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

Control.Lens.Review

Contents

Reviewing

Description

A Review is a type-restricted form of a Prism that can only be used for writing back via re , review , reuse .

Synopsis

type Review t b = forall p f. ( Choice p, Bifunctor p, Settable f) => Optic' p f t b
type AReview t b = Optic' Tagged Identity t b
unto :: ( Profunctor p, Bifunctor p, Functor f) => (b -> t) -> Optic p f s t a b
un :: ( Profunctor p, Bifunctor p, Functor f) => Getting a s a -> Optic' p f a s
re :: AReview t b -> Getter b t
review :: MonadReader b m => AReview t b -> m t
reviews :: MonadReader b m => AReview t b -> (t -> r) -> m r
reuse :: MonadState b m => AReview t b -> m t
reuses :: MonadState b m => AReview t b -> (t -> r) -> m r
(#) :: AReview t b -> b -> t
class Bifunctor (p :: Type -> Type -> Type ) where
- bimap :: (a -> b) -> (c -> d) -> p a c -> p b d
retagged :: ( Profunctor p, Bifunctor p) => p a b -> p s b
class ( Profunctor p, Bifunctor p) => Reviewable p
reviewing :: ( Bifunctor p, Functor f) => Optic Tagged Identity s t a b -> Optic' p f t b

Reviewing

type Review t b = forall p f. ( Choice p, Bifunctor p, Settable f) => Optic' p f t b Source #

This is a limited form of a Prism that can only be used for re operations.

Like with a Getter , there are no laws to state for a Review .

You can generate a Review by using unto . You can also use any Prism or Iso directly as a Review .

type AReview t b = Optic' Tagged Identity t b Source #

If you see this in a signature for a function, the function is expecting a Review (in practice, this usually means a Prism ).

unto :: ( Profunctor p, Bifunctor p, Functor f) => (b -> t) -> Optic p f s t a b Source #

An analogue of to for review .

unto :: (b -> t) -> Review' t b

unto = un . to

un :: ( Profunctor p, Bifunctor p, Functor f) => Getting a s a -> Optic' p f a s Source #

Turn a Getter around to get a Review

un = unto . view
unto = un . to

>>> un (to length) # [1,2,3]
3

re :: AReview t b -> Getter b t Source #

Turn a Prism or Iso around to build a Getter .

If you have an Iso , from is a more powerful version of this function that will return an Iso instead of a mere Getter .

>>> 5 ^.re _Left
Left 5

>>> 6 ^.re (_Left.unto succ)
Left 7

review  ≡ view  . re
reviews ≡ views . re
reuse   ≡ use   . re
reuses  ≡ uses  . re

re :: Prism s t a b -> Getter b t
re :: Iso s t a b   -> Getter b t

review :: MonadReader b m => AReview t b -> m t Source #

This can be used to turn an Iso or Prism around and view a value (or the current environment) through it the other way.

review ≡ view . re
review . unto ≡ id

>>> review _Left "mustard"
Left "mustard"

>>> review (unto succ) 5
6

Usually review is used in the (->) Monad with a Prism or Iso , in which case it may be useful to think of it as having one of these more restricted type signatures:

review :: Iso' s a   -> a -> s
review :: Prism' s a -> a -> s

However, when working with a Monad transformer stack, it is sometimes useful to be able to review the current environment, in which case it may be beneficial to think of it as having one of these slightly more liberal type signatures:

review :: MonadReader a m => Iso' s a   -> m s
review :: MonadReader a m => Prism' s a -> m s

reviews :: MonadReader b m => AReview t b -> (t -> r) -> m r Source #

This can be used to turn an Iso or Prism around and view a value (or the current environment) through it the other way, applying a function.

reviews ≡ views . re
reviews (unto f) g ≡ g . f

>>> reviews _Left isRight "mustard"
False

>>> reviews (unto succ) (*2) 3
8

Usually this function is used in the (->) Monad with a Prism or Iso , in which case it may be useful to think of it as having one of these more restricted type signatures:

reviews :: Iso' s a   -> (s -> r) -> a -> r
reviews :: Prism' s a -> (s -> r) -> a -> r

However, when working with a Monad transformer stack, it is sometimes useful to be able to review the current environment, in which case it may be beneficial to think of it as having one of these slightly more liberal type signatures:

reviews :: MonadReader a m => Iso' s a   -> (s -> r) -> m r
reviews :: MonadReader a m => Prism' s a -> (s -> r) -> m r

reuse :: MonadState b m => AReview t b -> m t Source #

This can be used to turn an Iso or Prism around and use a value (or the current environment) through it the other way.

