monocle.Lens.scala Maven / Gradle / Ivy
package monocle
import scalaz.{Applicative, Choice, Functor, Monoid, Split, \/}
/**
* A [[PLens]] can be seen as a pair of functions:
* - `get: S => A` i.e. from an `S`, we can extract an `A`
* - `set: (B, S) => T` i.e. if we replace an `A` by a `B` in an `S`, we obtain a `T`
*
* A [[PLens]] could also be defined as a weaker [[PIso]] where set requires
* an additional parameter than reverseGet.
*
* [[PLens]] stands for Polymorphic Lens as it set and modify methods change
* a type `A` to `B` and `S` to `T`.
* [[Lens]] is a type alias for [[PLens]] restricted to monomorphic updates:
* {{{
* type Lens[S, A] = PLens[S, S, A, A]
* }}}
*
* A [[PLens]] is also a valid [[Getter]], [[Fold]], [[POptional]],
* [[PTraversal]] and [[PSetter]]
*
* Typically a [[PLens]] or [[Lens]] can be defined between a Product
* (e.g. case class, tuple, HList) and one of it is component.
*
* @see [[monocle.law.LensLaws]]
*
* @tparam S the source of a [[PLens]]
* @tparam T the modified source of a [[PLens]]
* @tparam A the target of a [[PLens]]
* @tparam B the modified target of a [[PLens]]
*/
abstract class PLens[S, T, A, B] extends Serializable { self =>
/** get the target of a [[PLens]] */
def get(s: S): A
/** set polymorphically the target of a [[PLens]] using a function */
def set(b: B): S => T
/** modify polymorphically the target of a [[PLens]] using Functor function */
def modifyF[F[_]: Functor](f: A => F[B])(s: S): F[T]
/** modify polymorphically the target of a [[PLens]] using a function */
def modify(f: A => B): S => T
/** join two [[PLens]] with the same target */
@inline final def choice[S1, T1](other: PLens[S1, T1, A, B]): PLens[S \/ S1, T \/ T1, A, B] =
PLens[S \/ S1, T \/ T1, A, B](_.fold(self.get, other.get)){
b => _.bimap(self.set(b), other.set(b))
}
/** pair two disjoint [[PLens]] */
@inline final def split[S1, T1, A1, B1](other: PLens[S1, T1, A1, B1]): PLens[(S, S1), (T, T1), (A, A1), (B, B1)] =
PLens[(S, S1), (T, T1), (A, A1), (B, B1)]{
case (s, s1) => (self.get(s), other.get(s1))
}{ case (b, b1) => {
case (s, s1) => (self.set(b)(s), other.set(b1)(s1))
}
}
@inline final def first[C]: PLens[(S, C), (T, C), (A, C), (B, C)] =
PLens[(S, C), (T, C), (A, C), (B, C)]{
case (s, c) => (get(s), c)
}{ case (b, c) => {
case (s, _) => (set(b)(s), c)
}
}
@inline final def second[C]: PLens[(C, S), (C, T), (C, A), (C, B)] =
PLens[(C, S), (C, T), (C, A), (C, B)]{
case (c, s) => (c, get(s))
}{ case (c, b) => {
case (_, s) => (c, set(b)(s))
}
}
@deprecated("use choice", since = "1.2.0")
@inline final def sum[S1, T1](other: PLens[S1, T1, A, B]): PLens[S \/ S1, T \/ T1, A, B] =
choice(other)
@deprecated("use split", since = "1.2.0")
@inline final def product[S1, T1, A1, B1](other: PLens[S1, T1, A1, B1]): PLens[(S, S1), (T, T1), (A, A1), (B, B1)] =
split(other)
/***********************************************************/
/** Compose methods between a [[PLens]] and another Optics */
/***********************************************************/
/** compose a [[PLens]] with a [[Fold]] */
@inline final def composeFold[C](other: Fold[A, C]): Fold[S, C] =
asFold composeFold other
/** compose a [[PLens]] with a [[Getter]] */
@inline final def composeGetter[C](other: Getter[A, C]): Getter[S, C] =
asGetter composeGetter other
/** compose a [[PLens]] with a [[PSetter]] */
@inline final def composeSetter[C, D](other: PSetter[A, B, C, D]): PSetter[S, T, C, D] =
asSetter composeSetter other
/** compose a [[PLens]] with a [[PTraversal]] */
@inline final def composeTraversal[C, D](other: PTraversal[A, B, C, D]): PTraversal[S, T, C, D] =
asTraversal composeTraversal other
/** compose a [[PLens]] with an [[POptional]] */
@inline final def composeOptional[C, D](other: POptional[A, B, C, D]): POptional[S, T, C, D] =
asOptional composeOptional other
/** compose a [[PLens]] with a [[PPrism]] */
@inline final def composePrism[C, D](other: PPrism[A, B, C, D]): POptional[S, T, C, D] =
asOptional composeOptional other.asOptional
/** compose a [[PLens]] with a [[PLens]] */
@inline final def composeLens[C, D](other: PLens[A, B, C, D]): PLens[S, T, C, D] =
new PLens[S, T, C, D]{
def get(s: S): C =
