Data.Lens.Lens
This module defines functions for working with lenses.
#lens
lens :: forall s t a b. (s -> a) -> (s -> b -> t) -> Lens s t a b
Create a Lens
from a getter/setter pair.
> species = lens _.species $ _ {species = _}
> view species {species : "bovine"}
"bovine"
> _2 = lens Tuple.snd $ \(Tuple keep _) new -> Tuple keep new
Note: _2
is predefined in Data.Lens.Tuple
.
#ilens
ilens :: forall i s t a b. (s -> Tuple i a) -> (s -> b -> t) -> IndexedLens i s t a b
#ilens'
ilens' :: forall i s t a b. (s -> Tuple (Tuple i a) (b -> t)) -> IndexedLens i s t a b
#withIndexedLens
withIndexedLens :: forall i s t a b r. (AnIndexedLens i s t a b) -> ((s -> (Tuple i a)) -> (s -> b -> t) -> r) -> r
#cloneIndexedLens
cloneIndexedLens :: forall i s t a b. AnIndexedLens i s t a b -> IndexedLens i s t a b
#lensStore
lensStore :: forall s t a b. ALens s t a b -> s -> Tuple a (b -> t)
Converts a lens into the form that lens'
accepts.
Can be useful when defining a lens where the focus appears under multiple constructors of an algebraic data type. This function would be called for each case of the data type.
For example:
data LensStoreExample = LensStoreA Int | LensStoreB (Tuple Boolean Int)
lensStoreExampleInt :: Lens' LensStoreExample Int
lensStoreExampleInt = lens' case _ of
LensStoreA i -> map LensStoreA <$> lensStore identity i
LensStoreB i -> map LensStoreB <$> lensStore _2 i
Re-exports from Data.Lens.Types
#Lens'
type Lens' s a = Lens s s a a
Lens'
is a specialization of Lens
. An optic of type Lens'
can change only the value of its focus,
not its type. As an example, consider the Lens
_2
, which has this type:
_2 :: forall s t a b. Lens (Tuple s a) (Tuple t b) a b
_2
can produce a Tuple Int String
from a Tuple Int Int
:
set _2 "NEW" (Tuple 1 2) == (Tuple 1 "NEW")
If we specialize _2
's type with Lens'
, the following will not
type check:
set (_2 :: Lens' (Tuple Int Int) Int) "NEW" (Tuple 1 2)
^^^^^^^^^^^^^^^^^^^^^^^^^
See Data.Lens.Getter
and Data.Lens.Setter
for functions and operators
frequently used with lenses.
#Lens
type Lens s t a b = forall p. Strong p => Optic p s t a b
Given a type whose "focus element" always exists, a lens provides a convenient way to view, set, and transform that element.
For example, _2
is a tuple-specific Lens
available from Data.Lens
, so:
over _2 String.length $ Tuple "ignore" "four" == Tuple "ignore" 4
Note the result has a different type than the original tuple.
That is, the four Lens
type variables have been narrowed to:
s
isTuple String String
t
isTuple String Int
a
isString
b
isInt
See Data.Lens.Getter
and Data.Lens.Setter
for functions and operators
frequently used with lenses.
#IndexedLens'
type IndexedLens' i s a = IndexedLens i s s a a
#IndexedLens
type IndexedLens i s t a b = forall p. Strong p => IndexedOptic p i s t a b
An indexed lens.
#AnIndexedLens'
type AnIndexedLens' i s a = AnIndexedLens i s s a a
#AnIndexedLens
type AnIndexedLens i s t a b = IndexedOptic (Shop (Tuple i a) b) i s t a b
An indexed lens defined in terms of Shop
, which can be used
to avoid issues with impredicativity.
