Packages

trait Traverse[F[_]] extends Functor[F] with Foldable[F] with UnorderedTraverse[F]

Traverse, also known as Traversable.

Traversal over a structure with an effect.

Traversing with the cats.Id effect is equivalent to cats.Functor#map. Traversing with the cats.data.Const effect where the first type parameter has a cats.Monoid instance is equivalent to cats.Foldable#fold.

See: The Essence of the Iterator Pattern

Self Type
Traverse[F]
Annotations
@implicitNotFound( ... ) @typeclass( ... , ... )
Source
Traverse.scala
Linear Supertypes
Known Subclasses
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Inherited
  1. Traverse
  2. UnorderedTraverse
  3. Foldable
  4. FoldableNFunctions
  5. UnorderedFoldable
  6. Functor
  7. Invariant
  8. Serializable
  9. Serializable
  10. AnyRef
  11. Any
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Abstract Value Members

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

    Left associative fold on 'F' using the function 'f'.

    Left associative fold on 'F' using the function 'f'.

    Example:

    scala> import cats.Foldable, cats.implicits._
    scala> val fa = Option(1)
    
    Folding by addition to zero:
    scala> Foldable[Option].foldLeft(fa, Option(0))((a, n) => a.map(_ + n))
    res0: Option[Int] = Some(1)

    With syntax extensions, foldLeft can be used like:

    Folding `Option` with addition from zero:
    scala> fa.foldLeft(Option(0))((a, n) => a.map(_ + n))
    res1: Option[Int] = Some(1)
    
    There's also an alias `foldl` which is equivalent:
    scala> fa.foldl(Option(0))((a, n) => a.map(_ + n))
    res2: Option[Int] = Some(1)
    Definition Classes
    Foldable
  2. abstract def foldRight[A, B](fa: F[A], lb: Eval[B])(f: (A, Eval[B]) ⇒ Eval[B]): Eval[B]

    Right associative lazy fold on F using the folding function 'f'.

    Right associative lazy fold on F using the folding function 'f'.

    This method evaluates lb lazily (in some cases it will not be needed), and returns a lazy value. We are using (A, Eval[B]) => Eval[B] to support laziness in a stack-safe way. Chained computation should be performed via .map and .flatMap.

    For more detailed information about how this method works see the documentation for Eval[_].

    Example:

    scala> import cats.Foldable, cats.Eval, cats.implicits._
    scala> val fa = Option(1)
    
    Folding by addition to zero:
    scala> val folded1 = Foldable[Option].foldRight(fa, Eval.now(0))((n, a) => a.map(_ + n))
    Since `foldRight` yields a lazy computation, we need to force it to inspect the result:
    scala> folded1.value
    res0: Int = 1
    
    With syntax extensions, we can write the same thing like this:
    scala> val folded2 = fa.foldRight(Eval.now(0))((n, a) => a.map(_ + n))
    scala> folded2.value
    res1: Int = 1
    
    Unfortunately, since `foldRight` is defined on many collections - this
    extension clashes with the operation defined in `Foldable`.
    
    To get past this and make sure you're getting the lazy `foldRight` defined
    in `Foldable`, there's an alias `foldr`:
    scala> val folded3 = fa.foldr(Eval.now(0))((n, a) => a.map(_ + n))
    scala> folded3.value
    res1: Int = 1
    Definition Classes
    Foldable
  3. abstract def traverse[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit arg0: Applicative[G]): G[F[B]]

    Given a function which returns a G effect, thread this effect through the running of this function on all the values in F, returning an F[B] in a G context.

    Given a function which returns a G effect, thread this effect through the running of this function on all the values in F, returning an F[B] in a G context.

    Example:

    scala> import cats.implicits._
    scala> def parseInt(s: String): Option[Int] = Either.catchOnly[NumberFormatException](s.toInt).toOption
    scala> List("1", "2", "3").traverse(parseInt)
    res0: Option[List[Int]] = Some(List(1, 2, 3))
    scala> List("1", "two", "3").traverse(parseInt)
    res1: Option[List[Int]] = None

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    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(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  7. def collectFirst[A, B](fa: F[A])(pf: PartialFunction[A, B]): Option[B]
    Definition Classes
    Foldable
  8. def collectFirstSome[A, B](fa: F[A])(f: (A) ⇒ Option[B]): Option[B]

    Like collectFirst from scala.collection.Traversable but takes A => Option[B] instead of PartialFunctions.

    Like collectFirst from scala.collection.Traversable but takes A => Option[B] instead of PartialFunctions.

    scala> import cats.implicits._
    scala> val keys = List(1, 2, 4, 5)
    scala> val map = Map(4 -> "Four", 5 -> "Five")
    scala> keys.collectFirstSome(map.get)
    res0: Option[String] = Some(Four)
    scala> val map2 = Map(6 -> "Six", 7 -> "Seven")
    scala> keys.collectFirstSome(map2.get)
    res1: Option[String] = None
    Definition Classes
    Foldable
  9. def collectFirstSomeM[G[_], A, B](fa: F[A])(f: (A) ⇒ G[Option[B]])(implicit G: Monad[G]): G[Option[B]]

    Monadic version of collectFirstSome.

