| Copyright | (C) 2008-2015 Edward Kmett (C) 2004 Dave Menendez |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Stability | provisional |
| Portability | portable |
| Safe Haskell | Safe |
| Language | Haskell2010 |
Control.Comonad
Description
Synopsis
- class Functor w => Comonad w where
- liftW :: Comonad w => (a -> b) -> w a -> w b
- wfix :: Comonad w => w (w a -> a) -> a
- cfix :: Comonad w => (w a -> a) -> w a
- kfix :: ComonadApply w => w (w a -> a) -> w a
- (=>=) :: Comonad w => (w a -> b) -> (w b -> c) -> w a -> c
- (=<=) :: Comonad w => (w b -> c) -> (w a -> b) -> w a -> c
- (<<=) :: Comonad w => (w a -> b) -> w a -> w b
- (=>>) :: Comonad w => w a -> (w a -> b) -> w b
- class Comonad w => ComonadApply w where
- (<@@>) :: ComonadApply w => w a -> w (a -> b) -> w b
- liftW2 :: ComonadApply w => (a -> b -> c) -> w a -> w b -> w c
- liftW3 :: ComonadApply w => (a -> b -> c -> d) -> w a -> w b -> w c -> w d
- newtype Cokleisli w a b = Cokleisli {
- runCokleisli :: w a -> b
- class Functor (f :: Type -> Type) where
- (<$>) :: Functor f => (a -> b) -> f a -> f b
- ($>) :: Functor f => f a -> b -> f b
Comonads
class Functor w => Comonad w where Source #
There are two ways to define a comonad:
I. Provide definitions for extract and extend
satisfying these laws:
extendextract=idextract.extendf = fextendf .extendg =extend(f .extendg)
In this case, you may simply set fmap = liftW.
These laws are directly analogous to the laws for monads and perhaps can be made clearer by viewing them as laws stating that Cokleisli composition must be associative, and has extract for a unit:
f=>=extract= fextract=>=f = f (f=>=g)=>=h = f=>=(g=>=h)
II. Alternately, you may choose to provide definitions for fmap,
extract, and duplicate satisfying these laws:
extract.duplicate=idfmapextract.duplicate=idduplicate.duplicate=fmapduplicate.duplicate
In this case you may not rely on the ability to define fmap in
terms of liftW.
You may of course, choose to define both duplicate and extend.
In that case you must also satisfy these laws:
extendf =fmapf .duplicateduplicate=extendidfmapf =extend(f .extract)
These are the default definitions of extend and duplicate and
the definition of liftW respectively.
Instances
| Comonad Identity Source # | |
| Comonad NonEmpty Source # | |
| Comonad Tree Source # | |
| Comonad (Arg e) Source # | |
| Comonad ((,) e) Source # | |
| Comonad w => Comonad (EnvT e w) Source # | |
| Comonad w => Comonad (StoreT s w) Source # | |
| (Comonad w, Monoid m) => Comonad (TracedT m w) Source # | |
| Comonad (Tagged s) Source # | |
| Comonad w => Comonad (IdentityT w) Source # | |
| (Comonad f, Comonad g) => Comonad (Sum f g) Source # | |
| Monoid m => Comonad ((->) m) Source # | |
kfix :: ComonadApply w => w (w a -> a) -> w a Source #
Comonadic fixed point à la Kenneth Foner:
This is the evaluate function from his "Getting a Quick Fix on Comonads" talk.
(=>=) :: Comonad w => (w a -> b) -> (w b -> c) -> w a -> c infixr 1 Source #
Left-to-right Cokleisli composition
(=<=) :: Comonad w => (w b -> c) -> (w a -> b) -> w a -> c infixr 1 Source #
Right-to-left Cokleisli composition
(=>>) :: Comonad w => w a -> (w a -> b) -> w b infixl 1 Source #
extend with the arguments swapped. Dual to >>= for a Monad.
Combining Comonads
class Comonad w => ComonadApply w where Source #
ComonadApply is to Comonad like Applicative is to Monad.
Mathematically, it is a strong lax symmetric semi-monoidal comonad on the
category Hask of Haskell types. That it to say that w is a strong lax
symmetric semi-monoidal functor on Hask, where both extract and duplicate are
symmetric monoidal natural transformations.