Packages
assert
catenable-lists
const
convertable-options
datetime-parsing
debug
distributive
erl-atom
erl-gun
erl-lager
erl-logger
erl-maps
erl-modules
erl-nativerefs
erl-opentelemetry
- OpenTelemetry.Metrics
- OpenTelemetry.Metrics.Counter
- OpenTelemetry.Metrics.Meter
- OpenTelemetry.Metrics.SumObserver
- OpenTelemetry.Metrics.UpDownCounter
- OpenTelemetry.Metrics.UpDownSumObserver
- OpenTelemetry.Metrics.ValueObserver
- OpenTelemetry.Metrics.ValueRecorder
- OpenTelemetry.Tracing
- OpenTelemetry.Tracing.Baggage
- OpenTelemetry.Tracing.Ctx
- OpenTelemetry.Tracing.Propagator.TextMap
- OpenTelemetry.Tracing.Span
- OpenTelemetry.Tracing.Tracer
- Tracing.Attributes
erl-process
erl-queue
erl-ranch
erl-simplebus
erl-ssl
erl-test-eunit
erl-test-eunit-discovery
erl-tuples
erl-untagged-union
exceptions
exists
expect-inferred
functions
graphs
heterogeneous
identity
integers
invariant
js-uri
lazy
lcg
math
media-types
newtype
nonempty
nullable
ordered-collections
partial
prelude
- Control.Applicative
- Control.Apply
- Control.Bind
- Control.Category
- Control.Monad
- Control.Semigroupoid
- Data.Boolean
- Data.BooleanAlgebra
- Data.Bounded
- Data.Bounded.Generic
- Data.CommutativeRing
- Data.DivisionRing
- Data.Eq
- Data.Eq.Generic
- Data.EuclideanRing
- Data.Field
- Data.Function
- Data.Functor
- Data.Generic.Rep
- Data.HeytingAlgebra
- Data.HeytingAlgebra.Generic
- Data.Monoid
- Data.Monoid.Additive
- Data.Monoid.Conj
- Data.Monoid.Disj
- Data.Monoid.Dual
- Data.Monoid.Endo
- Data.Monoid.Generic
- Data.Monoid.Multiplicative
- Data.NaturalTransformation
- Data.Ord
- Data.Ord.Generic
- Data.Ordering
- Data.Ring
- Data.Ring.Generic
- Data.Semigroup
- Data.Semigroup.First
- Data.Semigroup.Generic
- Data.Semigroup.Last
- Data.Semiring
- Data.Semiring.Generic
- Data.Show
- Data.Show.Generic
- Data.Symbol
- Data.Unit
- Data.Void
- Record.Unsafe
- Type.Data.Row
- Type.Data.RowList
- Type.Proxy
profunctor-lenses
- Data.Lens.AffineTraversal
- Data.Lens.At
- Data.Lens.Common
- Data.Lens.Fold
- Data.Lens.Fold.Partial
- Data.Lens.Getter
- Data.Lens.Grate
- Data.Lens.Index
- Data.Lens.Indexed
- Data.Lens.Internal.Bazaar
- Data.Lens.Internal.Exchange
- Data.Lens.Internal.Focusing
- Data.Lens.Internal.Forget
- Data.Lens.Internal.Grating
- Data.Lens.Internal.Indexed
- Data.Lens.Internal.Market
- Data.Lens.Internal.Re
- Data.Lens.Internal.Shop
- Data.Lens.Internal.Stall
- Data.Lens.Internal.Tagged
- Data.Lens.Internal.Wander
- Data.Lens.Internal.Zipping
- Data.Lens.Iso
- Data.Lens.Iso.Newtype
- Data.Lens.Lens
- Data.Lens.Lens.Product
- Data.Lens.Lens.Tuple
- Data.Lens.Lens.Unit
- Data.Lens.Lens.Void
- Data.Lens.Prism
- Data.Lens.Prism.Coproduct
- Data.Lens.Prism.Either
- Data.Lens.Prism.Maybe
- Data.Lens.Record
- Data.Lens.Setter
- Data.Lens.Traversal
- Data.Lens.Types
- Data.Lens.Zoom
psci-support
quickcheck-laws
- Test.QuickCheck.Laws
- Test.QuickCheck.Laws.Control.Alt
- Test.QuickCheck.Laws.Control.Alternative
- Test.QuickCheck.Laws.Control.Applicative
