Attributes
- Companion
- object
- Source
- Alternative.scala
- Graph
-
- Supertypes
-
trait MonoidK[F]trait NonEmptyAlternative[F]trait SemigroupK[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 Serializableclass Objecttrait Matchableclass AnyShow all
- Self type
-
Alternative[F]
Members list
Grouped members
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
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
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
Value members
Concrete methods
Compose an Applicative[F] and an Applicative[G] into an Applicative[λ[α => F[G[α]]]].
Compose an Applicative[F] and an Applicative[G] into an Applicative[λ[α => F[G[α]]]].
Example:
scala> import cats.syntax.all._
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
- Definition Classes
- Source
- Alternative.scala
Attributes
- Source
- Alternative.scala
Attributes
- Source
- Alternative.scala
Return ().pure[F] if condition is true, empty otherwise
Return ().pure[F] if condition is true, empty otherwise
Example:
scala> import cats.syntax.all._
scala> def even(i: Int): Option[String] = Alternative[Option].guard(i % 2 == 0).as("even")
scala> even(2)
res0: Option[String] = Some(even)
scala> even(3)
res1: Option[String] = None
Attributes
- Source
- Alternative.scala
Separate the inner foldable values into the "lefts" and "rights".
Separate the inner foldable values into the "lefts" and "rights".
Example:
scala> val l: List[Either[String, Int]] = List(Right(1), Left("error"))
scala> Alternative[List].separate(l)
res0: (List[String], List[Int]) = (List(error),List(1))
Attributes
- Source
- Alternative.scala
Separate the inner foldable values into the "lefts" and "rights".
Separate the inner foldable values into the "lefts" and "rights".
A variant of separate that is specialized for Fs that have Foldable instances which allows for a single-pass implementation (as opposed to
separate
which is 2-pass).
Example:
scala> import cats.syntax.all._
scala> val l: List[Either[String, Int]] = List(Right(1), Left("error"))
scala> Alternative[List].separateFoldable(l)
res0: (List[String], List[Int]) = (List(error),List(1))
Attributes
- Source
- Alternative.scala
Fold over the inner structure to combine all of the values with our combine method inherited from MonoidK.
Fold over the inner structure to combine all of the values with our combine method inherited from MonoidK. The result is for us to accumulate all of the "interesting" values of the inner G, so if G is Option, we collect all the Some values, if G is Either, we collect all the Right values, etc.
Example:
scala> val x: List[Vector[Int]] = List(Vector(1, 2), Vector(3, 4))
scala> Alternative[List].unite(x)
res0: List[Int] = List(1, 2, 3, 4)
Attributes
- Source
- Alternative.scala
Inherited methods
Alias for productR.
Alias for productL.
Alias for ap.
Given a type A, create a concrete Monoid[F[A]].
Given a type A, create a concrete Monoid[F[A]].
Example:
scala> import cats.syntax.all._
scala> MonoidK[List].algebra[Long].empty
res0: List[Long] = List()
Attributes
- Definition Classes
- Inherited from:
- MonoidK
- Source
- MonoidK.scala
Given a value and a function in the Apply context, applies the function to the value.
Given a value and a function in the Apply context, applies the function to the value.
Example:
scala> import cats.syntax.all._
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.
ap2 is a binary version of ap, defined in terms of ap.
Attributes
- Inherited from:
- Apply
- Source
- Apply.scala
Lift a into F[_] and append it to fa.
Lift a into F[_] and append it to fa.
Example:
scala> NonEmptyAlternative[List].appendK(List(1, 2, 3), 4)
res0: List[Int] = List(1, 2, 3, 4)
Attributes
- Inherited from:
- NonEmptyAlternative
- Source
- NonEmptyAlternative.scala
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)
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Given a sequence of as, sum them using the monoidK and return the total.
Given a sequence of as, sum them using the monoidK and return the total.
Example:
scala> MonoidK[List].combineAllK(List(List("One"), List("Two"), List("Three")))
res0: List[String] = List(One, Two, Three)
scala> MonoidK[List].combineAllK[String](List.empty)
res1: List[String] = List()
Attributes
- Inherited from:
- MonoidK
- Source
- MonoidK.scala
Given a sequence of as, combine them and return the total.
Given a sequence of as, combine them and return the total.
If the sequence is empty, returns None. Otherwise, returns Some(total).
Example:
scala> SemigroupK[List].combineAllOptionK(List(List("One"), List("Two"), List("Three")))
res0: Option[List[String]] = Some(List(One, Two, Three))
scala> SemigroupK[List].combineAllOptionK[String](List.empty)
res1: Option[List[String]] = None
Attributes
- Inherited from:
- SemigroupK
- Source
- SemigroupK.scala
Combine two F[A] values.
Combine two F[A] values.
Example:
scala> import cats.syntax.all._
scala> SemigroupK[List].combineK(List(1, 2), List(3, 4))
res0: List[Int] = List(1, 2, 3, 4)
Attributes
- Inherited from:
- SemigroupK
- Source
- SemigroupK.scala
Similar to combineK but uses Eval to allow for laziness in the second argument. This can allow for "short-circuiting" of computations.
NOTE: the default implementation of combineKEval does not short-circuit computations. For data structures that can benefit from laziness, SemigroupK instances should override this method.
