Copyright	(C) 2012-16 Edward Kmett
License	BSD-style (see the file LICENSE)
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	provisional
Portability	Rank2Types
Safe Haskell	Trustworthy
Language	Haskell2010

Control.Lens.Getter

Contents

Getters
Building Getters
Combinators for Getters and Folds
Indexed Getters
- Indexed Getter Combinators
Implementation Details

Description

A Getter s a is just any function (s -> a), which we've flipped into continuation passing style, (a -> r) -> s -> r and decorated with Const to obtain:

type Getting r s a = (a -> Const r a) -> s -> Const r s

If we restrict access to knowledge about the type r, we could get:

type Getter s a = forall r. Getting r s a

However, for Getter (but not for Getting) we actually permit any functor f which is an instance of both Functor and Contravariant:

type Getter s a = forall f. (Contravariant f, Functor f) => (a -> f a) -> s -> f s

Everything you can do with a function, you can do with a Getter, but note that because of the continuation passing style (.) composes them in the opposite order.

Since it is only a function, every Getter obviously only retrieves a single value for a given input.

A common question is whether you can combine multiple Getters to retrieve multiple values. Recall that all Getters are Folds and that we have a Monoid m => Applicative (Const m) instance to play with. Knowing this, we can use <> to glue Folds together:

>>> (1, 2, 3, 4, 5) ^.. (_2 <> _3 <> _5)
[2,3,5]

Synopsis

type Getter s a = forall (f :: Type -> Type). (Contravariant f, Functor f) => (a -> f a) -> s -> f s
type IndexedGetter i s a = forall (p :: Type -> Type -> Type) (f :: Type -> Type). (Indexable i p, Contravariant f, Functor f) => p a (f a) -> s -> f s
type Getting r s a = (a -> Const r a) -> s -> Const r s
type IndexedGetting i m s a = Indexed i a (Const m a) -> s -> Const m s
type Accessing (p :: Type -> Type -> Type) m s a = p a (Const m a) -> s -> Const m s
to :: (Profunctor p, Contravariant f) => (s -> a) -> Optic' p f s a
ito :: (Indexable i p, Contravariant f) => (s -> (i, a)) -> Over' p f s a
like :: (Profunctor p, Contravariant f, Functor f) => a -> Optic' p f s a
ilike :: (Indexable i p, Contravariant f, Functor f) => i -> a -> Over' p f s a
(^.) :: s -> Getting a s a -> a
view :: MonadReader s m => Getting a s a -> m a
views :: MonadReader s m => LensLike' (Const r :: Type -> Type) s a -> (a -> r) -> m r
use :: MonadState s m => Getting a s a -> m a
uses :: MonadState s m => LensLike' (Const r :: Type -> Type) s a -> (a -> r) -> m r
listening :: MonadWriter w m => Getting u w u -> m a -> m (a, u)
listenings :: MonadWriter w m => Getting v w u -> (u -> v) -> m a -> m (a, v)
(^@.) :: s -> IndexedGetting i (i, a) s a -> (i, a)
iview :: MonadReader s m => IndexedGetting i (i, a) s a -> m (i, a)
iviews :: MonadReader s m => IndexedGetting i r s a -> (i -> a -> r) -> m r
iuse :: MonadState s m => IndexedGetting i (i, a) s a -> m (i, a)
iuses :: MonadState s m => IndexedGetting i r s a -> (i -> a -> r) -> m r
ilistening :: MonadWriter w m => IndexedGetting i (i, u) w u -> m a -> m (a, (i, u))
ilistenings :: MonadWriter w m => IndexedGetting i v w u -> (i -> u -> v) -> m a -> m (a, v)
class Contravariant (f :: Type -> Type) where
- contramap :: (a' -> a) -> f a -> f a'
- (>$) :: b -> f b -> f a
getting :: (Profunctor p, Profunctor q, Functor f, Contravariant f) => Optical p q f s t a b -> Optical' p q f s a
newtype Const a (b :: k) = Const {
- getConst :: a
}

Getters

type Getter s a = forall (f :: Type -> Type). (Contravariant f, Functor f) => (a -> f a) -> s -> f s Source #

A Getter describes how to retrieve a single value in a way that can be composed with other LensLike constructions.

Unlike a Lens a Getter is read-only. Since a Getter cannot be used to write back there are no Lens laws that can be applied to it. In fact, it is isomorphic to an arbitrary function from (s -> a).

Moreover, a Getter can be used directly as a Fold, since it just ignores the Applicative.

type IndexedGetter i s a = forall (p :: Type -> Type -> Type) (f :: Type -> Type). (Indexable i p, Contravariant f, Functor f) => p a (f a) -> s -> f s Source #

Every IndexedGetter is a valid IndexedFold and can be used for Getting like a Getter.

type Getting r s a = (a -> Const r a) -> s -> Const r s Source #

When you see this in a type signature it indicates that you can pass the function a Lens, Getter, Traversal, Fold, Prism, Iso, or one of the indexed variants, and it will just "do the right thing".

Most Getter combinators are able to be used with both a Getter or a Fold in limited situations, to do so, they need to be monomorphic in what we are going to extract with Const. To be compatible with Lens, Traversal and Iso we also restricted choices of the irrelevant t and b parameters.

If a function accepts a Getting r s a, then when r is a Monoid, then you can pass a Fold (or Traversal), otherwise you can only pass this a Getter or Lens.

type IndexedGetting i m s a = Indexed i a (Const m a) -> s -> Const m s Source #

Used to consume an IndexedFold.

type Accessing (p :: Type -> Type -> Type) m s a = p a (Const m a) -> s -> Const m s Source #

This is a convenient alias used when consuming (indexed) getters and (indexed) folds in a highly general fashion.

