trait MonoidK[F[_]] extends SemigroupK[F] with Serializable

MonoidK is a universal monoid which operates on kinds.

This type class is useful when its type parameter F[_] has a structure that can be combined for any particular type, and which also has an "empty" representation. Thus, MonoidK is like a Monoid for kinds (i.e. parametrized types).

A MonoidK[F] can produce a Monoid[F[A]] for any type A.

Here's how to distinguish Monoid and MonoidK:

  • Monoid[A] allows A values to be combined, and also means there is an "empty" A value that functions as an identity.
  • MonoidK[F] allows two F[A] values to be combined, for any A. It also means that for any A, there is an "empty" F[A] value. The combination operation and empty value just depend on the structure of F, but not on the structure of A.
Self Type
MonoidK[F]
Source
MonoidK.scala
Linear Supertypes
SemigroupK[F], Serializable, Serializable, AnyRef, Any
Known Subclasses
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Inherited
  1. MonoidK
  2. SemigroupK
  3. Serializable
  4. Serializable
  5. AnyRef
  6. Any
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Visibility
  1. Public
  2. All

Abstract Value Members

  1. abstract def combineK[A](x: F[A], y: F[A]): F[A]

    Combine two F[A] values.

    Combine two F[A] values.

    Example:

    scala> import cats.implicits._
    scala> SemigroupK[List].combineK(List(1, 2), List(3, 4))
    res0: List[Int] = List(1, 2, 3, 4)
    Definition Classes
    SemigroupK
    Annotations
    @op( "<+>" , true )
  2. abstract def empty[A]: F[A]

    Given a type A, create an "empty" F[A] value.

    Given a type A, create an "empty" F[A] value.

    Example:

    scala> import cats.implicits._
    scala> MonoidK[List].empty[Long]
    res0: List[Long] = List()

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 algebra[A]: Monoid[F[A]]

    Given a type A, create a concrete Monoid[F[A]].

    Given a type A, create a concrete Monoid[F[A]].

    Definition Classes
    MonoidKSemigroupK
  5. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  6. def clone(): AnyRef
    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  7. def compose[G[_]]: MonoidK[[α]F[G[α]]]

    "Compose" with a G[_] type to form a SemigroupK for λ[α => F[G[α]]].

    "Compose" with a G[_] type to form a SemigroupK for λ[α => F[G[α]]]. Note that this universally works for any G, because the "inner" structure isn't considered when combining two instances.

    Example:

    scala> import cats.implicits._
    scala> type ListOption[A] = List[Option[A]]
    scala> val s: SemigroupK[ListOption] = SemigroupK[List].compose[Option]
    scala> s.combineK(List(Some(1), None, Some(2)), List(Some(3), None))
    res0: List[Option[Int]] = List(Some(1), None, Some(2), Some(3), None)
    Definition Classes
    MonoidKSemigroupK
  8. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  9. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  10. def finalize(): Unit
    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  11. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  12. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  13. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  14. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  15. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  16. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  17. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  18. def toString(): String
    Definition Classes
    AnyRef → Any
  19. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  20. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  21. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )

Inherited from SemigroupK[F]

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

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