    Monadic version of collectFirstSome.

    If there are no elements, the result is None. collectFirstSomeM short-circuits, i.e. once a Some element is found, no further effects are produced.

    For example:

    scala> import cats.implicits._
    scala> def parseInt(s: String): Either[String, Int] = Either.catchOnly[NumberFormatException](s.toInt).leftMap(_.getMessage)
    scala> val keys1 = List("1", "2", "4", "5")
    scala> val map1 = Map(4 -> "Four", 5 -> "Five")
    scala> Foldable[List].collectFirstSomeM(keys1)(parseInt(_) map map1.get)
    res0: scala.util.Either[String,Option[String]] = Right(Some(Four))
    
    scala> val map2 = Map(6 -> "Six", 7 -> "Seven")
    scala> Foldable[List].collectFirstSomeM(keys1)(parseInt(_) map map2.get)
    res1: scala.util.Either[String,Option[String]] = Right(None)
    
    scala> val keys2 = List("1", "x", "4", "5")
    scala> Foldable[List].collectFirstSomeM(keys2)(parseInt(_) map map1.get)
    res2: scala.util.Either[String,Option[String]] = Left(For input string: "x")
    
    scala> val keys3 = List("1", "2", "4", "x")
    scala> Foldable[List].collectFirstSomeM(keys3)(parseInt(_) map map1.get)
    res3: scala.util.Either[String,Option[String]] = Right(Some(Four))
    Definition Classes
    Foldable
    Annotations
    @noop()
  10. def collectFold[A, B](fa: F[A])(f: PartialFunction[A, B])(implicit B: Monoid[B]): B

    Tear down a subset of this structure using a PartialFunction.

    Tear down a subset of this structure using a PartialFunction.

    scala> import cats.implicits._
    scala> val xs = List(1, 2, 3, 4)
    scala> Foldable[List].collectFold(xs) { case n if n % 2 == 0 => n }
    res0: Int = 6
    Definition Classes
    Foldable
    Annotations
    @noop()
  11. def collectFoldSome[A, B](fa: F[A])(f: (A) ⇒ Option[B])(implicit B: Monoid[B]): B

    Tear down a subset of this structure using a A => Option[M].

    Tear down a subset of this structure using a A => Option[M].

    scala> import cats.implicits._
    scala> val xs = List(1, 2, 3, 4)
    scala> def f(n: Int): Option[Int] = if (n % 2 == 0) Some(n) else None
    scala> Foldable[List].collectFoldSome(xs)(f)
    res0: Int = 6
    Definition Classes
    Foldable
  12. def combineAll[A](fa: F[A])(implicit arg0: Monoid[A]): A

    Alias for fold.

    Alias for fold.

    Definition Classes
    Foldable
  13. def combineAllOption[A](fa: F[A])(implicit ev: Semigroup[A]): Option[A]
    Definition Classes
    Foldable
  14. def compose[G[_]](implicit arg0: Traverse[G]): Traverse[[α]F[G[α]]]
  15. def compose[G[_]](implicit arg0: Foldable[G]): Foldable[[α]F[G[α]]]
    Definition Classes
    Foldable
  16. def compose[G[_]](implicit arg0: Functor[G]): Functor[[α]F[G[α]]]
    Definition Classes
    Functor
  17. 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
  18. 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
  19. 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
  20. def count[A](fa: F[A])(p: (A) ⇒ Boolean): Long

    Count the number of elements in the structure that satisfy the given predicate.

    Count the number of elements in the structure that satisfy the given predicate.

    For example:

    scala> import cats.implicits._
    scala> val map1 = Map[Int, String]()
    scala> val p1: String => Boolean = _.length > 0
    scala> UnorderedFoldable[Map[Int, *]].count(map1)(p1)
    res0: Long = 0
    
    scala> val map2 = Map(1 -> "hello", 2 -> "world", 3 -> "!")
    scala> val p2: String => Boolean = _.length > 1
    scala> UnorderedFoldable[Map[Int, *]].count(map2)(p2)
    res1: Long = 2
    Definition Classes
    UnorderedFoldable
    Annotations
    @noop()
  21. def dropWhile_[A](fa: F[A])(p: (A) ⇒ Boolean): List[A]

    Convert F[A] to a List[A], dropping all initial elements which match p.

    Convert F[A] to a List[A], dropping all initial elements which match p.

    Definition Classes
    Foldable
  22. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  23. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  24. def exists[A](fa: F[A])(p: (A) ⇒ Boolean): Boolean

    Check whether at least one element satisfies the predicate.

    Check whether at least one element satisfies the predicate.

    If there are no elements, the result is false.

    Definition Classes
    FoldableUnorderedFoldable
  25. def existsM[G[_], A](fa: F[A])(p: (A) ⇒ G[Boolean])(implicit G: Monad[G]): G[Boolean]

    Check whether at least one element satisfies the effectful predicate.

    Check whether at least one element satisfies the effectful predicate.

    If there are no elements, the result is false. existsM short-circuits, i.e. once a true result is encountered, no further effects are produced.

    For example:

    scala> import cats.implicits._
    scala> val F = Foldable[List]
    scala> F.existsM(List(1,2,3,4))(n => Option(n <= 4))
    res0: Option[Boolean] = Some(true)
    
    scala> F.existsM(List(1,2,3,4))(n => Option(n > 4))
    res1: Option[Boolean] = Some(false)
    
    scala> F.existsM(List(1,2,3,4))(n => if (n <= 2) Option(true) else Option(false))
    res2: Option[Boolean] = Some(true)
    
    scala> F.existsM(List(1,2,3,4))(n => if (n <= 2) Option(true) else None)
    res3: Option[Boolean] = Some(true)
    
    scala> F.existsM(List(1,2,3,4))(n => if (n <= 2) None else Option(true))
    res4: Option[Boolean] = None
    Definition Classes
    Foldable
  26. def filter_[A](fa: F[A])(p: (A) ⇒ Boolean): List[A]

    Convert F[A] to a List[A], only including elements which match p.

    Convert F[A] to a List[A], only including elements which match p.

    Definition Classes
    Foldable
  27. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  28. def find[A](fa: F[A])(f: (A) ⇒ Boolean): Option[A]

    Find the first element matching the predicate, if one exists.

    Find the first element matching the predicate, if one exists.

    Definition Classes
    Foldable
  29. def findM[G[_], A](fa: F[A])(p: (A) ⇒ G[Boolean])(implicit G: Monad[G]): G[Option[A]]

    Find the first element matching the effectful predicate, if one exists.

    Find the first element matching the effectful predicate, if one exists.

    If there are no elements, the result is None. findM short-circuits, i.e. once an element is found, no further effects are produced.

    For example:

    scala> import cats.implicits._
    scala> val list = List(1,2,3,4)
    scala> Foldable[List].findM(list)(n => (n >= 2).asRight[String])
    res0: Either[String,Option[Int]] = Right(Some(2))
    
    scala> Foldable[List].findM(list)(n => (n > 4).asRight[String])
    res1: Either[String,Option[Int]] = Right(None)
    
    scala> Foldable[List].findM(list)(n => Either.cond(n < 3, n >= 2, "error"))
    res2: Either[String,Option[Int]] = Right(Some(2))
    
    scala> Foldable[List].findM(list)(n => Either.cond(n < 3, false, "error"))
    res3: Either[String,Option[Int]] = Left(error)
    Definition Classes
    Foldable
    Annotations
    @noop()
  30. def flatSequence[G[_], A](fgfa: F[G[F[A]]])(implicit G: Applicative[G], F: FlatMap[F]): G[F[A]]

    Thread all the G effects through the F structure and flatten to invert the structure from F[G[F[A]]] to G[F[A]].

    Thread all the G effects through the F structure and flatten to invert the structure from F[G[F[A]]] to G[F[A]].

    Example:

    scala> import cats.implicits._
    scala> val x: List[Option[List[Int]]] = List(Some(List(1, 2)), Some(List(3)))
    scala> val y: List[Option[List[Int]]] = List(None, Some(List(3)))
    scala> x.flatSequence
    res0: Option[List[Int]] = Some(List(1, 2, 3))
    scala> y.flatSequence
    res1: Option[List[Int]] = None
  31. def flatTraverse[G[_], A, B](fa: F[A])(f: (A) ⇒ G[F[B]])(implicit G: Applicative[G], F: FlatMap[F]): G[F[B]]

    A traverse followed by flattening the inner result.

    A traverse followed by flattening the inner result.

    Example:

    scala> import cats.implicits._
    scala> def parseInt(s: String): Option[Int] = Either.catchOnly[NumberFormatException](s.toInt).toOption
    scala> val x = Option(List("1", "two", "3"))
    scala> x.flatTraverse(_.map(parseInt))
    res0: List[Option[Int]] = List(Some(1), None, Some(3))
  32. 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
  33. def fold[A](fa: F[A])(implicit A: Monoid[A]): A

    Fold implemented using the given Monoid[A] instance.

    Fold implemented using the given Monoid[A] instance.

    Definition Classes
    Foldable
  34. def foldA[G[_], A](fga: F[G[A]])(implicit G: Applicative[G], A: Monoid[A]): G[A]

    Fold implemented using the given Applicative[G] and Monoid[A] instance.

    Fold implemented using the given Applicative[G] and Monoid[A] instance.

    This method is similar to fold, but may short-circuit.

    For example:

    scala> import cats.implicits._
    scala> val F = Foldable[List]
    scala> F.foldA(List(Either.right[String, Int](1), Either.right[String, Int](2)))
    res0: Either[String, Int] = Right(3)

    See this issue for an explanation of @noop usage.

    Definition Classes
    Foldable
    Annotations
    @noop()
  35. def foldK[G[_], A](fga: F[G[A]])(implicit G: MonoidK[G]): G[A]

    Fold implemented using the given MonoidK[G] instance.

    Fold implemented using the given MonoidK[G] instance.

    This method is identical to fold, except that we use the universal monoid (MonoidK[G]) to get a Monoid[G[A]] instance.

    For example:

    scala> import cats.implicits._
    scala> val F = Foldable[List]
    scala> F.foldK(List(1 :: 2 :: Nil, 3 :: 4 :: 5 :: Nil))
    res0: List[Int] = List(1, 2, 3, 4, 5)
    Definition Classes
    Foldable
  36. final def foldLeftM[G[_], A, B](fa: F[A], z: B)(f: (B, A) ⇒ G[B])(implicit G: Monad[G]): G[B]

    Alias for foldM.

    Alias for foldM.

    Definition Classes
    Foldable
  37. def foldM[G[_], A, B](fa: F[A], z: B)(f: (B, A) ⇒ G[B])(implicit G: Monad[G]): G[B]

    Perform a stack-safe monadic left fold from the source context F into the target monad G.

    Perform a stack-safe monadic left fold from the source context F into the target monad G.

    This method can express short-circuiting semantics. Even when fa is an infinite structure, this method can potentially terminate if the foldRight implementation for F and the tailRecM implementation for G are sufficiently lazy.

    Instances for concrete structures (e.g. List) will often have a more efficient implementation than the default one in terms of foldRight.

    Definition Classes
    Foldable
  38. def foldMap[A, B](fa: F[A])(f: (A) ⇒ B)(implicit B: Monoid[B]): B

    Fold implemented by mapping A values into B and then combining them using the given Monoid[B] instance.

    Fold implemented by mapping A values into B and then combining them using the given Monoid[B] instance.

    Definition Classes
    Foldable
  39. def foldMapA[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: Applicative[G], B: Monoid[B]): G[B]

    Fold in an Applicative context by mapping the A values to G[B].

    Fold in an Applicative context by mapping the A values to G[B]. combining the B values using the given Monoid[B] instance.

    Similar to foldMapM, but will typically be less efficient.

    scala> import cats.Foldable
    scala> import cats.implicits._
    scala> val evenNumbers = List(2,4,6,8,10)
    scala> val evenOpt: Int => Option[Int] =
         |   i => if (i % 2 == 0) Some(i) else None
    scala> Foldable[List].foldMapA(evenNumbers)(evenOpt)
    res0: Option[Int] = Some(30)
    scala> Foldable[List].foldMapA(evenNumbers :+ 11)(evenOpt)
    res1: Option[Int] = None
    Definition Classes
    Foldable
  40. def foldMapK[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: MonoidK[G]): G[B]

    Fold implemented by mapping A values into B in a context G and then combining them using the MonoidK[G] instance.

    Fold implemented by mapping A values into B in a context G and then combining them using the MonoidK[G] instance.

    scala> import cats._, cats.implicits._
    scala> val f: Int => Endo[String] = i => (s => s + i)
    scala> val x: Endo[String] = Foldable[List].foldMapK(List(1, 2, 3))(f)
    scala> val a = x("foo")
    a: String = "foo321"
    Definition Classes
    Foldable
    Annotations
    @noop()
  41. def foldMapM[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: Monad[G], B: Monoid[B]): G[B]

    Monadic folding on F by mapping A values to G[B], combining the B values using the given Monoid[B] instance.

    Monadic folding on F by mapping A values to G[B], combining the B values using the given Monoid[B] instance.

    Similar to foldM, but using a Monoid[B]. Will typically be more efficient than foldMapA.

    scala> import cats.Foldable
    scala> import cats.implicits._
    scala> val evenNumbers = List(2,4,6,8,10)
    scala> val evenOpt: Int => Option[Int] =
         |   i => if (i % 2 == 0) Some(i) else None
    scala> Foldable[List].foldMapM(evenNumbers)(evenOpt)
    res0: Option[Int] = Some(30)
    scala> Foldable[List].foldMapM(evenNumbers :+ 11)(evenOpt)
    res1: Option[Int] = None
    Definition Classes
    Foldable
  42. def foldRightDefer[G[_], A, B](fa: F[A], gb: G[B])(fn: (A, G[B]) ⇒ G[B])(implicit arg0: Defer[G]): G[B]
    Definition Classes
    Foldable
  43. def forall[A](fa: F[A])(p: (A) ⇒ Boolean): Boolean

    Check whether all elements satisfy the predicate.

    Check whether all elements satisfy the predicate.

    If there are no elements, the result is true.

    Definition Classes
    FoldableUnorderedFoldable
  44. def forallM[G[_], A](fa: F[A])(p: (A) ⇒ G[Boolean])(implicit G: Monad[G]): G[Boolean]

    Check whether all elements satisfy the effectful predicate.

    Check whether all elements satisfy the effectful predicate.

    If there are no elements, the result is true. forallM short-circuits, i.e. once a false result is encountered, no further effects are produced.

    For example:

    scala> import cats.implicits._
    scala> val F = Foldable[List]
    scala> F.forallM(List(1,2,3,4))(n => Option(n <= 4))
    res0: Option[Boolean] = Some(true)
    
    scala> F.forallM(List(1,2,3,4))(n => Option(n <= 1))
    res1: Option[Boolean] = Some(false)
    
    scala> F.forallM(List(1,2,3,4))(n => if (n <= 2) Option(true) else Option(false))
    res2: Option[Boolean] = Some(false)
    
    scala> F.forallM(List(1,2,3,4))(n => if (n <= 2) Option(false) else None)
    res3: Option[Boolean] = Some(false)
    
    scala> F.forallM(List(1,2,3,4))(n => if (n <= 2) None else Option(false))
    res4: Option[Boolean] = None
    Definition Classes
    Foldable
  45. 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
  46. 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
  47. def get[A](fa: F[A])(idx: Long): Option[A]

    Get the element at the index of the Foldable.

    Get the element at the index of the Foldable.

    Definition Classes
    Foldable
  48. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  49. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  50. 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()
  51. 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
  52. def intercalate[A](fa: F[A], a: A)(implicit A: Monoid[A]): A

    Intercalate/insert an element between the existing elements while folding.

    Intercalate/insert an element between the existing elements while folding.

    scala> import cats.implicits._
    scala> Foldable[List].intercalate(List("a","b","c"), "-")
    res0: String = a-b-c
    scala> Foldable[List].intercalate(List("a"), "-")
    res1: String = a
    scala> Foldable[List].intercalate(List.empty[String], "-")
    res2: String = ""
    scala> Foldable[Vector].intercalate(Vector(1,2,3), 1)
    res3: Int = 8
    Definition Classes
    Foldable
  53. def intersperseList[A](xs: List[A], x: A): List[A]
    Attributes
    protected
    Definition Classes
    Foldable
  54. def isEmpty[A](fa: F[A]): Boolean

    Returns true if there are no elements.

    Returns true if there are no elements. Otherwise false.

    Definition Classes
    FoldableUnorderedFoldable
  55. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  56. 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
  57. def map[A, B](fa: F[A])(f: (A) ⇒ B): F[B]
    Definition Classes
    TraverseFunctor
  58. def mapWithIndex[A, B](fa: F[A])(f: (A, Int) ⇒ B): F[B]

    Akin to map, but also provides the value's index in structure F when calling the function.

  59. def maximumByList[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: Order[B]): List[A]

    Find all the maximum A items in this structure according to an Order.by(f).

    Find all the maximum A items in this structure according to an Order.by(f). For all elements in the result Order.eqv(x, y) is true. Preserves order.

    Definition Classes
    Foldable
    See also

    Reducible#maximumByNel for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    minimumByList for minimum instead of maximum.

  60. def maximumByOption[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: Order[B]): Option[A]

    Find the maximum A item in this structure according to an Order.by(f).

    Find the maximum A item in this structure according to an Order.by(f).

    returns

    None if the structure is empty, otherwise the maximum element wrapped in a Some.

    Definition Classes
    Foldable
    See also

    Reducible#maximumBy for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    minimumByOption for minimum instead of maximum.

  61. def maximumList[A](fa: F[A])(implicit A: Order[A]): List[A]

    Find all the maximum A items in this structure.

    Find all the maximum A items in this structure. For all elements in the result Order.eqv(x, y) is true. Preserves order.

    Definition Classes
    Foldable
    See also

    Reducible#maximumNel for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    minimumList for minimum instead of maximum.

  62. def maximumOption[A](fa: F[A])(implicit A: Order[A]): Option[A]

    Find the maximum A item in this structure according to the Order[A].

    Find the maximum A item in this structure according to the Order[A].

    returns

    None if the structure is empty, otherwise the maximum element wrapped in a Some.

    Definition Classes
    Foldable
    See also

    Reducible#maximum for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    minimumOption for minimum instead of maximum.

  63. def minimumByList[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: Order[B]): List[A]

    Find all the minimum A items in this structure according to an Order.by(f).

    Find all the minimum A items in this structure according to an Order.by(f). For all elements in the result Order.eqv(x, y) is true. Preserves order.

    Definition Classes
    Foldable
    See also

    Reducible#minimumByNel for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    maximumByList for maximum instead of minimum.

  64. def minimumByOption[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: Order[B]): Option[A]

    Find the minimum A item in this structure according to an Order.by(f).

    Find the minimum A item in this structure according to an Order.by(f).

    returns

    None if the structure is empty, otherwise the minimum element wrapped in a Some.

    Definition Classes
    Foldable
    See also

    Reducible#minimumBy for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    maximumByOption for maximum instead of minimum.

  65. def minimumList[A](fa: F[A])(implicit A: Order[A]): List[A]

    Find all the minimum A items in this structure.

    Find all the minimum A items in this structure. For all elements in the result Order.eqv(x, y) is true. Preserves order.

    Definition Classes
    Foldable
    See also

    Reducible#minimumNel for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    maximumList for maximum instead of minimum.

  66. def minimumOption[A](fa: F[A])(implicit A: Order[A]): Option[A]

    Find the minimum A item in this structure according to the Order[A].