reuse ≡ use . re
reuse . unto ≡ gets

>>> evalState (reuse _Left) 5
Left 5

>>> evalState (reuse (unto succ)) 5
6

reuse :: MonadState a m => Prism' s a -> m s
reuse :: MonadState a m => Iso' s a   -> m s

reuses :: MonadState b m => AReview t b -> (t -> r) -> m r Source #

This can be used to turn an Iso or Prism around and use the current state through it the other way, applying a function.

reuses ≡ uses . re
reuses (unto f) g ≡ gets (g . f)

>>> evalState (reuses _Left isLeft) (5 :: Int)
True

reuses :: MonadState a m => Prism' s a -> (s -> r) -> m r
reuses :: MonadState a m => Iso' s a   -> (s -> r) -> m r

(#) :: AReview t b -> b -> t infixr 8 Source #

An infix alias for review .

unto f # x ≡ f x
l # x ≡ x ^. re l

This is commonly used when using a Prism as a smart constructor.

>>> _Left # 4
Left 4

But it can be used for any Prism

>>> base 16 # 123
"7b"

(#) :: Iso'      s a -> a -> s
(#) :: Prism'    s a -> a -> s
(#) :: Review    s a -> a -> s
(#) :: Equality' s a -> a -> s

class Bifunctor (p :: Type -> Type -> Type ) where Source #

A bifunctor is a type constructor that takes two type arguments and is a functor in both arguments. That is, unlike with Functor , a type constructor such as Either does not need to be partially applied for a Bifunctor instance, and the methods in this class permit mapping functions over the Left value or the Right value, or both at the same time.

Formally, the class Bifunctor represents a bifunctor from Hask -> Hask .

Intuitively it is a bifunctor where both the first and second arguments are covariant.

You can define a Bifunctor by either defining bimap or by defining both first and second .

If you supply bimap , you should ensure that:

bimap id id ≡ id

If you supply first and second , ensure:

first id ≡ id
second id ≡ id

If you supply both, you should also ensure:

bimap f g ≡ first f . second g

These ensure by parametricity:

bimap  (f . g) (h . i) ≡ bimap f h . bimap g i
first  (f . g) ≡ first  f . first  g
second (f . g) ≡ second f . second g

Since: base-4.8.0.0

Minimal complete definition

bimap | first , second

Methods

bimap :: (a -> b) -> (c -> d) -> p a c -> p b d Source #

Map over both arguments at the same time.

bimap f g ≡ first f . second g

Examples

Expand

>>> bimap toUpper (+1) ('j', 3)
('J',4)

>>> bimap toUpper (+1) (Left 'j')
Left 'J'

