abstract class NonEmptyReducible[F[_], G[_]] extends Reducible[F]
This class defines a Reducible[F]
in terms of a Foldable[G]
together with a split
method, F[A]
=> (A, G[A])
.
This class can be used on any type where the first value (A
) and
the "rest" of the values (G[A]
) can be easily found.
This class is only a helper, does not define a typeclass and should not be used outside of Cats. Also see the discussion: PR #3541 and issue #3069.
- Alphabetic
- By Inheritance
- NonEmptyReducible
- Reducible
- Foldable
- UnorderedFoldable
- Serializable
- Serializable
- AnyRef
- Any
- Hide All
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- Public
- All
Abstract Value Members
- abstract def split[A](fa: F[A]): (A, G[A])
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
- Definition Classes
- AnyRef → Any
-
final
def
==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
def
clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()
-
def
collectFirst[A, B](fa: F[A])(pf: PartialFunction[A, B]): Option[B]
- Definition Classes
- Foldable
-
def
collectFirstSome[A, B](fa: F[A])(f: (A) ⇒ Option[B]): Option[B]
Like
collectFirst
fromscala.collection.Traversable
but takesA => Option[B]
instead ofPartialFunction
s.Like
collectFirst
fromscala.collection.Traversable
but takesA => Option[B]
instead ofPartialFunction
s.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
-
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()
-
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()
-
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
-
def
combineAll[A](fa: F[A])(implicit arg0: Monoid[A]): A
Alias for fold.
-
def
combineAllOption[A](fa: F[A])(implicit ev: Semigroup[A]): Option[A]
- Definition Classes
- Foldable
-
def
compose[G[_]](implicit arg0: Reducible[G]): Reducible[[α]F[G[α]]]
- Definition Classes
- Reducible
-
def
compose[G[_]](implicit arg0: Foldable[G]): Foldable[[α]F[G[α]]]
- Definition Classes
- Foldable
-
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()
-
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
- NonEmptyReducible → Foldable
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
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
- NonEmptyReducible → Foldable → UnorderedFoldable
-
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 atrue
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
-
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
- NonEmptyReducible → Foldable
-
def
finalize(): Unit
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
-
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
- NonEmptyReducible → Foldable
-
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()
-
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
- NonEmptyReducible → Foldable
-
def
foldA[G[_], A](fga: F[G[A]])(implicit G: Applicative[G], A: Monoid[A]): G[A]
Fold implemented using the given
Applicative[G]
andMonoid[A]
instance.Fold implemented using the given
Applicative[G]
andMonoid[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()
-
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 aMonoid[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
-
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
- NonEmptyReducible → Foldable
-
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.
-
def
foldM[H[_], A, B](fa: F[A], z: B)(f: (B, A) ⇒ H[B])(implicit H: Monad[H]): H[B]
Perform a stack-safe monadic left fold from the source context
F
into the target monadG
.Perform a stack-safe monadic left fold from the source context
F
into the target monadG
.This method can express short-circuiting semantics. Even when
fa
is an infinite structure, this method can potentially terminate if thefoldRight
implementation forF
and thetailRecM
implementation forG
are sufficiently lazy.Instances for concrete structures (e.g.
List
) will often have a more efficient implementation than the default one in terms offoldRight
.- Definition Classes
- NonEmptyReducible → Foldable
-
def
foldMap[A, B](fa: F[A])(f: (A) ⇒ B)(implicit B: Monoid[B]): B
Fold implemented by mapping
A
values intoB
and then combining them using the givenMonoid[B]
instance.Fold implemented by mapping
A
values intoB
and then combining them using the givenMonoid[B]
instance.- Definition Classes
- Foldable
-
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 toG[B]
.Fold in an Applicative context by mapping the
A
values toG[B]
. combining theB
values using the givenMonoid[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
-
def
foldMapK[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: MonoidK[G]): G[B]
Fold implemented by mapping
A
values intoB
in a contextG
and then combining them using theMonoidK[G]
instance.Fold implemented by mapping
A
values intoB
in a contextG
and then combining them using theMonoidK[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()
-
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 mappingA
values toG[B]
, combining theB
values using the givenMonoid[B]
instance.Monadic folding on
F
by mappingA
values toG[B]
, combining theB
values using the givenMonoid[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
-
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
- NonEmptyReducible → Foldable
-
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
-
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
- NonEmptyReducible → Foldable → UnorderedFoldable
-
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 afalse
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
-
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
- NonEmptyReducible → Foldable
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
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
-
def
intersperseList[A](xs: List[A], x: A): List[A]
- Attributes
- protected
- Definition Classes
- Foldable
-
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
- Reducible → Foldable → UnorderedFoldable
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
-
def
maximum[A](fa: F[A])(implicit A: Order[A]): A
- Definition Classes
- Reducible
-
def
maximumBy[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: Order[B]): A
Find the maximum
A
item in this structure according to anOrder.by(f)
. -
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 anOrder.by(f)
.Find the maximum
A
item in this structure according to anOrder.by(f)
.- returns
None
if the structure is empty, otherwise the maximum element wrapped in aSome
.
