zipper

Type Members

1. trait Unzip[A] extends AnyRef

   

   A typeclass that defines how a certain data structure can be unzipped and zipped back.

   A typeclass that defines how a certain data structure can be unzipped and zipped back.

   An instance of Unzip can be automatically derived for a case class C with a single field of type List[C]. In a similar situation, but with a different collection class used, say, Vector, an instance can still be derived like so:

   implicit val instance = Unzip.For[C, Vector].derive

   Annotations

   @implicitNotFound( ... )

2. case class Zipper[A](left: List[A], focus: A, right: List[A], top: Option[Zipper[A]])(implicit unzip: Unzip[A]) extends Product with Serializable

   

   A Zipper allows to move around a recursive immutable data structure and perform updates.

   A Zipper allows to move around a recursive immutable data structure and perform updates.

   Example:

   case class Tree(x: Int, c: List[Tree] = List.empty)
   
   val before = Tree(1, List(Tree(2)))
   val after = Tree(1, List(Tree(2), Tree(3)))
   
   Zipper(before).moveDownRight.insertRight(Tree(3, Nil)).commit shouldEqual after

   See https://www.st.cs.uni-saarland.de/edu/seminare/2005/advanced-fp/docs/huet-zipper.pdf.