t

cats

CoflatMap 

Companion object CoflatMap

trait CoflatMap[F[_]] extends Functor[F]

`CoflatMap` is the dual of `FlatMap`.

Must obey the laws in cats.laws.CoflatMapLaws

Annotations
@implicitNotFound( ... ) @typeclass( ... , ... )
Source
CoflatMap.scala
Linear Supertypes
Functor[F], Invariant[F], Serializable, Serializable, AnyRef, Any
Known Subclasses
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Inherited
1. CoflatMap
2. Functor
3. Invariant
4. Serializable
5. Serializable
6. AnyRef
7. Any
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Visibility
1. Public
2. All

Abstract Value Members

1. abstract def coflatMap[A, B](fa: F[A])(f: (F[A]) ⇒ B): F[B]

`coflatMap` is the dual of `flatMap` on `FlatMap`.

`coflatMap` is the dual of `flatMap` on `FlatMap`. It applies a value in a context to a function that takes a value in a context and returns a normal value.

Example:

```scala> import cats.implicits._
scala> import cats.CoflatMap
scala> val fa = Some(3)
scala> def f(a: Option[Int]): Int = a match {
| case Some(x) => 2 * x
| case None => 0 }
scala> CoflatMap[Option].coflatMap(fa)(f)
res0: Option[Int] = Some(6)```
2. abstract def map[A, B](fa: F[A])(f: (A) ⇒ B): F[B]
Definition Classes
Functor

Concrete Value Members

1. final def !=(arg0: Any)
Definition Classes
AnyRef → Any
2. final def ##(): Int
Definition Classes
AnyRef → Any
3. final def ==(arg0: Any)
Definition Classes
AnyRef → Any
4. def as[A, B](fa: F[A], b: B): F[B]

Replaces the `A` value in `F[A]` with the supplied value.

Replaces the `A` value in `F[A]` with the supplied value.

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForList

scala> Functor[List].as(List(1,2,3), "hello")
res0: List[String] = List(hello, hello, hello)```
Definition Classes
Functor
5. final def asInstanceOf[T0]: T0
Definition Classes
Any
6. def clone()
Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws( ... ) @native() @IntrinsicCandidate()
7. def coflatten[A](fa: F[A]): F[F[A]]

`coflatten` is the dual of `flatten` on `FlatMap`.

`coflatten` is the dual of `flatten` on `FlatMap`. Whereas flatten removes a layer of `F`, coflatten adds a layer of `F`

Example:

```scala> import cats.implicits._
scala> import cats.CoflatMap
scala> val fa = Some(3)
fa: Option[Int] = Some(3)
scala> CoflatMap[Option].coflatten(fa)
res0: Option[Option[Int]] = Some(Some(3))```
8. def compose[G[_]](implicit arg0: Functor[G]): Functor[[α]F[G[α]]]
Definition Classes
Functor
9. def compose[G[_]](implicit arg0: Invariant[G]): Invariant[[α]F[G[α]]]

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.implicits._
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)```
Definition Classes
Invariant
10. def composeContravariant[G[_]](implicit arg0: Contravariant[G]): Contravariant[[α]F[G[α]]]

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.implicits._
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```
Definition Classes
FunctorInvariant
11. def composeFunctor[G[_]](implicit arg0: Functor[G]): Invariant[[α]F[G[α]]]

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.implicits._
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)```
Definition Classes
Invariant
12. final def eq(arg0: AnyRef)
Definition Classes
AnyRef
13. def equals(arg0: Any)
Definition Classes
AnyRef → Any
14. final def fmap[A, B](fa: F[A])(f: (A) ⇒ B): F[B]

Alias for map, since map can't be injected as syntax if the implementing type already had a built-in `.map` method.

Alias for map, since map can't be injected as syntax if the implementing type already had a built-in `.map` method.

