pSVecTraverse
cats.Traverse — the instance Traversal's .modifyA / .all route through when the carrier is MultiFocus[PSVec]. Effects run left-to-right in index order, results land in one pre-sized backing array threaded through G.map2 (no per-element vector rebuild).
Attributes
- Source
- PSVec.scala
- Graph
-
- Supertypes
-
trait UnorderedTraverse[PSVec]trait FoldableNFunctions[PSVec]trait UnorderedFoldable[PSVec]trait Serializableclass Objecttrait Matchableclass AnyShow all
- Self type
-
pSVecTraverse.type
Members list
Grouped members
FoldableSlidingN
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Attributes
- Inherited from:
- FoldableNFunctions
- Source
- FoldableNFunctions.scala
Value members
Concrete methods
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)
Attributes
- Source
- PSVec.scala
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
Attributes
- Source
- PSVec.scala
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.syntax.all._
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
Attributes
- Source
- PSVec.scala
Inherited methods
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.syntax.all._
scala> List(1,2,3).as("hello")
res0: List[String] = List(hello, hello, hello)
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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))
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Tear down a subset of this structure using a PartialFunction.
Tear down a subset of this structure using a PartialFunction.
scala> import cats.syntax.all._
scala> val xs = List(1, 2, 3, 4)
scala> Foldable[List].collectFold(xs) { case n if n % 2 == 0 => n }
res0: Int = 6
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Alias for fold.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Inherited from:
- Functor
- Source
- Functor.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
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 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
Tests if fa contains v using the Eq instance for A
Tests if fa contains v using the Eq instance for A
Attributes
- Inherited from:
- UnorderedFoldable
- Source
- UnorderedFoldable.scala
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.syntax.all._
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
Attributes
- Inherited from:
- UnorderedFoldable
- Source
- UnorderedFoldable.scala
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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Definition Classes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
scala> val F = Foldable[List]
scala> F.existsM(List(1,2,3,4))(n => Option(n 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 F.existsM(List(1,2,3,4))(n => if (n F.existsM(List(1,2,3,4))(n => if (n <= 2) None else Option(true))
res4: Option[Boolean] = None
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Find the first element matching the predicate, if one exists.
Find the first element matching the predicate, if one exists.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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)
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
A traverse followed by flattening the inner result.
A traverse followed by flattening the inner result.
Example:
scala> import cats.syntax.all._
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))
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.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
Fold implemented using the given Monoid[A] instance.
Fold implemented using the given Monoid[A] instance.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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)
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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)
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Alias for foldM.
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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Fold in an Applicative context by mapping the A values to G[B]. combining the B values using the given Monoid[B] instance.
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.syntax.all._
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
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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"
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Check whether all elements satisfy the predicate.
Check whether all elements satisfy the predicate.
If there are no elements, the result is true.
Attributes
- Definition Classes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
scala> val F = Foldable[List]
scala> F.forallM(List(1,2,3,4))(n => Option(n F.forallM(List(1,2,3,4))(n => Option(n F.forallM(List(1,2,3,4))(n => if (n F.forallM(List(1,2,3,4))(n => if (n F.forallM(List(1,2,3,4))(n => if (n <= 2) None else Option(false))
res4: Option[Boolean] = None
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.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.syntax.all._
scala> Option(42).fproduct(_.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.syntax.all._
scala> Option(42).fproductLeft(_.toString)
res0: Option[(String, Int)] = Some((42,42))
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Get the element at the index of the Foldable.
Get the element at the index of the Foldable.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Lifts if to Functor
Lifts if to Functor
Example:
scala> import cats.Functor
scala> import cats.syntax.all._
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
Intercalate/insert an element between the existing elements while folding.
Intercalate/insert an element between the existing elements while folding.
scala> import cats.syntax.all._
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
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Returns true if there are no elements. Otherwise false.
Returns true if there are no elements. Otherwise false.
Attributes
- Definition Classes
- Inherited from:
- Foldable
- Source
- Foldable.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.syntax.all._
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:
- Traverse
- Source
- Traverse.scala
Akin to map, but allows to keep track of a state value when calling the function.
Akin to map, but allows to keep track of a state value when calling the function.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Modifies the A value in F[A] with the supplied function, if the function is defined for the value. Example:
Modifies the A value in F[A] with the supplied function, if the function is defined for the value. Example:
scala> import cats.syntax.all._
scala> List(1, 2, 3).mapOrKeep { case 2 => 42 }
res0: List[Int] = List(1, 42, 3)
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Akin to map, but also provides the value's index in structure F when calling the function.
Akin to map, but also provides the value's index in structure F when calling the function.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Same as mapWithIndex but the index type is Long instead of Int.
Same as mapWithIndex but the index type is Long instead of Int.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
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.
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.
Attributes
- See also
-
Reducible#maximumByNel for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.minimumByList for minimum instead of maximum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
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).
Attributes
- Returns
-
Noneif the structure is empty, otherwise the maximum element wrapped in aSome. - See also
-
Reducible#maximumBy for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.minimumByOption for minimum instead of maximum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
Find all the maximum A items in this structure. For all elements in the result Order.eqv(x, y) is true. Preserves order.
Find all the maximum A items in this structure. For all elements in the result Order.eqv(x, y) is true. Preserves order.
Attributes
- See also
-
Reducible#maximumNel for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.minimumList for minimum instead of maximum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
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].
