Zipper update

[Peter Schmitz]

With Zipper I can get and put (overwrite) the element at the current cursor postion.

But how can I update this element with a function?

For example:

  case class SubModel(i: Int)
  case class Model(sub: SubModel, s: String)
  val model = Model(SubModel(0), "-")
  model.toZipper.down.updateBy(_ + 1).root.reify // Model(SubModel(1),"-")

Thanks in advance,

Peter

[Peter Schmitz]

My proposal:

  import shapeless._
  import syntax.zipper._

  case class SubModel(i: Int)
  case class Model(sub: SubModel, s: String)

  implicit class ZipperModify[C, L <: HList, R <: HList, P](private val zipper: Zipper[C, L, R, P]) extends AnyVal {
    import shapeless.ops.zipper._
    def modify[A, B](f: A => B)(implicit get: Get[zipper.Self] { type Out = A }, put: Put[zipper.Self, B]): put.Out = put(zipper, f(get(zipper)))

  }

  val model = Model(SubModel(0), "-")

  model.toZipper.down.modify { i: Int => i + 1 }.root.reify // Model(SubModel(1),-)

Did I overlook something or can this be added to the Zipper API (without implicit class, of course)?

[Miles Sabin]

Hi Peter,

The shapeless-dev list is deprecated in favour of either shapeless's
gitter channel,

https://gitter.im/milessabin/shapeless

or the typelevel mailing list,

https://groups.google.com/group/typelevel

You'll find the most activity by far on gitter ...

Cheers,


Miles

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