Laws:
(.)<$>u<@>v<@>w = u<@>(v<@>w)extract(p<@>q) =extractp (extractq)duplicate(p<@>q) = (<@>)<$>duplicatep<@>duplicateq
If our type is both a ComonadApply and Applicative we further require
(<*>) = (<@>)
Finally, if you choose to define (<@) and (@>), the results of your
definitions should match the following laws:
a@>b =constid<$>a<@>b a<@b =const<$>a<@>b
Minimal complete definition
Nothing
Methods
(<@>) :: w (a -> b) -> w a -> w b infixl 4 Source #
Instances
| ComonadApply Identity Source # | |
| ComonadApply NonEmpty Source # | |
| ComonadApply Tree Source # | |
| Semigroup m => ComonadApply ((,) m) Source # | |
| (Semigroup e, ComonadApply w) => ComonadApply (EnvT e w) Source # | |
| (ComonadApply w, Semigroup s) => ComonadApply (StoreT s w) Source # | |
| (ComonadApply w, Monoid m) => ComonadApply (TracedT m w) Source # | |
| ComonadApply w => ComonadApply (IdentityT w) Source # | |
| Monoid m => ComonadApply ((->) m) Source # | |
(<@@>) :: ComonadApply w => w a -> w (a -> b) -> w b infixl 4 Source #
A variant of <@> with the arguments reversed.
liftW2 :: ComonadApply w => (a -> b -> c) -> w a -> w b -> w c Source #
Lift a binary function into a Comonad with zipping
liftW3 :: ComonadApply w => (a -> b -> c -> d) -> w a -> w b -> w c -> w d Source #
Lift a ternary function into a Comonad with zipping
Cokleisli Arrows
newtype Cokleisli w a b Source #
Constructors
| Cokleisli | |
Fields
| |
Instances
| Comonad w => Category (Cokleisli w :: Type -> Type -> Type) Source # | |
| Comonad w => Arrow (Cokleisli w) Source # | |
Defined in Control.Comonad | |
| Comonad w => ArrowApply (Cokleisli w) Source # | |
Defined in Control.Comonad | |
| Comonad w => ArrowChoice (Cokleisli w) Source # | |
Defined in Control.Comonad | |
| ComonadApply w => ArrowLoop (Cokleisli w) Source # | |
Defined in Control.Comonad | |
| Applicative (Cokleisli w a) Source # | |
Defined in Control.Comonad Methods pure :: a0 -> Cokleisli w a a0 (<*>) :: Cokleisli w a (a0 -> b) -> Cokleisli w a a0 -> Cokleisli w a b liftA2 :: (a0 -> b -> c) -> Cokleisli w a a0 -> Cokleisli w a b -> Cokleisli w a c (*>) :: Cokleisli w a a0 -> Cokleisli w a b -> Cokleisli w a b (<*) :: Cokleisli w a a0 -> Cokleisli w a b -> Cokleisli w a a0 | |
| Functor (Cokleisli w a) Source # | |
| Monad (Cokleisli w a) Source # | |
Functors
class Functor (f :: Type -> Type) where #
Minimal complete definition
Instances
| Functor ZipList | |
Defined in Control.Applicative | |
| Functor Complex | |
Defined in Data.Complex | |
| Functor Identity | |
Defined in Data.Functor.Identity | |
| Functor First | |
Defined in Data.Monoid | |
| Functor Last | |
Defined in Data.Monoid | |
| Functor First | |
Defined in Data.Semigroup | |
| Functor Last | |
Defined in Data.Semigroup | |
| Functor Max | |
Defined in Data.Semigroup | |
| Functor Min | |
Defined in Data.Semigroup | |
| Functor Dual | |
Defined in Data.Semigroup.Internal | |
| Functor Product | |
Defined in Data.Semigroup.Internal | |
| Functor Sum | |
Defined in Data.Semigroup.Internal | |
| Functor NonEmpty | |
| Functor Par1 | |
Defined in GHC.Generics | |
| Functor P | |
Defined in Text.ParserCombinators.ReadP | |
| Functor ReadP | |
Defined in Text.ParserCombinators.ReadP | |
| Functor IntMap | |
Defined in Data.IntMap.Internal | |
| Functor Digit | |
Defined in Data.Sequence.Internal | |
| Functor Elem | |
Defined in Data.Sequence.Internal | |
| Functor FingerTree | |
Defined in Data.Sequence.Internal | |
| Functor Node | |
Defined in Data.Sequence.Internal | |
| Functor Seq | |
Defined in Data.Sequence.Internal | |
| Functor ViewL | |
Defined in Data.Sequence.Internal | |
| Functor ViewR | |
