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trait IsCovariant[F[_]] extends AnyRef

Type constructors that are covariant with respect to subtyping.

A type constructor F[_] admits an instance IsCovariant[F] iff F[A] is a subtype of F[B] whenever A is a subtype of B.

The Scala language represents this natively using the [+A] notation on type constructors. The factory scalaCovariant provides an instance of this typeclass for any such type. However, type constructors which behave covariantly despite not being thus notated can also implement this typeclass. The factory force constructs an instance of IsCovariant for any type, based on the programmer's assertion that it is indeed covariant.

Note the relationship between this typeclass and Functor: whereas Functor instances are covariant functors in the "category" of Scala types and functions, instances of this typeclass are covariant functors in the "category" of Scala types and subtyping relations.

Self Type
IsCovariant[F]
Source
IsCovariant.scala
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Abstract Value Members

  1. abstract def liftLiskovCo[A, B](implicit ev: <~<[A, B]): <~<[F[A], F[B]]

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
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  3. final def ==(arg0: Any): Boolean
    Definition Classes
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  4. final def asInstanceOf[T0]: T0
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  5. def clone(): AnyRef
    Attributes
    protected[lang]
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    @throws( ... ) @native()
  6. final def eq(arg0: AnyRef): Boolean
    Definition Classes
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  7. def equals(arg0: Any): Boolean
    Definition Classes
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  8. def finalize(): Unit
    Attributes
    protected[lang]
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    @throws( classOf[java.lang.Throwable] )
  9. final def getClass(): Class[_]
    Definition Classes
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    Annotations
    @native()
  10. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  11. val isCovariantSyntax: IsCovariantSyntax[F]
  12. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  13. final def ne(arg0: AnyRef): Boolean
    Definition Classes
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  14. final def notify(): Unit
    Definition Classes
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    Annotations
    @native()
  15. final def notifyAll(): Unit
    Definition Classes
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    @native()
  16. def substCo[G[+_], A, B](g: G[F[A]])(implicit ev: <~<[A, B]): G[F[B]]
  17. def substCt[G[-_], A, B](g: G[F[B]])(implicit ev: <~<[A, B]): G[F[A]]
  18. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
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  19. def toString(): String
    Definition Classes
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  20. final def wait(): Unit
    Definition Classes
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    @throws( ... )
  21. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
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    @throws( ... )
  22. final def wait(arg0: Long): Unit
    Definition Classes
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    @throws( ... ) @native()
  23. def widen[A, B](fa: F[A])(implicit ev: <~<[A, B]): F[B]

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