trait Covariant[F[+_]] extends CovariantSubset[F, AnyType] with Invariant[F]
Covariant[F]
provides implicit evidence that F[+_]
is a covariant
endofunctor in the category of Scala objects.
Covariant instances of type F[A]
"produce" values of type A
in some
sense. In some cases, such as with a List[A]
, this means that they
contain values of type A
, in which case we can simply access the elements
of the collection. In other cases it means that output values of type A
which may not already exists, such as with a Function0[A]
that produces
A
values when invoked.
Common examples of covariant instances in ZIO includes effects with respect to their error and value types, sinks with respect to their error and output types, and queues and references with respect to their error and output types.
Covariant
instances support a map
operation which allows transforming
the output type given a function from the old output type to the new output
type. For example, if we have a List[String]
and a function
String => Int
that returns the length of a string, then we can construct
a List[Int]
with the length of each string.
- Self Type
- Covariant[F]
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- Covariant
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- CovariantSubset
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Abstract Value Members
-
abstract
def
map[A, B](f: (A) ⇒ B): (F[A]) ⇒ F[B]
Lift a function from
A
toB
to a function fromF[A]
toF[B]
.
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
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-
final
def
==(arg0: Any): Boolean
- Definition Classes
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-
final
def
asInstanceOf[T0]: T0
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-
def
clone(): AnyRef
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- protected[lang]
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- @throws( ... ) @native()
-
final
def
compose[G[-_]](implicit g: Contravariant[G]): Contravariant[[-A]F[G[A]]]
Compose covariant and contravariant functors.
-
final
def
compose[G[+_]](implicit g: Covariant[G]): Covariant[[+A]F[G[A]]]
Compose two covariant functors.
-
final
def
compose[G[_]](implicit g: Invariant[G]): Invariant[[A]F[G[A]]]
Compose two invariant functors.
Compose two invariant functors.
- Definition Classes
- Invariant
-
def
compositionLaw[A, B, C](fa: F[A], f: <=>[A, B], g: <=>[B, C])(implicit equal: Equal[F[C]]): Boolean
- Definition Classes
- Invariant
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
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-
def
finalize(): Unit
- Attributes
- protected[lang]
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- @throws( classOf[java.lang.Throwable] )
- def fproduct[A, B](f: (A) ⇒ B): (F[A]) ⇒ F[(A, B)]
- def fproductLeft[A, B](f: (A) ⇒ B): (F[A]) ⇒ F[(B, A)]
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
def
identityLaw1[A](fa: F[A])(implicit equal: Equal[F[A]]): Boolean
- Definition Classes
- Invariant
- final def invmap[A, B](f: <=>[A, B]): <=>[F[A], F[B]]
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
-
final
def
mapSubset[A, B](f: (A) ⇒ B)(implicit arg0: AnyType[B]): (F[A]) ⇒ F[B]
- Definition Classes
- Covariant → CovariantSubset
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
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-
final
def
notify(): Unit
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- @native()
-
final
def
notifyAll(): Unit
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- @native()
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
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-
def
toString(): String
- Definition Classes
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-
final
def
wait(): Unit
- Definition Classes
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- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
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- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
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- @throws( ... ) @native()