Building Getters

to :: (Profunctor p, Contravariant f) => (s -> a) -> Optic' p f s a Source #

Build an (index-preserving) Getter from an arbitrary Haskell function.

to f . to g ≡ to (g . f)

a ^. to f ≡ f a

>>> a ^.to f
f a

>>> ("hello","world")^.to snd
"world"

>>> 5^.to succ
6

>>> (0, -5)^._2.to abs
5

to :: (s -> a) -> IndexPreservingGetter s a

ito :: (Indexable i p, Contravariant f) => (s -> (i, a)) -> Over' p f s a Source #

ito :: (s -> (i, a)) -> IndexedGetter i s a

like :: (Profunctor p, Contravariant f, Functor f) => a -> Optic' p f s a Source #

Build an constant-valued (index-preserving) Getter from an arbitrary Haskell value.

like a . like b ≡ like b
a ^. like b ≡ b
a ^. like b ≡ a ^. to (const b)

This can be useful as a second case failing a Fold e.g. foo failing like 0

like :: a -> IndexPreservingGetter s a

ilike :: (Indexable i p, Contravariant f, Functor f) => i -> a -> Over' p f s a Source #

ilike :: i -> a -> IndexedGetter i s a

Combinators for Getters and Folds

(^.) :: s -> Getting a s a -> a infixl 8 Source #

View the value pointed to by a Getter or Lens or the result of folding over all the results of a Fold or Traversal that points at a monoidal values.

This is the same operation as view with the arguments flipped.

The fixity and semantics are such that subsequent field accesses can be performed with (.).

>>> (a,b)^._2
b

>>> ("hello","world")^._2
"world"

>>> import Data.Complex
>>> ((0, 1 :+ 2), 3)^._1._2.to magnitude
2.23606797749979

(^.) ::             s -> Getter s a     -> a
(^.) :: Monoid m => s -> Fold s m       -> m
(^.) ::             s -> Iso' s a       -> a
(^.) ::             s -> Lens' s a      -> a
(^.) :: Monoid m => s -> Traversal' s m -> m

view :: MonadReader s m => Getting a s a -> m a Source #

View the value pointed to by a Getter, Iso or Lens or the result of folding over all the results of a Fold or Traversal that points at a monoidal value.

view . to ≡ id

>>> view (to f) a
f a

>>> view _2 (1,"hello")
"hello"

>>> view (to succ) 5
6

>>> view (_2._1) ("hello",("world","!!!"))
"world"

As view is commonly used to access the target of a Getter or obtain a monoidal summary of the targets of a Fold, It may be useful to think of it as having one of these more restricted signatures:

view ::             Getter s a     -> s -> a
view :: Monoid m => Fold s m       -> s -> m
view ::             Iso' s a       -> s -> a
view ::             Lens' s a      -> s -> a
view :: Monoid m => Traversal' s m -> s -> m

In a more general setting, such as when working with a Monad transformer stack you can use:

view :: MonadReader s m             => Getter s a     -> m a
view :: (MonadReader s m, Monoid a) => Fold s a       -> m a
view :: MonadReader s m             => Iso' s a       -> m a
view :: MonadReader s m             => Lens' s a      -> m a
view :: (MonadReader s m, Monoid a) => Traversal' s a -> m a

views :: MonadReader s m => LensLike' (Const r :: Type -> Type) s a -> (a -> r) -> m r Source #

View a function of the value pointed to by a Getter or Lens or the result of folding over the result of mapping the targets of a Fold or Traversal.

views l f ≡ view (l . to f)

>>> views (to f) g a
g (f a)

>>> views _2 length (1,"hello")
5

As views is commonly used to access the target of a Getter or obtain a monoidal summary of the targets of a Fold, It may be useful to think of it as having one of these more restricted signatures:

views ::             Getter s a     -> (a -> r) -> s -> r
views :: Monoid m => Fold s a       -> (a -> m) -> s -> m
views ::             Iso' s a       -> (a -> r) -> s -> r
views ::             Lens' s a      -> (a -> r) -> s -> r
views :: Monoid m => Traversal' s a -> (a -> m) -> s -> m

In a more general setting, such as when working with a Monad transformer stack you can use:

views :: MonadReader s m             => Getter s a     -> (a -> r) -> m r
views :: (MonadReader s m, Monoid r) => Fold s a       -> (a -> r) -> m r
views :: MonadReader s m             => Iso' s a       -> (a -> r) -> m r
views :: MonadReader s m             => Lens' s a      -> (a -> r) -> m r
views :: (MonadReader s m, Monoid r) => Traversal' s a -> (a -> r) -> m r

views :: MonadReader s m => Getting r s a -> (a -> r) -> m r

use :: MonadState s m => Getting a s a -> m a Source #

Use the target of a Lens, Iso, or Getter in the current state, or use a summary of a Fold or Traversal that points to a monoidal value.

>>> evalState (use _1) (a,b)
a

>>> evalState (use _1) ("hello","world")
"hello"

use :: MonadState s m             => Getter s a     -> m a
use :: (MonadState s m, Monoid r) => Fold s r       -> m r
use :: MonadState s m             => Iso' s a       -> m a
use :: MonadState s m             => Lens' s a      -> m a
use :: (MonadState s m, Monoid r) => Traversal' s r -> m r

uses :: MonadState s m => LensLike' (Const r :: Type -> Type) s a -> (a -> r) -> m r Source #

Use the target of a Lens, Iso or Getter in the current state, or use a summary of a Fold or Traversal that points to a monoidal value.

>>> evalState (uses _1 length) ("hello","world")
5

uses :: MonadState s m             => Getter s a     -> (a -> r) -> m r
uses :: (MonadState s m, Monoid r) => Fold s a       -> (a -> r) -> m r
uses :: MonadState s m             => Lens' s a      -> (a -> r) -> m r
uses :: MonadState s m             => Iso' s a       -> (a -> r) -> m r
uses :: (MonadState s m, Monoid r) => Traversal' s a -> (a -> r) -> m r

uses :: MonadState s m => Getting r s t a b -> (a -> r) -> m r

listening :: MonadWriter w m => Getting u w u -> m a -> m (a, u) Source #

This is a generalized form of listen that only extracts the portion of the log that is focused on by a Getter. If given a Fold or a Traversal then a monoidal summary of the parts of the log that are visited will be returned.

listening :: MonadWriter w m             => Getter w u     -> m a -> m (a, u)
listening :: MonadWriter w m             => Lens' w u      -> m a -> m (a, u)
listening :: MonadWriter w m             => Iso' w u       -> m a -> m (a, u)
listening :: (MonadWriter w m, Monoid u) => Fold w u       -> m a -> m (a, u)
listening :: (MonadWriter w m, Monoid u) => Traversal' w u -> m a -> m (a, u)
listening :: (MonadWriter w m, Monoid u) => Prism' w u     -> m a -> m (a, u)

listenings :: MonadWriter w m => Getting v w u -> (u -> v) -> m a -> m (a, v) Source #

This is a generalized form of listen that only extracts the portion of the log that is focused on by a Getter. If given a Fold or a Traversal then a monoidal summary of the parts of the log that are visited will be returned.

listenings :: MonadWriter w m             => Getter w u     -> (u -> v) -> m a -> m (a, v)
listenings :: MonadWriter w m             => Lens' w u      -> (u -> v) -> m a -> m (a, v)
listenings :: MonadWriter w m             => Iso' w u       -> (u -> v) -> m a -> m (a, v)
listenings :: (MonadWriter w m, Monoid v) => Fold w u       -> (u -> v) -> m a -> m (a, v)
listenings :: (MonadWriter w m, Monoid v) => Traversal' w u -> (u -> v) -> m a -> m (a, v)
listenings :: (MonadWriter w m, Monoid v) => Prism' w u     -> (u -> v) -> m a -> m (a, v)

Indexed Getters

Indexed Getter Combinators

(^@.) :: s -> IndexedGetting i (i, a) s a -> (i, a) infixl 8 Source #

View the index and value of an IndexedGetter or IndexedLens.

This is the same operation as iview with the arguments flipped.

The fixity and semantics are such that subsequent field accesses can be performed with (.).

(^@.) :: s -> IndexedGetter i s a -> (i, a)
(^@.) :: s -> IndexedLens' i s a  -> (i, a)

The result probably doesn't have much meaning when applied to an IndexedFold.

iview :: MonadReader s m => IndexedGetting i (i, a) s a -> m (i, a) Source #

View the index and value of an IndexedGetter into the current environment as a pair.

When applied to an IndexedFold the result will most likely be a nonsensical monoidal summary of the indices tupled with a monoidal summary of the values and probably not whatever it is you wanted.

iviews :: MonadReader s m => IndexedGetting i r s a -> (i -> a -> r) -> m r Source #

View a function of the index and value of an IndexedGetter into the current environment.

When applied to an IndexedFold the result will be a monoidal summary instead of a single answer.

iviews ≡ ifoldMapOf

iuse :: MonadState s m => IndexedGetting i (i, a) s a -> m (i, a) Source #

Use the index and value of an IndexedGetter into the current state as a pair.

When applied to an IndexedFold the result will most likely be a nonsensical monoidal summary of the indices tupled with a monoidal summary of the values and probably not whatever it is you wanted.

iuses :: MonadState s m => IndexedGetting i r s a -> (i -> a -> r) -> m r Source #

Use a function of the index and value of an IndexedGetter into the current state.

When applied to an IndexedFold the result will be a monoidal summary instead of a single answer.

ilistening :: MonadWriter w m => IndexedGetting i (i, u) w u -> m a -> m (a, (i, u)) Source #

This is a generalized form of listen that only extracts the portion of the log that is focused on by a Getter. If given a Fold or a Traversal then a monoidal summary of the parts of the log that are visited will be returned.

ilistening :: MonadWriter w m             => IndexedGetter i w u     -> m a -> m (a, (i, u))
ilistening :: MonadWriter w m             => IndexedLens' i w u      -> m a -> m (a, (i, u))
ilistening :: (MonadWriter w m, Monoid u) => IndexedFold i w u       -> m a -> m (a, (i, u))
ilistening :: (MonadWriter w m, Monoid u) => IndexedTraversal' i w u -> m a -> m (a, (i, u))

ilistenings :: MonadWriter w m => IndexedGetting i v w u -> (i -> u -> v) -> m a -> m (a, v) Source #

This is a generalized form of listen that only extracts the portion of the log that is focused on by a Getter. If given a Fold or a Traversal then a monoidal summary of the parts of the log that are visited will be returned.

ilistenings :: MonadWriter w m             => IndexedGetter w u     -> (i -> u -> v) -> m a -> m (a, v)
ilistenings :: MonadWriter w m             => IndexedLens' w u      -> (i -> u -> v) -> m a -> m (a, v)
ilistenings :: (MonadWriter w m, Monoid v) => IndexedFold w u       -> (i -> u -> v) -> m a -> m (a, v)
ilistenings :: (MonadWriter w m, Monoid v) => IndexedTraversal' w u -> (i -> u -> v) -> m a -> m (a, v)

Implementation Details

class Contravariant (f :: Type -> Type) where #

The class of contravariant functors.

Whereas in Haskell, one can think of a Functor as containing or producing values, a contravariant functor is a functor that can be thought of as consuming values.

As an example, consider the type of predicate functions a -> Bool. One such predicate might be negative x = x < 0, which classifies integers as to whether they are negative. However, given this predicate, we can re-use it in other situations, providing we have a way to map values to integers. For instance, we can use the negative predicate on a person's bank balance to work out if they are currently overdrawn:

newtype Predicate a = Predicate { getPredicate :: a -> Bool }

instance Contravariant Predicate where
  contramap :: (a' -> a) -> (Predicate a -> Predicate a')
  contramap f (Predicate p) = Predicate (p . f)
                                         |   `- First, map the input...
                                         `----- then apply the predicate.

overdrawn :: Predicate Person
overdrawn = contramap personBankBalance negative

Any instance should be subject to the following laws:

Identity: contramap id = id
Composition: contramap (g . f) = contramap f . contramap g

Note, that the second law follows from the free theorem of the type of contramap and the first law, so you need only check that the former condition holds.

Minimal complete definition

contramap

Methods

contramap :: (a' -> a) -> f a -> f a' #

(>$) :: b -> f b -> f a infixl 4 #

Replace all locations in the output with the same value. The default definition is contramap . const, but this may be overridden with a more efficient version.

Instances

Instances details

Contravariant Comparison #	A `Comparison` is a `Contravariant` `Functor`, because `contramap` can apply its function argument to each input of the comparison function.
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Comparison a -> Comparison a' # (>$) :: b -> Comparison b -> Comparison a #
Contravariant Equivalence #	Equivalence relations are `Contravariant`, because you can apply the contramapped function to each input to the equivalence relation.
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Equivalence a -> Equivalence a' # (>$) :: b -> Equivalence b -> Equivalence a #
Contravariant Predicate #	A `Predicate` is a `Contravariant` `Functor`, because `contramap` can apply its function argument to the input of the predicate. Without newtypes `contramap f` equals precomposing with `f` (= `(. f)`). contramap :: (a' -> a) -> (Predicate a -> Predicate a') contramap f (Predicate g) = Predicate (g . f)
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Predicate a -> Predicate a' # (>$) :: b -> Predicate b -> Predicate a #
Contravariant (Op a) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a0) -> Op a a0 -> Op a a' # (>$) :: b -> Op a b -> Op a a0 #
Contravariant (Proxy :: Type -> Type) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Proxy a -> Proxy a' # (>$) :: b -> Proxy b -> Proxy a #
Contravariant (U1 :: Type -> Type) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> U1 a -> U1 a' # (>$) :: b -> U1 b -> U1 a #
Contravariant (V1 :: Type -> Type) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> V1 a -> V1 a' # (>$) :: b -> V1 b -> V1 a #
Contravariant (Coyoneda f) Source #
Instance details Defined in Data.Functor.Contravariant.Coyoneda Methods contramap :: (a' -> a) -> Coyoneda f a -> Coyoneda f a' # (>$) :: b -> Coyoneda f b -> Coyoneda f a #
Contravariant (Yoneda f) Source #
Instance details Defined in Data.Functor.Contravariant.Yoneda Methods contramap :: (a' -> a) -> Yoneda f a -> Yoneda f a' # (>$) :: b -> Yoneda f b -> Yoneda f a #
Contravariant f => Contravariant (Indexing f) Source #
Instance details Defined in Control.Lens.Internal.Indexed Methods contramap :: (a' -> a) -> Indexing f a -> Indexing f a' # (>$) :: b -> Indexing f b -> Indexing f a #
Contravariant f => Contravariant (Indexing64 f) Source #
Instance details Defined in Control.Lens.Internal.Indexed Methods contramap :: (a' -> a) -> Indexing64 f a -> Indexing64 f a' # (>$) :: b -> Indexing64 f b -> Indexing64 f a #
Contravariant f => Contravariant (WrappedDivisible f) Source #	Since: semigroupoids-5.3.6
Instance details Defined in Data.Functor.Contravariant.Divise Methods contramap :: (a' -> a) -> WrappedDivisible f a -> WrappedDivisible f a' # (>$) :: b -> WrappedDivisible f b -> WrappedDivisible f a #
Contravariant m => Contravariant (MaybeT m) #
Instance details Defined in Control.Monad.Trans.Maybe Methods contramap :: (a' -> a) -> MaybeT m a -> MaybeT m a' # (>$) :: b -> MaybeT m b -> MaybeT m a #
(Contravariant f, Functor g) => Contravariant (ComposeCF f g) Source #
Instance details Defined in Data.Functor.Contravariant.Compose Methods contramap :: (a' -> a) -> ComposeCF f g a -> ComposeCF f g a' # (>$) :: b -> ComposeCF f g b -> ComposeCF f g a #
(Functor f, Contravariant g) => Contravariant (ComposeFC f g) Source #
Instance details Defined in Data.Functor.Contravariant.Compose Methods contramap :: (a' -> a) -> ComposeFC f g a -> ComposeFC f g a' # (>$) :: b -> ComposeFC f g b -> ComposeFC f g a #
Contravariant (Const a :: Type -> Type) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a0) -> Const a a0 -> Const a a' # (>$) :: b -> Const a b -> Const a a0 #
Contravariant f => Contravariant (Alt f) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Alt f a -> Alt f a' # (>$) :: b -> Alt f b -> Alt f a #
Contravariant f => Contravariant (Rec1 f) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Rec1 f a -> Rec1 f a' # (>$) :: b -> Rec1 f b -> Rec1 f a #
Contravariant (Day f g) Source #
Instance details Defined in Data.Functor.Contravariant.Day Methods contramap :: (a' -> a) -> Day f g a -> Day f g a' # (>$) :: b -> Day f g b -> Day f g a #
Contravariant f => Contravariant (AlongsideLeft f b) Source #
Instance details Defined in Control.Lens.Internal.Getter Methods contramap :: (a' -> a) -> AlongsideLeft f b a -> AlongsideLeft f b a' # (>$) :: b0 -> AlongsideLeft f b b0 -> AlongsideLeft f b a #
Contravariant f => Contravariant (AlongsideRight f a) Source #
Instance details Defined in Control.Lens.Internal.Getter Methods contramap :: (a' -> a0) -> AlongsideRight f a a0 -> AlongsideRight f a a' # (>$) :: b -> AlongsideRight f a b -> AlongsideRight f a a0 #
Contravariant (Effect m r) Source #
Instance details Defined in Control.Lens.Internal.Zoom Methods contramap :: (a' -> a) -> Effect m r a -> Effect m r a' # (>$) :: b -> Effect m r b -> Effect m r a #
Contravariant f => Contravariant (Backwards f) #	Derived instance.
Instance details Defined in Control.Applicative.Backwards Methods contramap :: (a' -> a) -> Backwards f a -> Backwards f a' # (>$) :: b -> Backwards f b -> Backwards f a #
Contravariant m => Contravariant (ExceptT e m) #
Instance details Defined in Control.Monad.Trans.Except Methods contramap :: (a' -> a) -> ExceptT e m a -> ExceptT e m a' # (>$) :: b -> ExceptT e m b -> ExceptT e m a #
Contravariant f => Contravariant (IdentityT f) #
Instance details Defined in Control.Monad.Trans.Identity Methods contramap :: (a' -> a) -> IdentityT f a -> IdentityT f a' # (>$) :: b -> IdentityT f b -> IdentityT f a #
Contravariant m => Contravariant (ReaderT r m) #
Instance details Defined in Control.Monad.Trans.Reader Methods contramap :: (a' -> a) -> ReaderT r m a -> ReaderT r m a' # (>$) :: b -> ReaderT r m b -> ReaderT r m a #
Contravariant m => Contravariant (StateT s m) #
Instance details Defined in Control.Monad.Trans.State.Lazy Methods contramap :: (a' -> a) -> StateT s m a -> StateT s m a' # (>$) :: b -> StateT s m b -> StateT s m a #
Contravariant m => Contravariant (StateT s m) #
Instance details Defined in Control.Monad.Trans.State.Strict Methods contramap :: (a' -> a) -> StateT s m a -> StateT s m a' # (>$) :: b -> StateT s m b -> StateT s m a #
Contravariant m => Contravariant (WriterT w m) #
Instance details Defined in Control.Monad.Trans.Writer.Lazy Methods contramap :: (a' -> a) -> WriterT w m a -> WriterT w m a' # (>$) :: b -> WriterT w m b -> WriterT w m a #
Contravariant m => Contravariant (WriterT w m) #
Instance details Defined in Control.Monad.Trans.Writer.Strict Methods contramap :: (a' -> a) -> WriterT w m a -> WriterT w m a' # (>$) :: b -> WriterT w m b -> WriterT w m a #
Contravariant (Constant a :: Type -> Type) #
Instance details Defined in Data.Functor.Constant Methods contramap :: (a' -> a0) -> Constant a a0 -> Constant a a' # (>$) :: b -> Constant a b -> Constant a a0 #
Contravariant f => Contravariant (Reverse f) #	Derived instance.
Instance details Defined in Data.Functor.Reverse Methods contramap :: (a' -> a) -> Reverse f a -> Reverse f a' # (>$) :: b -> Reverse f b -> Reverse f a #
(Contravariant f, Contravariant g) => Contravariant (Product f g) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Product f g a -> Product f g a' # (>$) :: b -> Product f g b -> Product f g a #
(Contravariant f, Contravariant g) => Contravariant (Sum f g) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Sum f g a -> Sum f g a' # (>$) :: b -> Sum f g b -> Sum f g a #
(Contravariant f, Contravariant g) => Contravariant (f :*: g) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> (f :: g) a -> (f :: g) a' # (>$) :: b -> (f :: g) b -> (f :: g) a #
(Contravariant f, Contravariant g) => Contravariant (f :+: g) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> (f :+: g) a -> (f :+: g) a' # (>$) :: b -> (f :+: g) b -> (f :+: g) a #
Contravariant (K1 i c :: Type -> Type) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> K1 i c a -> K1 i c a' # (>$) :: b -> K1 i c b -> K1 i c a #
Contravariant (Forget r a :: Type -> Type) Source #
Instance details Defined in Data.Profunctor.Types Methods contramap :: (a' -> a0) -> Forget r a a0 -> Forget r a a' # (>$) :: b -> Forget r a b -> Forget r a a0 #
Contravariant f => Contravariant (Star f a) Source #
Instance details Defined in Data.Profunctor.Types Methods contramap :: (a' -> a0) -> Star f a a0 -> Star f a a' # (>$) :: b -> Star f a b -> Star f a a0 #
(Functor f, Contravariant g) => Contravariant (Compose f g) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> Compose f g a -> Compose f g a' # (>$) :: b -> Compose f g b -> Compose f g a #
(Functor f, Contravariant g) => Contravariant (f :.: g) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> (f :.: g) a -> (f :.: g) a' # (>$) :: b -> (f :.: g) b -> (f :.: g) a #
Contravariant f => Contravariant (M1 i c f) #
Instance details Defined in Data.Functor.Contravariant Methods contramap :: (a' -> a) -> M1 i c f a -> M1 i c f a' # (>$) :: b -> M1 i c f b -> M1 i c f a #
(Profunctor p, Contravariant g) => Contravariant (BazaarT p g a b) Source #
Instance details Defined in Control.Lens.Internal.Bazaar Methods contramap :: (a' -> a0) -> BazaarT p g a b a0 -> BazaarT p g a b a' # (>$) :: b0 -> BazaarT p g a b b0 -> BazaarT p g a b a0 #
(Profunctor p, Contravariant g) => Contravariant (BazaarT1 p g a b) Source #
Instance details Defined in Control.Lens.Internal.Bazaar Methods contramap :: (a' -> a0) -> BazaarT1 p g a b a0 -> BazaarT1 p g a b a' # (>$) :: b0 -> BazaarT1 p g a b b0 -> BazaarT1 p g a b a0 #
(Profunctor p, Contravariant g) => Contravariant (PretextT p g a b) Source #
Instance details Defined in Control.Lens.Internal.Context Methods contramap :: (a' -> a0) -> PretextT p g a b a0 -> PretextT p g a b a' # (>$) :: b0 -> PretextT p g a b b0 -> PretextT p g a b a0 #
Contravariant f => Contravariant (TakingWhile p f a b) Source #
Instance details Defined in Control.Lens.Internal.Magma Methods contramap :: (a' -> a0) -> TakingWhile p f a b a0 -> TakingWhile p f a b a' # (>$) :: b0 -> TakingWhile p f a b b0 -> TakingWhile p f a b a0 #
Contravariant (EffectRWS w st m s) Source #
Instance details Defined in Control.Lens.Internal.Zoom Methods contramap :: (a' -> a) -> EffectRWS w st m s a -> EffectRWS w st m s a' # (>$) :: b -> EffectRWS w st m s b -> EffectRWS w st m s a #
Contravariant m => Contravariant (RWST r w s m) #
Instance details Defined in Control.Monad.Trans.RWS.Lazy Methods contramap :: (a' -> a) -> RWST r w s m a -> RWST r w s m a' # (>$) :: b -> RWST r w s m b -> RWST r w s m a #
Contravariant m => Contravariant (RWST r w s m) #
Instance details Defined in Control.Monad.Trans.RWS.Strict Methods contramap :: (a' -> a) -> RWST r w s m a -> RWST r w s m a' # (>$) :: b -> RWST r w s m b -> RWST r w s m a #

getting :: (Profunctor p, Profunctor q, Functor f, Contravariant f) => Optical p q f s t a b -> Optical' p q f s a Source #

Coerce a Getter-compatible Optical to an Optical'. This is useful when using a Traversal that is not simple as a Getter or a Fold.

getting :: Traversal s t a b          -> Fold s a
getting :: Lens s t a b               -> Getter s a
getting :: IndexedTraversal i s t a b -> IndexedFold i s a
getting :: IndexedLens i s t a b      -> IndexedGetter i s a

newtype Const a (b :: k) #

The Const functor.

Examples

Expand

>>> fmap (++ "World") (Const "Hello")
Const "Hello"

Because we ignore the second type parameter to Const, the Applicative instance, which has (<*>) :: Monoid m => Const m (a -> b) -> Const m a -> Const m b essentially turns into Monoid m => m -> m -> m, which is (<>)

>>> Const [1, 2, 3] <*> Const [4, 5, 6]
Const [1,2,3,4,5,6]

Constructors

Const
Fields getConst :: a

Instances

Instances details

Semigroupoid (Const :: Type -> Type -> Type) Source #

Instance details

Defined in Data.Semigroupoid

Methods

o :: Const j k1 -> Const i j -> Const i k1 Source #

Generic1 (Const a :: k -> Type) #

Instance details

Defined in GHC.Internal.Data.Functor.Const

Associated Types

type Rep1 (Const a :: k -> Type)	Since: base-4.9.0.0
Instance details Defined in GHC.Internal.Data.Functor.Const type Rep1 (Const a :: k -> Type) = D1 ('MetaData "Const" "GHC.Internal.Data.Functor.Const" "ghc-internal" 'True) (C1 ('MetaCons "Const" 'PrefixI 'True) (S1 ('MetaSel ('Just "getConst") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))

Methods

from1 :: forall (a0 :: k). Const a a0 -> Rep1 (Const a :: k -> Type) a0 #

to1 :: forall (a0 :: k). Rep1 (Const a :: k -> Type) a0 -> Const a a0 #

FoldableWithIndex Void (Const e :: Type -> Type) Source #

Instance details

Defined in WithIndex

Methods

ifoldMap :: Monoid m => (Void -> a -> m) -> Const e a -> m Source #

ifoldMap' :: Monoid m => (Void -> a -> m) -> Const e a -> m Source #

ifoldr :: (Void -> a -> b -> b) -> b -> Const e a -> b Source #

ifoldl :: (Void -> b -> a -> b) -> b -> Const e a -> b Source #

ifoldr' :: (Void -> a -> b -> b) -> b -> Const e a -> b Source #

ifoldl' :: (Void -> b -> a -> b) -> b -> Const e a -> b Source #

FunctorWithIndex Void (Const e :: Type -> Type) Source #

Instance details

Defined in WithIndex

Methods

imap :: (Void -> a -> b) -> Const e a -> Const e b Source #

TraversableWithIndex Void (Const e :: Type -> Type) Source #

Instance details

Defined in WithIndex

Methods

itraverse :: Applicative f => (Void -> a -> f b) -> Const e a -> f (Const e b) Source #

Unbox a => Vector Vector (Const a b) #

Instance details

Defined in Data.Vector.Unboxed.Base

Methods

basicUnsafeFreeze :: Mutable Vector s (Const a b) -> ST s (Vector (Const a b))

basicUnsafeThaw :: Vector (Const a b) -> ST s (Mutable Vector s (Const a b))

basicLength :: Vector (Const a b) -> Int

basicUnsafeSlice :: Int -> Int -> Vector (Const a b) -> Vector (Const a b)

basicUnsafeIndexM :: Vector (Const a b) -> Int -> Box (Const a b)

basicUnsafeCopy :: Mutable Vector s (Const a b) -> Vector (Const a b) -> ST s ()

elemseq :: Vector (Const a b) -> Const a b -> b0 -> b0

Unbox a => MVector MVector (Const a b) #

Instance details

Defined in Data.Vector.Unboxed.Base

Methods

basicLength :: MVector s (Const a b) -> Int

basicUnsafeSlice :: Int -> Int -> MVector s (Const a b) -> MVector s (Const a b)

basicOverlaps :: MVector s (Const a b) -> MVector s (Const a b) -> Bool

basicUnsafeNew :: Int -> ST s (MVector s (Const a b))

basicInitialize :: MVector s (Const a b) -> ST s ()

basicUnsafeReplicate :: Int -> Const a b -> ST s (MVector s (Const a b))

basicUnsafeRead :: MVector s (Const a b) -> Int -> ST s (Const a b)

basicUnsafeWrite :: MVector s (Const a b) -> Int -> Const a b -> ST s ()

basicClear :: MVector s (Const a b) -> ST s ()

basicSet :: MVector s (Const a b) -> Const a b -> ST s ()

basicUnsafeCopy :: MVector s (Const a b) -> MVector s (Const a b) -> ST s ()

basicUnsafeMove :: MVector s (Const a b) -> MVector s (Const a b) -> ST s ()

basicUnsafeGrow :: MVector s (Const a b) -> Int -> ST s (MVector s (Const a b))

Assoc (Const :: Type -> Type -> Type) Source #

Instance details

Defined in Data.Bifunctor.Assoc

Methods

assoc :: Const (Const a b) c -> Const a (Const b c) Source #

unassoc :: Const a (Const b c) -> Const (Const a b) c Source #

Bifoldable (Const :: Type -> Type -> Type) #

Since: base-4.10.0.0

Instance details

Defined in Data.Bifoldable

Methods

bifold :: Monoid m => Const m m -> m #

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Const a b -> m #

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Const a b -> c #

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Const a b -> c #

Bifoldable1 (Const :: Type -> Type -> Type) #

Instance details

Defined in Data.Bifoldable1

Methods

bifold1 :: Semigroup m => Const m m -> m #

bifoldMap1 :: Semigroup m => (a -> m) -> (b -> m) -> Const a b -> m #

Bifunctor (Const :: Type -> Type -> Type) #

Since: base-4.8.0.0

Instance details

Defined in Data.Bifunctor

Methods

bimap :: (a -> b) -> (c -> d) -> Const a c -> Const b d #

first :: (a -> b) -> Const a c -> Const b c #

second :: (b -> c) -> Const a b -> Const a c #

Bitraversable (Const :: Type -> Type -> Type) #

Since: base-4.10.0.0

Instance details

Defined in Data.Bitraversable

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Const a b -> f (Const c d) #

Eq2 (Const :: Type -> Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> Const a c -> Const b d -> Bool #

Ord2 (Const :: Type -> Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> Const a c -> Const b d -> Ordering #

Read2 (Const :: Type -> Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (Const a b) #

liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [Const a b] #

liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (Const a b) #

liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [Const a b] #

Show2 (Const :: Type -> Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> Const a b -> ShowS #

liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [Const a b] -> ShowS #

Biapplicative (Const :: Type -> Type -> Type) Source #

Instance details

Defined in Data.Biapplicative

Methods

bipure :: a -> b -> Const a b Source #

(<<*>>) :: Const (a -> b) (c -> d) -> Const a c -> Const b d Source #

biliftA2 :: (a -> b -> c) -> (d -> e -> f) -> Const a d -> Const b e -> Const c f Source #

(*>>) :: Const a b -> Const c d -> Const c d Source #

(<<*) :: Const a b -> Const c d -> Const a b Source #

NFData2 (Const :: Type -> Type -> Type) #

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf2 :: (a -> ()) -> (b -> ()) -> Const a b -> () #

Hashable2 (Const :: Type -> Type -> Type) Source #

Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt2 :: (Int -> a -> Int) -> (Int -> b -> Int) -> Int -> Const a b -> Int Source #

Biapply (Const :: Type -> Type -> Type) Source #

Instance details

Defined in Data.Functor.Bind.Class

Methods

(<<.>>) :: Const (a -> b) (c -> d) -> Const a c -> Const b d Source #

(.>>) :: Const a b -> Const c d -> Const c d Source #

(<<.) :: Const a b -> Const c d -> Const a b Source #

Bitraversable1 (Const :: Type -> Type -> Type) Source #

Instance details

Defined in Data.Semigroup.Traversable.Class

Methods

bitraverse1 :: Apply f => (a -> f b) -> (c -> f d) -> Const a c -> f (Const b d) Source #

bisequence1 :: Apply f => Const (f a) (f b) -> f (Const a b) Source #

Eq a => Eq1 (Const a :: Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a0 -> b -> Bool) -> Const a a0 -> Const a b -> Bool #

Ord a => Ord1 (Const a :: Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a0 -> b -> Ordering) -> Const a a0 -> Const a b -> Ordering #

Read a => Read1 (Const a :: Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftReadsPrec :: (Int -> ReadS a0) -> ReadS [a0] -> Int -> ReadS (Const a a0) #

liftReadList :: (Int -> ReadS a0) -> ReadS [a0] -> ReadS [Const a a0] #

liftReadPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec (Const a a0) #

liftReadListPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec [Const a a0] #

Show a => Show1 (Const a :: Type -> Type) #

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftShowsPrec :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> Int -> Const a a0 -> ShowS #

liftShowList :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> [Const a a0] -> ShowS #

Contravariant (Const a :: Type -> Type) #

Instance details

Defined in Data.Functor.Contravariant

Methods

contramap :: (a' -> a0) -> Const a a0 -> Const a a' #

(>$) :: b -> Const a b -> Const a a0 #

Monoid m => Divisible (Const m :: Type -> Type) Source #

Instance details

Defined in Data.Functor.Contravariant.Divisible

Methods

divide :: (a -> (b, c)) -> Const m b -> Const m c -> Const m a Source #

conquer :: Const m a Source #

NFData a => NFData1 (Const a :: Type -> Type) #

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf :: (a0 -> ()) -> Const a a0 -> () #

Monoid m => Applicative (Const m :: Type -> Type) #

Since: base-2.0.1

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

pure :: a -> Const m a #

(<*>) :: Const m (a -> b) -> Const m a -> Const m b #

liftA2 :: (a -> b -> c) -> Const m a -> Const m b -> Const m c #

(*>) :: Const m a -> Const m b -> Const m b #

(<*) :: Const m a -> Const m b -> Const m a #

Functor (Const m :: Type -> Type) #

Since: base-2.1

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

fmap :: (a -> b) -> Const m a -> Const m b #

(<$) :: a -> Const m b -> Const m a #

Foldable (Const m :: Type -> Type) #

Since: base-4.7.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

fold :: Monoid m0 => Const m m0 -> m0 #

foldMap :: Monoid m0 => (a -> m0) -> Const m a -> m0 #

foldMap' :: Monoid m0 => (a -> m0) -> Const m a -> m0 #

foldr :: (a -> b -> b) -> b -> Const m a -> b #

foldr' :: (a -> b -> b) -> b -> Const m a -> b #

foldl :: (b -> a -> b) -> b -> Const m a -> b #

foldl' :: (b -> a -> b) -> b -> Const m a -> b #

foldr1 :: (a -> a -> a) -> Const m a -> a #

foldl1 :: (a -> a -> a) -> Const m a -> a #

toList :: Const m a -> [a] #

null :: Const m a -> Bool #

length :: Const m a -> Int #

elem :: Eq a => a -> Const m a -> Bool #

maximum :: Ord a => Const m a -> a #

minimum :: Ord a => Const m a -> a #

sum :: Num a => Const m a -> a #

product :: Num a => Const m a -> a #

Traversable (Const m :: Type -> Type) #

Since: base-4.7.0.0

Instance details

Defined in GHC.Internal.Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Const m a -> f (Const m b) #

sequenceA :: Applicative f => Const m (f a) -> f (Const m a) #

mapM :: Monad m0 => (a -> m0 b) -> Const m a -> m0 (Const m b) #

sequence :: Monad m0 => Const m (m0 a) -> m0 (Const m a) #

Hashable a => Hashable1 (Const a :: Type -> Type) Source #

Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt :: (Int -> a0 -> Int) -> Int -> Const a a0 -> Int Source #

Semigroup m => Apply (Const m :: Type -> Type) Source #

A Const m is not Applicative unless its m is a Monoid, but it is an instance of Apply

Instance details

Defined in Data.Functor.Bind.Class

Methods

(<.>) :: Const m (a -> b) -> Const m a -> Const m b Source #

(.>) :: Const m a -> Const m b -> Const m b Source #

(<.) :: Const m a -> Const m b -> Const m a Source #

liftF2 :: (a -> b -> c) -> Const m a -> Const m b -> Const m c Source #

Semigroup m => Divise (Const m :: Type -> Type) Source #

Unlike Divisible, requires only Semigroup on m.

