[GHC] #13026: RFC functions for sums and products
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.0.1 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'll ask on the libraries mailing list depending on feedback. Adding these to `Data.Functor.Sum`, `Data.Functor.Product` a la `Control.Arrow` {{{!hs (||||) :: (f a -> b) -> (g a -> b) -> ((Sum f g) a -> b) f |||| g = \case InL fa -> f fa InR ga -> g ga (&&&&) :: (a -> f b) -> (a -> g b) -> (a -> (Product f g) b) (f &&&& g) a = f a `Pair` g a }}} `||||` is used in "Monad transformers and modular algebraic effects: What binds them together" in section 2.4, the names are up for discussion -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: @@ -6,1 +6,1 @@ - {{{!hs + {{{#!hs New description: I'll ask on the libraries mailing list depending on feedback. Adding these to `Data.Functor.Sum`, `Data.Functor.Product` a la `Control.Arrow` {{{#!hs (||||) :: (f a -> b) -> (g a -> b) -> ((Sum f g) a -> b) f |||| g = \case InL fa -> f fa InR ga -> g ga (&&&&) :: (a -> f b) -> (a -> g b) -> (a -> (Product f g) b) (f &&&& g) a = f a `Pair` g a }}} `||||` is used in "Monad transformers and modular algebraic effects: What binds them together" in section 2.4, the names are up for discussion -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Some other {{{#!hs type f ~> g = forall x. f x -> g x (****) :: f ~> f' -> g ~> g' -> Product f g ~> Product f' g' (f **** g) (fa `Pair` ga) = f fa `Pair` g ga first' :: f ~> f' -> Product f g ~> Product f' g first' = (**** id) second' :: g ~> g' -> Product f g ~> Product f g' second' = (id ****) (++++) :: f ~> f' -> g ~> g' -> Sum f g ~> Sum f' g' f ++++ g = \case InL fa -> InL (f fa) InR ga -> InR (g ga) left' :: f ~> f' -> Sum f g ~> Sum f' g left' = (++++ id) right' :: g ~> g' -> Sum f g ~> Sum f g' right' = (id ++++) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Stolen from `Data.Tuple`, I have never needed them but who knows {{{#!hs fst' :: Product f g ~> f fst' (Pair fa _) = fa snd' :: Product f g ~> g snd' (Pair _ ga) = ga curry' :: (Product f g ~> h) -> (forall a. f a -> g a -> h a) curry' nat fa ga = nat (Pair fa ga) uncurry' :: (forall a. f a -> g a -> h a) -> (Product f g ~> h) uncurry' f (Pair fa ga) = f fa ga swap' :: Product f g ~> Product g f swap' (Pair fa ga) = Pair ga fa }}} and from `Data.Either` {{{#!hs lefts' :: [(Sum f g) a] -> [f a] lefts' sums = [ fa | InL fa <- sums ] rights' :: [(Sum f g) a] -> [g a] rights' sums = [ ga | InR ga <- sums ] isInL :: Sum f g a -> Bool isInL InL{} = True isInL _ = False isInR :: Sum f g a -> Bool isInR InR{} = True isInR _ = False sum' :: (f a -> c) -> (g a -> c) -> (Sum f g a -> c) sum' f _ (InL x) = f x sum' _ g (InR y) = g y partitionSums :: [Sum f g a] -> ([f a], [g a]) partitionSums = foldr (sum' left right) ([], []) where left a ~(l, r) = (a:l, r) right a ~(l, r) = (l, a:r) }}} With the `lens` vocabulary we could write {{{#!hs _InL :: Prism (Sum f g a) (Sum f' g a) (f a) (f' a) _InL = prism InL (\case InL fa -> Right fa InR ga -> Left (InR ga)) _InR :: Prism (Sum f g a) (Sum f g' a) (g a) (g' a) _InR = prism InR (\case InR ga -> Right ga InL fa -> Left (InL fa)) instance Field1 (Product f g a) (Product f' g a) (f a) (f' a) where _1 :: Lens (Product f g a) (Product f' g a) (f a) (f' a) _1 = lens fst' (\(Pair _ ga) fa -> Pair fa ga) instance Field2 (Product f g a) (Product f g' a) (g a) (g' a) where _2 :: Lens (Product f g a) (Product f g' a) (g a) (g' a) _2 = lens snd' (\(Pair fa _) ga -> Pair fa ga) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): [https://mail.haskell.org/pipermail/libraries/2016-December/027489.html libraries discussion] -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Some more functions (would be `Iso`s in lens) {{{#!hs runSum :: Sum f g a -> Either (f a) (g a) runSum = Left |||| Right runProduct :: Product f g a -> (f a, g a) runProduct (Pair fa ga) = (fa, ga) }}} Used [https://github.com/bitemyapp/nt-in- haskell/blob/2563047caaffa1a88c540128424a250f0d267aaf/answers/src/NT/Answers/D.hs here]. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): These functions and more are defined [https://github.com/sboosali /commands- core/blob/6bcfe72aef9b55f366a4e215720a9475de2d2e6f/sources/Data/HTypes.hs here] {{{#!hs (.|||.) :: (f1 :~> g) -> (f2 :~> g) -> ((f1 :+: f2) :~> g) (<|||>) :: (f1 :~> (m :. g)) -> (f2 :~> (m :. g)) -> ((f1 :+: f2) :~> (m :. g) getFirst, outL :: (f :*: g) :~> f getSecond, inL :: (f :*: g) :~> g getSecond (Pair _ g) = g (.