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CommutativeApplicative

cats.CommutativeApplicative

See theCommutativeApplicative companion object

trait CommutativeApplicative[F[_]] extends Applicative[F] with CommutativeApply[F]

Commutative Applicative.

Further than an Applicative, which just allows composition of independent effectful functions, in a Commutative Applicative those functions can be composed in any order, which guarantees that their effects do not interfere.

Must obey the laws defined in cats.laws.CommutativeApplicativeLaws.

Attributes

Companion:: object
Source:: CommutativeApplicative.scala
Graph
Supertypes: trait CommutativeApply[F]
trait Applicative[F]
trait InvariantMonoidal[F]
trait Apply[F]
trait ApplyArityFunctions[F]
trait InvariantSemigroupal[F]
trait Semigroupal[F]
trait Functor[F]
trait Invariant[F]
trait Serializable
class Object
trait Matchable
class Any
Known subtypes: trait CommutativeMonad[F]

Members list

Concise view

MapArity

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

ApArity

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

TupleArity

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

Value members

Inherited methods

Alias for productR.

Attributes

Inherited from:: Apply
Source:: Apply.scala

Alias for productL.

Attributes

Inherited from:: Apply
Source:: Apply.scala

Alias for ap.

Attributes

Inherited from:: Apply
Source:: Apply.scala

Given a value and a function in the Apply context, applies the function to the value.

Example:

scala> import cats.implicits._

scala> val someF: Option[Int => Long] = Some(_.toLong + 1L)
scala> val noneF: Option[Int => Long] = None
scala> val someInt: Option[Int] = Some(3)
scala> val noneInt: Option[Int] = None

scala> Apply[Option].ap(someF)(someInt)
res0: Option[Long] = Some(4)

scala> Apply[Option].ap(noneF)(someInt)
res1: Option[Long] = None

scala> Apply[Option].ap(someF)(noneInt)
res2: Option[Long] = None

scala> Apply[Option].ap(noneF)(noneInt)
res3: Option[Long] = None

Attributes

Inherited from:: Apply
Source:: Apply.scala

ap2 is a binary version of ap, defined in terms of ap.

Attributes

Inherited from:: Apply
Source:: Apply.scala

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)

Attributes

Inherited from:: Functor
Source:: Functor.scala

Compose an Apply[F] and an Apply[G] into an Apply[λ[α => F[G[α]]]].

Example:

scala> import cats.implicits._

scala> val alo = Apply[List].compose[Option]

scala> alo.product(List(None, Some(true), Some(false)), List(Some(2), None))
res1: List[Option[(Boolean, Int)]] = List(None, None, Some((true,2)), None, Some((false,2)), None)

Attributes

Inherited from:: Apply
Source:: Apply.scala

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)

Attributes

Inherited from:: Invariant
Source:: Invariant.scala

Attributes

Inherited from:: Functor
Source:: Functor.scala

Compose an Applicative[F] and an Applicative[G] into an Applicative[λ[α => F[G[α]]]].

Example:

scala> import cats.implicits._

scala> val alo = Applicative[List].compose[Option]

scala> alo.pure(3)
res0: List[Option[Int]] = List(Some(3))

scala> alo.product(List(None, Some(true), Some(false)), List(Some(2), None))
res1: List[Option[(Boolean, Int)]] = List(None, None, Some((true,2)), None, Some((false,2)), None)

Attributes

Inherited from:: Applicative
Source:: Applicative.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.

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

Attributes

Definition Classes: Functor -> Invariant
Inherited from:: Functor
Source:: Functor.scala

Compose an Applicative[F] and a ContravariantMonoidal[G] into a ContravariantMonoidal[λ[α => F[G[α]]]].

Example:

scala> import cats.kernel.Comparison
scala> import cats.implicits._

// compares strings by alphabetical order
scala> val alpha: Order[String] = Order[String]

// compares strings by their length
scala> val strLength: Order[String] = Order.by[String, Int](_.length)

scala> val stringOrders: List[Order[String]] = List(alpha, strLength)

// first comparison is with alpha order, second is with string length
scala> stringOrders.map(o => o.comparison("abc", "de"))
res0: List[Comparison] = List(LessThan, GreaterThan)

scala> val le = Applicative[List].composeContravariantMonoidal[Order]

// create Int orders that convert ints to strings and then use the string orders
scala> val intOrders: List[Order[Int]] = le.contramap(stringOrders)(_.toString)

// first comparison is with alpha order, second is with string length
scala> intOrders.map(o => o.comparison(12, 3))
res1: List[Comparison] = List(LessThan, GreaterThan)