Since: semigroupoids-5.3.6

Instance details

Defined in Data.Functor.Contravariant.Divise

Methods

divise :: (a -> (b, c)) -> Const m b -> Const m c -> Const m a Source #

ComonadCofree (Const b :: Type -> Type) ((,) b) Source #

Instance details

Defined in Control.Comonad.Cofree.Class

Methods

unwrap :: (b, a) -> Const b (b, a) Source #

Sieve (Forget r :: Type -> Type -> Type) (Const r :: Type -> Type) Source #

Instance details

Defined in Data.Profunctor.Sieve

Methods

sieve :: Forget r a b -> a -> Const r b Source #

NFData a => NFData (Const a b) #

Since: deepseq-1.4.0.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: Const a b -> () #

Monoid a => Monoid (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

mempty :: Const a b #

mappend :: Const a b -> Const a b -> Const a b #

mconcat :: [Const a b] -> Const a b #

Semigroup a => Semigroup (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

(<>) :: Const a b -> Const a b -> Const a b #

sconcat :: NonEmpty (Const a b) -> Const a b #

stimes :: Integral b0 => b0 -> Const a b -> Const a b #

Bits a => Bits (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

(.&.) :: Const a b -> Const a b -> Const a b #

(.|.) :: Const a b -> Const a b -> Const a b #

xor :: Const a b -> Const a b -> Const a b #

complement :: Const a b -> Const a b #

shift :: Const a b -> Int -> Const a b #

rotate :: Const a b -> Int -> Const a b #

zeroBits :: Const a b #

bit :: Int -> Const a b #

setBit :: Const a b -> Int -> Const a b #

clearBit :: Const a b -> Int -> Const a b #

complementBit :: Const a b -> Int -> Const a b #

testBit :: Const a b -> Int -> Bool #

bitSizeMaybe :: Const a b -> Maybe Int #

bitSize :: Const a b -> Int #

isSigned :: Const a b -> Bool #

shiftL :: Const a b -> Int -> Const a b #

unsafeShiftL :: Const a b -> Int -> Const a b #

shiftR :: Const a b -> Int -> Const a b #

unsafeShiftR :: Const a b -> Int -> Const a b #

rotateL :: Const a b -> Int -> Const a b #

rotateR :: Const a b -> Int -> Const a b #

popCount :: Const a b -> Int #

FiniteBits a => FiniteBits (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

finiteBitSize :: Const a b -> Int #

countLeadingZeros :: Const a b -> Int #

countTrailingZeros :: Const a b -> Int #

(Typeable k, Data a, Typeable b) => Data (Const a b) #

Since: base-4.10.0.0

Instance details

Defined in GHC.Internal.Data.Data

Methods

gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> Const a b -> c (Const a b) #

gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Const a b) #

toConstr :: Const a b -> Constr #

dataTypeOf :: Const a b -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Const a b)) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Const a b)) #

gmapT :: (forall b0. Data b0 => b0 -> b0) -> Const a b -> Const a b #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Const a b -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Const a b -> r #

gmapQ :: (forall d. Data d => d -> u) -> Const a b -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Const a b -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Const a b -> m (Const a b) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Const a b -> m (Const a b) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Const a b -> m (Const a b) #

Bounded a => Bounded (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

minBound :: Const a b #

maxBound :: Const a b #

Enum a => Enum (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

succ :: Const a b -> Const a b #

pred :: Const a b -> Const a b #

toEnum :: Int -> Const a b #

fromEnum :: Const a b -> Int #

enumFrom :: Const a b -> [Const a b] #

enumFromThen :: Const a b -> Const a b -> [Const a b] #

enumFromTo :: Const a b -> Const a b -> [Const a b] #

enumFromThenTo :: Const a b -> Const a b -> Const a b -> [Const a b] #

Floating a => Floating (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

pi :: Const a b #

exp :: Const a b -> Const a b #

log :: Const a b -> Const a b #

sqrt :: Const a b -> Const a b #

(**) :: Const a b -> Const a b -> Const a b #

logBase :: Const a b -> Const a b -> Const a b #

sin :: Const a b -> Const a b #

cos :: Const a b -> Const a b #

tan :: Const a b -> Const a b #

asin :: Const a b -> Const a b #

acos :: Const a b -> Const a b #

atan :: Const a b -> Const a b #

sinh :: Const a b -> Const a b #

cosh :: Const a b -> Const a b #

tanh :: Const a b -> Const a b #

asinh :: Const a b -> Const a b #

acosh :: Const a b -> Const a b #

atanh :: Const a b -> Const a b #

log1p :: Const a b -> Const a b #

expm1 :: Const a b -> Const a b #

log1pexp :: Const a b -> Const a b #

log1mexp :: Const a b -> Const a b #

RealFloat a => RealFloat (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

floatRadix :: Const a b -> Integer #

floatDigits :: Const a b -> Int #

floatRange :: Const a b -> (Int, Int) #

decodeFloat :: Const a b -> (Integer, Int) #

encodeFloat :: Integer -> Int -> Const a b #

exponent :: Const a b -> Int #

significand :: Const a b -> Const a b #

scaleFloat :: Int -> Const a b -> Const a b #

isNaN :: Const a b -> Bool #

isInfinite :: Const a b -> Bool #

isDenormalized :: Const a b -> Bool #

isNegativeZero :: Const a b -> Bool #

isIEEE :: Const a b -> Bool #

atan2 :: Const a b -> Const a b -> Const a b #

Storable a => Storable (Const a b) #

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

sizeOf :: Const a b -> Int #

alignment :: Const a b -> Int #

peekElemOff :: Ptr (Const a b) -> Int -> IO (Const a b) #

pokeElemOff :: Ptr (Const a b) -> Int -> Const a b -> IO () #

peekByteOff :: Ptr b0 -> Int -> IO (Const a b) #

pokeByteOff :: Ptr b0 -> Int -> Const a b -> IO () #

peek :: Ptr (Const a b) -> IO (Const a b) #

poke :: Ptr (Const a b) -> Const a b -> IO () #

Generic (Const a b) #

Instance details

Defined in GHC.Internal.Data.Functor.Const

Associated Types

type Rep (Const a b)	Since: base-4.9.0.0
Instance details Defined in GHC.Internal.Data.Functor.Const type Rep (Const a b) = D1 ('MetaData "Const" "GHC.Internal.Data.Functor.Const" "ghc-internal" 'True) (C1 ('MetaCons "Const" 'PrefixI 'True) (S1 ('MetaSel ('Just "getConst") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))