trait SemigroupK[F[_]] extends Serializable

SemigroupK is a universal semigroup 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. Thus, SemigroupK is like a Semigroup for kinds (i.e. parametrized types).

A SemigroupK[F] can produce a Semigroup[F[A]] for any type A.

Here's how to distinguish Semigroup and SemigroupK:

  • Semigroup[A] allows two A values to be combined.
  • SemigroupK[F] allows two F[A] values to be combined, for any A. The combination operation just depends on the structure of F, but not the structure of A.
Self Type
SemigroupK[F]
Source
SemigroupK.scala
Linear Supertypes
Serializable, Serializable, Any
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  1. SemigroupK
  2. Serializable
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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)
    Annotations
    @op( "<+>" , true )
  2. abstract def getClass(): Class[_]
    Definition Classes
    Any

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
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  2. final def ##(): Int
    Definition Classes
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  3. final def ==(arg0: Any): Boolean
    Definition Classes
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  4. def algebra[A]: Semigroup[F[A]]

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

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

    Example:

    scala> import cats.implicits._
    scala> val s: Semigroup[List[Int]] = SemigroupK[List].algebra[Int]
  5. final def asInstanceOf[T0]: T0
    Definition Classes
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  6. def compose[G[_]]: SemigroupK[[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)
  7. def equals(arg0: Any): Boolean
    Definition Classes
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  8. def hashCode(): Int
    Definition Classes
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  9. final def isInstanceOf[T0]: Boolean
    Definition Classes
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  10. def toString(): String
    Definition Classes
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Inherited from Serializable

Inherited from Serializable

Inherited from Any

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