&&&.) :: (f :~> g1) -> (f :~> g2) -> (f :~> (g1 :*: g2)) (<&&&>) :: (Applicative m) => (f :~> (m :. g1)) -> (f :~> (m :. g2)) -> (f :~> (m :. (g1 :*: g2))) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Purescript also includes this function for `Data.Functor.Compose` {{{#!hs bihoistCompose :: forall f g h i . Functor f => (f ~> h) -> (g ~> i) -> Compose f g ~> Compose h i bihoistCompose natF natG (Compose fga) = Compose (natF (map natG fga)) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: @@ -18,0 +18,4 @@ + + **Edit**: [http://hackage.haskell.org/package/comonad- + transformers-3.1/docs/Data-Functor-Coproduct.html coproduct] is one name + for `||||` New description: I'll ask on the libraries mailing list depending on feedback. Adding these to `Data.Functor.Sum`, `Data.Functor.Product` a la `Control.Arrow` {{{#!hs (||||) :: (f a -> b) -> (g a -> b) -> ((Sum f g) a -> b) f |||| g = \case InL fa -> f fa InR ga -> g ga (&&&&) :: (a -> f b) -> (a -> g b) -> (a -> (Product f g) b) (f &&&& g) a = f a `Pair` g a }}} `||||` is used in "Monad transformers and modular algebraic effects: What binds them together" in section 2.4, the names are up for discussion **Edit**: [http://hackage.haskell.org/package/comonad- transformers-3.1/docs/Data-Functor-Coproduct.html coproduct] is one name for `||||` -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Here is an interesting one, witnessing the isomorphism between `Sum Identity` and [https://hackage.haskell.org/package/transformers-0.3.0.0/docs/Control- Applicative-Lift.html Control.Applicative.Lift.Lift] {{{#!hs toLift :: Sum Identity g ~> Lift g toLift = \case InL (Identity a) -> Pure a InR ga -> Other ga }}} if it ever gets added to ''base''. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): {{{#!hs e1 :: (f a -> b) -> (g a -> b) -> (f :+: g) a -> b e1 f _ (L1 l) = f l e1 _ f (R1 r) = f r fst1 :: (f :*: g) a -> f a fst1 (l :*: _) = l snd1 :: (f :*: g) a -> g a snd1 (_ :*: r) = r }}} are defined in [https://hackage.haskell.org/package/one-liner-0.7/docs/src /Generics-OneLiner-Internal.html one-liner] -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): Please consider these functions from a [http://stackoverflow.com/a/25817530/165806 StackOverflow answer] {{{#!hs liftO :: (Functor f, Applicative g) => f ~> Compose f g liftO = Compose . fmap pure liftI :: Applicative f => g ~> Compose f g liftI = Compose . pure hoistO :: f ~> f' -> Compose f g ~> Compose f' g hoistO eta = Compose . eta . getCompose hoistI :: Functor f => g ~> g' -> Compose f g ~> Compose f g' hoistI eta = Compose . fmap eta . getCompose }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#13026: RFC functions for sums and products -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): Can I give you some honest advice, Iceland_jack? I barely have any idea what this proposal is even about anymore. That's because you have been clogging this thread with clutter that doesn't pertain to the original proposal. Your argument doesn't become more convincing the more definitions you throw at us - in fact, it has quite the opposite effect! This thread is now so overloaded with tangentially related cruft that I suspect no one except the most masochistic lurkers will dare attempt to read it. Sorry if that was harsh, but I feel that it needed to be said. Proposals are best kept to a small, self-contained unit of information that is easily digestible. You did the right thing by starting a libraries mailing list [https://mail.haskell.org/pipermail/libraries/2016-December/027489.html discussion] about `(||||)` and `(&&&&)` (and //only// `(||||)` and `(&&&&)`)! In the particular case of this proposal, it hasn't seemed to have reached a consensus on the naming - and that's fine! All you need to do is figure out names that a majority of the community can agree with, and argue convincingly for it. These other functions that you've put above are just distracting from the main thing you're trying to advocate for. Perhaps small subsets of them could be interesting proposals on their own. If so, start separate libraries discussions for them! But please don't bog down your own proposal by including everything under the sun. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13026#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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