// create the `product` of the string order list and the int order list
// `p` contains a list of the following orders:
// 1. (alpha comparison on strings followed by alpha comparison on ints)
// 2. (alpha comparison on strings followed by length comparison on ints)
// 3. (length comparison on strings followed by alpha comparison on ints)
// 4. (length comparison on strings followed by length comparison on ints)
scala> val p: List[Order[(String, Int)]] = le.product(stringOrders, intOrders)

scala> p.map(o => o.comparison(("abc", 12), ("def", 3)))
res2: List[Comparison] = List(LessThan, LessThan, LessThan, GreaterThan)

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

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)

Attributes

Inherited from:: Invariant
Source:: Invariant.scala

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!)

Attributes

Inherited from:: Functor
Source:: Functor.scala

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))

Attributes

Inherited from:: Functor
Source:: Functor.scala

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))

Attributes

Inherited from:: Functor
Source:: Functor.scala

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)

Attributes

Inherited from:: Functor
Source:: Functor.scala

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

Attributes

Definition Classes: Functor -> Invariant
Inherited from:: Functor
Source:: Functor.scala

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)

Attributes

Inherited from:: Functor
Source:: Functor.scala

Attributes

Definition Classes: Applicative -> Functor
Inherited from:: Applicative
Source:: Applicative.scala

Applies the pure (binary) function f to the effectful values fa and fb.

map2 can be seen as a binary version of cats.Functor#map.

Example:

scala> import cats.implicits._

scala> val someInt: Option[Int] = Some(3)
scala> val noneInt: Option[Int] = None
scala> val someLong: Option[Long] = Some(4L)
scala> val noneLong: Option[Long] = None

scala> Apply[Option].map2(someInt, someLong)((i, l) => i.toString + l.toString)
res0: Option[String] = Some(34)

scala> Apply[Option].map2(someInt, noneLong)((i, l) => i.toString + l.toString)
res0: Option[String] = None

scala> Apply[Option].map2(noneInt, noneLong)((i, l) => i.toString + l.toString)
res0: Option[String] = None

scala> Apply[Option].map2(noneInt, someLong)((i, l) => i.toString + l.toString)
res0: Option[String] = None

Attributes

Inherited from:: Apply
Source:: Apply.scala

Similar to map2 but uses Eval to allow for laziness in the F[B] argument. This can allow for "short-circuiting" of computations.

NOTE: the default implementation of map2Eval does not short-circuit computations. For data structures that can benefit from laziness, Apply instances should override this method.

In the following example, x.map2(bomb)(_ + _) would result in an error, but map2Eval "short-circuits" the computation. x is None and thus the result of bomb doesn't even need to be evaluated in order to determine that the result of map2Eval should be None.

scala> import cats.{Eval, Later}
scala> import cats.implicits._
scala> val bomb: Eval[Option[Int]] = Later(sys.error("boom"))
scala> val x: Option[Int] = None
scala> x.map2Eval(bomb)(_ + _).value
res0: Option[Int] = None

Attributes

Inherited from:: Apply
Source:: Apply.scala

point lifts any value into a Monoidal Functor.

Example:

scala> import cats.implicits._

scala> InvariantMonoidal[Option].point(10)
res0: Option[Int] = Some(10)

Attributes

Inherited from:: InvariantMonoidal
Source:: InvariantMonoidal.scala

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.implicits._

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

Definition Classes: Apply -> Semigroupal
Inherited from:: Apply
Source:: Apply.scala

Compose two actions, discarding any value produced by the second.

Attributes

See also:

productR to discard the value of the first instead. Example:

scala> import cats.implicits._
scala> import cats.data.Validated
scala> import Validated.{Valid, Invalid}
scala> type ErrOr[A] = Validated[String, A]
scala> val validInt: ErrOr[Int] = Valid(3)
scala> val validBool: ErrOr[Boolean] = Valid(true)
scala> val invalidInt: ErrOr[Int] = Invalid("Invalid int.")
scala> val invalidBool: ErrOr[Boolean] = Invalid("Invalid boolean.")
scala> Apply[ErrOr].productL(validInt)(validBool)
res0: ErrOr[Int] = Valid(3)
scala> Apply[ErrOr].productL(invalidInt)(validBool)
res1: ErrOr[Int] = Invalid(Invalid int.)
scala> Apply[ErrOr].productL(validInt)(invalidBool)
res2: ErrOr[Int] = Invalid(Invalid boolean.)
scala> Apply[ErrOr].productL(invalidInt)(invalidBool)
res3: ErrOr[Int] = Invalid(Invalid int.Invalid boolean.)