- 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.
-
def
maximumOption[A](fa: F[A])(implicit A: Order[A]): Option[A]
Find the maximum
A
item in this structure according to theOrder[A]
.Find the maximum
A
item in this structure according to theOrder[A]
.- returns
None
if the structure is empty, otherwise the maximum element wrapped in aSome
.
- Definition Classes
- Reducible → 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.
-
def
minimum[A](fa: F[A])(implicit A: Order[A]): A
- Definition Classes
- Reducible
-
def
minimumBy[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: Order[B]): A
Find the minimum
A
item in this structure according to anOrder.by(f)
. -
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 anOrder.by(f)
.Find the minimum
A
item in this structure according to anOrder.by(f)
.- returns
None
if the structure is empty, otherwise the minimum element wrapped in aSome
.
- 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.
-
def
minimumOption[A](fa: F[A])(implicit A: Order[A]): Option[A]
Find the minimum
A
item in this structure according to theOrder[A]
.Find the minimum
A
item in this structure according to theOrder[A]
.- returns
None
if the structure is empty, otherwise the minimum element wrapped in aSome
.
- Definition Classes
- Reducible → 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.
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
nonEmpty[A](fa: F[A]): Boolean
- Definition Classes
- Reducible → Foldable → UnorderedFoldable
-
def
nonEmptyIntercalate[A](fa: F[A], a: A)(implicit A: Semigroup[A]): A
Intercalate/insert an element between the existing elements while reducing.
Intercalate/insert an element between the existing elements while reducing.
scala> import cats.implicits._ scala> import cats.data.NonEmptyList scala> val nel = NonEmptyList.of("a", "b", "c") scala> Reducible[NonEmptyList].nonEmptyIntercalate(nel, "-") res0: String = a-b-c scala> Reducible[NonEmptyList].nonEmptyIntercalate(NonEmptyList.of("a"), "-") res1: String = a
- Definition Classes
- Reducible
-
def
nonEmptyPartition[A, B, C](fa: F[A])(f: (A) ⇒ Either[B, C]): Ior[NonEmptyList[B], NonEmptyList[C]]
Partition this Reducible by a separating function
A => Either[B, C]
Partition this Reducible by a separating function
A => Either[B, C]
scala> import cats.data.NonEmptyList scala> val nel = NonEmptyList.of(1,2,3,4) scala> Reducible[NonEmptyList].nonEmptyPartition(nel)(a => if (a % 2 == 0) Left(a.toString) else Right(a)) res0: cats.data.Ior[cats.data.NonEmptyList[String],cats.data.NonEmptyList[Int]] = Both(NonEmptyList(2, 4),NonEmptyList(1, 3)) scala> Reducible[NonEmptyList].nonEmptyPartition(nel)(a => Right(a * 4)) res1: cats.data.Ior[cats.data.NonEmptyList[Nothing],cats.data.NonEmptyList[Int]] = Right(NonEmptyList(4, 8, 12, 16))
- Definition Classes
- Reducible
-
def
nonEmptySequence_[G[_], A](fga: F[G[A]])(implicit G: Apply[G]): G[Unit]
Sequence
F[G[A]]
usingApply[G]
.Sequence
F[G[A]]
usingApply[G]
.This method is similar to Foldable.sequence_ but requires only an Apply instance for
G
instead of Applicative. See the nonEmptyTraverse_ documentation for a description of the differences.- Definition Classes
- Reducible
-
def
nonEmptyTraverse_[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: Apply[G]): G[Unit]
Traverse
F[A]
usingApply[G]
.Traverse
F[A]
usingApply[G]
.A
values will be mapped intoG[B]
and combined usingApply#map2
.This method is similar to Foldable.traverse_. There are two main differences:
1. We only need an Apply instance for
G
here, since we don't need to call Applicative.pure for a starting value. 2. This performs a strict left-associative traversal and thus must always traverse the entire data structure. Prefer Foldable.traverse_ if you have an Applicative instance available forG
and want to take advantage of short-circuiting the traversal.- Definition Classes
