b g a haddockWithGhc :: (forall a. [Flag] -> Ghc a -> IO a) -> [String] -> IO () newtype Alt f a = Alt { _runAlt :: forall g. Alternative g => (forall x. f x -> g x) -> g a } newtype Builder = Builder (forall r. BuildStep r -> BuildStep r) data Zipper t a = Zipper (forall b. Seq b -> t b) {-# UNPACK #-} !Int !(Seq a) class MonadCatch m => MonadMask m where mask :: ((forall a. m a -> m a) -> m b) -> m b }}} becomes {{{#!hs unLift :: Applicative f => Lift f ~> f mapLift :: f ~> g -> Lift f ~> Lift g mapFreeT :: (Functor f, Functor m) => m ~> m' -> FreeT f m ~> FreeT f m' vmap :: (a -> a') -> Vec a ~> Vec a' liftIO :: MonadIO m => IO ~> m hoist :: Monad m => m ~> n -> t m ~> t n trans :: (Monad m, Monad m') => m ~> m' -> Bundle m v ~> Bundle m' v process :: Monad m => k ~> (i -> ) -> MachineT m k ~> ProcessT m i runAlt :: Alternative g => f ~> g -> Alt f ~> g hoistAlt :: f ~> g -> Alt f ~> Alt g fromCurried :: Functor f => (k ~> Curried f h) -> Day f k ~> h hoistScope :: Functor f => f ~> g -> Scope b f ~> Scope b g haddockWithGhc :: ([Flag] -> Ghc ~> IO) -> [String] -> IO () newtype Alt f a = Alt { _runAlt :: forall g. Alternative g => (f ~> g) -> g a } newtype Builder = Builder (BuildStep ~> BuildStep) data Zipper t a = Zipper (Seq ~> t) {-# UNPACK #-} !Int !(Seq a) class MonadCatch m => MonadMask m where mask :: ((m ~> m) -> m b) -> m b }}} these examples are pretty similar. ---- Same for {{{#!hs mapBlock :: (forall e x. n e x -> n' e x) -> Block n e x -> Block n' e x mapGraph :: (forall e x. n e x -> n' e x) -> Graph n e x -> Graph n' e x mapGraphNodes1 :: (forall e x. CmmNode e x -> CmmNode e x) -> CmmGraph -> CmmGraph foldCat :: (Catenated t, Category s) => (forall a b. r a b -> s a b) -> t r a b -> s a b mapCat :: Catenated t => (forall a b. r a b -> s a b) -> t r a b -> t s a b newtype Copastro p a b = Copastro { runCopastro :: forall r. Costrong r => (forall x y. p x y -> r x y) -> r a b } newtype CopastroSum p a b = CopastroSum { runCopastroSum :: forall r. Cochoice r => (forall x y. p x y -> r x y) -> r a b } }}} vs {{{#!hs type f1 ~~> f2 = forall a b. f1 a b -> f2 a b mapBlock :: n ~~> n' -> Block n ~~> Block n' mapGraph :: n ~~> n' -> Graph n ~~> Graph n' mapGraphNodes1 :: CmmNode ~~> CmmNode -> CmmGraph -> CmmGraph foldCat :: (Catenated t, Category s) => r ~~> s -> t r ~~> s mapCat :: Catenated t => r ~~> s -> t r ~~> t s newtype Copastro p a b = Copastro { runCopastro :: forall r. Costrong r => (p ~~> r) -> r a b } newtype CopastroSum p a b = CopastroSum { runCopastroSum :: forall r. Cochoice r => (p ~~> r) -> r a b } }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12772#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler