TraverseFilter, also known as Witherable, represents list-like structures that can essentially have a traverse and a filter applied as a single combined operation (traverseFilter).
Based on Haskell's Data.Witherable
Attributes
- Companion
- object
- Source
- TraverseFilter.scala
- Graph
-
- Supertypes
Members list
Value members
Abstract methods
Attributes
- Source
- TraverseFilter.scala
A combined traverse and filter. Filtering is handled via Option instead of Boolean such that the output type B can be different than the input type A.
Example:
scala> import cats.syntax.all._
scala> val m: Map[Int, String] = Map(1 -> "one", 3 -> "three")
scala> val l: List[Int] = List(1, 2, 3, 4)
scala> def asString(i: Int): Eval[Option[String]] = Now(m.get(i))
scala> val result: Eval[List[String]] = l.traverseFilter(asString)
scala> result.value
res0: List[String] = List(one, three)
Attributes
- Source
- TraverseFilter.scala
Concrete methods
Filter values inside a G context.
Filter values inside a G context.
This is a generalized version of Haskell's filterM. This StackOverflow question about filterM may be helpful in understanding how it behaves.
Example:
scala> import cats.syntax.all._
scala> val l: List[Int] = List(1, 2, 3, 4)
scala> def odd(i: Int): Eval[Boolean] = Now(i % 2 == 1)
scala> val res: Eval[List[Int]] = l.filterA(odd)
scala> res.value
res0: List[Int] = List(1, 3)
scala> List(1, 2, 3).filterA(_ => List(true, false))
res1: List[List[Int]] = List(List(1, 2, 3), List(1, 2), List(1, 3), List(1), List(2, 3), List(2), List(3), List())
Attributes
- Source
- TraverseFilter.scala
Attributes
- Definition Classes
- Source
- TraverseFilter.scala
Removes duplicate elements from a list, keeping only the first occurrence.
Removes duplicate elements from a list, keeping only the first occurrence. This is usually faster than ordDistinct, especially for things that have a slow comparion (like String).
Attributes
- Source
- TraverseFilter.scala
A combined map and filter.
A combined map and filter. Filtering is handled via Option instead of Boolean such that the output type B can be different than the input type A.
Example:
scala> import cats.syntax.all._
scala> val m: Map[Int, String] = Map(1 -> "one", 3 -> "three")
scala> val l: List[Int] = List(1, 2, 3, 4)
scala> def asString(i: Int): Option[String] = m.get(i)
scala> l.mapFilter(asString)
res0: List[String] = List(one, three)
Attributes
- Definition Classes
- Source
- TraverseFilter.scala
Removes duplicate elements from a list, keeping only the first occurrence.
Removes duplicate elements from a list, keeping only the first occurrence.
Attributes
- Source
- TraverseFilter.scala
scala> import cats.syntax.all._
scala> val a: List[Either[String, Option[Int]]] = List(Right(Some(1)), Right(Some(5)), Right(Some(3)))
scala> val b: Either[String, List[Int]] = TraverseFilter[List].sequenceFilter(a)
b: Either[String, List[Int]] = Right(List(1, 5, 3))
Attributes
- Source
- TraverseFilter.scala
A combined traverse and collect.
scala> import cats.syntax.all._ scala> val m: Map[Int, String] = Map(1 -> "one", 2 -> "two") scala> val l: List[Int] = List(1, 2, 3, 4) scala> def asString: PartialFunction[Int, Eval[Option[String]]] = { case n if n % 2 == 0 => Now(m.get(n)) } scala> val result: Eval[List[Option[String]]] = l.traverseCollect(asString) scala> result.value res0: List[Option[String]] = List(Some(two), None)
Attributes
- Source
- TraverseFilter.scala
Like traverseFilter, but uses Either instead of Option and allows for an action to be run on each filtered value.
Like traverseFilter, but uses Either instead of Option and allows for an action to be run on each filtered value.
Attributes
- Source
- TraverseFilter.scala
Inherited methods
Similar to mapFilter but uses a partial function instead of a function that returns an Option.
Similar to mapFilter but uses a partial function instead of a function that returns an Option.
Example:
scala> import cats.syntax.all._
scala> val l: List[Int] = List(1, 2, 3, 4)
scala> FunctorFilter[List].collect(l){
| case 1 => "one"
| case 3 => "three"
| }
res0: List[String] = List(one, three)
Attributes
- Inherited from:
- FunctorFilter
- Source
- FunctorFilter.scala
Apply a filter to a structure such that the output structure contains all A elements in the input structure that satisfy the predicate f but none that don't.
Apply a filter to a structure such that the output structure contains all A elements in the input structure that satisfy the predicate f but none that don't.
Attributes
- Inherited from:
- FunctorFilter
- Source
- FunctorFilter.scala
Apply a filter to a structure such that the output structure contains all A elements in the input structure that do not satisfy the predicate f.
Apply a filter to a structure such that the output structure contains all A elements in the input structure that do not satisfy the predicate f.
Attributes
- Inherited from:
- FunctorFilter
- Source
- FunctorFilter.scala
"Flatten" out a structure by collapsing Options.
"Flatten" out a structure by collapsing Options. Equivalent to using mapFilter with identity.
Example:
scala> import cats.syntax.all._
scala> val l: List[Option[Int]] = List(Some(1), None, Some(3), None)
scala> l.flattenOption
res0: List[Int] = List(1, 3)
Attributes
- Inherited from:
- FunctorFilter
- Source
- FunctorFilter.scala