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]
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- @implicitNotFound( ... ) @typeclass( ... , ... )
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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)
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final
def
!=(arg0: Any): Boolean
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final
def
##(): Int
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final
def
==(arg0: Any): Boolean
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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]
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final
def
asInstanceOf[T0]: T0
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clone(): AnyRef
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def
compose[G[_]]: SemigroupK[[α]F[G[α]]]
"Compose" with a
G[_]
type to form aSemigroupK
forλ[α => F[G[α]]]
."Compose" with a
G[_]
type to form aSemigroupK
forλ[α => F[G[α]]]
. Note that this universally works for anyG
, 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)
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eq(arg0: AnyRef): Boolean
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equals(arg0: Any): Boolean
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def
finalize(): Unit
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getClass(): Class[_]
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notifyAll(): Unit
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def
sum[A, B](fa: F[A], fb: F[B])(implicit F: Functor[F]): F[Either[A, B]]
Combines
F[A]
andF[B]
into aF[Either[A,B]]]
.Combines
F[A]
andF[B]
into aF[Either[A,B]]]
.Example:
scala> import cats.SemigroupK scala> import cats.data.NonEmptyList scala> SemigroupK[NonEmptyList].sum(NonEmptyList.one("abc"), NonEmptyList.one(2)) res0: NonEmptyList[Either[String,Int]] = NonEmptyList(Left(abc), Right(2))
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synchronized[T0](arg0: ⇒ T0): T0
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