- Reducible
-
final
def
notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
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 someBifoldable[H]
Equivalent toFunctor#map
and thenAlternative#separate
.Separate this Foldable into a Tuple by a separating function
A => H[B, C]
for someBifoldable[H]
Equivalent toFunctor#map
and thenAlternative#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()
-
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 someBifoldable[H]
Equivalent toTraverse#traverse
overAlternative#separate
Separate this Foldable into a Tuple by an effectful separating function
A => G[H[B, C]]
for someBifoldable[H]
Equivalent toTraverse#traverse
overAlternative#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()
-
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 toFunctor#map
and thenAlternative#separate
.Separate this Foldable into a Tuple by a separating function
A => Either[B, C]
Equivalent toFunctor#map
and thenAlternative#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
-
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 toTraverse#traverse
overAlternative#separate
Separate this Foldable into a Tuple by an effectful separating function
A => G[Either[B, C]]
Equivalent toTraverse#traverse
overAlternative#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()
-
def
reduce[A](fa: F[A])(implicit A: Semigroup[A]): A
Reduce a
F[A]
value using the givenSemigroup[A]
.Reduce a
F[A]
value using the givenSemigroup[A]
.- Definition Classes
- Reducible
-
def
reduceA[G[_], A](fga: F[G[A]])(implicit G: Apply[G], A: Semigroup[A]): G[A]
Reduce a
F[G[A]]
value usingApplicative[G]
andSemigroup[A]
, a universal semigroup forG[_]
.Reduce a
F[G[A]]
value usingApplicative[G]
andSemigroup[A]
, a universal semigroup forG[_]
.This method is similar to reduce, but may short-circuit.
See this issue for an explanation of
@noop
usage.- Definition Classes
- Reducible
- Annotations
- @noop()
-
def
reduceK[G[_], A](fga: F[G[A]])(implicit G: SemigroupK[G]): G[A]
Reduce a
F[G[A]]
value usingSemigroupK[G]
, a universal semigroup forG[_]
.Reduce a
F[G[A]]
value usingSemigroupK[G]
, a universal semigroup forG[_]
.This method is a generalization of
reduce
.- Definition Classes
- Reducible
-
def
reduceLeft[A](fa: F[A])(f: (A, A) ⇒ A): A
Left-associative reduction on
F
using the functionf
.Left-associative reduction on
F
using the functionf
.Implementations should override this method when possible.
- Definition Classes
- Reducible
-
def
reduceLeftM[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(g: (B, A) ⇒ G[B])(implicit G: FlatMap[G]): G[B]
Monadic variant of reduceLeftTo.
Monadic variant of reduceLeftTo.
- Definition Classes
- Reducible
-
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 thef
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
-
def
reduceLeftTo[A, B](fa: F[A])(f: (A) ⇒ B)(g: (B, A) ⇒ B): B
Apply
f
to the "initial element" offa
and combine it with every other value using the given functiong
.Apply
f
to the "initial element" offa
and combine it with every other value using the given functiong
.- Definition Classes
- NonEmptyReducible → Reducible
-
def
reduceLeftToOption[A, B](fa: F[A])(f: (A) ⇒ B)(g: (B, A) ⇒ B): Option[B]
Overridden from Foldable for efficiency.
-
def
reduceMap[A, B](fa: F[A])(f: (A) ⇒ B)(implicit B: Semigroup[B]): B
Apply
f
to each element offa
and combine them using the givenSemigroup[B]
.Apply
f
to each element offa
and combine them using the givenSemigroup[B]
.- Definition Classes
- Reducible
-
def
reduceMapA[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: Apply[G], B: Semigroup[B]): G[B]
Reduce in an Apply context by mapping the
A
values toG[B]
.Reduce in an Apply context by mapping the
A
values toG[B]
. combining theB
values using the givenSemigroup[B]
instance.Similar to reduceMapM, but may be less efficient.