Inherited from:

Apply

Source:

Apply.scala

Compose two actions, discarding any value produced by the first.

Attributes

See also:

productL to discard the value of the second instead. Example:

scala> import cats.implicits._
scala> import cats.data.Validated
scala> import Validated.{Valid, Invalid}
scala> type ErrOr[A] = Validated[String, A]
scala> val validInt: ErrOr[Int] = Valid(3)
scala> val validBool: ErrOr[Boolean] = Valid(true)
scala> val invalidInt: ErrOr[Int] = Invalid("Invalid int.")
scala> val invalidBool: ErrOr[Boolean] = Invalid("Invalid boolean.")
scala> Apply[ErrOr].productR(validInt)(validBool)
res0: ErrOr[Boolean] = Valid(true)
scala> Apply[ErrOr].productR(invalidInt)(validBool)
res1: ErrOr[Boolean] = Invalid(Invalid int.)
scala> Apply[ErrOr].productR(validInt)(invalidBool)
res2: ErrOr[Boolean] = Invalid(Invalid boolean.)
scala> Apply[ErrOr].productR(invalidInt)(invalidBool)
res3: ErrOr[Boolean] = Invalid(Invalid int.Invalid boolean.)

Inherited from:

Apply

Source:

Apply.scala

pure lifts any value into the Applicative Functor.

Example:

scala> import cats.implicits._

scala> Applicative[Option].pure(10)
res0: Option[Int] = Some(10)

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

Given fa and n, apply fa n times to construct an F[List[A]] value.

Example:

scala> import cats.data.State

scala> type Counter[A] = State[Int, A]
scala> val getAndIncrement: Counter[Int] = State { i => (i + 1, i) }
scala> val getAndIncrement5: Counter[List[Int]] =
    | Applicative[Counter].replicateA(5, getAndIncrement)
scala> getAndIncrement5.run(0).value
res0: (Int, List[Int]) = (5,List(0, 1, 2, 3, 4))

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

Given fa and n, apply fa n times discarding results to return F[Unit].

Example:

scala> import cats.data.State

scala> type Counter[A] = State[Int, A]
scala> val getAndIncrement: Counter[Int] = State { i => (i + 1, i) }
scala> val getAndIncrement5: Counter[Unit] =
    | Applicative[Counter].replicateA_(5, getAndIncrement)
scala> getAndIncrement5.run(0).value
res0: (Int, Unit) = (5,())

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

Attributes

Inherited from:: ApplyArityFunctions
Source:: ApplyArityFunctions.scala

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))

Attributes

Inherited from:: Functor
Source:: Functor.scala

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))

Attributes

Inherited from:: Functor
Source:: Functor.scala

Returns an F[Unit] value, equivalent with pure(()).

A useful shorthand, also allowing implementations to optimize the returned reference (e.g. it can be a val).

Example:

scala> import cats.implicits._

scala> Applicative[Option].unit
res0: Option[Unit] = Some(())

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

Returns the given argument (mapped to Unit) if cond is false, otherwise, unit lifted into F.

Example:

scala> import cats.implicits._

scala> Applicative[List].unlessA(true)(List(1, 2, 3))
res0: List[Unit] = List(())

scala> Applicative[List].unlessA(false)(List(1, 2, 3))
res1: List[Unit] = List((), (), ())

scala> Applicative[List].unlessA(true)(List.empty[Int])
res2: List[Unit] = List(())

scala> Applicative[List].unlessA(false)(List.empty[Int])
res3: List[Unit] = List()

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

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))

Attributes

Inherited from:: Functor
Source:: Functor.scala

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((), (), ())

Attributes

Inherited from:: Functor
Source:: Functor.scala

Returns the given argument (mapped to Unit) if cond is true, otherwise, unit lifted into F.

Example:

scala> import cats.implicits._

scala> Applicative[List].whenA(true)(List(1, 2, 3))
res0: List[Unit] = List((), (), ())

scala> Applicative[List].whenA(false)(List(1, 2, 3))
res1: List[Unit] = List(())

scala> Applicative[List].whenA(true)(List.empty[Int])
res2: List[Unit] = List()

scala> Applicative[List].whenA(false)(List.empty[Int])
res3: List[Unit] = List(())

Attributes

Inherited from:: Applicative
Source:: Applicative.scala

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)

Attributes

Inherited from:: Functor
Source:: Functor.scala

Deprecated and Inherited methods

Attributes

Deprecated: true
Inherited from:: Apply
Source:: Apply.scala

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