    Find the minimum A item in this structure according to the Order[A].

    returns

    None if the structure is empty, otherwise the minimum element wrapped in a Some.

    Definition Classes
    Foldable
    See also

    Reducible#minimum for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty.

    maximumOption for maximum instead of minimum.

  67. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  68. def nonEmpty[A](fa: F[A]): Boolean
    Definition Classes
    FoldableUnorderedFoldable
  69. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  70. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  71. def partitionBifold[H[_, _], A, B, C](fa: F[A])(f: (A) ⇒ H[B, C])(implicit A: Alternative[F], H: Bifoldable[H]): (F[B], F[C])

    Separate this Foldable into a Tuple by a separating function A => H[B, C] for some Bifoldable[H] Equivalent to Functor#map and then Alternative#separate.

    Separate this Foldable into a Tuple by a separating function A => H[B, C] for some Bifoldable[H] Equivalent to Functor#map and then Alternative#separate.

    scala> import cats.implicits._, cats.Foldable, cats.data.Const
    scala> val list = List(1,2,3,4)
    scala> Foldable[List].partitionBifold(list)(a => ("value " + a.toString(), if (a % 2 == 0) -a else a))
    res0: (List[String], List[Int]) = (List(value 1, value 2, value 3, value 4),List(1, -2, 3, -4))
    scala> Foldable[List].partitionBifold(list)(a => Const[Int, Nothing with Any](a))
    res1: (List[Int], List[Nothing with Any]) = (List(1, 2, 3, 4),List())
    Definition Classes
    Foldable
    Annotations
    @noop()
  72. def partitionBifoldM[G[_], H[_, _], A, B, C](fa: F[A])(f: (A) ⇒ G[H[B, C]])(implicit A: Alternative[F], M: Monad[G], H: Bifoldable[H]): G[(F[B], F[C])]

    Separate this Foldable into a Tuple by an effectful separating function A => G[H[B, C]] for some Bifoldable[H] Equivalent to Traverse#traverse over Alternative#separate

    Separate this Foldable into a Tuple by an effectful separating function A => G[H[B, C]] for some Bifoldable[H] Equivalent to Traverse#traverse over Alternative#separate

    scala> import cats.implicits._, cats.Foldable, cats.data.Const
    scala> val list = List(1,2,3,4)
    `Const`'s second parameter is never instantiated, so we can use an impossible type:
    scala> Foldable[List].partitionBifoldM(list)(a => Option(Const[Int, Nothing with Any](a)))
    res0: Option[(List[Int], List[Nothing with Any])] = Some((List(1, 2, 3, 4),List()))
    Definition Classes
    Foldable
    Annotations
    @noop()
  73. def partitionEither[A, B, C](fa: F[A])(f: (A) ⇒ Either[B, C])(implicit A: Alternative[F]): (F[B], F[C])

    Separate this Foldable into a Tuple by a separating function A => Either[B, C] Equivalent to Functor#map and then Alternative#separate.

    Separate this Foldable into a Tuple by a separating function A => Either[B, C] Equivalent to Functor#map and then Alternative#separate.

    scala> import cats.implicits._
    scala> val list = List(1,2,3,4)
    scala> Foldable[List].partitionEither(list)(a => if (a % 2 == 0) Left(a.toString) else Right(a))
    res0: (List[String], List[Int]) = (List(2, 4),List(1, 3))
    scala> Foldable[List].partitionEither(list)(a => Right(a * 4))
    res1: (List[Nothing], List[Int]) = (List(),List(4, 8, 12, 16))
    Definition Classes
    Foldable
  74. def partitionEitherM[G[_], A, B, C](fa: F[A])(f: (A) ⇒ G[Either[B, C]])(implicit A: Alternative[F], M: Monad[G]): G[(F[B], F[C])]

    Separate this Foldable into a Tuple by an effectful separating function A => G[Either[B, C]] Equivalent to Traverse#traverse over Alternative#separate

    Separate this Foldable into a Tuple by an effectful separating function A => G[Either[B, C]] Equivalent to Traverse#traverse over Alternative#separate

    scala> import cats.implicits._, cats.Foldable, cats.Eval
    scala> val list = List(1,2,3,4)
    scala> val partitioned1 = Foldable[List].partitionEitherM(list)(a => if (a % 2 == 0) Eval.now(Either.left[String, Int](a.toString)) else Eval.now(Either.right[String, Int](a)))
    Since `Eval.now` yields a lazy computation, we need to force it to inspect the result:
    scala> partitioned1.value
    res0: (List[String], List[Int]) = (List(2, 4),List(1, 3))
    scala> val partitioned2 = Foldable[List].partitionEitherM(list)(a => Eval.later(Either.right(a * 4)))
    scala> partitioned2.value
    res1: (List[Nothing], List[Int]) = (List(),List(4, 8, 12, 16))
    Definition Classes
    Foldable
    Annotations
    @noop()
  75. def productAll[A](fa: F[A])(implicit A: Numeric[A]): A
    Definition Classes
    Foldable
  76. def reduceLeftOption[A](fa: F[A])(f: (A, A) ⇒ A): Option[A]

    Reduce the elements of this structure down to a single value by applying the provided aggregation function in a left-associative manner.