Example:

```scala> import cats.implicits._

scala> val m: Map[Int, String] = Map(1 -> "hi", 2 -> "there", 3 -> "you")

scala> m.fmap(_ ++ "!")
res0: Map[Int,String] = Map(1 -> hi!, 2 -> there!, 3 -> you!)```
Definition Classes
Functor
15. def fproduct[A, B](fa: F[A])(f: (A) ⇒ B): F[(A, B)]

Tuple the values in fa with the result of applying a function with the value

Tuple the values in fa with the result of applying a function with the value

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> Functor[Option].fproduct(Option(42))(_.toString)
res0: Option[(Int, String)] = Some((42,42))```
Definition Classes
Functor
16. def fproductLeft[A, B](fa: F[A])(f: (A) ⇒ B): F[(B, A)]

Pair the result of function application with `A`.

Pair the result of function application with `A`.

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> Functor[Option].fproductLeft(Option(42))(_.toString)
res0: Option[(String, Int)] = Some((42,42))```
Definition Classes
Functor
17. final def getClass(): Class[_]
Definition Classes
AnyRef → Any
Annotations
@native() @IntrinsicCandidate()
18. def hashCode(): Int
Definition Classes
AnyRef → Any
Annotations
@native() @IntrinsicCandidate()
19. def ifF[A](fb: F[Boolean])(ifTrue: ⇒ A, ifFalse: ⇒ A): F[A]

Lifts `if` to Functor

Lifts `if` to Functor

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForList

scala> Functor[List].ifF(List(true, false, false))(1, 0)
res0: List[Int] = List(1, 0, 0)```
Definition Classes
Functor
Annotations
@noop()
20. def imap[A, B](fa: F[A])(f: (A) ⇒ B)(g: (B) ⇒ A): F[B]

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.implicits._
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```
Definition Classes
FunctorInvariant
21. final def isInstanceOf[T0]
Definition Classes
Any
22. def lift[A, B](f: (A) ⇒ B): (F[A]) ⇒ F[B]

Lift a function f to operate on Functors

Lift a function f to operate on Functors

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> val o = Option(42)
scala> Functor[Option].lift((x: Int) => x + 10)(o)
res0: Option[Int] = Some(52)```
Definition Classes
Functor
23. final def ne(arg0: AnyRef)
Definition Classes
AnyRef
24. final def notify(): Unit
Definition Classes
AnyRef
Annotations
@native() @IntrinsicCandidate()
25. final def notifyAll(): Unit
Definition Classes
AnyRef
Annotations
@native() @IntrinsicCandidate()
26. final def synchronized[T0](arg0: ⇒ T0): T0
Definition Classes
AnyRef
27. def toString(): String
Definition Classes
AnyRef → Any
28. def tupleLeft[A, B](fa: F[A], b: B): F[(B, A)]

Tuples the `A` value in `F[A]` with the supplied `B` value, with the `B` value on the left.

Tuples the `A` value in `F[A]` with the supplied `B` value, with the `B` value on the left.

Example:

```scala> import scala.collection.immutable.Queue
scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForQueue

scala> Functor[Queue].tupleLeft(Queue("hello", "world"), 42)
res0: scala.collection.immutable.Queue[(Int, String)] = Queue((42,hello), (42,world))```
Definition Classes
Functor
29. def tupleRight[A, B](fa: F[A], b: B): F[(A, B)]

Tuples the `A` value in `F[A]` with the supplied `B` value, with the `B` value on the right.

Tuples the `A` value in `F[A]` with the supplied `B` value, with the `B` value on the right.

Example:

```scala> import scala.collection.immutable.Queue
scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForQueue

scala> Functor[Queue].tupleRight(Queue("hello", "world"), 42)
res0: scala.collection.immutable.Queue[(String, Int)] = Queue((hello,42), (world,42))```
Definition Classes
Functor
30. def unzip[A, B](fab: F[(A, B)]): (F[A], F[B])

Un-zips an `F[(A, B)]` consisting of element pairs or Tuple2 into two separate F's tupled.

Un-zips an `F[(A, B)]` consisting of element pairs or Tuple2 into two separate F's tupled.

NOTE: Check for effect duplication, possibly memoize before

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForList

scala> Functor[List].unzip(List((1,2), (3, 4)))
res0: (List[Int], List[Int]) = (List(1, 3),List(2, 4))```
Definition Classes
Functor
Annotations
@noop()
31. def void[A](fa: F[A]): F[Unit]

Empty the fa of the values, preserving the structure

Empty the fa of the values, preserving the structure

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForList

scala> Functor[List].void(List(1,2,3))
res0: List[Unit] = List((), (), ())```
Definition Classes
Functor
32. final def wait(arg0: Long, arg1: Int): Unit
Definition Classes
AnyRef
Annotations
@throws( ... )
33. final def wait(arg0: Long): Unit
Definition Classes
AnyRef
Annotations
@throws( ... ) @native()
34. final def wait(): Unit
Definition Classes
AnyRef
Annotations
@throws( ... )
35. def widen[A, B >: A](fa: F[A]): F[B]

Lifts natural subtyping covariance of covariant Functors.

Lifts natural subtyping covariance of covariant Functors.

NOTE: In certain (perhaps contrived) situations that rely on universal equality this can result in a `ClassCastException`, because it is implemented as a type cast. It could be implemented as `map(identity)`, but according to the functor laws, that should be equal to `fa`, and a type cast is often much more performant. See this example of `widen` creating a `ClassCastException`.

Example:

```scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> val s = Some(42)
scala> Functor[Option].widen(s)
res0: Option[Int] = Some(42)```
Definition Classes
Functor

Deprecated Value Members

1. def finalize(): Unit
Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] ) @Deprecated
Deprecated