>>> bimap toUpper (+1) (Right 3)
Right 4

Instances

Instances details

Bifunctor Either	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> Either a c -> Either b d Source # first :: (a -> b) -> Either a c -> Either b c Source # second :: (b -> c) -> Either a b -> Either a c Source #
Bifunctor (,)	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> (a, c) -> (b, d) Source # first :: (a -> b) -> (a, c) -> (b, c) Source # second :: (b -> c) -> (a, b) -> (a, c) Source #
Bifunctor Arg	Since: base-4.9.0.0
Instance details Defined in Data.Semigroup Methods bimap :: (a -> b) -> (c -> d) -> Arg a c -> Arg b d Source # first :: (a -> b) -> Arg a c -> Arg b c Source # second :: (b -> c) -> Arg a b -> Arg a c Source #
Bifunctor Pair
Instance details Defined in Data.Strict.Tuple Methods bimap :: (a -> b) -> (c -> d) -> Pair a c -> Pair b d Source # first :: (a -> b) -> Pair a c -> Pair b c Source # second :: (b -> c) -> Pair a b -> Pair a c Source #
Bifunctor These
Instance details Defined in Data.Strict.These Methods bimap :: (a -> b) -> (c -> d) -> These a c -> These b d Source # first :: (a -> b) -> These a c -> These b c Source # second :: (b -> c) -> These a b -> These a c Source #
Bifunctor Either
Instance details Defined in Data.Strict.Either Methods bimap :: (a -> b) -> (c -> d) -> Either a c -> Either b d Source # first :: (a -> b) -> Either a c -> Either b c Source # second :: (b -> c) -> Either a b -> Either a c Source #
Bifunctor These
Instance details Defined in Data.These Methods bimap :: (a -> b) -> (c -> d) -> These a c -> These b d Source # first :: (a -> b) -> These a c -> These b c Source # second :: (b -> c) -> These a b -> These a c Source #
Bifunctor ( (,,) x1)	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> (x1, a, c) -> (x1, b, d) Source # first :: (a -> b) -> (x1, a, c) -> (x1, b, c) Source # second :: (b -> c) -> (x1, a, b) -> (x1, a, c) Source #
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 Source # first :: (a -> b) -> Const a c -> Const b c Source # second :: (b -> c) -> Const a b -> Const a c Source #
Functor f => Bifunctor ( FreeF f)
Instance details Defined in Control.Monad.Trans.Free Methods bimap :: (a -> b) -> (c -> d) -> FreeF f a c -> FreeF f b d Source # first :: (a -> b) -> FreeF f a c -> FreeF f b c Source # second :: (b -> c) -> FreeF f a b -> FreeF f a c Source #
Functor f => Bifunctor ( CofreeF f)
Instance details Defined in Control.Comonad.Trans.Cofree Methods bimap :: (a -> b) -> (c -> d) -> CofreeF f a c -> CofreeF f b d Source # first :: (a -> b) -> CofreeF f a c -> CofreeF f b c Source # second :: (b -> c) -> CofreeF f a b -> CofreeF f a c Source #
Bifunctor ( Constant :: Type -> Type -> Type )
Instance details Defined in Data.Functor.Constant Methods bimap :: (a -> b) -> (c -> d) -> Constant a c -> Constant b d Source # first :: (a -> b) -> Constant a c -> Constant b c Source # second :: (b -> c) -> Constant a b -> Constant a c Source #
Bifunctor ( Tagged :: Type -> Type -> Type )
Instance details Defined in Data.Tagged Methods bimap :: (a -> b) -> (c -> d) -> Tagged a c -> Tagged b d Source # first :: (a -> b) -> Tagged a c -> Tagged b c Source # second :: (b -> c) -> Tagged a b -> Tagged a c Source #
Functor f => Bifunctor ( AlongsideRight f) Source #
Instance details Defined in Control.Lens.Internal.Getter Methods bimap :: (a -> b) -> (c -> d) -> AlongsideRight f a c -> AlongsideRight f b d Source # first :: (a -> b) -> AlongsideRight f a c -> AlongsideRight f b c Source # second :: (b -> c) -> AlongsideRight f a b -> AlongsideRight f a c Source #
Functor f => Bifunctor ( AlongsideLeft f) Source #
Instance details Defined in Control.Lens.Internal.Getter Methods bimap :: (a -> b) -> (c -> d) -> AlongsideLeft f a c -> AlongsideLeft f b d Source # first :: (a -> b) -> AlongsideLeft f a c -> AlongsideLeft f b c Source # second :: (b -> c) -> AlongsideLeft f a b -> AlongsideLeft f a c Source #
Bifunctor ( K1 i :: Type -> Type -> Type )	Since: base-4.9.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> K1 i a c -> K1 i b d Source # first :: (a -> b) -> K1 i a c -> K1 i b c Source # second :: (b -> c) -> K1 i a b -> K1 i a c Source #
Bifunctor ( (,,,) x1 x2)	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> (x1, x2, a, c) -> (x1, x2, b, d) Source # first :: (a -> b) -> (x1, x2, a, c) -> (x1, x2, b, c) Source # second :: (b -> c) -> (x1, x2, a, b) -> (x1, x2, a, c) Source #