    Reduce the elements of this structure down to a single value by applying the provided aggregation function in a left-associative manner.

    returns

    None if the structure is empty, otherwise the result of combining the cumulative left-associative result of the f operation over all of the elements.

    Definition Classes
    Foldable
    See also

    reduceRightOption for a right-associative alternative.

    Reducible#reduceLeft for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty. Example:

    scala> import cats.implicits._
    scala> val l = List(6, 3, 2)
    This is equivalent to (6 - 3) - 2
    scala> Foldable[List].reduceLeftOption(l)(_ - _)
    res0: Option[Int] = Some(1)
    
    scala> Foldable[List].reduceLeftOption(List.empty[Int])(_ - _)
    res1: Option[Int] = None
  77. def reduceLeftToOption[A, B](fa: F[A])(f: (A) ⇒ B)(g: (B, A) ⇒ B): Option[B]
    Definition Classes
    Foldable
  78. def reduceRightOption[A](fa: F[A])(f: (A, Eval[A]) ⇒ Eval[A]): Eval[Option[A]]

    Reduce the elements of this structure down to a single value by applying the provided aggregation function in a right-associative manner.

    Reduce the elements of this structure down to a single value by applying the provided aggregation function in a right-associative manner.

    returns

    None if the structure is empty, otherwise the result of combining the cumulative right-associative result of the f operation over the A elements.

    Definition Classes
    Foldable
    See also

    reduceLeftOption for a left-associative alternative

    Reducible#reduceRight for a version that doesn't need to return an Option for structures that are guaranteed to be non-empty. Example:

    scala> import cats.implicits._
    scala> val l = List(6, 3, 2)
    This is equivalent to 6 - (3 - 2)
    scala> Foldable[List].reduceRightOption(l)((current, rest) => rest.map(current - _)).value
    res0: Option[Int] = Some(5)
    
    scala> Foldable[List].reduceRightOption(List.empty[Int])((current, rest) => rest.map(current - _)).value
    res1: Option[Int] = None
  79. def reduceRightToOption[A, B](fa: F[A])(f: (A) ⇒ B)(g: (A, Eval[B]) ⇒ Eval[B]): Eval[Option[B]]
    Definition Classes
    Foldable
  80. def sequence[G[_], A](fga: F[G[A]])(implicit arg0: Applicative[G]): G[F[A]]

    Thread all the G effects through the F structure to invert the structure from F[G[A]] to G[F[A]].

    Thread all the G effects through the F structure to invert the structure from F[G[A]] to G[F[A]].

    Example:

    scala> import cats.implicits._
    scala> val x: List[Option[Int]] = List(Some(1), Some(2))
    scala> val y: List[Option[Int]] = List(None, Some(2))
    scala> x.sequence
    res0: Option[List[Int]] = Some(List(1, 2))
    scala> y.sequence
    res1: Option[List[Int]] = None
  81. def sequence_[G[_], A](fga: F[G[A]])(implicit arg0: Applicative[G]): G[Unit]

    Sequence F[G[A]] using Applicative[G].

    Sequence F[G[A]] using Applicative[G].

    This is similar to traverse_ except it operates on F[G[A]] values, so no additional functions are needed.

    For example:

    scala> import cats.implicits._
    scala> val F = Foldable[List]
    scala> F.sequence_(List(Option(1), Option(2), Option(3)))
    res0: Option[Unit] = Some(())
    scala> F.sequence_(List(Option(1), None, Option(3)))
    res1: Option[Unit] = None
    Definition Classes
    Foldable
  82. def size[A](fa: F[A]): Long

    The size of this UnorderedFoldable.

    The size of this UnorderedFoldable.

    This is overridden in structures that have more efficient size implementations (e.g. Vector, Set, Map).

    Note: will not terminate for infinite-sized collections.

    Definition Classes
    UnorderedFoldable
  83. def sliding10[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  84. def sliding11[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  85. def sliding12[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  86. def sliding13[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  87. def sliding14[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  88. def sliding15[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  89. def sliding16[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  90. def sliding17[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  91. def sliding18[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  92. def sliding19[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  93. def sliding2[A](fa: F[A]): List[(A, A)]

    Definition Classes
    FoldableNFunctions
  94. def sliding20[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  95. def sliding21[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  96. def sliding22[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  97. def sliding3[A](fa: F[A]): List[(A, A, A)]

    Definition Classes
    FoldableNFunctions
  98. def sliding4[A](fa: F[A]): List[(A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  99. def sliding5[A](fa: F[A]): List[(A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  100. def sliding6[A](fa: F[A]): List[(A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  101. def sliding7[A](fa: F[A]): List[(A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  102. def sliding8[A](fa: F[A]): List[(A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  103. def sliding9[A](fa: F[A]): List[(A, A, A, A, A, A, A, A, A)]

    Definition Classes
    FoldableNFunctions
  104. def sumAll[A](fa: F[A])(implicit A: Numeric[A]): A
    Definition Classes
    Foldable
  105. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  106. def takeWhile_[A](fa: F[A])(p: (A) ⇒ Boolean): List[A]

    Convert F[A] to a List[A], retaining only initial elements which match p.

