Optional
monocle.Optional$
object Optional
Attributes
- Source:
- Optional.scala
- Graph
- Supertypes
- class Objecttrait Matchableclass Any
- Self type
- Optional.type
Members list
Concise view
Value members
Concrete methods
alias for POptional apply restricted to monomorphic update
Select all the elements which satisfies the predicate.
Select all the elements which satisfies the predicate.
val positiveNumbers = Traversal.fromTraverse[List, Int] composeOptional filter[Int](_ >= 0)
positiveNumbers.getAll(List(1,2,-3,4,-5)) == List(1,2,4)
positiveNumbers.modify(_ * 10)(List(1,2,-3,4,-5)) == List(10,20,-3,40,-5)
filter can break the fusion property, if replace or modify do not preserve the predicate. For example, here
the first modify (x - 3) transform the positive number 1 into the negative number -2.
val positiveNumbers = Traversal.fromTraverse[List, Int] composeOptional Optional.filter[Int](_ >= 0)
val list = List(1, 5, -3)
val firstStep = positiveNumbers.modify(_ - 3)(list) // List(-2, 2, -3)
val secondStep = positiveNumbers.modify(_ * 2)(firstStep) // List(-2, 4, -3)
val bothSteps = positiveNumbers.modify(x => (x - 3) * 2)(list) // List(-4, 4, -3)
secondStep != bothSteps
Attributes
- See also:
This method is called
filteredin Haskell Lens.- Source:
- Optional.scala
Optional that points to nothing
Deprecated methods
Attributes
- Deprecated
[Since version 3.0.0-M4]- Source:
- Optional.scala
Attributes
- Deprecated
[Since version 3.0.0-M2]- Source:
- Optional.scala