Attributes
- Returns
-
Noneif the structure is empty, otherwise the maximum element wrapped in aSome. - See also
-
Reducible#maximum for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.minimumOption for minimum instead of maximum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
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.
Attributes
- See also
-
Reducible#minimumByNel for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.maximumByList for maximum instead of minimum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
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).
Attributes
- Returns
-
Noneif the structure is empty, otherwise the minimum element wrapped in aSome. - See also
-
Reducible#minimumBy for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.maximumByOption for maximum instead of minimum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
Find all the minimum A items in this structure. For all elements in the result Order.eqv(x, y) is true. Preserves order.
Find all the minimum A items in this structure. For all elements in the result Order.eqv(x, y) is true. Preserves order.
Attributes
- See also
-
Reducible#minimumNel for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.maximumList for maximum instead of minimum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
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].
Attributes
- Returns
-
Noneif the structure is empty, otherwise the minimum element wrapped in aSome. - See also
-
Reducible#minimum for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty.maximumOption for maximum instead of minimum.
- Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Definition Classes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._, 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())
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._, 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()))
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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))
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._, 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))
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Returns
-
Noneif the structure is empty, otherwise the result of combining the cumulative left-associative result of thefoperation over all of the elements. - See also
-
reduceRightOption for a right-associative alternative.
Reducible#reduceLeft for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty. Example:scala> import cats.syntax.all._ 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 - Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Returns
-
Noneif the structure is empty, otherwise the result of combining the cumulative right-associative result of thefoperation over theAelements. - See also
-
reduceLeftOption for a left-associative alternative
Reducible#reduceRight for a version that doesn't need to return an
Optionfor structures that are guaranteed to be non-empty. Example:scala> import cats.syntax.all._ 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 - Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.syntax.all._
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
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Sequence F[G[A]] using Applicative[G].
Sequence F[G[A]] using Applicative[G].
This is similar to traverseVoid except it operates on F[G[A]] values, so no additional functions are needed.
For example:
scala> import cats.syntax.all._
scala> val F = Foldable[List]
scala> F.sequenceVoid(List(Option(1), Option(2), Option(3)))
res0: Option[Unit] = Some(())
scala> F.sequenceVoid(List(Option(1), None, Option(3)))
res1: Option[Unit] = None
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Alias for sequenceVoid.
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.
Attributes
- Inherited from:
- UnorderedFoldable
- Source
- UnorderedFoldable.scala
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Convert F[A] to a List[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.syntax.all._
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))
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
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.syntax.all._
scala> def parseInt(s: String): Option[Int] = Either.catchOnly[NumberFormatException](s.toInt).toOption
scala> val F = Foldable[List]
scala> F.traverseVoid(List("333", "444"))(parseInt)
res0: Option[Unit] = Some(())
scala> F.traverseVoid(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.
Attributes
- Inherited from:
- Foldable
- Source
- Foldable.scala
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.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Same as traverseWithIndexM but the index type is Long instead of Int.
Same as traverseWithIndexM but the index type is Long instead of Int.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Alias for traverseVoid.
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.syntax.all._
scala> Queue("hello", "world").tupleLeft(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.syntax.all._
scala> Queue("hello", "world").tupleRight(42)
res0: scala.collection.immutable.Queue[(String, Int)] = Queue((hello,42), (world,42))
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
Attributes
- Definition Classes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Attributes
- Definition Classes
- Inherited from:
- Foldable
- Source
- Foldable.scala
Fold in a CommutativeApplicative context by mapping the A values to G[B]. combining the B values using the given CommutativeMonoid[B] instance.
Fold in a CommutativeApplicative context by mapping the A values to G[B]. combining the B values using the given CommutativeMonoid[B] instance.
scala> import cats.UnorderedFoldable
scala> import cats.syntax.all._
scala> val evenNumbers = Set(2,4,6,8,10)
scala> val evenOpt: Int => Option[Int] =
| i => if (i % 2 == 0) Some(i) else None
scala> UnorderedFoldable[Set].unorderedFoldMapA(evenNumbers)(evenOpt)
res0: Option[Int] = Some(30)
scala> UnorderedFoldable[Set].unorderedFoldMapA(evenNumbers + 11)(evenOpt)
res1: Option[Int] = None
Attributes
- Inherited from:
- UnorderedFoldable
- Source
- UnorderedFoldable.scala
Attributes
- Definition Classes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Attributes
- Definition Classes
- Inherited from:
- Traverse
- Source
- Traverse.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.syntax.all._
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
If fa contains the element at index idx, return the copy of fa where the element at idx is replaced with b. If there is no element with such an index, return None.
If fa contains the element at index idx, return the copy of fa where the element at idx is replaced with b. If there is no element with such an index, return None.
The behavior is consistent with the Scala collection library's updated for collections such as List.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Empty the fa of the values, preserving the structure
Empty the fa of the values, preserving the structure
Example:
scala> import cats.syntax.all._
scala> List(1,2,3).void
res0: List[Unit] = List((), (), ())
Attributes
- Inherited from:
- Functor
- Source
- Functor.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.syntax.all._
scala> val l = List(Some(42))
scala> l.widen[Option[Int]]
res0: List[Option[Int]] = List(Some(42))
Attributes
- Inherited from:
- Functor
- Source
- Functor.scala
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.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala
Same as zipWithIndex but the index type is Long instead of Int.
Same as zipWithIndex but the index type is Long instead of Int.
Attributes
- Inherited from:
- Traverse
- Source
- Traverse.scala