    Convert F[A] to a List[A], retaining only initial elements which match p.

    Definition Classes
    Foldable
  107. def toIterable[A](fa: F[A]): Iterable[A]

    Convert F[A] to an Iterable[A].

    Convert F[A] to an Iterable[A].

    This method may be overridden for the sake of performance, but implementers should take care not to force a full materialization of the collection.

    Definition Classes
    Foldable
  108. def toList[A](fa: F[A]): List[A]

    Convert F[A] to a List[A].

    Convert F[A] to a List[A].

    Definition Classes
    Foldable
  109. def toString(): String
    Definition Classes
    AnyRef → Any
  110. def traverseTap[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit arg0: Applicative[G]): G[F[A]]

    Given a function which returns a G effect, thread this effect through the running of this function on all the values in F, returning an F[A] in a G context, ignoring the values returned by provided function.

    Given a function which returns a G effect, thread this effect through the running of this function on all the values in F, returning an F[A] in a G context, ignoring the values returned by provided function.

    Example:

    scala> import cats.implicits._
    scala> import java.io.IOException
    scala> type IO[A] = Either[IOException, A]
    scala> def debug(msg: String): IO[Unit] = Right(())
    scala> List("1", "2", "3").traverseTap(debug)
    res1: IO[List[String]] = Right(List(1, 2, 3))
  111. def traverseWithIndexM[G[_], A, B](fa: F[A])(f: (A, Int) ⇒ G[B])(implicit G: Monad[G]): G[F[B]]

    Akin to traverse, but also provides the value's index in structure F when calling the function.

    Akin to traverse, but also provides the value's index in structure F when calling the function.

    This performs the traversal in a single pass but requires that effect G is monadic. An applicative traversal can be performed in two passes using zipWithIndex followed by traverse.

  112. def traverse_[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: Applicative[G]): G[Unit]

    Traverse F[A] using Applicative[G].

    Traverse F[A] using Applicative[G].

    A values will be mapped into G[B] and combined using Applicative#map2.

    For example:

    scala> import cats.implicits._
    scala> def parseInt(s: String): Option[Int] = Either.catchOnly[NumberFormatException](s.toInt).toOption
    scala> val F = Foldable[List]
    scala> F.traverse_(List("333", "444"))(parseInt)
    res0: Option[Unit] = Some(())
    scala> F.traverse_(List("333", "zzz"))(parseInt)
    res1: Option[Unit] = None

    This method is primarily useful when G[_] represents an action or effect, and the specific A aspect of G[A] is not otherwise needed.

    Definition Classes
    Foldable
  113. 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
  114. 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
  115. def unorderedFold[A](fa: F[A])(implicit arg0: CommutativeMonoid[A]): A
    Definition Classes
    FoldableUnorderedFoldable
  116. def unorderedFoldMap[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: CommutativeMonoid[B]): B
    Definition Classes
    FoldableUnorderedFoldable
  117. def unorderedSequence[G[_], A](fga: F[G[A]])(implicit arg0: CommutativeApplicative[G]): G[F[A]]
    Definition Classes
    TraverseUnorderedTraverse
  118. def unorderedTraverse[G[_], A, B](sa: F[A])(f: (A) ⇒ G[B])(implicit arg0: CommutativeApplicative[G]): G[F[B]]
    Definition Classes
    TraverseUnorderedTraverse
  119. 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()
  120. 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
  121. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  122. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  123. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  124. 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
  125. def zipWithIndex[A](fa: F[A]): F[(A, Int)]

    Traverses through the structure F, pairing the values with assigned indices.

    Traverses through the structure F, pairing the values with assigned indices.

    The behavior is consistent with the Scala collection library's zipWithIndex for collections such as List.

Inherited from UnorderedTraverse[F]

Inherited from Foldable[F]

Inherited from FoldableNFunctions[F]

Inherited from UnorderedFoldable[F]

Inherited from Functor[F]

Inherited from Invariant[F]

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

Ungrouped

foldable arity

Group sequential elements into fixed sized tuples by passing a "sliding window" over them. A foldable with fewer elements than the window size will return an empty list unlike Iterable#sliding(size: Int). Example:

import cats.Foldable
scala> Foldable[List].sliding2((1 to 10).toList)
val res0: List[(Int, Int)] = List((1,2), (2,3), (3,4), (4,5), (5,6), (6,7), (7,8), (8,9), (9,10))

scala> Foldable[List].sliding4((1 to 10).toList)
val res1: List[(Int, Int, Int, Int)] = List((1,2,3,4), (2,3,4,5), (3,4,5,6), (4,5,6,7), (5,6,7,8), (6,7,8,9), (7,8,9,10))

scala> Foldable[List].sliding4((1 to 2).toList)
val res2: List[(Int, Int, Int, Int)] = List()