In the following example, x.combineK(bomb) would result in an error, but combineKEval "short-circuits" the computation. x is Some and thus the result of bomb doesn't even need to be evaluated in order to determine that the result of combineKEval should be x.
scala> import cats.{Eval, Later}
scala> import cats.syntax.all._
scala> val bomb: Eval[Option[Int]] = Later(sys.error("boom"))
scala> val x: Option[Int] = Some(42)
scala> x.combineKEval(bomb).value
res0: Option[Int] = Some(42)
Attributes
- Inherited from:
- SemigroupK
- Source
- SemigroupK.scala
Return a combined with itself n times.
Return a combined with itself n times.
Example:
scala> SemigroupK[List].combineNK(List(1), 5)
res0: List[Int] = List(1, 1, 1, 1, 1)
scala> MonoidK[List].combineNK(List("ha"), 0)
res1: List[String] = List()
Attributes
- Definition Classes
- Inherited from:
- =0")elseif(n.==(0))MonoidK.this.empty[A]elseMonoidK.this.repeatedCombineNK[A](a,n)">MonoidK
- Source
- MonoidK.scala
Given a kind G, create an "composed" MonoidK[F[G[_]]
Given a kind G, create an "composed" MonoidK[F[G[_]]
Example:
scala> import cats.syntax.all._
scala> val monoidK = MonoidK[List].compose[Option]
scala> monoidK.combineK(List(Some(1)), List(Some(2), None))
res0: List[Option[Int]] = List(Some(1), Some(2), None)
Attributes
- Definition Classes
- Inherited from:
- MonoidK
- Source
- MonoidK.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
Compose an Apply[F] and an Apply[G] into an Apply[λ[α => F[G[α]]]].
Compose an Apply[F] and an Apply[G] into an Apply[λ[α => F[G[α]]]].
Example:
scala> import cats.syntax.all._
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
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Attributes
- Inherited from:
- InvariantSemigroupal
- Source
- InvariantSemigroupal.scala
Attributes
- Inherited from:
- Functor
- Source
- Functor.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
- Definition Classes
- Inherited from:
- Functor
- Source
- Functor.scala
Compose an Applicative[F] and a ContravariantMonoidal[G] into a ContravariantMonoidal[λ[α => F[G[α]]]].
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.syntax.all._
// 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.
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
- Inherited from:
- Invariant
- Source
- Invariant.scala
Given a type A, create an "empty" F[A] value.
Given a type A, create an "empty" F[A] value.
Example:
scala> import cats.syntax.all._
scala> MonoidK[List].empty[Long]
res0: List[Long] = List()
Attributes
- Inherited from:
- MonoidK
- Source
- MonoidK.scala
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.syntax.all._
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
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.
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
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.
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:
- Functor
- Source
- Functor.scala
Tests if a is the identity.
Tests if a is the identity.
Example:
scala> MonoidK[List].isEmpty(List.empty[String])
res0: Boolean = true
scala> MonoidK[List].isEmpty(List("something"))
res1: Boolean = false
Attributes
- Inherited from:
- MonoidK
- Source
- MonoidK.scala
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)
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Attributes
- Definition Classes
- Inherited from:
- Applicative
- Source
- Applicative.scala
Applies the pure (binary) function f to the effectful values fa and fb.
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.syntax.all._
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.syntax.all._
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.
point lifts any value into a Monoidal Functor.
Example:
scala> import cats.syntax.all._
scala> InvariantMonoidal[Option].point(10)
res0: Option[Int] = Some(10)
Attributes
- Inherited from:
- InvariantMonoidal
- Source
- InvariantMonoidal.scala
Lift a into F[_] and prepend it to fa.
Lift a into F[_] and prepend it to fa.
Example:
scala> NonEmptyAlternative[List].prependK(1, List(2, 3, 4))
res0: List[Int] = List(1, 2, 3, 4)
Attributes
- Inherited from:
- NonEmptyAlternative
- Source
- NonEmptyAlternative.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
- Definition Classes
-
Apply -> Semigroupal
- Inherited from:
- Apply
- Source
- Apply.scala
Compose two actions, discarding any value produced by the second.
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.syntax.all._ 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.
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.syntax.all._ 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.
pure lifts any value into the Applicative Functor.
Example:
scala> import cats.syntax.all._
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.
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].
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
return a semigroupK that reverses the order so combineK(a, b) == reverse.combineK(b, a)
return a semigroupK that reverses the order so combineK(a, b) == reverse.combineK(b, a)
Attributes
- Definition Classes
- Inherited from:
- MonoidK
- Source
- MonoidK.scala
Combines F[A] and F[B] into a F[Either[A,B]]].
Combines F[A] and F[B] into a F[Either[A,B]]].
Example:
scala> import cats.SemigroupK
scala> import cats.data.NonEmptyList
scala> SemigroupK[NonEmptyList].sum(NonEmptyList.one("abc"), NonEmptyList.one(2))
res0: NonEmptyList[Either[String,Int]] = NonEmptyList(Left(abc), Right(2))
Attributes
- Inherited from:
- SemigroupK
- Source
- SemigroupK.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.
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.
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(()).
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.syntax.all._
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.
Returns the given argument (mapped to Unit) if cond is false, otherwise, unit lifted into F.
Example:
scala> import cats.syntax.all._
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.
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
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.
Returns the given argument (mapped to Unit) if cond is true, otherwise, unit lifted into F.
Example:
scala> import cats.syntax.all._
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.
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