other.get(self.get(s))
def set(d: D): S => T =
self.modify(other.set(d))
def modifyF[F[_]: Functor](f: C => F[D])(s: S): F[T] =
self.modifyF(other.modifyF(f))(s)
def modify(f: C => D): S => T =
self.modify(other.modify(f))
}
/** compose a [[PLens]] with an [[PIso]] */
@inline final def composeIso[C, D](other: PIso[A, B, C, D]): PLens[S, T, C, D] =
composeLens(other.asLens)
/********************************************/
/** Experimental aliases of compose methods */
/********************************************/
/** alias to composeTraversal */
@inline final def ^|->>[C, D](other: PTraversal[A, B, C, D]): PTraversal[S, T, C, D] =
composeTraversal(other)
/** alias to composeOptional */
@inline final def ^|-?[C, D](other: POptional[A, B, C, D]): POptional[S, T, C, D] =
composeOptional(other)
/** alias to composePrism */
@inline final def ^<-?[C, D](other: PPrism[A, B, C, D]): POptional[S, T, C, D] =
composePrism(other)
/** alias to composeLens */
@inline final def ^|->[C, D](other: PLens[A, B, C, D]): PLens[S, T, C, D] =
composeLens(other)
/** alias to composeIso */
@inline final def ^<->[C, D](other: PIso[A, B, C, D]): PLens[S, T, C, D] =
composeIso(other)
/************************************************************************************************/
/** Transformation methods to view a [[PLens]] as another Optics */
/************************************************************************************************/
/** view a [[PLens]] as a [[Fold]] */
@inline final def asFold: Fold[S, A] =
new Fold[S, A] {
def foldMap[M: Monoid](f: A => M)(s: S): M =
f(get(s))
}
/** view a [[PLens]] as a [[Getter]] */
@inline final def asGetter: Getter[S, A] =
new Getter[S, A]{
def get(s: S): A =
self.get(s)
}
/** view a [[PLens]] as a [[PSetter]] */
@inline final def asSetter: PSetter[S, T, A, B] =
new PSetter[S, T, A, B]{
def modify(f: A => B): S => T =
self.modify(f)
def set(b: B): S => T =
self.set(b)
}
/** view a [[PLens]] as a [[PTraversal]] */
@inline final def asTraversal: PTraversal[S, T, A, B] =
new PTraversal[S, T, A, B] {
def modifyF[F[_]: Applicative](f: A => F[B])(s: S): F[T] =
self.modifyF(f)(s)
}
/** view a [[PLens]] as an [[POptional]] */
@inline final def asOptional: POptional[S, T, A, B] =
new POptional[S, T, A, B] {
def getOrModify(s: S): T \/ A =
\/.right(get(s))
def set(b: B): S => T =
self.set(b)
def getOption(s: S): Option[A] =
Some(self.get(s))
def modify(f: A => B): S => T =
self.modify(f)
def modifyF[F[_]: Applicative](f: A => F[B])(s: S): F[T] =
self.modifyF(f)(s)
}
}
object PLens extends LensInstances {
def id[S, T]: PLens[S, T, S, T] =
PIso.id[S, T].asLens
def codiagonal[S, T]: PLens[S \/ S, T \/ T, S, T] =
PLens[S \/ S, T \/ T, S, T](
_.fold(identity, identity)
)(t => _.bimap(_ => t, _ => t))
/**
* create a [[PLens]] using a pair of functions: one to get the target, one to set the target.
* @see macro module for methods generating [[PLens]] with less boiler plate
*/
def apply[S, T, A, B](_get: S => A)(_set: B => S => T): PLens[S, T, A, B] =
new PLens[S, T, A, B]{
def get(s: S): A =
_get(s)
def set(b: B): S => T =
_set(b)
def modifyF[F[_]: Functor](f: A => F[B])(s: S): F[T] =
Functor[F].map(f(_get(s)))(_set(_)(s))
def modify(f: A => B): S => T =
s => _set(f(_get(s)))(s)
}
}
object Lens {
def id[A]: Lens[A, A] =
Iso.id[A].asLens
def codiagonal[S]: Lens[S \/ S, S] =
PLens.codiagonal
/** alias for [[PLens]] apply with a monomorphic set function */
def apply[S, A](get: S => A)(set: A => S => S): Lens[S, A] =
PLens(get)(set)
}
sealed abstract class LensInstances extends LensInstances0 {
implicit val lensChoice: Choice[Lens] = new Choice[Lens] {
def choice[A, B, C](f: => Lens[A, C], g: => Lens[B, C]): Lens[A \/ B, C] =
f choice g
def id[A]: Lens[A, A] =
Lens.id
def compose[A, B, C](f: Lens[B, C], g: Lens[A, B]): Lens[A, C] =
g composeLens f
}
}
sealed abstract class LensInstances0 {
implicit val lensSplit: Split[Lens] = new Split[Lens] {
def split[A, B, C, D](f: Lens[A, B], g: Lens[C, D]): Lens[(A, C), (B, D)] =
f split g
def compose[A, B, C](f: Lens[B, C], g: Lens[A, B]): Lens[A, C] =
g composeLens f
}
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