Defined in Data.Sequence.Internal | |
| Functor Tree | |
| Functor IO | |
| Functor AnnotDetails | |
Defined in Text.PrettyPrint.Annotated.HughesPJ | |
| Functor Doc | |
Defined in Text.PrettyPrint.Annotated.HughesPJ | |
| Functor Span | |
Defined in Text.PrettyPrint.Annotated.HughesPJ | |
| Functor Q | |
Defined in Language.Haskell.TH.Syntax | |
| Functor TyVarBndr | |
Defined in Language.Haskell.TH.Syntax | |
| Functor Maybe | |
| Functor Solo | |
| Functor List | |
| Monad m => Functor (WrappedMonad m) | |
Defined in Control.Applicative | |
| Arrow a => Functor (ArrowMonad a) | |
Defined in Control.Arrow | |
| Functor (Either a) | |
Defined in Data.Either | |
| Functor (Proxy :: Type -> Type) | |
Defined in Data.Proxy | |
| Functor (Arg a) | |
Defined in Data.Semigroup | |
| Functor (Array i) | |
| Functor (U1 :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (V1 :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (Map k) | |
Defined in Data.Map.Internal | |
| Functor ((,) a) | |
| Arrow a => Functor (WrappedArrow a b) | |
Defined in Control.Applicative | |
| Functor m => Functor (Kleisli m a) | |
Defined in Control.Arrow | |
| Functor (Const m :: Type -> Type) | |
Defined in Data.Functor.Const | |
| Functor f => Functor (Ap f) | |
Defined in Data.Monoid | |
| Functor f => Functor (Alt f) | |
Defined in Data.Semigroup.Internal | |
| (Generic1 f, Functor (Rep1 f)) => Functor (Generically1 f) | |
Defined in GHC.Generics | |
| Functor f => Functor (Rec1 f) | |
Defined in GHC.Generics | |
| Functor (URec (Ptr ()) :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (URec Char :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (URec Double :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (URec Float :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (URec Int :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (URec Word :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor w => Functor (EnvT e w) Source # | |
| Functor w => Functor (StoreT s w) Source # | |
| Functor w => Functor (TracedT m w) Source # | |
| (Applicative f, Monad f) => Functor (WhenMissing f x) | |
Defined in Data.IntMap.Internal | |
| Functor f => Functor (Indexing f) | |
| Functor (Tagged s) | |
Defined in Data.Tagged | |
| Functor f => Functor (Backwards f) | |
Defined in Control.Applicative.Backwards | |
| Functor m => Functor (IdentityT m) | |
| Functor m => Functor (ReaderT r m) | |
Defined in Control.Monad.Trans.Reader | |
| Functor (Constant a :: Type -> Type) | |
Defined in Data.Functor.Constant | |
| Functor f => Functor (Reverse f) | |
Defined in Data.Functor.Reverse | |
| Functor ((,,) a b) | |
| (Functor f, Functor g) => Functor (Sum f g) | |
Defined in Data.Functor.Sum | |
| (Functor f, Functor g) => Functor (f :*: g) | |
Defined in GHC.Generics | |
| (Functor f, Functor g) => Functor (f :+: g) | |
Defined in GHC.Generics | |
| Functor (K1 i c :: Type -> Type) | |
Defined in GHC.Generics | |
| Functor (Cokleisli w a) Source # | |
| Functor f => Functor (WhenMatched f x y) | |
Defined in Data.IntMap.Internal | |
| (Applicative f, Monad f) => Functor (WhenMissing f k x) | |
Defined in Data.Map.Internal | |
| Functor ((,,,) a b c) | |
| Functor ((->) r) | |
| (Functor f, Functor g) => Functor (Compose f g) | |
Defined in Data.Functor.Compose | |
| (Functor f, Functor g) => Functor (f :.: g) | |
Defined in GHC.Generics | |
| Functor f => Functor (M1 i c f) | |
Defined in GHC.Generics | |
| Functor f => Functor (WhenMatched f k x y) | |
Defined in Data.Map.Internal | |
| Functor ((,,,,) a b c d) | |
| Functor ((,,,,,) a b c d e) | |
| Functor ((,,,,,,) a b c d e f) | |