Packages

  • package root
    Definition Classes
    root
  • package cats

    The cats root package contains all the trait signatures of most Scala type classes.

    The cats root package contains all the trait signatures of most Scala type classes.

    Cats type classes are implemented using the approach from the Type classes as objects and implicits article.

    For each type class, cats provides three pieces: - Its signature: a trait that is polymorphic on a type parameter. Type class traits inherit from other type classes to indicate that any implementation of the lower type class (e.g. Applicative) can also serve as an instance for the higuer type class (e.g. Functor). - Type class 'instances, which are classes and objects that implement one or more type class signatures for some specific types. Type class instances for several data types from the Java or Scala standard libraries are declared in the subpackage cats.instances. - Syntax extensions, each of which provides the methods of the type class defines as extension methods (which in Scala 2 are encoded as implicit classes) for values of any type F; given that an instance of the type class for the receiver type (this) is in the implicit scope. Symtax extensions are declared in the cats.syntax package. - A set of laws, that are also generic on the type of the class, and are only defined on the operations of the type class. The purpose of these laws is to declare some algebraic relations (equations) between Scala expressions involving the operations of the type class, and test (but not verify) that implemented instances satisfy those equations. Laws are defined in the cats-laws package.

    Although most of cats type classes are declared in this package, some are declared in other packages: - type classes that operate on base types (kind *), and their implementations for standard library types, are contained in cats.kernel, which is a different SBT project. However, they are re-exported from this package. - type classes of kind F[_, _], such as cats.arrow.Profunctor" or cats.arrow.Arrow, which are relevant for Functional Reactive Programming or optics, are declared in the cats.arrow package. - Also, those type classes that abstract over (pure or impure) functional runtime effects are declared in the cats-effect library. - Some type classes for which no laws can be provided are left out of the main road, in a small and dirty alley. These are the alleycats.

    Definition Classes
    root
  • package arrow
    Definition Classes
    cats
  • Arrow
  • ArrowChoice
  • Category
  • Choice
  • CommutativeArrow
  • Compose
  • FunctionK
  • Profunctor
  • Strong

trait FunctionK[F[_], G[_]] extends Serializable

FunctionK[F[_], G[_]] is a functor transformation from F to G in the same manner that function A => B is a morphism from values of type A to B. An easy way to create a FunctionK instance is to use the Polymorphic lambdas provided by typelevel/kind-projector v0.9+. E.g.

val listToOption = λ[FunctionK[List, Option]](_.headOption)
Self Type
FunctionK[F, G]
Source
FunctionK.scala
Linear Supertypes
Serializable, Serializable, AnyRef, Any
Type Hierarchy
Ordering
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Inherited
  1. FunctionK
  2. Serializable
  3. Serializable
  4. AnyRef
  5. Any
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Visibility
  1. Public
  2. All

Abstract Value Members

  1. abstract def apply[A](fa: F[A]): G[A]

    Applies this functor transformation from F to G

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. def and[H[_]](h: FunctionK[F, H]): FunctionK[F, [γ$2$]Tuple2K[G, H, γ$2$]]

    Composes two instances of FunctionK into a new FunctionK that transforms one single functor to a cats.data.Tuple2K of two functors.

    Composes two instances of FunctionK into a new FunctionK that transforms one single functor to a cats.data.Tuple2K of two functors.

    scala> import cats.arrow.FunctionK
    scala> val list2option = λ[FunctionK[List, Option]](_.headOption)
    scala> val list2vector = λ[FunctionK[List, Vector]](_.toVector)
    scala> val optionAndVector = list2option and list2vector
    scala> optionAndVector(List(1,2,3))
    res0: cats.data.Tuple2K[Option,Vector,Int] = Tuple2K(Some(1),Vector(1, 2, 3))
  5. def andThen[H[_]](f: FunctionK[G, H]): FunctionK[F, H]

    Composes two instances of FunctionK into a new FunctionK with this transformation applied first.

  6. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  7. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native() @HotSpotIntrinsicCandidate()
  8. def compose[E[_]](f: FunctionK[E, F]): FunctionK[E, G]

    Composes two instances of FunctionK into a new FunctionK with this transformation applied last.

  9. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  10. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  11. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  12. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  13. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  14. def narrow[F0[x] <: F[x]]: FunctionK[F0, G]

    Narrows the input type of this FunctionK from F to F0

  15. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  16. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  17. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  18. def or[H[_]](h: FunctionK[H, G]): FunctionK[[γ$0$]EitherK[F, H, γ$0$], G]

    Composes two instances of FunctionK into a new FunctionK that transforms a cats.data.EitherK to a single functor.

    Composes two instances of FunctionK into a new FunctionK that transforms a cats.data.EitherK to a single functor.

    This transformation will be used to transform left F values while h will be used to transform right H values.

  19. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  20. def toString(): String
    Definition Classes
    AnyRef → Any
  21. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  22. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  23. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  24. def widen[G0[x] >: G[x]]: FunctionK[F, G0]

    Widens the output type of this FunctionK from G to G0

Deprecated Value Members

  1. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] ) @Deprecated @deprecated
    Deprecated

    (Since version ) see corresponding Javadoc for more information.

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

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