scala> import cats.Reducible scala> import cats.data.NonEmptyList scala> import cats.implicits._ scala> val evenOpt: Int => Option[Int] = | i => if (i % 2 == 0) Some(i) else None scala> val allEven = NonEmptyList.of(2,4,6,8,10) allEven: cats.data.NonEmptyList[Int] = NonEmptyList(2, 4, 6, 8, 10) scala> val notAllEven = allEven ++ List(11) notAllEven: cats.data.NonEmptyList[Int] = NonEmptyList(2, 4, 6, 8, 10, 11) scala> Reducible[NonEmptyList].reduceMapA(allEven)(evenOpt) res0: Option[Int] = Some(30) scala> Reducible[NonEmptyList].reduceMapA(notAllEven)(evenOpt) res1: Option[Int] = None
- Definition Classes
- Reducible
-
def
reduceMapK[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: SemigroupK[G]): G[B]
Apply
f
to each element offa
and combine them using the givenSemigroupK[G]
.Apply
f
to each element offa
and combine them using the givenSemigroupK[G]
.scala> import cats._, cats.data._, cats.implicits._ scala> val f: Int => Endo[String] = i => (s => s + i) scala> val x: Endo[String] = Reducible[NonEmptyList].reduceMapK(NonEmptyList.of(1, 2, 3))(f) scala> val a = x("foo") a: String = "foo321"
- Definition Classes
- Reducible
- Annotations
- @noop()
-
def
reduceMapM[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: FlatMap[G], B: Semigroup[B]): G[B]
Reduce in an FlatMap context by mapping the
A
values toG[B]
.Reduce in an FlatMap context by mapping the
A
values toG[B]
. combining theB
values using the givenSemigroup[B]
instance.Similar to reduceLeftM, but using a
Semigroup[B]
. May be more efficient than reduceMapA.scala> import cats.Reducible scala> import cats.data.NonEmptyList scala> import cats.implicits._ scala> val evenOpt: Int => Option[Int] = | i => if (i % 2 == 0) Some(i) else None scala> val allEven = NonEmptyList.of(2,4,6,8,10) allEven: cats.data.NonEmptyList[Int] = NonEmptyList(2, 4, 6, 8, 10) scala> val notAllEven = allEven ++ List(11) notAllEven: cats.data.NonEmptyList[Int] = NonEmptyList(2, 4, 6, 8, 10, 11) scala> Reducible[NonEmptyList].reduceMapM(allEven)(evenOpt) res0: Option[Int] = Some(30) scala> Reducible[NonEmptyList].reduceMapM(notAllEven)(evenOpt) res1: Option[Int] = None
- Definition Classes
- Reducible
-
def
reduceRight[A](fa: F[A])(f: (A, Eval[A]) ⇒ Eval[A]): Eval[A]
Right-associative reduction on
F
using the functionf
.Right-associative reduction on
F
using the functionf
.- Definition Classes
- Reducible
-
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 thef
operation over theA
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
-
def
reduceRightTo[A, B](fa: F[A])(f: (A) ⇒ B)(g: (A, Eval[B]) ⇒ Eval[B]): Eval[B]
Apply
f
to the "initial element" offa
and lazily combine it with every other value using the given functiong
.Apply
f
to the "initial element" offa
and lazily combine it with every other value using the given functiong
.- Definition Classes
- NonEmptyReducible → Reducible
-
def
reduceRightToOption[A, B](fa: F[A])(f: (A) ⇒ B)(g: (A, Eval[B]) ⇒ Eval[B]): Eval[Option[B]]
Overridden from Foldable for efficiency.
-
def
sequence_[G[_], A](fga: F[G[A]])(implicit arg0: Applicative[G]): G[Unit]
Sequence
F[G[A]]
usingApplicative[G]
.Sequence
F[G[A]]
usingApplicative[G]
.This is similar to
traverse_
except it operates onF[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
-
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
- NonEmptyReducible → UnorderedFoldable
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
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
- NonEmptyReducible → Foldable
-
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
-
def
toList[A](fa: F[A]): List[A]
Convert F[A] to a List[A].
Convert F[A] to a List[A].
- Definition Classes
- NonEmptyReducible → Foldable
-
def
toNonEmptyList[A](fa: F[A]): NonEmptyList[A]
- Definition Classes
- NonEmptyReducible → Reducible
-
def
toString(): String
- Definition Classes
- AnyRef → Any
-
def
traverse_[G[_], A, B](fa: F[A])(f: (A) ⇒ G[B])(implicit G: Applicative[G]): G[Unit]
Traverse
F[A]
usingApplicative[G]
.Traverse
F[A]
usingApplicative[G]
.A
values will be mapped intoG[B]
and combined usingApplicative#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 specificA
aspect ofG[A]
is not otherwise needed.- Definition Classes
- Foldable
-
def
unorderedFold[A](fa: F[A])(implicit arg0: CommutativeMonoid[A]): A
- Definition Classes
- Foldable → UnorderedFoldable
-
def
unorderedFoldMap[A, B](fa: F[A])(f: (A) ⇒ B)(implicit arg0: CommutativeMonoid[B]): B
- Definition Classes
- Foldable → UnorderedFoldable
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()