ContravariantSemigroupal is nothing more than something both contravariant and Semigroupal. It comes up enough to be useful, and composes well
Attributes
- Companion
- object
- Source
- ContravariantSemigroupal.scala
- Graph
-
- Supertypes
-
trait Contravariant[F]trait InvariantSemigroupal[F]trait Invariant[F]trait Semigroupal[F]trait Serializableclass Objecttrait Matchableclass AnyShow all
- Known subtypes
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trait ContravariantMonoidal[F]
- Self type
Members list
Value members
Concrete methods
Compose Invariant F[_] and Functor G[_] then produce Invariant[F[G[_]]] using F's imap and G's map.
Compose Invariant F[_] and Functor G[_] then produce Invariant[F[G[_]]] using F's imap and G's map.
Example:
scala> import cats.syntax.all._
scala> import scala.concurrent.duration._
scala> val durSemigroupList: Semigroup[List[FiniteDuration]] =
| Invariant[Semigroup]
| .composeFunctor[List]
| .imap(Semigroup[List[Long]])(Duration.fromNanos)(_.toNanos)
scala> durSemigroupList.combine(List(2.seconds, 3.seconds), List(4.seconds))
res1: List[FiniteDuration] = List(2 seconds, 3 seconds, 4 seconds)
Attributes
- Definition Classes
- Source
- ContravariantSemigroupal.scala
Inherited methods
Attributes
- Inherited from:
- Contravariant
- Source
- Contravariant.scala
Compose Invariant F[_] and G[_] then produce Invariant[F[G[_]]] using their imap.
Compose Invariant F[_] and G[_] then produce Invariant[F[G[_]]] using their imap.
Example:
scala> import cats.syntax.all._
scala> import scala.concurrent.duration._
scala> val durSemigroupList: Semigroup[List[FiniteDuration]] =
| Invariant[Semigroup].compose[List].imap(Semigroup[List[Long]])(Duration.fromNanos)(_.toNanos)
scala> durSemigroupList.combine(List(2.seconds, 3.seconds), List(4.seconds))
res1: List[FiniteDuration] = List(2 seconds, 3 seconds, 4 seconds)
Attributes
- Inherited from:
- Invariant
- Source
- Invariant.scala
Attributes
- Inherited from:
- InvariantSemigroupal
- Source
- InvariantSemigroupal.scala
Compose Invariant F[_] and Contravariant G[_] then produce Invariant[F[G[_]]] using F's imap and G's contramap.
Compose Invariant F[_] and Contravariant G[_] then produce Invariant[F[G[_]]] using F's imap and G's contramap.
Example:
scala> import cats.syntax.all._
scala> import scala.concurrent.duration._
scala> type ToInt[T] = T => Int
scala> val durSemigroupToInt: Semigroup[ToInt[FiniteDuration]] =
| Invariant[Semigroup]
| .composeContravariant[ToInt]
| .imap(Semigroup[ToInt[Long]])(Duration.fromNanos)(_.toNanos)
// semantically equal to (2.seconds.toSeconds.toInt + 1) + (2.seconds.toSeconds.toInt * 2) = 7
scala> durSemigroupToInt.combine(_.toSeconds.toInt + 1, _.toSeconds.toInt * 2)(2.seconds)
res1: Int = 7
Attributes
- Inherited from:
- Invariant
- Source
- Invariant.scala
Attributes
- Inherited from:
- Contravariant
- Source
- Contravariant.scala
Transform an F[A] into an F[B] by providing a transformation from A to B and one from B to A.
Transform an F[A] into an F[B] by providing a transformation from A to B and one from B to A.
Example:
scala> import cats.syntax.all._
scala> import scala.concurrent.duration._
scala> val durSemigroup: Semigroup[FiniteDuration] =
| Invariant[Semigroup].imap(Semigroup[Long])(Duration.fromNanos)(_.toNanos)
scala> durSemigroup.combine(2.seconds, 3.seconds)
res1: FiniteDuration = 5 seconds
Attributes
- Definition Classes
- Inherited from:
- Contravariant
- Source
- Contravariant.scala
Attributes
- Inherited from:
- Contravariant
- Source
- Contravariant.scala
Lifts natural subtyping contravariance of contravariant Functors.
Lifts natural subtyping contravariance of contravariant Functors. could be implemented as contramap(identity), but the Functor laws say this is equivalent
Attributes
- Inherited from:
- Contravariant
- Source
- Contravariant.scala
Combine an F[A] and an F[B] into an F[(A, B)] that maintains the effects of both fa and fb.
Combine an F[A] and an F[B] into an F[(A, B)] that maintains the effects of both fa and fb.
Example:
scala> import cats.syntax.all._
scala> val noneInt: Option[Int] = None
scala> val some3: Option[Int] = Some(3)
scala> val noneString: Option[String] = None
scala> val someFoo: Option[String] = Some("foo")
scala> Semigroupal[Option].product(noneInt, noneString)
res0: Option[(Int, String)] = None
scala> Semigroupal[Option].product(noneInt, someFoo)
res1: Option[(Int, String)] = None
scala> Semigroupal[Option].product(some3, noneString)
res2: Option[(Int, String)] = None
scala> Semigroupal[Option].product(some3, someFoo)
res3: Option[(Int, String)] = Some((3,foo))
Attributes
- Inherited from:
- Semigroupal
- Source
- Semigroupal.scala