Bifunctor ( (,,,,) x1 x2 x3)	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> (x1, x2, x3, a, c) -> (x1, x2, x3, b, d) Source # first :: (a -> b) -> (x1, x2, x3, a, c) -> (x1, x2, x3, b, c) Source # second :: (b -> c) -> (x1, x2, x3, a, b) -> (x1, x2, x3, a, c) Source #
Bifunctor p => Bifunctor ( WrappedBifunctor p)
Instance details Defined in Data.Bifunctor.Wrapped Methods bimap :: (a -> b) -> (c -> d) -> WrappedBifunctor p a c -> WrappedBifunctor p b d Source # first :: (a -> b) -> WrappedBifunctor p a c -> WrappedBifunctor p b c Source # second :: (b -> c) -> WrappedBifunctor p a b -> WrappedBifunctor p a c Source #
Functor g => Bifunctor ( Joker g :: Type -> Type -> Type )
Instance details Defined in Data.Bifunctor.Joker Methods bimap :: (a -> b) -> (c -> d) -> Joker g a c -> Joker g b d Source # first :: (a -> b) -> Joker g a c -> Joker g b c Source # second :: (b -> c) -> Joker g a b -> Joker g a c Source #
Bifunctor p => Bifunctor ( Flip p)
Instance details Defined in Data.Bifunctor.Flip Methods bimap :: (a -> b) -> (c -> d) -> Flip p a c -> Flip p b d Source # first :: (a -> b) -> Flip p a c -> Flip p b c Source # second :: (b -> c) -> Flip p a b -> Flip p a c Source #
Functor f => Bifunctor ( Clown f :: Type -> Type -> Type )
Instance details Defined in Data.Bifunctor.Clown Methods bimap :: (a -> b) -> (c -> d) -> Clown f a c -> Clown f b d Source # first :: (a -> b) -> Clown f a c -> Clown f b c Source # second :: (b -> c) -> Clown f a b -> Clown f a c Source #
Bifunctor ( (,,,,,) x1 x2 x3 x4)	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> (x1, x2, x3, x4, a, c) -> (x1, x2, x3, x4, b, d) Source # first :: (a -> b) -> (x1, x2, x3, x4, a, c) -> (x1, x2, x3, x4, b, c) Source # second :: (b -> c) -> (x1, x2, x3, x4, a, b) -> (x1, x2, x3, x4, a, c) Source #
( Bifunctor p, Bifunctor q) => Bifunctor ( Sum p q)
Instance details Defined in Data.Bifunctor.Sum Methods bimap :: (a -> b) -> (c -> d) -> Sum p q a c -> Sum p q b d Source # first :: (a -> b) -> Sum p q a c -> Sum p q b c Source # second :: (b -> c) -> Sum p q a b -> Sum p q a c Source #
( Bifunctor f, Bifunctor g) => Bifunctor ( Product f g)
Instance details Defined in Data.Bifunctor.Product Methods bimap :: (a -> b) -> (c -> d) -> Product f g a c -> Product f g b d Source # first :: (a -> b) -> Product f g a c -> Product f g b c Source # second :: (b -> c) -> Product f g a b -> Product f g a c Source #
Bifunctor ( (,,,,,,) x1 x2 x3 x4 x5)	Since: base-4.8.0.0
Instance details Defined in Data.Bifunctor Methods bimap :: (a -> b) -> (c -> d) -> (x1, x2, x3, x4, x5, a, c) -> (x1, x2, x3, x4, x5, b, d) Source # first :: (a -> b) -> (x1, x2, x3, x4, x5, a, c) -> (x1, x2, x3, x4, x5, b, c) Source # second :: (b -> c) -> (x1, x2, x3, x4, x5, a, b) -> (x1, x2, x3, x4, x5, a, c) Source #
( Functor f, Bifunctor p) => Bifunctor ( Tannen f p)
Instance details Defined in Data.Bifunctor.Tannen Methods bimap :: (a -> b) -> (c -> d) -> Tannen f p a c -> Tannen f p b d Source # first :: (a -> b) -> Tannen f p a c -> Tannen f p b c Source # second :: (b -> c) -> Tannen f p a b -> Tannen f p a c Source #
( Bifunctor p, Functor f, Functor g) => Bifunctor ( Biff p f g)
Instance details Defined in Data.Bifunctor.Biff Methods bimap :: (a -> b) -> (c -> d) -> Biff p f g a c -> Biff p f g b d Source # first :: (a -> b) -> Biff p f g a c -> Biff p f g b c Source # second :: (b -> c) -> Biff p f g a b -> Biff p f g a c Source #

retagged :: ( Profunctor p, Bifunctor p) => p a b -> p s b Source #

This is a profunctor used internally to implement Review

It plays a role similar to that of Accessor or Const do for Control.Lens.Getter

class ( Profunctor p, Bifunctor p) => Reviewable p Source #

This class is provided mostly for backwards compatibility with lens 3.8, but it can also shorten type signatures.

Instances

Instances details

( Profunctor p, Bifunctor p) => Reviewable p Source #
Instance details Defined in Control.Lens.Internal.Review

reviewing :: ( Bifunctor p, Functor f) => Optic Tagged Identity s t a b -> Optic' p f t b Source #

Coerce a polymorphic Prism to a Review .

reviewing :: Iso s t a b -> Review t b
reviewing :: Prism s t a b -> Review t b