- Test.QuickCheck.Laws.Control.Apply
- Test.QuickCheck.Laws.Control.Bind
- Test.QuickCheck.Laws.Control.Category
- Test.QuickCheck.Laws.Control.Comonad
- Test.QuickCheck.Laws.Control.Extend
- Test.QuickCheck.Laws.Control.Monad
- Test.QuickCheck.Laws.Control.MonadPlus
- Test.QuickCheck.Laws.Control.MonadZero
- Test.QuickCheck.Laws.Control.Plus
- Test.QuickCheck.Laws.Control.Semigroupoid
- Test.QuickCheck.Laws.Data.BooleanAlgebra
- Test.QuickCheck.Laws.Data.Bounded
- Test.QuickCheck.Laws.Data.BoundedEnum
- Test.QuickCheck.Laws.Data.CommutativeRing
- Test.QuickCheck.Laws.Data.DivisionRing
- Test.QuickCheck.Laws.Data.Eq
- Test.QuickCheck.Laws.Data.EuclideanRing
- Test.QuickCheck.Laws.Data.Field
- Test.QuickCheck.Laws.Data.Foldable
- Test.QuickCheck.Laws.Data.Functor
- Test.QuickCheck.Laws.Data.FunctorWithIndex
- Test.QuickCheck.Laws.Data.HeytingAlgebra
- Test.QuickCheck.Laws.Data.Monoid
- Test.QuickCheck.Laws.Data.Ord
- Test.QuickCheck.Laws.Data.Ring
- Test.QuickCheck.Laws.Data.Semigroup
- Test.QuickCheck.Laws.Data.Semiring
random
rationals
record-prefix
refs
safe-coerce
semirings
simple-json
strings
- Data.Char
- Data.Char.Gen
- Data.String.CaseInsensitive
- Data.String.CodePoints
- Data.String.CodeUnits
- Data.String.Common
- Data.String.Gen
- Data.String.NonEmpty.CaseInsensitive
- Data.String.NonEmpty.CodePoints
- Data.String.NonEmpty.CodeUnits
- Data.String.NonEmpty.Internal
- Data.String.Pattern
- Data.String.Regex
- Data.String.Regex.Flags
- Data.String.Regex.Unsafe
- Data.String.Unsafe
tailrec
transformers
- Control.Comonad.Env
- Control.Comonad.Env.Class
- Control.Comonad.Env.Trans
- Control.Comonad.Store
- Control.Comonad.Store.Class
- Control.Comonad.Store.Trans
- Control.Comonad.Traced
- Control.Comonad.Traced.Class
- Control.Comonad.Traced.Trans
- Control.Comonad.Trans.Class
- Control.Monad.Cont
- Control.Monad.Cont.Class
- Control.Monad.Cont.Trans
- Control.Monad.Error.Class
- Control.Monad.Except
- Control.Monad.Except.Trans
- Control.Monad.Identity.Trans
- Control.Monad.List.Trans
- Control.Monad.Maybe.Trans
- Control.Monad.RWS
- Control.Monad.RWS.Trans
- Control.Monad.Reader
- Control.Monad.Reader.Class
- Control.Monad.Reader.Trans
- Control.Monad.State
- Control.Monad.State.Class
- Control.Monad.State.Trans
- Control.Monad.Trans.Class
- Control.Monad.Writer
- Control.Monad.Writer.Class
- Control.Monad.Writer.Trans
type-equality
undefinable
unfoldable
unsafe-coerce
unsafe-reference
uri
- URI.AbsoluteURI
- URI.Authority
- URI.Common
- URI.Extra.MultiHostPortPair
- URI.Extra.QueryPairs
- URI.Extra.UserPassInfo
- URI.Fragment
- URI.HierarchicalPart
- URI.Host
- URI.Host.Gen
- URI.Host.IPv4Address
- URI.Host.IPv6Address
- URI.Host.RegName
- URI.HostPortPair
- URI.HostPortPair.Gen
- URI.Path
- URI.Path.Absolute
- URI.Path.NoScheme
- URI.Path.Rootless
- URI.Path.Segment
- URI.Port
- URI.Port.Gen
- URI.Query
- URI.RelativePart
- URI.RelativeRef
- URI.Scheme
- URI.Scheme.Common
- URI.URI
- URI.URIRef
- URI.UserInfo